ASTRO SOLAR SYSTEM
ASTRO SOLAR SYSTEM ASTR 1010
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Date Created: 09/12/15
p t N M 5 Equot 0 What are the four major features of our solar system that provide clues to how it formed Describe each one brie y Patterns of motionThe Sun planets and large moons generally orbit and rotate in a very organized way Terrestrial small rocky close together and close to the Sun and Jovian planets large gaseous further apart and farther from the Sun Asteroids and Comets huge numbers orbit the Sun locations orbits and compositions follow patterns Exceptions Earth s large moon Uranus39 sideways tilt Venus backward orbit What is the nebular theory and why is it widely accepted by scientists today The solar system formed from an interstellar cloud of gas and dust Testable prediction because it successfully predicts much of what we have discovered about other planetary systems What do we mean by the solar nebula What was it made of and where did it come from piece of interstellar cloud from which our solar system formed Made of cold low density hydrogen and helium gas from the Big Bang Describe each of the three key processes that led the solar nebula to take the form of a spinning disk What observational evidence supports this scenario Heating temperature increased as it collapsed gravitational potential energy into kinetic energy into thermal energy Spinning rotated faster as it shrank in radius conservation of angular momentum led to greater average rotation which led to be more spread out Flattening attened into disk random movement became more orderly as it collapsed consequence of collisions of particles they collided and merged new clumps had the average velocity of the clumps that formed it Must heat up to collapse particles moving so much and collisions create thermal energy if they didn t produce thermal energy why would it not collapse Gravitational potential energy does not allow you to move in and collapse so it must change to kinetic energy which changes to thermal energy Other disks forming around other stars give off thermal energy which we pick up with telescopes List the four categories of materials in the solar nebula by their condensation properties and abundance Which ingredients are present in terrestrial planets In jovian planets In comets and asteroids Explain why Hydrogen amp Helium 98 H compounds 14 Rock 4 Metal 2 Terrestrial rock and ice Jovian H HE and H compounds What was the frost line in the solar nebula Explain how temperature differences led to the formation of two distinct types of planets Distance at which ice was cold enough to condense it lays between Mars and Jupiter Within frost line rocks and metals condense and hydrogen compounds stay gaseous Beyond frost line hydrogen compounds rock and metals condense Warrn inner regions are where the Terrestrial planets are while the cool outer regions are where the Jovian planets are 7 Brie y describe the process by which terrestrial planets are thought to have formed Accretion particles stuck together by electrostatic forces gravity aided process until it grew in to planetesimals 8 How was the formation of jovian planets similar to that of the terrestrial planets How was it different Accretion as well but solar system has more condensation so they have large amounts of we 10 Earth masses Jovian planets had enough energy to grab hydrogen and helium Why so large compared to Terrestrial More hydrogen compounds to collect versus rock 9 Why did the Jovian planets end up with so many moons Heating Spinning and Flattening surrounded by its own disk of gas spinning in same direction as rotation moons accreted and ended up with nearly circular orbits Why a lot of large moons strong gravitational pull Why a lot of small moons supply and gravitational pull 10 What is the solar wind and what roles did it play in the early solar system Solar wind is stream of charged particles ejected from the Sun and swept into space cleans gas out but not planetesimals Jovian planets gathered hydrogen and helium Younger sun rotated faster and had a stronger solar wind 11 In the context of planet formation what are asteroids and comets Brie y explain why we find asteroids in the asteroid belt and comets in the Kuiper belt and 0011 cloud Asteroids rocky leftover planetesimals of the inner solar system The asteroid belt is between Mars and Jupiter where no other planet formed Comets ice rich planetesimals of the outer solar system Kuiper Belt comets that are larger and follow orbital patterns of the planets Oort Cloud quotkicked outquot and have randomly oriented orbits General rule time when there was mixing icv and terrestrial stuff 12 What was the heavy bombardment and when did it occur Heavy bombardment period in the rst few hundred million years after the solar system formed during which the tail end of planetary accretion created most of the craters found on ancient planetary surface planetesimals collisions creates craters Just moon shows crater Earth got hit but craters eradicated by geological activity ovian anets interact an s ii I move I iron 1 Ianetesimals and their orbits mess with 39 39 39 planetary vibrations 39 39 39 cleaned out very few around after bombardment 13 How do we think the Moon formed and what evidence supp01ts this hypothesis The moon formed when large planetesimal collided with Earth and got stuck in orbit Composition of moon is same as outer layer of earth Moon has smaller proportion of vaporized material because the heat of impact would have vaporized the material 14 Describe the technique of radiometric dating What is a half life 1 What is planetary geology Brie y summarize the different geological appearances of the ve terrestrial worlds gtprocesses that change a planet s surface long after formation such as volcanism tectonics and erosion Venus has volcanos but no active ow Mercury heavily cratered Earth everything Moon heavily cratered Mars dry riverbeds has volcanic activity Olympus Mons 2 For the terrestrial objects how does the pressure and temperature change from the surface to the center Core under the most pressurehighest temperature TempPressure decrease going out from the core gtWhy is there more pressure in the center gravity pushes it in atmospheres gtwhy is it hotter in the center than on the outside heat loss is from moving from inside to the outside of something Inside of something is always the warmest coffee 3 Why does the Ealth have both a solid and liquid core Inner and outer are both made of iron and nickel depends on what its made out of then based on temp or pressure as soon as temp is above melting point it will remain a liquid then when pressure is high enough it becomes solid again all depends on type of material temperature and pressure if you put dry ice under enough pressure you can liquefy it Differentiation provides a chemical separation the core is iron and nickel Outer core does not have as high temperature or pressure Solid liquid or gas depends on temperature pressure and composition 4 What is the structure of the moons core Partially molten layer like earth It has a liquid and solid core Up until 2010 astronomers thought that core was only a big lump core but now we know it s more like Earth39s 5 What is differentiation and how did it lead to the core mantle crust structures of the terrestrial worlds gtProcess by which gravity separates materials by density Uranium is heavy element apart of crust Combine with lighter materials iron oxide oats to the top We have asteroids that are the same throughout if you cut it down the middle What does it do to the chemistry of the surface of Earth makes it less dense quotWe have been cheated of ironquot We must have iron so how did the iron stay on the surface take the iron make iron oxide makes it light oats to the top Lighter iron compounds come from the top 6 What do we mean by the lithosphere How does lithospheric thickness vary among the ve terrestrial worlds Lithosphere outer layer that consists of relatively cool and rigid rock Smaller worlds tend to have thicker lithospheres Earth and Venus have smaller lithospheres while Mars Mercury and moon have thicker Thin lithosphere brittle crack easily Thick strong and inhibits the passage of any molten rock from below 7 Summarize the processes by which planetary interiors get hot Heat of accretion differentiation radioactive decay Accretion Transferring kinetic energy into thermal energy DifferentiationConverting gravitational potential energy into thermal energy EX Rain heats as it falls water evaporates and cools Radioactive decayParticles nucleus falling apart Accretion is most important Summarize the processes by which planetary interiors cool off In the center of the earth when solids are compressed it causes little temperature increase If all the radioactive elements decay Earth s interior will cool Can only remain high if there is a source of heat for the interior such as accretion differentiation or radioactive decay Solids cant convect earth solids layer rises and cools and falls 9 Why do large planets retain internal heat longer than smaller planets Matter of volume vs surface takes longer for heat to go from core to outer layer 10 Describe the interiors of the ve terrestrial objects and tell Why there is a difference Smaller ones interior cools rapidly less energy coming out Mars If its not as hot the thicker the lithosphere Matter of having a live surface or dead surface Deadest Mercury and our moon Live Venus and Earth Smaller ones interior cools rapidly Warmer interior with mantel convection Not as hot thicker lithosphere Live surface vs dead surface Mercury and mars half dead Venus and earth most active 11 Why does Earth have a global magnetic eld Why don39t the other terrestrial worlds have similarly strong magnetic elds Magnetosphere region surrounding a planet in which charged particles are trapped by the planet s magnetic eld Earth39s magnetosphere diverts paths of highenergy charged particles coming from the Sun Other terrestrial worlds do NOT have similarly strong magnetic fields WHY Moon core has long since cooled and ceased convecting Mars not enough heat to drive convection rotating plenty fast does not have a liquid core not much volcanism Venus either convection or 243day rotation period is too slow to generate magnetic field Mercury has a measurable magnetic field and we don t know why maybe bc of huge metal core gtearth has a liquid conductive core rapid rotation and is convective Internal heat causes to rise and fall Interior region of conducting rapid rotation Convection uid 12 Suggest how you might turn on or turn off the terrestrial magnetic elds Slow down the rotation Cooling the core so there is no liquid core Mars does not have very much of a magnetic eld its rotating in 24 hrs it does not have a convective inner core Mercury has a magnetic field despite its small size big size core some of its liquid but slow rotation Moon little liquid core rotation is low Jupiter has a magnetic eld 1000s x bigger than Earthliquid hydrogen core Turn off by slowing down rotation synchronizing with moon cooling the core Venus rotates slowly so it does not have a magnetic eld Mars does not have very much of a magnetic eld not convecting no convecting inner core Mercury a little magnetic eld rotation is slow Moon fails little liquid little convection Earth Jupiter the boss magnetic eld thousands time earth liquid hydrogen core De ne each of the four major geological processes and give examples of features shaped by each process Do not con ne your examples to one planet E Impact cratering craters on the moon Mercury Volcanism Mount Fuji Venus and Mars biggest volcano in solar system Erosion Grande Canyon river bed on Mars Tectonics Appalachian mountains Impact Cratering The excavation of bowlshaped depressions impact craters by asteroids or comets striking a planet39s surface Impacts vaporize solid rock and excavate large generally circular craters The lithosphere is cracked to allow for ooding by lava At the small extreme micrometeorites pulverize surface rock on bodies without signi cant atmospheres Impact cratering is the most universal of the geological processes Craters on the moon Volcanism The eruption of molten rock or lava from a planets interior onto its surface Eruptions occur when underground lava nds a path through the lithosphere to the surface It occurs in planets with high internal temperatures and thin lithospheres In addition to resurfacing outgassing through volcanic activity is responsible for the atmospheres of the terrestrial planets Volcanism is a feature of the larger worlds that have retained internal heat Mount fuji Venus and mars olympus mns Tectonics The disruption of a planets surface by internal force and stress Compression of the crust can create mountain ranges when the crust is pulled apart valleys and cliffs form Tectonics is a feature of the larger worlds that have retained internal heat Appalachian mountains Erosion The wearing down or building up of geological features by wind water ice and other phenomena of planetary weather Examples include wind rain ice rivers and glaciers Erosion is found on planets with substantial atmospheres and faster rotation River beds on mars Grand canyon 14 What is outgassing and why is it so important to our existence gt process of releasing gases from a planetary interior usually through volcanic eruptions Earth Venus and Mars If you don t have volcanism it would be hard to have an atmosphere You get atmospheres from any body that outgasses 15 Why is the Moon so much more heavily cratered than Earth Most of Earth39s impact craters have been erased with time by other geological processes such as volcanic eruptions tectonics and erosion The Moon39s impact craters remain undisturbed because the Moon is geologically dead Mercury 2nd most blemished 16 Explain how crater counts tell us the age of a surface Surfaces crowded with craters must still look much as they did billion of years ago at the end of heavy bombardment Smooth surfaces have been repaved Smooth surface younger than cratered surface Mars all of it has been repaved a little bit Wind and dust erosion 17 Summarize the ways in which a terrestrial world39s size distance from the Sun and rotation rate each affect its relative level of impact cratering volcanism tectonics and erosion Size Smaller planets cool rapidly so tectonic and volcanic activity cease after a billion years or so which leaves craters Lack of volcanism means little outgassing No atmosphere means no erosion Larger planets had warmer interiors which causes mantle convection which causes tectonic and volcanic activity which erases craters Outgassing produces atmosphere and strong gravity holds it allowing erosion Core may be molten which produces a magnetic eld if the rotation is fast enough Mercury is small and has lots of craters Earth is large and has less cratering Distance Planets close to the Sun have hot surfaces that don t allow for rain snow or ice thus no erosion occurs Also high atmospheric temperatures allow gas to escape easier Planet s at intermediate distances from the Sun there are moderate temperatures on the surfaces which allows for oceans rain snow and ice which leads to substantial erosion Also there is enough gravity to hold atmospheric gases Planets far from the Sun have low surface temperatures that allow for snow and ice but not rain or oceans So erosion is limited Also atmosphere may exist on the planets but gases condense easier and create surface ice Rotation Rate Slow rotation means less wind and weather which leads to less erosion even with substantial atmosphere Also a slow rotation causes a weak magnetic eld Rapid rotation creates more wind and weather which creates more erosion Furthermore the rapid rotation is necessary for a global magnetic eld 18 Brie y summarize the geological history of the Moon How did the lunar maria form Heavy bombardment caused craters to cover entirety of Moon39s surface Hundreds of millions of years after radioactive decay released heat in Moon39s interior and molten rock bled through into larger craters and solidi ed The lava was very runny so it carved H P N N out many long winding channels rilles Small scale tectonic stresses arose from when the lava ooded and cooled and contracted Difference in altitude allowed for lava to only ll up craters on the near side of the Moon Moon is geologically dead now What is regolith Regolith is a layer of loose heterogeneous material covering solid rock It includes dust soil broken rock and other related materials and is present on the Moon some asteroids and other terrestrial planets and moons Earth does not have regolith Regolithdry ground up rock only in places without atmosphere Name four consequences of not having an atmosphere on the moon and how lack of an atmosphere brings them about 1 runny lava makes channels 2 sand blasting consistent surface 3 no water no pressure 4 no weather no atmosphere no erosion 5 no temperature regulation just heat of Sun 6 No sound Brie y summarize the geological history of Mercury How are Mercury39s great cliffs thought to have formed Mercury has craters but they are less crowded which leads to the belief that radioactive decay released heat accumulated and melted part of the mantle Mercury had as much volcanic activity as the Moon Also the Caloris Basin is a huge impact crater half the size of Mercury39s radius It was so violent that there is evidence of surface shaking on the opposite side of Mercury Cliffs are 3 or more kilometers higher and hundreds of kilometers long Tectonic forces compressed the crust and crumpled the surface of Mercury It39s large iron core gained internal heat from accretion and differentiation and swelled the Moon As Mercury cooled the planet contracted 20 kilometers in radius Contraction generated tectonic stresses and created the great cliffs Choose ve features on a global map of Mars and explain the nature and likely origin of each 1 Olympus Mons tallest known volcano in the solar system It was created by long lived plume of rising mantle material that bulged the surface upward and provided the molten rock for the eruptions 2 Valles Marineris is a huge set of valleys that extend a fifth of the way along Mar s equator created in part by tectonic stresses accompanying the uplift of material that created the Tharsis Bulge cracking the surface and leaving the tall cliff of the valleys 3 Dry channels were carved by water 4 Heavily cratered southern highlands lack of small craters argues there were once ancient rainfalls because eroded crater rims and absence of small craters shows erosion 5 Floor of eroded crater appears to be layers of sedimentary rock that were laid down at a time when the crater may have been filled with water Southern Hemisphere has more impact cratering Ice caps 23 Why isn39t liquid water stable on Mars today and why do we nonetheless think it owed on Mars in the distant past It is so cold that is either freezes or evaporates There are ancient water channels and sediment build up on the bottoms of craters 24 Choose at least three major geological features of Venus and explain how we think each one formed 1 Few impact cratering heavy bombardment 2 Volcanism lava planes and volcanic mountains Runniest are lava plains Runny lava created shield volcanoes High viscosity lava created volcanoes with strato volcanoes steeper sides 3 Contorted Crust fractured regular pattern created by tectonics Coronae formed by hot rising plumes in the mantle 25 What evidence tells us that Venus was quotrepavedquot about 750 million years ago Relatively few impact craters are distributed fairly uniformly over the planet suggesting that the surface is about the same age everywhere Precise crater counts 26 What might account for the lack of plate tectonics on Venus How did Earth and Venus get to be so different geologically It s possible that plate tectonics played a role before and during the repavement only to stop after the repaving episode It may have weaker mantle convection or the lithosphere resists fracturing Venus higher surface temperature is so hot that any water in its crust and mantle has baked out over time 27 Describe the conveyorlike action of plate tectonics on Earth How does this action explain the differences between sea oor crust and continental crust 12 plates make up mantle Mantle material erupts onto the ocean oor pushing apart the existing sea oor on either side Mantle convection New sea oor crust continually emerges at sites of sea oor spreading while the wide age range of continental crust tells us that the continents have gradually built up over time 28 Brie y explain how each of the following geological features of Earth is formed sea oors continents islands mountain ranges rift valleys and faults Sea oors Mantle material rises upward basaltic crust cools and contracts moves across ocean bottom and is recycled into mantle Continentscontinental crust is not recycled just builds up over billions of years volcanism stresses and erosion Islands volcanoes that built up hot spots Mountain ranges tectonic processes plate subduction collisions of continent bearing plates Rift valleys where continental plates are pulling apart and the crust thins Fau1ts places where plates slip sideways relative to each other fractures on the lithospheres 29 Contrast the surfaces of the ve terrestrial objects Name the types of features and give reasons for the differences Mercury amp Moon unpaved 1 N E 5 V39 9 Brie y summarize the atmospheric properties of the five terrestrial worlds How do they differ in surface temperature pressure and composition Mercury little atmosphere no clouds composition helium sodium and oxygen airless world SP10 14 bar ST Day 425 0 Night 175 0 Venus thick atmosphere sulfuric acid clouds 96 C02 35 N2 slow winds no violent storms acid rain hot and harsh SP 90 bar ST 470 c Ea1th hospitable for human life HZO Clouds Pollution 77 N2 21 O2 1 Argon H20 variable winds hurricanes rain and snow SP 1 bar ST 15 0 Moon little atmosphere helium sodium argon airless world SP 10 14 ST Day 125C Night 175 c Mars air is thin H2O amp CO2 Clouds dust 95 CO2 27 N2 16 argon wind and dust storms SP 007 bar ST 50 c What do we mean by atmospheric pressure Why does pressure decrease with altitude What is 1 bar of pressure The surface pressure resulting from the overlying weight of an atmosphere pushes in all directions gas is held down by gravity The higher you go in an atmosphere the less weight of the gas above you and this lesser weight means less pressure 1 bar of pressure is the pressure at sea level on Earth Is there any atmosphere at the orbital altitude of the Space Station above Earth Explain Yes Atmosphere gradually fades away as the pressure and density decrease with increasing altitude At some point the density becomes so low that we can t consider it air because molecular collisions are so rare The atmosphere at the orbital altitude of the Space Station are low density gas that can t be felt but still exert orbiting drag on the station What is the greenhouse effect Describe how it warms a planet The process by which greenhouse gases in an atmosphere make a planet s surface temperature warmer than it would be in the absence of an atmosphere The greenhouse gases tend to slow the escape of infrared radiation from the lower atmosphere while there molecular motions heat the surrounding air Ifthere were no greenhouse effect what factors would determine a planet39s surface temperature How do the quotno greenhousequot temperatures of the terrestrial planets compare to their actual temperatures and why how much sunlight it absorbs planet s distance from the Sun the planet39s overall re ectivity composition and color colder on all the planets especially those with a lot of greenhouse effect Describe Earth39s basic atmospheric structure from the ground up How do interactions of sunlight and gases explain the existence of each of the atmospheric layers The troposphere is the lowest layer of the atmosphere The temperature drops with altitude in the troposphere something you ve probably noticed if you ve ever climbed a gt1 temp mountain important The stratosphere begins where the temperature stops dropping and instead begins to rise with altitude High in the stratosphere the temperature falls againSK Heated by UV light no convection The thermosphere begins at a high altitude where the temperature again starts to rise X rays and UV heat and ionize gases The exosphere is the uppermost region in which the atmosphere gradually fades away into space Heated by X rays and UV39 fastmoving gas Why are these temperature pro les different Varying amounts of the greenhouse effect on different planets Diiferent distances from Sun Thickness of atmosphere Earth and ozone Lack of ozone layers on planets or other ultraviolet absorbers vs height on three terrestrial planets that have atmosphere gases trap infrared radiation from the ground I can escape to space Different surface temp greenhouse effects Venus strophoshere really hot because of greenhouse effect Mars they not much greenhouse effect get cooler as they go up on scale eventually turn around and get hot at top Earth ozone layer gets hotter then cooler 8 Why is the sky blue Why are sunrises and sunsets red Scattering of visible light The difference in scattering is so great that for practical purposes we can imagine that only the blue light gets scattered When the Sun is overhead this scattered blue light reaches our eyes from all directions and the sky appears blue At sunset or sunrise the sunlight must pass through a greater amount of atmosphere on its way to us Most of the blue light is scattered away leaving only red light to color the sky If light didn39t scatter we would just see a black sky Water vapor scatters light At sea level there is always water vapor which is why blue skies look different at the beach Mars doesn39t have water vapor so the sky isn39t really blue Martian skies tend to be white or pinkish haze because of dust 9 Why does convection occur in the troposphere leading to active weather but not in the stratosphere Convection occurs when there is strong heating from below In the troposphere the heating from the ground can drive convection The primary cause of storms is the churning of air by convection in which warm air rises and cool air falls The lower stratosphere gets warmer with increasing altitude Convection cannot occur in the lower stratosphere because heat cannot rise if the air is even hotter higher up 10 l l 3 Once you get circulation you get weather patterns What is ozone How does the absence of ozone on Venus and Mars explain why these planets lack a stratosphere Ozone The molecule 03 which is particularly good absorber of ultraviolet light Lack of oxygen planet can only have a stratosphere if its atmosphere contains molecules that are particularly good at absorbing ultraviolet photons What is a magnetosphere Describe its role in protecting any atmosphere from the solar wind and in creating auroras Magnetosphere the region surrounding a planet in which charged particles are trapped by the planet39s magnetic field Magnetospheres divert charged particles in solar wind from impact on the surface of atmospheres of planets A few particles still get through and become trapped They create a beautiful spectacle of light known as the aurora by colliding with atmospheric atoms and molecules The collisions cause the atoms and molecules to radiate and produce the moving lights of the aurora Northem Lights Aurora emission spectrum of nitrogen and oxygen What causes seasons How and why do seasons on Mars differ from seasons on Earth This is review The Earth has seasons because of the Earth39s tilt of its rotation axis 23 degrees As we orbit the sun in an elliptical motion different parts of the Earth move farther or closer to the sun The orientation of the axis relative to the sun changes over the course of each orbit the seasons are opposite in the two hemispheres pg36 A way the Earth would not have seasons would be if the earth39s axis changed its tilt during the orbiting of the sun Ifit had no tilt the earth would be hottest at the equator and steadily get colder as you moved north and south from there Mars is different because it has a different axial tilt and it is more elliptical Describe Earth39s global wind patterns and the role of circulation cells How does rotation affect these cells Equatorial winds blow from east to west mid latitude winds blow from west to east and high altitude winds blow from east to west The Coriolis effect diverts the air owing northsouth into eastwest winds which causes the single circulation cells in each hemisphere to become three cells If Earth s rotation did not influence the process the result would be two huge circulation cells which transport heat from both the lower to the higher altitudes and from the equator to the poles which makes the polar regions warmer Weather in Georgia comes from Alabama Weather usually comes from East Affected by atmospheric heating Equatorial regions receive excess heat from the Sun which makes the atmosphere expand above the equator so that it rises up and ows towards the poles Near the poles cool air descends and ows towards the Equator and planeta rotation Low pressure regions draw air in from surrounding areas and the Coriolis effect causes the air to circulate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere Regions near the equator move at faster speed around the aXis than regions near the polls Gas giants rotate faster more east west cells earth wind patterns produced by heating of equator poles cold circulation pattern that runs wind at surface from north to south Coriolis effect north to south turns wind west In order to get winds in other direction winds must go south to north circulation cells 1 to 3 because rotate so fast coriolis effect sends winds east 14 Describe each of the four factors that can lead to longterm climate change Solar brightening the Sun has grown gradually brighter with time increasing the amount of warming sunlight that reaches the planets Changes in axis tilt the tilt of the Earth and the other planets can change over long periods oftirne changes seasons Changes in re ectivity an increase in a planet39s re ectivity means a decrease in the amount of sunlight that it absorbs and vice versa Changes in greenhouse gas abundance More abundant greenhouse gases result in greater warming by the atmosphere 15 Describe each process by which atmospheres gain or lose gas What factors control thermal escape Which loss processes are permanent Which are temporary Sources Outgassing impacts that broughttrapped water and gas in interiors of planets Evaporationsublimation adds gas released by surface liquids or ices Impacts of particles and photons on worlds without atmospheres can eject small amounts of gas from the surface Losses Condensation returns gas to the surface as rain snow or frost Chemical reactions can incorporate gas into surface materials Large impacts can blast atmospheric gas into space The solar wind can sweep particles into space Thermal escape occurs when atoms or achieve escane velocitV The planet39s escape velocity the atmospheric temperature and the mass of the gas particles 16 Why do the Moon and Mercury have so little atmospheric gas How is it possible that they might nonetheless have water ice in polar craters no ongoing source of outgassing lost through impacts or stripping by the solar wind thermal escape M ercury cannot hold much atmosphere because its small size and high daytime temperature mean that nearly all gas particles eventually achieve escape velocity The bottoms of some polar craters lie in nearly perpetually shadow keeping them quite cold and it is possible that over time water from the impacts of ice rich comets has condensed and accumulated as ice in these craters don t have atmosphere because at their temp their molecules are moving faster than escape velocity Get ice because you keep it cold put in polar or dark side of the moon keep away from sunlight get icy stuff everywhere keep it warm when you form planetismals if you don t you get icy terrestrial object More ice than rock probably bigger icy super earths More internal heat more geological activity 17 How do we think that Mars lost atmospheric gas What basic planetary property size distance from the Sun or rotation rate would have had to be different for Mars to have retained a thicker atmosphere The magnetic eld weakened as the small planet cooled and the core convention eventually ceased leaving the atmosphere vuhierable to solar wind particles which stripped gas out of the atmosphere Mars lacks an ultraviolet absorbing stratosphere atmospheric water molecules would have been easily broken apart by ultraviolet photons Break apart and lost in space by thermal escape Larger Size form core out icy material but clear before hyhe form icy planet without hyhe not jovian make seas but clean it out 810 mass icy planets Fewer moons 18 What do we mean by a runaway greenhouse effect Explain why this process occurred on Venus but not on Earth Runaway greenhouse effect a positive feedback cycle in which heating caused by the greenhouse effect causes more greenhouse gases to enter the atmosphere which further enhances the greenhouse effect Earth retained its outgassed water because temperatures were low enough for water vapor to condense into rain and thereby form oceans Describe several ways in which Earth s atmosphere is unique among the terrestrial worlds and how each unique feature is important to our existence 0 Earth retains most of its outgassed water Temperatures were low enough for water vapor to condense into rain and form oceans 0 Earth has very little carbon dioxide Oceans explain why there is little COZ because most of the C02 outgassed by volcanism on earth dissolved into the oceans o Composed primarily of nitrogen and oxygen Nitrogen is the 3rd most common gas released by outgassing Oxygen would disappear from our atmosphere if not continuously resupplied LIFE plants photosynthesis pg 305 0 Has an ultra violet absorbing stratosphere Life and oxygen chemical reactions form some of the 02 molecules into 03 ozone absorbs solar ultraviolet energy because it is more weakly bound O gtthe long term existence of Earth s oceans tells us that our planet has enjoyed remarkable climate stability contrasting the dramatic climate changes of Mars and Venus Oxygen comes from photosynthesis 1 What do we mean by acceleration What is the acceleration of gravity 2 What is momentum How can momentum be affected by a force What do we mean when we say that momentum will be changed only by a net force 3 What is freefall and why does it make you weightless 4 The densities of Jupiter 133 the Sun 141 and Satum s moons Dione 144 and Rhea 133 are all about the same in spite of having HUGE differences in gravity holding them together Numerically how can this be What is the underlying physical cause that gravity does not make the most massive object the densest 5 State each of Newton s three laws of motion For each law give an example of its application 6 What are the laws of conservation of momentum conservation of angular momentum and conservation of energy For each give an example of how it is important in astronomy 7 Imagine you are out in space and push away from you an object having a mass identical to your own What happens Explain 8 De ne kinetic energy radiative energy and potential energy for each type of energy give at least two examples of objects that either have it or use it 9 De ne temperature and thermal energy How are they related How are they different 10 What do we mean by massenergy Is it a form of kinetic radiative or potential energy 11 Summarize the universal law of gravitation in words 12 Consider an object shot upward from the earth with less than escape velocity Describe its motion 13 Why do objects fall at the same rate 14 How could I double the Earth s escape velocity more than one way but the universal gravitational constant remains the same 15 What is the difference between a bound and an unbound orbit What orbital shapes are possible ON State then explain Kepler39s three laws l How did Newton s understanding of gravity extend Kepler s Laws 00 What quantities do we need to know if we want to measure an object s mass with Newton s version of Kepler s third law Explain O Explain why orbits cannot change spontaneously How can a gravitational encounter cause an orbit to change How can an object achieve escape velocity N O Explain how the Moon creates tides on Earth Why do we have two high and low tides each day N How do the tides vary with the phase of the Moon Why N N How would you make ocean tides stronger or weaker More or less frequent Be careful to state what you would change and what effect it would have on the frequency of tides mess with speed of moons orbit move moon or sun closer or farther away N L Describe the tides if any if we had no moon N 4 What is tidal friction What effects does it have on Earth How does it explain the Moon39s synchronous rotation N Ul Would you fall at the same rate on the Moon as on Earth Decide whether the statement makes sense or is clearly true or does not make sense or is clearly false Explain clearly not all of these have de nitive answers so your explanation is more important than your chosen answer Astronomy 1010 Questions CH 1 1 2 3 Describe this picture What does it tell us about the Universe 1 It shows that the universe is made of up clusters and super clusters and is very large It is also a portion of the observable universe and how vast that actually is How can you use the apparent brightness of an object to tell its distance 1 You can tell its distance because objects that are brighter will have a greater intensity of light than those that are farther away You have to know Where are we in the Universe 1 We are in the Milky Way Galaxy 28000 light years away from the center in a cluster of galaxies called a local group 4 How can you use the angular size of an object to tell its distance V39 9 gt1 1 An object s angular size is the angle between the lines of sight to its two opposite sides For example the angular size ofthe horizon is about 180 degrees An object s angular size is a measure of how large the object actually appears to be which is a function of both actual size and distance away In astronomy the angular sizes of most objects are much smaller than even a single degree To measure these tiny angular sizes astronomers use units of arc minutes C and arcseconds quot There are 60 arcminutes in a degree and 60 arcseconds in an arcminute so there are 648000 arcseconds in the horizon What do we mean by a geocentric universe In broad terms contrast a geocentric view of the universe with our modern view of the universe Brie y describe the major levels of structure such as planet star galaxy in the universe 1 Geocentric means that the Earth is at the center of the universe We don t believe this theory anymore Now we believe in the Copernicunrevolution which means that we know the earth is not the center of the universe but that the sun is the center of the solar system in which the earth rotates around What do we mean when we say that the universe is expanding How does expansion lead to the idea of the Big Bang When we say that it is expanding we mean that over time everything in the universe is moving away from the center This proves the theory of the big bang because in the beginning the big bang means that when the universe started everything was together and they began to travel apart from each other The expanding universe today helps to support the theory of the big ang What determines the chemistry of the universe 1 Stars mainly compose of hydrogen and helium So that is mostly what the universe is made of up with only about 2 foreign materialsThe nuclear fusions and nuclear reactions from stars determine the chemistry of our universe The early universe only contained hydrogen helium and a trace N of lithium However over time stars have manufactured carbon nitrogen oxygen and iron Are there variations in chemical composition from place to place in the Universe If so what causes them Think small scale and then large scale 1 Each generation of star would differ in the chemical content of the galaxy because they used recycled materials thus making more and more heavy elements depending on what elements where recycled from the last star There is creation and there is refinement But nothing extreme The farther out stars and galaxies will have less chemical composition because they are newer than stuff in the closer in What did Carl Sagan mean when he said that we are quotstar stuff quot 1 He meant that we are leftover matter from when stars were created and that gravity has slowly over time compacted excess matter from stars and created planets such as earth What does chemical change have to do with the abundance of life in the Universe Is timing important 1 Life is entirely dependent on the elements and chemicals in the Universe Earth being a prime example If it weren t for the chemicals we have on our planet life would not be the way it is today When our solar system formed 45 billion years ago earlier stars had converted 2 of the hydrogen and helium in our galaxy into other elements Because of this important timing life was able to blossom on Earth How would the Universe be different if it were 1 billion years old Ifit were 100 billion years old If it were a billion the galaxies would be closer together out solar system wouldn t even exist yet If it were 100 billion the galaxies would be farther apart many would have exploded and new ones would have formed And our galaxy might not even exist anymore Explain the statement The farther away we look in distance the further back we look in time l The light takes time to travel so what we see is actually light from billions of years ago based on how far away in light years the star actually is How old is the universe How can we tell 1 The universe is around 14 billions years old because the farther objects we can see are about 14 billion light years away This means that the light we see is 14 billions years old Ifthat is the only light we can see we can assume And this concludes that this is our observable universe What key observations by Edwin Hubble lead us to conclude that the universe is expanding Use the raisin cake model to explain how these observations imply expansion 1 It is like if you put raisins in a cake and then when you baked it the raisins would expand and get farther apart when the cake was being baked It would starts with all the matter in the universe which would be infinity raisins The only problem with this theory is that this would mean the universe is finite It is not an explosion from a single special point Edwin Hubble saw that every galaxy outside of the local group is moving away from us and the further away the other galaxy the faster it appears to be mov1n 15 What do we mean by the observable universe Is it the same thing as the entire universe 1 When we say the observable universe we mean only the objects that we can see The farthest we can see into the universe is 14 billion light years away We don t know if that is the entire universe because there could be objects that are father whose light just has not reached the earth yet 16 What is the shape of the Milky Way Galaxy Where is our solar system located within the galaxy How does our solar system move within the galaxy 1 The Milky Way is a diskshaped galaxy We are located a little more than halfway from the galactic center to the edge of the galactic disk Our solar system moves among the stars of of the local solar neighborhood and also orbits the center of the Milky Way Galaxy An orbit every 230 million years 17 Distinguish between our galaxy39s disk and halo Where do most visible stars reside Where does the mysterious dark matter seem to reside 1 The disc is the visible mass of the galaxy and the halo is the stuff we can t see Most of the mass is in the unobservable halo which is believed to consist of dark matter 18 How are we moving in the universe 1 We are randomly moving 400000 miles per hour relative to nearby stars CH 2 1 What are constellations How did they get their names A constellation is a region of the sky with welldefined borders the familiar patterns of stars merely help us locate the constellations The names and borders of the 88 official constellations were chosen in 1928 by members of the International Astronomical Union IAU Most of the IAU members lived in Europe or the United States so they chose names familiar in the western world Before the IAU though ancient Greeks and Romans came up with names as well 2 On a clear dark night the sky may appear to be full of stars Does this appearance accurately re ect the way stars are distributed in space Explain This appearance does not accurately re ect the way stars are distributed in space this is because though they may appear to lie close together in reality they may lie at very different distances from Earth This illusion occurs because we lack depth perception when we look into space because the stars are so far away 3 Define horizon zenith and meridian How do we describe the location of an object in the local sky What are right ascension and declination The horizon is the boundary between Earth and the sky The point directly overhead is the zenith The meridian is an imaginary half circle stretching from the horizon due south through the zenith to the horizon due north We can pinpoint the position of any object in the local sky by stating its direction along the horizon and its altitude above the horizon Right ascension is the celestial equivalent of longitude and declination is the celestial equivalent of latitude They are measured in hours rather than degrees We use hours to measure right ascension and declination because time is set to the rotation of the globe 4 Explain why we can measure only angular sizes and angular distances for objects in the sky What are arcminutes and arcseconds We can measure only angular sizes and angular distances for objects in the sky because our lack of depth perception on the celestial sphere means we have no way to judge the true sizes or separations ofthe objects we see in the sky An arcminute is 160 of 1 in a circle and an arcsecond is 160 of an arcminute or 13600 of 1 in a circle 5 What are circumpolar stars Are more stars circumpolar at the North Pole or at Athens Georgia Explain Circumpolar stars are stars relatively near the north celestial pole that remain perpetually above the horizon They never rise or set but instead make daily counterclockwise circles around the north celestial pole Stars are more circumpolar at the North Pole because those stars are closer in proximity to the north celestial pole 6 What are earth latitude and longitude Does the sky you observe vary as you change latitude Does it vary with longitude Explain Latitude measures northsouth position it is de ned to be 0 at the equator increasing to 90N at the North Pole and 90S at the South Pole Longitude measures eastwest position so lines of longitude are semicircles extending from the North Pole to the South Pole Latitude affects the constellations we see because it affects the locations of the horizon and zenith relative to the celestial sphere Although the sky varies with latitude it does not vary with longitude Longitude makes a difference with the time you re going to see stuff 7 You are living on a planet where the sidereal day is 4 min longer than the mean solar day How can this be You would have to be rotating in the opposite direction as you were revolving 8 Suppose a star rose at 10pm today How do you calculate when it will rise a certain number of days from now Because we know that the sidereal days is the time of 23 hours 56 minutes and 409 seconds between successive appearances of any particular star on the meridian we would simply have to add that amount of time to each day as it passes to calculate when that star would rise a certain number of days from now 9 Describe the path that a star on the celestial equator follows from the time it rises until it sets for a person at a latitude of 34 degrees N N pole S pole equator Give times as well as position Do the same for a star at 35 degrees declination 34N rises due east crosses the meridian at 56N and sets due west North Pole rises due east crosses the meridian at the equator sets due west South Pole rises due east crosses the meridian at the equator sets due west Equator rises due east circles the horizon and sets due west 35 degrees declination 34N circumpolar circle from east to west North Pole rise north of due east and set north of due west crossing the meridian at 84N South Pole rise north of due east and set north of due west crossing the meridian at 84S Equator circumpolar circle from east to west 10 An astronomer sees a star rise due west and set due east How can this be The astronomer must be looking at a star with 0 declination meaning that is lies on the celestial equator Therefore it rises due east crosses the meridian at the zenith and sets due west 11 What is the zodiac and why do we see different parts of it at different times of the year The zodiac is the group of constellations on the celestial sphere through which the ecliptic passes The Sun s apparent location along the ecliptic determines which constellations we see at night For example the Sun appears to be in Leo in late August We therefore cannot see Leo in late August because it moves with the Sun through the daytime sky However we can see Aquarius all night long since it is opposite Leo on the celestial sphere Six months later in February we see Leo at night while Aquarius is above the horizon only in the daytime l2 Explain why the Earth has seasons Suggest a way that it would NOT have seasons The tilt of the Earth s axis causes the seasons The axis points in the same direction throughout the year so as Earth orbits the sun sunlight hits different parts of Earth more directly at different times of the year We wouldn t have seasons if the Earth wasn t tilted on its axis 13 Brie y describe what is special about the summer and winter solstices and the spring and fall equinoxes The summer June solstice occurs around June 21st and is the moment when the Northern Hemisphere is tipped most directly toward the sun and the Southern Hemisphere is tipped most directly away The winter December solstice occurs around December 21st is the moment when the Northern Hemisphere is tipped most directly away from the sun and the Southern Hemisphere is tipped most directly toward it The spring March equinox occurs around March 21st and is when the Northern Hemisphere goes from being tipped slightly away from the sun to being tipped slightly toward the sun The fall September equinox occurs around September 22nd and is the moment when the Northern Hemisphere first starts to be tipped away from the sun 14 How does the Sun move with respect to the constellations over the year The sun moves in the sky just like any other star As we orbit the sun over the course of a year the sun appears to move against the background of the distant stars in the constellations We don t see the sun and the stars at the same time but if we could we d notice the sun gradually moving eastward along the ecliptic completing one circuit each year The sun s apparent location along the ecliptic determines which constellations we see at night 15 How are Martian seasons different than Earth s Why Although distance from the sun plays no role in the Earth s seasons the same isn t necessarily true for planets like Mars Mars is more than 20 closer to the sun during its Southern Hemisphere summer than its Northern Hemisphere summer This gives its Southern Hemisphere much more extreme seasons than its Northern Hemisphere even though Mars has nearly the same axis tilt as Earth 16 What is precession and how does it affect the sky that we see from Earth Precession is a gradual wobble that alters the orientation of Earth s axis in space Precession doesn t alter the amount of the axis tilt but because the solstices and equinoxes correspond to points in Earth s orbit that depend on the direction the axis points in space their positions in the orbit gradually shift with the cycle of precession As a result the constellations associated with the solstices and equinoxes gradually change 17 How could you eliminate precession If Earth were a perfect sphere or if it were not affected by the gravitational tugs from the sun and moon precession of the Earth wouldn t occur 18 Brie y describe the Moon39s cycle of phases Can you ever see a full moon at noon from Athens Georgia Explain During the full moon the moon is directly across from the sun and therefore we see the entirety of the illuminated side When the opposite occurs it s known as the new moon Phases from full to new are waning decreasing while phases from new to full are said to be waxing increasing You couldn t ever see a full moon at noon in Athens because full moons tend to rise around 6PM reach their highest at midnight and set by 6AM 19 Describe the phases of the moon in terms of the moon39s position in the sky relative to the sun During the new moon the sun earth and moon are in a line The sun lights up the side of the moon we do not see During the full moon they are lined up but we see the side of the moon the sun lights up During the rst quarter and third quarter the moon is perpendicular to the earth and sun Because of this we only see half of the lit side of the moon 20 Many people incorrectly guess that the phases of the Moon are caused by Earth39s shadow falling on the Moon How would you go about convincing a friend that the phases of the Moon have nothing to do with Earth39s shadow Describe the observations you would use to show that Earth39s shadow couldn t be the cause of phases I would take my friend outside with me to demonstrate how the phases of the moon have nothing to do with the Earth s shadow If you take a ball out on a sunny day and hold it at arm s length to represent the moon and have your head represent the Earth you can slowly spin around so that the ball goes around you just as the moon orbits the Earth As you turn you ll see the ball go through phases just like the moon 21 What do we mean when we say that the Moon exhibits synchronous rotation What does this tell us about the Moon s periods of rotation and orbit Synchronous rotation occurs because the moon rotates on its axis in the same amount of time that it takes to orbit Earth This tells us that the moon will always go through a full rotation by the time it orbits the Earth meaning that we will always see all of the phases by the time a full orbit is completed 22 Describe the motion of the moon 1 With respect to the sky over one night 2 With respect to the sky over the entire month 3 With respect to the constellations over an entire month Include the path and the rate of motion along the path The moon like the Earth appears to reside on the celestial sphere Because of this in one night the Moon appears to rise in the east and set in the west With respect to the entire month the Moon rises and sets every night and changes phases throughout the 27 13 day cycle With respect to the constellations over a month the Moon appears to be constantly moving eastward through them In addition the Moon rotates on its axis in the same amount of time it takes to orbit the Earth which is called synchronous rotation Because of this we only ever see the same face from here on Earth 23 Why don t we see an eclipse at every new and full moon Describe the conditions needed for a solar or lunar eclipse We don t see an eclipse at every new and full moon because of the inclination of the Moon s orbit Because of its inclination the Moon is usually above or below the ecliptic plane s surface The moon only crosses through the plane s surface twice during each orbit at the nodes An eclipse can only occur when the nodes are aligned with the Sun and the Earth and when the phase of the moon is new for a solar eclipse or full for a lunar eclipse 24 Describe the circumstance and appearance of all three types of lunar eclipse A sketch might help Choose one of the types and describe how it would look if you were on the moon during that eclipse There are three types of lunar eclipse total lunar eclipse partial lunar eclipse and a penumbral lunar eclipse A total lunar eclipse occurs if the Sun Earth and Moon are nearly perfectly aligned and the Moon passes through Earth s umbra During a total lunar eclipse the Moon becomes dark and red during totality the time during which the Moon is completely engulfed in the umbra A partial lunar eclipse occurs if the alignment is not exactly perfect and only part of the moon passes through the umbra The Earth s umbral shadow clearly darkens part ofthe Moon s face during a partial lunar eclipse A penumbral lunar eclipse occurs if the Moon passes through Earth s penumbra and nothing else It s the least impressive looking as the full moon on darkens slightly If on the moon and observing a total lunar eclipse the surface of the moon would be dark except for the red glow coming that seems to be emanating from the Earth but in truth is a result of the sun s light 25 Describe the astronomical conditions necessary for the occurrence of a total solar and total lunar eclipse For atotal lunar eclipse the Sun Earth and Moon all need to be nearly perfectly aligned as the Moon passes through the Earth s umbra For a total solar eclipse the Moon s umbra needs to touch a small area of Earth s surface when the Moon is relatively close to Earth in its orbit The area of Earth s surface that can be covered by the Moon s umbra can be no more than 270 kilometer in diameter 26 Describe the 3 types of solar eclipses and suggest two circumstances might result in more total solar eclipses The three types of solar eclipses are total solar eclipses partial solar eclipses and annular eclipses A total solar eclipse involves the Moon s umbra touching a very small area of Earth s surface while being close to it in its orbit There are only a few minutes of totality but during them the Moon completely blocks the visible disk of the sun which allows the corona to be seen During a partial solar eclipse only part of the Sun is blocked from view in the region of totality that falls within the Moon s penumbral shadow An annular eclipse occurs when the Moon is rather far away from Earth in its orbit It occurs in the small region of Earth directly behind the umbra and you ll see a ring of sunlight surround the disk of the Moon If the area of Earth s surface where atotal solar eclipse could occur was increased more would occur Additionally if the orbital paths of the Moon and Earth were changed to intersect more often more eclipses would occur 27 How could you eliminate eclipses How could we have more eclipses In order to eliminate eclipses you would have to either have no phases of the moon or change the orbital path of the Moon so its nodes never line up with the Sun and Earth In order to increase the frequency of eclipses one could decrease the distance travelled on the orbital path on the Moon Ifthe Moon had to travel less it would reach its node periods more frequently If you brought the orbit of the moon closer to the earth it would make the apparent size of the moon bigger thus creating more eclipses 28 Assume you live on the Moon near the center of the face that looks toward Earth a Suppose you see a full earth in your sky What phase of the Moon would people on Earth see Explain If I saw a full earth in the sky it would mean the moon is in the new moon phase I would be facing Earth s daytime side The Earth and Moon generally are in opposite phases b Suppose people on Earth see a full moon What phase would you see for Earth Explain If people on Earth see a full moon that means Earth would be in the new earth phase Because the Moon is in between the Sun and Earth seeing the daytime side ofthe Moon would mean the Moon is seeing the nighttime side of the Earth New and full are also considered opposite phases and the Moon and Earth typically are in opposite phases c Suppose people on Earth see a waxing gibbous moon What phase would you see for Earth Explain If people on Earth see a waxing gibbous moon it means Earth is in the waning crescent moon phase The gibbous phase and the crescent phase are opposite phases d Suppose people on Earth are viewing a total lunar eclipse What would you see from your home on the Moon Explain preople on Earth are viewing a total lunar eclipse people on the moon would be in complete darkness aside from the red glow coming that seems to be coming from the Earth 29 Ifyou lived on the moon how often would you see a The sun rise and set Once every 15 days b The earth rise and set Its either always in the sky or never in the sky depending on where you are on the moon c A solar eclipse Whenever the earth has a lunar eclipse the moon has a solar eclipse 1 had trouble with nding the answers to this one and Google wasn t a big help 30 Suppose you lived on the Sun and could ignore the heat Would you still see the Moon go through phases as it orbits Earth Why or why not No you wouldn t see the Moon go through phases as it orbits Earth You wouldn t because the Moon and Earth are orbiting the Sun and Earth will usually be in the way of the Moon The Sun will only see the Moon in the full or new phases when an eclipse happens 31 What do we mean by the apparent retrograde motion of the planets Why was it dif cult for ancient astronomers to explain How do we explain it today The apparent retrograde motion of the planets is when they appear to reverse course and move westward through the zodiac when they typically move eastward through the zodiac It was dif cult for ancient astronomers to explain because they believed the universe was geocentric and could not gure out or understand why the planets would suddenly change orbit every so often Nowadays we explain it much more simply than the ancient astronomers thought possible due to the accepted fact that our solar system is heliocentric The planets don t actually change direction they only appear to change direction from our position on Earth as we pass the other planets in our orbit 32 Describe the motion of a superior planet with respect to the constellations A planet s sidereal period is the time the planet takes to orbit the sun Each planet has a different sidereal period because they are all different distances from the sun but each sidereal period is the length of time it takes the planet to move through the constellations of the zodiac 33 Which planets can never be seen at opposition At inferior conjunction Mercury and Venus can never be seen at opposition because they are inferior planets The other planets don t have an inferior conjunction because that would infer that they come between the Earth and the sun at some point in their orbit however this isn t possible because the rest of the planets are farther from the sun than the Earth is 34 What is stellar parallax Stellar parallax is the difference in direction of a celestial object as seen by an observer from two widely separated points It can be used to determine the distance from Earth to another star 35 The constellation Orion didn t exist when my grandfather was a child False Although it may not have been called Orion at the time the stars formed the same shape when my grandfather was a child Additionally because we are observing from light years away we name the constellation based on what it looked like years in the past 36 When I looked into the dark lanes of the Milky Way with my binoculars I saw what must have been a cluster of distant galaxies It was likely that you saw molecular dust clouds created by proto stars within our Milky Way galaxy located about 300 light years away 37 Last night the Moon was so big that it stretched for a mile across the sky This statement does not make sense because a mile is a physical distance and we can measure only angular sizes or distances when we observe objects in the sky 38 I live in the United States and during my first trip to Argentina I saw many constellations that I39d never seen before This statement makes sense because the constellations visible in the sky depend on latitude Since Argentina is in the Southern Hemisphere the constellations visible there include many that are not visible from the United States 39 Last night I saw Jupiter right in the middle of the Big Dipper Hint Is the Big Dipper part ofthe zodiac False Jupiter like all the planets is always found very close to the ecliptic in the sky The ecliptic passes through the constellations of the zodiac so Jupiter can only appear in the middle of the 12 zodiac constellations Since the Big Dipper part of the constellation Ursa Major is not among these Jupiter cannot appear within the Big Dipper 40 Last night I saw Mars move westward through the sky in its apparent retrograde motion False Apparent retrograde motion is noticeable only over many nights not during a single night Of course like all celestial objects Mars moves from east to west over the course of EVERY night 41 Although all the known stars appear to rise in the east and set in the west we might someday discover a star that will appear to rise in the west and set in the east True because when Earth s magnetic fields are slowly changing and will eventually turn North to South and change all other directions accordingly 42 If Earth s orbit were a perfect circle we would not have seasons False the seasons are due to the tilt of the Earth s axis not its distance from the Sun 43 Because of precession someday it will be summer everywhere on Earth at the same time False precession only changes the direction in which the North Pole points and has nothing to do with the seasons 44 This morning I saw the full moon setting at about the same time the Sun was rising True because the sun earth and moon are nearly in a straight line This means that right when the moon sets the sun will be rising Ch 3 1 What are the differences between science pseudoscience and nonscience Give some examples and explain your choice Science is the search for knowledge that can be used to explain or predict natural phenomena in a way that can be confirmed by rigorous observations or experiments An example of this is the subject of astronomy several studies have been completed by accredited scientists that completed them using the scientific method Pseudoscience is something that purports to be science or may appear to be scientif1c but that does not adhere to the testing and veri cation requirements of the scientific method An example of this may be an article in a nonaccredited newspaper or magazine that appears to be knowledgable but in fact does not have any true scientific claim to truth Nonscience is defined in the book as any way of searching for knowledge that makes no claim to follow the scientific method such as seeking knowledge through intuition tradition or faith An example of this would be any type of religion 2 How are the following pseudoscience astrology homeopathic medicine psychic phenomena UFOlogy Astrology is pseudoscience because it claims to be based on the study of the stars but in reality the constellations that astrology is based on are continuously changing and therefore is not true to the scientific method Homeopathic medicine is considered pseudoscience because it is an alternative approach to medicine based on a belief that natural substances can restore health better than common medicines can Psychic phenomena is a pseudoscience because it sounds like it could potentially be scientific but studies have shown that seers can predict the future no better than they would be able to by chance UFOlogy is pseudoscience because although many people believe strongly in the fact that their is extraterrestrial life and things like crop circles and other signs may exist studies have shown given no proof to the idea that aliens have been to Earth 3 Can one use science to disprove pseudoscience Examples Yes one can use science to disprove pseudoscience One example of this would be astrology Many people believed in the study of astrology for many years but science has proved that astrological predictions do not prove to be accurate more than we can expect by pure chance showing that the predictions have no scientific validity UFOs are another example of using science to disprove pseudoscience The exsitence of UFOs is based solely on heresay people simply tell what they thought happened There isn39t any hard evidence and therefore UFOs aren39t credible 4 Can one use science to disprove nonscience Examples No science can not be used to disprove nonscience This is because scienti c testing of the supernatural or of any higher being simply can not be completed due to what the de nition of what faith andor deity is 5 Have you experienced the supernatural If God is considered a supernatural being then yes Ibelieve I have experienced the supernatural in simply my being here 6 Have you dealt with the supernatural in a scienti c manner I don t necessarily think it s possibly to deal with the supernatural in a scienti c manner I think that believing in anything supernatural is completely based on faith the idea that you believe in something without being able to scienti cally prove it 7 How do you think scientists should deal with the supernatural I don t think scientists will ever truly be able to deal with the supernatural because Ithink it s based on faith which is something that scientists can t necessarily have if they want to work in the scienti c eld Ch 4 1 What do we mean by acceleration What is the acceleration of gravity 1 It is a change in velocity The acceleration of gravity is an objects change in velocity due to the force of gravity 981 ms 2 What is momentum How can a force affect momentum What do we mean when we say that only a net force will change momentum 1 Momentum is a product of an obj ect s mass X velocity You can affect momentum by either changing the mass of the object changing the speed of the object or changing the direction of the object You have to have the net force to change momentum because the net force will be what changes and affects the over all change in momentum because of the affects on both speed and direction combined of all acting forces 3 What is freefall and why does it make you weightless 1 It is falling without any resistance to slow you down The oor drops away at the same rate that you fall allowing you to oat freely above it and the scale reads zero because you are not longer held to it In other words your freefall has made you weightless 4 The densities of Jupiter 133 the Sun 141 and Saturn39s moons Dione 144 and Rhea 133 are all about the same in spite of having HUGE differences in gravity holding them together Numerically how can this be What is the V39 0 gt1 8 underlying physical cause that gravity does not make the most massive object the densest 1 It is because they have different masses in different amounts of areas which gives them all about the same density Density of m V which means that proportionally they are all the same with different masses over different areas proportionally giving them about the same density Because of how gravity reacts with different materials it then determines the density of the planet or star State each of Newton s three laws of motion For each law give an example of its application 1 An object moves at a constant velocity if there is not net force acting upon it 2 Force Mass X Acceleration Fma 3 For any force there is always an equal and opposite reaction force What are the laws of conservation of momentum conservation of angular momentum and conservation of energy For each give an example of how it is important in astronomy 1 Momentum the total momentum of interacting objects cannot change as long as no external force is acting on them that is their total momentum is conserved This is important to rockets because when you fire a rocket engine the total momentum of the rocket and the hot gases it shoots out must be the same 2 Recall that rotating objects have angular momentum because they are moving in circles or going around curves and that angular momentum can be changed only by a twisting force or torque States that as long as there is no external torque the total angular momentum of a set of interacting objects cannot change This is important because of earth s angular momentum around the sun and how it would be affected 3 Energy cannot appear out of nowhere or disappear into nothingness This is important because the universe is always in a state of a transfer of matter to energy and vise versa Imagine you are out in space and push away from you an object having a mass identical to your own What happens Explain You both move in opposite directions at equal velocities from that pointbecause of Newton s third law that every action has an equal and opposite reaction And with no friction or outside forces acting on either object they would move apart a equal and opposite directions and speed Define kinetic energy radiative energy and potential energy for each type of energy give at least two examples of objects that either have it or use it Kinetic energy is the energy of motion given by the formula l2mvA2Two examples of kinetic energy are falling rocks and orbiting planets Radiative energy is energy carried by light the energy of a photon is Planck s constant times it s frequency or hf Two examples of radiative energy are the sun or a lamp Potential energy is energy stored for later conversion into kinetic energy includes gravitational potential energy electrical potential energy and chemical potential energy Two examples of potential energy are a rock perched on an edge which has gravitational potential energy or gasoline which contains chemical potential energy 9 De ne temperature and thermal energy How are they related How are they different Temperatureaverage kinetic energy energy of motion or average speed of all the particles in a material a higher temp particles move faster and farther apart b lower temp particles move slower and closer together Thermal Energy otal kinetic energy of all particles in a material 10 What do we mean by massenergy Is it a form of kinetic radiative or potential energy It is a form of potential energy because it is the concept that the mass of a body is the measure of its energy content and the two properties are connected by a constant 11 Summarize the universal law of gravitation in words Newton39s law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them 12 Consider an object shot upward from the earth with less than escape velocity Describe its motion In physics escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero It is the speed needed to quotbreak freequot from a gravitational eld without further propulsion If it does not reach this escape velocity it will not break free of gravity s hold and will either fa ll kms 13 Why do objects fall at the same rate Objects fall at the same rate because the force of gravity 981 msz acts on all objects the same The only thing that makes objects in the real world not fall the same rate because of air resistance If there were not such thing as air resistance all objects would fall at the same rate because of the equal force of gravity acting on all of them 14 How could I double the Earth s escape velocity more than one way but the universal gravitational constant remains the same In order to double the Earth39s escape velocity you must increase its mass by a factor of four or decrease its radius by a factor of four 15 What is the difference between a bound and an unbound orbit What orbital shapes are possible An object on a bound orbit follows the same path around the Sun over and over while an object on an unbound orbit approaches the Sun just once and then never returns 16 State then explain Kepler s three laws 1 The orbit of each planet about the Sun is an ellipsewith the Sun at one focus size semi major axis shape 7 eccentricity orbits can be ellipses but also parabolas and hyperbolas motion about center of mass 2 As a planet moves around its orbit it sweeps out equal areas in equal times closer is faster conservation of angular momentum 3 Orbital period in year2 average distance in AU3 p2 a3 movie generalized for any two objects 17 How did Newton39s understanding of gravity extend Kepler s Laws Newton used the mathematical expressions of his laws of gravity and motion to show that a planet orbiting the sun should automatically have an elliptical orbit that obeys Kepler39s laws By doing this Newton removed virtually all remaining doubt about the legitimacy of the suncentered solar system In addition Newton found that Kepler39s laws were only part of the story of how objects move in response to gravity Newton discovered that Kepler39s laws are just one special case of a more general set of rules about orbiting objects He discovered four things 1 planets are not the only objects with elliptical orbits 2 ellipses are not the only possibly orbital paths 3 objects orbit their common center of mass and 4 orbital characteristics tell us the masses of distant objects 18 What quantities do we need to know if we want to measure an object39s mass with Newton s version of Kepler39s third law Explain My understanding about this issue is that it depends on the sizes of the objects you are interested in For stars and planets you measure the masses by investigating the relationships between those monsters For small objects I think you essentially use Newton39s three laws of motion For example fma In the space you slap on an object and then you check the velocity to come up with the acceleration a Another exmaple is the free vibration mxquotkx0 Suppose you know the frequency w and the spring stiffness k then wquot2km 19 Explain why orbits cannot change spontaneously How can a gravitational encounter cause an orbit to change How can an object achieve escape velocity Orbits cannot change spontaneously because as long as no other object causes the planet to gain or lose orbital energy its orbital energy cannot change and its orbit must remain the same A gravitational encounter occurs when two ob39ects pass near enough so that each can feel the effects of the other39s gravity An object that gains orbital energy moves into an orbit with a higher average altitude If the object gets enough orbital energy it may end up in an unbound orbit that allows it to escape earth completely 20 Explain how the Moon creates tides on Earth Why do we have two high and low tides each day Because the strength of gravity declines with distance the gravitational attraction of each part of the earth to the moon becomes weaker as we go from the side of the earth facing the moon to the side facing awa from the moon This difference in attraction creates a quotstretching forcequot or tidal force that stretches the entire earth into two tidal bulgesone facing the moon and one facing away from the moon Earth39s rotational carries any location through each of the two bulges each day creating two high tides Low tides occur when the location is at the points halfway between the two tidal bulges 21 How do the tides vary with the phase of the Moon Why When the tidal forces of the sun and the moon work together as is the case at both new moon and full moon we get the especially pronounced spring tides When the tidal forces of the sun and moon counteract each other as is the case at the first and thirdquarter moon we get the relatively small tides known as neaptides The tides are higher when the sun and moon work together and smaller when they counteract each other 22 How would you make ocean tides stronger or weaker More or less frequent Be careful to state what you would change and what effect it would have on the frequency of tides You could make the tides stronger by moving the moon closer to the earth and weaker by moving the moon furtherfrmo the earth You could make the tides more frequent by making the phases of the moon change more frequently and less frequent by making the phases of the moon change less frequently 23 Describe the tides if any if we had no moon We would still have tides but they would be much less great than the lunar tides we currently have The sun still causes tides but the sun doesn39t play as large of a role in the tides as the moon 24 What is tidal friction What effects does it have on Earth How does it explain the Moon39s synchronous rotation Tidal friction is friction within an object that is caused by a tidal force In essence the moon39s gravity tries to keep the tidal bulges on the earthmoon line while earth39s rotation tries to pull the bulges around with it Because earth is much more massive than the moon earth39s tidal force on the moon has a much greater effect than the moon39s tidal force on earth This total force gives the moon two tidal bulges that the moon creates on earth If the moon rotated through its tidal bulges in the same way as earth the resulting friction would cause the moon39s rotatino to slow down 25 Would you fall at the same rate on the Moon as on Earth No the gravitational pull of the moon is less than the gravitational pull of the earth Because of this you would fall at a slower rate on the moon than you would on the earth 26 If you bought a pound of chocolate on the Moon using a pound scale from a store on Earth you39d get a lot more chocolate than if you bought a pound on Ea True The gravitational pull on the moon is less than that of the earth so if you bought a pound of chocolate on the moon using an earth scale bringing back to earth would cause the chocolate to weigh more 27 Suppose you could enter a vacuum chamber on Earth that is a chamber with no air in it Inside this chamber if you dropped a hammer and a feather from the same height at the same time both would hit the bottom at the same time True Due to the earth39s gravitational pull all objects fall at the same rate However air resistance is a key factor for what makes this fact seem false If there was no air resistance though like in a vacuum then the hammer and feather would hit the bottom at the same time 28 When an astronaut goes on a space walk outside the Space Station she will quickly float away from the station unless she has a tether holding her to the station or constantly fires thrusters on her space suit If she pushes herself away from the station then she would need to have a tether to hold her there Because space has no gravity Newton39s first law states that she would continue to move at a constant velocity away from the space station However if she didn39t push herself away from the station she would not need to tether herself because she wouldn39t move anywhere 29 I used Newton39s version of Kepler39s third law to calculate Saturn39s mass from orbital characteristics of its moon Titan True As long as you knew the orbital period of its moon and the distance between the two bodies you could use Newton39s version of Kepler39s third law to calculate Saturn39s mass 30 If we could somehow replace the Sun with a giant rock that has precisely the same mass Earth39s orbit would not change False The giant rock would also have to have the same volume making the density of both the rock and the sun the same Only then would the orbit of the earth not change 31 The fact that the Moon rotates once in precisely the time it takes to orbit Earth once is such an astonishing coincidence that scientists probably neverwill be able to explain it False This happens because of the moon39s sychronus rotation which is the rotation of an object that always shows the same face to an object that it is orbiting because its rotation period and orbital period are the same 32 If an asteroid passed by Earth atjust the right distance Earth39s gravity would capture it and make it our second moon True However it39s unlikely The asteroid would have to be a certain size traveling atjust the right speed and grazing by Earth atjust the right angle in order for the earth39s gravity to capture it and make it our second moon 33 When I drive my car at 30 miles per hour it has more kinetic energy than it does at 10 miles per hour True Because KE 12mvquot2 the kinetic energy increases with any increase in velocity 34 Someday soon scientists are likely to build an engine that produces more energy than it consumes False This statement does not make sense because such an engine would violate the law of conservation of energy Questions for Chapter 5 1 What is this What are the dark lines 1 It is the electromagnetic spectrum of Visible light The Black lines are elements that come from the sun that are not light but still show up inthe electromagnetic spectrum N E 4 V39 9 gt1 9 gt0 On a very strange whim Ihave painted my windowless room blue 450nm with a white ceiling and a black oor Itum on a red 650nm light What do I see What if I had a detector sensitive to the infrared 1 You see heat detections if you have an infrared sensor And the room would be red on the ceiling and black on both the oor and the wall would be black because the black or the blue paint does not re ect the red light Think of three very different ways I could create the red light for the demonstration above 1 White light and then have a red filter Separate the white light and cut a piece right where the red slit is Produce an emission line and get an element that only produces red light What is a spectrum and how do we see one 1 It is the complete spectrum light including radio waves infrared light visible light X rays and gamma rays You can see only visible light Give an example from everyday life of each of the four major types of interaction between matter and light 1 Emission of light from a light bulb 2 When you touch something that is warm you absorb some of the light which warms your handabsorption 3 Transmissionwvhen the sun shines through your window in the morning and wakes you up 4 Re ectionscattering whenever you look in the mirror everyday Define wavelength frequency and speed for a wave 1 Wavelength he distance from one peak to the next of a wave of light 2 Frequency he number of peaks passing by any point each second of a light wave 3 Speed ells us how fast their peaks travel across a certain distance It is how fast the energy travels from one place to another What do we mean when we say that light is an electromagnetic wave 1 It means that light waves are vibrations of both electric and magnetic fields cause by the motion of charged particles What is a photon In what way is a photon like a particle In what way is it like a wave 1 A photon so to say is an individual piece of light because light acts both particles and waves Photons of light are like particles because they can be counted individually and can hit a wall one at atime Also photons are like waves because each photon is characterized by a wavelength and a frequency It is also like a particle because each one carries a certain amount of kinetic energy That energy just depends on the wavelength and the frequency List the different forms of light in order from lowest to highest energy Would the list be different if you went in order from lowest to highest frequency From shortest to longest wavelength Explain 1 Radio wavesinfrared raysvisible light ultraviolet xrays gamma rays 2 No it would be the same if it were organized by frequency 3 Yes they would they would be backwards if they were organized by wavelength because the ones with higher frequency and energy have a shorter wavelength 10 Brie y describe the structure of an atom How big is an atom How big is the nucleus in comparison to the entire atom 1 Each chemical element consists of different types of atom and atoms are in turn made of particles that we call protons neutrons and electrons Protons and neutrons are found in the tiny nucleus at the center of the atom The rest of the atom s volume contains electrons which surround the nucleus Although the nucleus is very small compared to the atom as a whole it contains most of the atom s mass because protons and neutrons are each about 2000K as massive as an electron Note that atoms are incredibly small millions could fit end to end across the period at the end of a sentence The number of atoms in a single drop of water may exceed the number of stars in the observable universe 11 What determines an atom s atomic number Under what conditions are two atoms different isotopes of the same element What is amolecule l The number or protons and neutrons made up the atom s atomic number Versions of an element with different numbers of neutrons are isotopes Molecules are atoms that combined together and make up different things that have different properties than the atoms themselves 12 What is electrical charge Will an electron and a proton attract or repel one another Will two electrons attract or repel one another Explain l The electric charge is a fundamental property of matter that is described by its amount and as either positive or negative more technically a measure of how a particle responds to the electromagnetic force Yes protons will attract electrons because of the electrical charge of both of the m Protons are positive and electrons are negative this is the force that holds atoms together Protons and protons will repel one another because they both have the same electrical charge 13 Describe the phase changes of water as you heat it starting from its solid phase ice What happens at very high temperatures What is a plasma Water will be in a solid form as ice and as it heats up it becomes a liquid form in what is known water When it obtains enough energy it will become its gaseous form through a process called evaporationA plasma is a type of hot gas in which atoms have ionized Because a plasma contains many charged particles its interactions with light are different from those of a gas consisting of neutral atoms which is one reason that plasma is sometimes referred to as the fourth phase of matter 14 What do we mean when we say that energy levels are quantized in atoms Under what circumstances can energy level transitions occur 1 The fact that energy levels are quantized in atoms simply means that it is measured in levels Energy level transitions can only occur when an electron gains or loses the specific amount of energy separating two levels 15 How do we convert a continuous spectrum shown as a band of light like a rainbow into a graph of the spectrum 1 You use a spectroscope You use a graph that compares intensity to wavelengths Where the bands of light along the wavelength the graph will go up Where we see bright emission lines at speci c wavelengths the graph shows an upward spike at the wavelength on the emission line It can also be converted where there are dark lines on the emission spectrum those are dips in the intensity at the wavelength on the graph 16 How do we convert a continuous spectrum shown as a band of light like a rainbow into a graph of the spectrum Often it is more useful to display spectra as graphs that show the amount of radiation or intensity at different wavelengths The graphs of intensity in the book simply show the relative amount of energy received from an object in each wavelength of light In other words the intensity at a given wavelength is proportional to the number of photons observed at that wavelength times the energy of those photons l Atoms are composed of electrons that surround a nucleus which is filled with protons and neutrons The atoms in any cloud of gas are constantly colliding with one another exchanging energy in each collision Most of the collisions simply send the atoms flying off in new directions However a few of the collisions transfer the right amount of energy to bump an electron from a low energy level to a higher energy level Electrons always fall back down to the ground state level 1 usually in a tiny fraction of a second The bright emission lines appear at the wavelengths that correspond to downward transitions of electrons and the rest of the spectrum is dark In an absorption line spectra hydrogen atoms can absorb photons that have the right amount of energy needed to raise an electron from a low energy level to a higher one Two things can happen after an electron absorbs a photon and rises to a higher energy level The first is that the electron quickly returns to its original level emitting a photon of the same energy that it absorbed However the emitted photon can be going in any random direction which means that we still see an absorption line because photons that were coming toward us are redirected away from our line of sight Alternatively the electron can lose its energy in some other way either by dropping back down to a different energy level or by transferring its energy to another particle in subsequent collision Again we are left with an absorption line because photons of a specific wavelength have been removed from the spectrum of light that39s coming toward us emisison electron has to go from higher orbital to lower orbital heat it up absorption gas clou l6 Explain the atomic structure of the atom Tell how this creates the distinctive patterns of emission and absorption spectra Atoms are composed of electrons that surround a nucleus which is lled with protons and neutrons The atoms in any cloud of gas are constantly colliding with one another exchanging energy in each collision Most of the collisions simply send the atoms ying off in new directions However a few of the collisions transfer the right amount of energy to bump an electron from a low energy level to a higher energy level Electrons always fall back down to the ground state level 1 usually in a tiny fraction of a second The bright emission lines appear at the wavelengths that correspond to downward transitions of electrons and the rest of the spectrum is dark In an absorption line spectra hydrogen atoms can absorb photons that have the right amount of energy needed to raise an electron from a low energy level to a higher one Two things can happen after an electron absorbs a photon and rises to a higher energy level The first is that the electron quickly returns to its original level emitting a photon of the same energy that it absorbed However the emitted photon can be going in any random direction which means that we still see an absorption line because photons that were coming toward us are redirected away from our line of sight Alternatively the electron can lose its energy in some other way either by dropping back down to a different energy level or by transferring its energy to another particle in subsequent collision Again we are left with an absorption line because photons of a speci c wavelength have been removed from the spectrum of light that s coming toward us 17 Describe the conditions that would cause us to see each of the three basic types of spectra What do we see in the Sun s spectrum shown on the opening page of this chapter The spectrum of an ordinary light bulb is a rainbow of color Because the rainbow spans a broad range of wavelengths without interruption we call it a continuous spectrum A thin or lowdensity cloud of gas does not produce a continuous spectrum Instead it emits light only at speci c wavelengths that depend on its composition and temperature The spectrum therefore consists of bright emission lines against a black background and is called an emission line spectrum Ifthe cloud of gas lies between us and a light bulb we still see most of the continuous light emitted by the light bulb However the cloud absorbs light of speci c wavelengths so the spectrum shows dark absorption lines over the background rainbow from the light bulb We call this an absorption line spectrum The sun39s spectrum shown on the opening page of this chapter was an absorption line spectrum 18 How can we use emission or absorption lines to determine the chemical composition of a distant object Emission and absorption lines form as a direct consequence of the fact that each type of atom ion or molecule possesses a unique set of energy levels This fact allows us to learn the compositions of distant objects in the universe as we can see by considering what happens in a cloud of gas consisting of solely hydrogen atoms Hydrogen 19 How do the properties of light allow us to determine the physical properties of stars The properties of light allow us to determine the physical properties of stars mainly based on their temperatures The rst law of thermal radiation states that each square meter of a hotter obj ect39s surface emits more light at all wavelengths The second law of thermal radiation states that hotter objects emit photons with a higher average energy Use the absorption spectrum which gives you the chemical composition Blue stars are hot red stars are cool 20 Describe two ways in which the thermal radiation spectrum of an 8000K star would differ from that of a 4000 K star The 8000K star would emit a lot more light at every wavelength than each square meter of the 3000K star and the hotter star emits light at some ultraviolet wavelengths that the cooler star does not emit at all The peak for the 8000K star would also be at a shorter wavelength than that of the 4000K star 21 Describe each of the key features of the Martian spectrum and explain what it tells us about the object The Martian spectrum shows us where the intensity oscillates and compares it to the thermal emission of the sun It shows us that Mars re ects red which is what causes it to have a rustcolored surface 22 Describe the Doppler effect for light and what we can learn from it What does it mean to say that radio waves are blue shifted Why does the Doppler effect widen the spectral lines of rotating objects The Doppler effect causes similar shifts in wavelengths to ligh as it does to wavelengths of sound If an object is moving toward us the light waves bunch up between us and the object so that its entire spectrum is shifted to shorter wavelengths Because shorter wavelengths of visible light are bluer the Doppler shift of an object coming toward us is called a blueshift If an object is moving away from us its light is shifted to longer wavelengths We call this a redshift because longer wavelengths of visible light are redder As an object rotates light from the part of the object rotating toward us will be blueshifted light from the part rotating away from us will be redshifted and light from the center of the object won t be shifted at all The net effect if we look at the whole object at once is to make each spectral line appear wider than it would if the object were not rotating Decide whether the statement makes sense or is clearly true or does not make sense or is clearly false Explain clearly Not all of these have de nitive answers so your explanation is more important than your chosen answer 23 The walls of my room are transparent to radio waves True The fact that the walls are transparent to radio waves means that they would allow the radio waves to enter into the room which is an accurate statement 24 Because of their higher frequencies X rays must travel through space fasterthan radio waves True X rays have both a higher energy and frequency and therefore will travel through space faster than radio waves 25 If you could see infrared light you would see a glow from the backs of your eyelids when you closed your eyes True The infrared light would be able to penetrate through my eyelids because they are not completely opaque to wavelengths 26 If you had Xray vision you could read this entire book without turning any pages False If you were using xray vision you would not be able to resolve the letters on individual pages 27 Two isotopes of the element rubidium differ in their number of protons False Isotopes of the same element must differ in the number of neutrons not protons If the isotopes differed in the number of protons they would be completely different elements 28 If you could view a spectrum of light reflecting off a blue sweatshirt you39d find the entire rainbow of color False You would see only blue coloring Blue objects absorb all of the colors of the rainbow other than blue 29 A white hotquot object is hotterthan a red hot object True An object must emit a red color from heat before it can emit a white color because white is all of the colors combined 30 If the Sun39s surface became much hotter while the Sun39s size remained the same the Sun would emit more ultraviolet light but less visible light than it currently emits True When heat increases so does the frequency and energy of the wavelengths Because of this some visible light would be converted to ultraviolet light 31 Galaxies that show redshifts must be red in color False For distant galaxies the light spectrum is wrong The frequency lines of the spectrum are all too low One possible explanation of the incorrect spectrum is that those stars and galaxies are moving away from us and that the spectrum is shifted toward the red end of the color spectrum because of the Doppler effect 32 If a distant galaxy has a substantial redshift as viewed from our galaxy then anyone living in that galaxy would see a substantial redshift in a spectrum of the Milky Way Galaxy True The increasing distance between the two galaxies will red shift light traveling between them in either direction CH 6 Questions 1 How does your eye focus light How is a glass lens similar What do we mean by the focal plane of a lens The bending of light by your eye makes vision possible The retina contains lightsensitive cells that cones and rods that when triggered by light send signals to the brain through the optic nerve The lens of your eye creates an image on your retina because it bends light just like a glass lens The focal plane is the place where an image created appears in focus 2 For purposes of astronomy what advantages does a CCD camera have overthe human eye One advantage of a camera is that a recorded image is much more reliable and detailed Second we can control the exposure time with a camera Longer exposure time means more photons reach the detector allowing the detector to record finer details 3 What are the two key properties of a telescope and why is each important The first key property of a telescope is the lightcollecting area which tells us how much total light the telescope can collect at one time The second key property is the angular resolution which is the smallest angle over which we can tell that two stars are distinct 4 What is the diffraction limit and how does it depend on a telescope39s size and the wavelength of light being observed The diffraction limit is the angular resolution that a telescope could achieve if it were limited only by the interference of light waves A larger telescope has a smaller diffraction limit allowing it to achieve a better angular resolution The diffraction limit is larger for longer wavelength light 6 How do reflecting telescopes differ from refracting telescopes A refracting telescope is just like the human eye using transparent glass lenses to collect and focus light A refracting telescope though uses a curved primary mirror to gather light that then reflects onto a secondary mirror that lies in front of it The secondary mirror then reflects the light to a focus place 8 Which type of telescope refractor or reflector is more commonly used by professional astronomers and why Reflectors are more commonly used because unlike with a refractor the quality and shape of the mirrors glass is not a factor Also glass lenses are very heavy and hard to hold in place however its easier to use them in reflectors because they are mounted at the bottom of the telescope where its weight doesn t present such an Issue 9 What are the three basic categories of astronomical observation and how is each conducted The three basic categories of astronomical observation are imaging which yields photographs of astronomical objects spectroscopy in which astronomers obtain and study spectra and timing which tracks how an object changes with time 10 What do we mean when we speak of images made from invisible light such as Xray or infrared images What do the colors in these images mean We can t see invisible light however we can make detectors that undergo changes when they are hit by this light For instance the X rays that pass through your arm at the doctor s office are recorded on a piece of Xray sensitive film We can t see the rays themselves but we can see the image they leave behind on the film lmages made with invisible light cannot have natural color since color only belongs to visible light but we can still color code the images to show different energy levels intensity of light or physical properties 11 What do we mean by spectral resolution Why is higher spectral resolution more difficult to achieve Spectral resolution is the degree of detail that can be seen in a spectrum The higher the spectral resolution the more detail we can see Its difficult to achieve though because a telescope only collects so much light in a given amount of time and the spectral resolution depends on how widely the spectrograph spreads out the light Higher spectral resolution therefore requires longer exposure time 12 List at least three ways in which Earth39s atmosphere can hinder astronomical observations and explain why putting a telescope into space helps in each case What are the disadvantages to space telescopes The first way our atmosphere hinders astronomical observations is through pollution humanmade light that obscures ourview of the sky If we put a telescope into space it will be above the reflection of our lights and will therefore be able to see the sky better Another way is distortion of light by turbulence in the atmosphere If we put a telescope into space it will have no winds to worry blur the images The final way is that most forms of light cannot reach through our atmosphere to hit the ground at all By putting a telescope up into space the light will be able to reach it 14 How do adaptive optics work What atmospheric problem can adaptive optics help with Adaptive optics eliminate the blurring of astronomical images by our atmosphere Blurring occurs because turbulence in the atmosphere causes the light of the star to dance when viewed through the telescope Adaptive optics work by making the telescope s mirrors do an opposite dance by changing the shape of the mirrors each second to compensate for the changing distortions This cancels out the atmospheric distortions 18 What is interferometry and how can it improve astronomical observations Interferometry is a telescopic technique in which two or more telescopes are used in tandem to produce much better angular resolution than the telescopes could achieve individually It improves astronomical observations by taking advantage of the wavelike properties of light that cause interference Ch 7 1 What would the solar system look like to your naked eye if you could view it from beyond the orbit of Neptune Remember that the Sun and the planets are all quite small compared to the distance between them so small that if we viewed them from the outskirts of our solar system on a planet such as Neptune the planets would be only pinpoints of light and even the Sun would be just a small bright dot in the sky 2 Brie y describe the overall layout of the solar system 1 The Solar System consists of the Sun and the Astronomical objects gravitationally bound in orbit around it all of which formed from the collapse of a giant molecular cloud approximately 46 billion years ago The vast majority of the system s mass is in the Sun Of the many objects that orbit the Sun most of the mass is contained within eight relatively solitary planets whose orbits are almost circular and lie within a nearly at disc called the ecliptic plane The four smaller inner planets Mercury Venus Earth and Mars also called the terrestrial plants are primarily composed of rock and metal The four outer planets the gas giants are substantially more massive than the terrestrials The two largest Jupiter and Saturn are composed mainly of hydrogen and helium the two outermost planets Uranus and Neptune are composed largely of ices such as water ammonia and methane and are often referred to separately as quotice giantsquot 3 How do astronomers measure the following planetary properties A MassThe only way we can measure a planet39s mass is through its gravity This has been the way Earth39s mass was measured too we can39t directly probe what s in Earth39s interior but we can measure the gravity on the surface Since nobody ever visited other planets and was able to measure gravity on the spot we usually have to resort to other methods The most commonly used technique is to observe a body orbiting or passing close to the planet and see how its path is affected by the planet s gravity B Rotation rateThe Sun planets and large moons generally orbit and rotate in a very organized way All planetary orbits are nearly circular and lie nearly in the same plane All planets orbit the Sun in the same direction counterclockwise as viewed from high above Earth s North Pole Most planets rotate in the same direction in which they orbit with fairly small axis tilts The Sun also rotates in this same direction You can measure the rotation rate by finding a spot on the planet and find out how far it moves over the course ofa period oftime C TemperatureThe easiest way is to measure the amount and for bonus spectrum of the radiated heat All objects greater than Absolute Zero radiate a certain amount of energy The wavelength spectrum can be detemiined by Planck s Law and the amount of energy by the StefanBoltzmann Law So to determine the temperature all one needs to do is measure the energy over the waveband of interest and one can get the temperature 4 What is the most abundant element in the Solar System What is the second most abundant Hydrogen is the most common element in the universe because it is the simplest element in the universe A hydrogen atom has one proton one electron and no neutrons making it the lightest element The larger an object is the stronger its gravitational pull and thus the more hydrogen it has The sun is primarily made out of hydrogen as are the four gas giant planets Jupiter Saturn Uranus and Neptune The initial formation of the solar system was approximately 75 percent hydrogenHelium is the second most common element in the universe and like hydrogen it is relatively simple as it has two protons and two electrons Helium made up about 25 percent of the solar system when it was originally forming however an isotope of helium is also produced in the sun during nuclear fusion Nuclear fusion involves four hydrogen atoms coming together to form the helium isotope that has two protons and two neutrons Helium is also the secondmost abundant element in the gas giants Study the planetary data in this table to answer each of the following 5 Notice the relationship between distance from the Sun and surface temperature Describe the trend explain why it exists and explain any notable exceptions to the trend The notable trend is that the farther away the planet is from the sun the lower the temperature in Kelvins The only exception to this is on Mercury On Mercury the temperature goes down all the way to 100K Tidal forces from the Sun have forced Mercury into an unusual rotation pattern It s a 586 day rotation period which means it rotates exactly three times for every two of its 879 day orbits of the Sun This combination of rotation and orbit gives Mercury days and nights that last about 3 Earth months each Daytime temperatures reach about 4250 C nearly as hot as hot coals At night the temperature falls below 1500 C far colder than Antarctica in winter The text says that planets can be classi ed as either terrestrial or jovian with Pluto fitting neither category Describe in general how the columns for density composition and distance from the Sun support this classification The terrestrial planets are all closer denser and are made of rocks and hard metals Thej ovian planets are made of H He and hydrogen compounds are much further from the sun and are much less dense This means that the planets that are close to the sun are denser and have different chemical compositions because of the Sun s gravitational pull Pluto does not t this because it is the furthest planet from the Sun but is made of rock and is denser than the jovian planets Describe the trend you see in orbital periods of planets around the sun and explain the trend in terms of Kepler39s third law This trend says that the further away the planet is from the Sun the longer the orbital period is In terms of Kepler s third law The square of the orbital period of a 9 gt1 planet is directly proportional to the cube of the semimaj or axis of its orbit This means that the further away the planet is the law states that the orbit will be greater 8 0 N Which planet has the shortest days Do you see any notable differences in the length of a day for the different types of planets Explain Jupiter has the shortest days But in a trend the Jovian planets tend to have shorter days than the terrestrial planets Earth and mars both have relatively short rotation periods but all of the Jovian planets follow the same pattern and have shorter rotational periods than the terrestrial planets Which planets should not have seasons Why Mercury and Jupiter should not have seasons because they both have none or a slight tilt overall thus resulting in no seasonal differences Which column tells you how much a planet39s orbit deviates from a perfect circle Based on that column are there any planets for which you would expect the surface temperature to vary significantly over its orbit Explain What are the four major features of our solar system that provide clues to how it formed Describe each one brie y We have already seen that our solar system is not a random collection of worlds but rather a family of worlds with common characteristics that would be difficult to attribute to coincidence We could list these characteristics in a variety of ways but from the purposes of seeking a solar system formation theory it is useful to group them into the following set of four major feartures each called out by one of the numbered steps 1 Patterns of motion among large bodies The Sun planets and large moons generally orbit and rotate in a very organized way 2 Two major types of planets The eight official planets divide clearly into two groups the small rocky planets that are close together and close to the Sun and the large gaseous planets that are farther apart and farther from the Sun Asteroids and Comets Between and beyond the planets huge numbers of asteroid and comets orbit the Sun The locations orbits and composition of these asteroid and comets follow distinct patterns 4 Exceptions to the rules We find a few notable exceptions to the general patterns observed in the solar system For example Earth is the only inner planet with its axis essentially tipped on its side A successful theory mist make allowances for such exceptions even as it explains the general rules What are the basic differences between the terrestrial and jovian planets Which planets fall into each group The terrestrial planets are the four planets that are closest to the Sun Mercury Venus Earth Mars These planets are relatively small and dense with rocky surfaces and an abundance of metals in their cores They have few moons if any and no rings We count out moon as a fifth terrestrial world because the same processes that have shaped the other terrestrial planets have shaped its history The Jovian planets are the four large planets of the outer solar system Jupiter Saturn Uranus Neptune The Jovian planets are much larger in size and lower in average density than the terrestrial planets They also have rings and numerous L V moons Their compositions are also quite different from those of the terrestrial worlds They are made mostly of hydrogen helium and hydrogen compounds Because these substances are gases under earthly conditions the Jovian planets are sometimes called gas giants 13 Which terrestrial planets have had volcanic activity at some point in their histories Volcanic activity was part of the early geological history of all the terrestrial planets plus the Moon The moon and Mercury have been geologically dead for at least a billion years Spacecraft discovered indirect evidence of recent volcanic activity on Venus but have not observed any active volcanic eruptions Giant volcanoes on Mars may have erupted in the last few million years and a few may be dormant 14 What do we mean by hydrogen compounds In what kinds of planets andor small bodies are they major ingredients Hydrogen compounds are compounds that contain hydrogen such as water ammonia and methane Because these substances are gases under earthly conditions the Jovian planets are sometimes called gas giants because that s where the hydrogen compounds are major ingredients 15 What are asteroids Where do we find most asteroids in our solar system Asteroids are rocky bodies that orbit the Sun much like planets but they are much smaller Even the largest of the asteroids have radii of only a few hundred kilometers which means they are dwarfed by our moon Most asteroids are found within the asteroid belt between the orbits of Mars and Jupiter 16 What are comets How do they differ from asteroids Comets are also small objects that orbit the Sun but they are made largely of ices such as water ice ammonia ice and methane ice mixed with rock You are probably familiar with the occasional appearance of comets in the inner solar system where they may become visible to the naked eye with long beautiful tails These visitors which may delight sky watchers for a few weeks or months are actually quite rare among comets The vast majority of comets never visit the inner solar system They orbit at great distances from the Sun where they remain frozen and lack tails 17 What is the difference between a planet a dwarf planet and most asteroids and Kuiper Belt Objects 1 Pluto and Eris belong to a differentclass of objects that the first eight planets They are just the largest known of hundreds of large ice balls essentially large comets located in the Kuiper belt The Kuiper belt probably contains at least 100000 ice balls of which Pluto and Eris are the largest All the objects in this orbit in the same direction with the Sun But Pluto and Eris are too small to be considered planets but they are dwarf planets along with Ceres and other objects within the Kuiper Belt 18 What is the Kuiper belt What is the Oort cloud How do the orbits of comets differ in the two regions 1 They Kuiper belt is the first donut shaped region beyond the orbit of Neptune The Kuiper belt probably contains at least 100000 ice balls of which Pluto and Eris are the largest All the objects in this orbit in the same direction with the Sun The Oort cloud is much farther from the Sun its most distant comets may sometimes reside nearly onequarter of the distance to the nearest stars Comets of the Oort cloud have orbits randomly inclined to the ecliptic plane giving the Oort cloud a shape that is roughly spherical 19 Describe at least two quotexceptions to the rulesquot that we nd in our solar system While most planets rotate in the same direction as they orbit Uranus rotates nearly on its side and Venus rotates backward clockwise rather that counterclockwise as viewed from high above Earth s North Pole Similarly while most large moons orbit their planets in the same direction as their planets rotate many small moons have much more unusual orbits Triton Decide whether the statement makes sense or is clearly true or does not make sense or is clearly false Explain clearly not all of these have de nitive answers so your explanation is more important than your chosen answer 20 Pluto orbits the Sun in the opposite direction of all the other planets 1 False Pluto orbits the Sun in the same direction as all the other planets 2l IfPluto were as large as the planet Mercury we would classify it as a terrestrial planet No because it does not contain metals and is not close to the Sun 22 Comets in the Kuiper belt and Oort cloud have long beautiful tails that we can see when we look through telescopes False those are only the comets that rarely enter into the inner solar system 23 Our Moon is about the same size as moons of the other terrestrial planets False although not the largest the moon is relatively large compared to all the other moons in the solar system 24 On average Venus is the hottest planet in the solar systemeven hotter than Mercury True We now know that an extreme greenhouse effect bakes Venus s surface to an incredible 470K trapping heat so effectively that nighttime offers no relief The weather conditions on Mars today are much different than they were in the distant past True the weather of Mars was different in the past because there are traces of water and riverbeds volcanic action and minerals that would suggest there was water But now the air pressure is very thin and the temperatures are very cold 26 Moons cannot have atmospheres active volcanoes or liquid water N VI 27 Saturn is the only planet in the solar system with rings False all the jovian planets have rings Ch 8 1 What are the four major features of our solar system that provide clues to how it formed Describe each one brie y 1 It must explain the patterns of motion we discussed in Chapter 7 2 It must explain why planets fall into two major categories small rocky terrestrial planets near the Sun and large hydrogenrich jovian planets farther out 3 It must explain the existence of huge numbers of asteroids and comets and why these objects reside primarily in the regions we call the asteroid belt the Kuiper belt and the Oort cloud 4 It must explain the general patterns while at the same time making allowances for exceptions to the general rule such as the odd axis tilt of Uranus and the existence of the Earth s large moon 2 What is the nebular theory and why is it widely accepted by scientists today 1 While the close encounter hypothesis was losing favor new discoveries about the physics of planet formation led to modifications of the nebular hypothesis Using more sophisticated models of the processes that occur in a collapsing cloud of gas scientists found that the nebular hypothesis offered natural explanations for all four general features of our solar system By the latter decades of the 201h century so much evidence had accumulated in favor of the nebular hypothesis that is achieved the status of a scientific theorythe nebular theory of solar system s birth Although recent discoveries of planets around other stars have forced scientists to add new features to the theory the fact that it successfully predicted the existence of other planetary systems has put it on even fumer footing today 3 What do we mean by the solar nebula What was it made of and where did it come from 1 The nebular theory begins with the idea that our solar system was born from a cloud of gas called the solar nebula which collapsed under its own gravity But where did this gas come from It was a product of billions of years of galactic recycling that occurred before the Sun and planets were born 4 Describe each of the three key processes that led the solar nebula to take the form of a spinning disk What observational evidencesupports this scenario 1 Heating The temperature of the solar system nebula increased as it collapsed Such heating represents energy conservation in action As the cloud shrank its gravitational potential energy was converted to kinetic energy of individual gas particles falling inward These particles crashed into one another converting the kinetic energy of their inward fall to the random motions of the thermal energy The Sun formed in the center where temperatures and densities were highest 2 Spinning Like an ice skater pulling in her arms as she spins the solar nebula rotated faster and faster as it shrank in radius This increase in rotation rate represents conservation of angular momentum in action The rotation of the cloud may have been imperceptibly slow before its collapse began but the cloud s shrinkage made fast rotation inevitable The rapid rotation helped ensure that not all the material in the solar nebula collapsed into the center The greater the angular momentum of a rotation cloud the more spread out it will be 3 4 Flattening The solar nebula attened into a disk This attening is a natural consequence of collisions between particles in a spinning cloud A cloud may start with any size or shape and different clumps of gas within the cloud may be moving in random directions at random speeds These clumps collide and merge as the cloud collapses and each new clump has the average velocity of the clumps that formed it The random motions of the original cloud therefore become more orderly as the cloud collapsed changing the cloud s original lumpy shape into a rotating attened disk Similarly collisions between clumps of material in highly elliptical orbits reduce their eccentricities making their orbits more circular The circular motion of the planets in our solar system supports this theory 5 List the four categories of materials in the solar nebula by their condensation properties and abundance Which ingredients are present in terrestrial planets In jovian planets In comets and asteroids Explain why 1 N E 4 Hydrogen and helium gas98 of the solar nebula These gases never condense in interstellar space Hydrogen compounds 14 of the solar nebula Materials such as water methane and ammonia can solidify into ices at low temperatures below about 150 K under the low pressure of the solar nebula Rock4 of the solar nebula Rocky material is gaseous at very high temperatures but condenses into solid bits of mineral at temperatures between 500K and 1300K depending on the type of rock A mineral is a type of rock with a particular chemical composition and structure Metal2 of the solar nebula Metals such as iron nickel and aluminum are also gaseous at very high temperatures but condense into solid form at higher temperatures than rocktypically in the range of 1000K to 1600K Terrestrial planets have rock and metals Jovian planets have hydrogen and helium gas and hydrogen compounds Comets and asteroids consist of rock and ices 6 What was the frost line in the solar nebula Explain how temperature differences led to the formation of two distinct types of planets 1 Hydrogen compounds could condense into ices only beyond the frost line which is the distance at which it was cold enough for ices to condense This lays between the presentday orbits of Mars and Jupiter The frost line marked the key transition between the warm inner regions of the solar system where terrestrial planets formed and the cool outer regions where jovian planets formed Inside the frost line only metal and rock could condense into solid seeds sot the terrestrial planets ended up being made of metal and rock Beyond the frost line where it was cold enough for hydrogen compounds to condense into ices the solid seeds were built of ice along with metal and rock Moreover because hydrogen compounds were nearly three times as abundant in the nebula as metal and rock combined the total amount of solid material was far greater beyond the frost line than within it The stage was set for the birth of two types of planets planets born from seeds of metal and rock in the inner solar system and planets born from seeds of ice as well as metal and rock in the outer solar system 7 Brie y describe the process by which terrestrial planets are thought to have formed 1 The solid seeds of metal and rock gradually grew into the terrestrial planets we see today Because rock and metal made up such a smaller amount on the material in the solar nebula the terrestrial planets achieved only relatively modest sizes The process by which seeds grew into planets is called accretion This began with the microscopic solid particles that condensed from the gas of the solar nebula These particles orbited the forming Sun with the same orderly circular paths as the gas from which they condensed Individual particles therefore moved at nearly the same speed as neighboring particles so collisions were more like gentle touches Although the particles were far too small to attract each other gravitationally at this point they were able to stick together through electrostatic forces the same static electricity that makes hair stick to a comb Small particles thereby began to combine into larger ones As the particles grew into mass gravity began to aid the process of their sticking together accelerating their growth into boulders large enough to count as planetesimals which means pieces of planets Then those grew rapidly at first and then slower then became planets 8 How was the formation of j ovian planets similar to that of the terrestrial planets How was it different 1 These planets formed as gravity drew gas around icerich planetesimals much more massive than earth Because of their large mass these planetesimals had gravity strong enough to capture and hold some of the hydrogen and helium gas that made up that vast majority of material in the surrounding solar nebula This added gas made their gravity even stronger so they could collect even more gas Ultimately the jovian planets collected so much gas that they bore little resemblance to the icy seeds from which they grew So it is similar because they accreted their materials but it is different because these materials hard rock was not being pulled together but gases were being pulled around ice planetesimals 9 Why did the jovian planets end up with so many moons l The same processes of heating spnning and attening that made the disk of the solar nebula should also have affected the gas drawn by gravity to the young jovian planets Each jovian planets came to be surrounded by its own disk of gas spinning in the same direction that the planet rotated Moons that accreted form icerich planetesimals within these disks ended up with nearly circular orbits going in the same direction as their planet s rotation and lying close to their planets equatorial plane 10 What is the solar wind and what roles did it play in the early solar system 1 A solar wind is a stream of charged particles such as protons and electrons continually blown outward in all directions from the Sun Although the solar wind is fairly weak today observations of winds from other stars show that such winds tend to be much stronger in young stars The young Sun therefore also should have had a strong solar wind This swept the hydrogen and helium that made up the solar nebula into interstellar space by some combination of radiation from the young Sun 11 11 In the context of planet formation what are asteroids and comets Brie y explain why we nd asteroids in the asteroid belt and comets in the Kuiper belt and Oort cloud Asteroids are the rocky leftover planetesimals of the inner solar system No planets formed between Mars and Jupiter so this region 7 the asteroid belt 7 was very dense with rocky planetesimals resulting in asteroids Comets are the ice rich leftover planetesimals of the outer solar system Comets occupied much of the outer solar system beyond Neptune even and remained in the original orbit which means they now occupy the donutshaped region known as the Kuiper belt In contrast comets between the jovian planets dealt with a lot of gravitational encounters thus throwing them off their original orbits and resulting in them being carried far away from the Sun They no longer display the original orderly motion of the disk in which the planets are formed and thus now populate the Oort cloud with randomly oriented orbits far from the Sun 12 What was the heavy bombardment and when did it occur The heavy bombardment was the period in the first few hundred million years after the solar system formed during which the tail end of planetary accretion created most of the craters found on ancient planetary surfaces 13 How do we think the Moon formed and what evidence supports this hypothesis The leading hypothesis for explaining the formation of our Moon is the idea of a giant impact A Marssize object may have collided with young Earth and 7 depending on exactly where and how fast the object struck Earth 7 titled Earth s axis changed its rotation rate or may have completely shattered our planet Using computer simulations if we consider an impact at a speed and angle that would have blasted rock from Earth s outer layers in space we can see that this material could have collected into orbit around our planet and accretion within this ring of debris could have formed the Moon Evidence that supports this hypothesis is two features of the Moon s composition First the Moon s overall composition is quite similar to that of Earth s outer layers Second the Moon has a much smaller proportion of easily vaporized ingredients than Earth This supports the hypothesis because the heat of the impact would have vaporized these ingredients 14 Describe the technique of radiometric dating What is a halflife Radiometric dating is the process of determining the age of a rock by comparing the present amount of a radioactive substance to the amount of its decay product This method relies on careful measurement of the proportions of various atoms and isotopes in the rock A halflife is the time it takes for half of the nuclei in a given quantity of a radioactive substance to decay 15 How old is the solar system and how do we know We can validate the 45 billion year radiometric age for the solar system as a whole by comparing it to an age based on detailed study of the Sun Theoretical models of the Sun along with observations of other stars show that stars slowly expand and brighten as they age The model ages are not nearly as precise as radiometric ages but they con rm that the Sun and solar system are between about 4 and 5 billion years old 16 Suppose the entire solar nebula had cooled to 50 K before the solar wind cleared it away How would the composition and sizes of the planets of the inner solar system be different from what we see today Explain your answer in a few sentences The sizes of the planets probably would have been smaller This is because the planets would have had less time to cool down and hence would have been broken into smaller pieces 17 Suppose the solar wind had cleared away the solar nebula before the seeds of the jovian planets could gravitationally draw in hydrogen and helium gas How would the planets of the outer solar system be different Would they still have many moons Explain your answer in a few sentences If the gas giants lacked their massive gaseous atmospheres they wouldn t have nearly as many moons as they do now due to the huge mass loss that would result The less mass they have means the less gravitational pull they have which means they have less ability to hold moons in orbit 18 Suppose our solar nebula had begun with much more angular momentum than it did Do you think planets could still have formed Why or why not What if the solar nebula had started with zero angular momentum In either case planets would not exist because if it began with much more angular momentum than it did then an increase in its rotational speed must be balanced by a decrease in the size of a rotating mass The planets would just continue to get smaller and smaller until they couldn39t hold anything in their gravitational pull as an orbit The solar nebula had to start with some angular momentum in order for the planets to form in the rst place 19 Our bodies and most living things are made mostly of water HZO Summarize the quothistoryquot of a typical hydrogen atom from its creation to the formation of Earth Do the same for a typical oxygen atom The typical hydrogen atom is rst seen in the big bang over time they clump together and begin to form compounds such as ammonia These compounds are part of the disk they freeze and accrete into planets Oxygen created in the center of a star through nuclear fusion and is shot off into space Both of them get into the disk freeze if they re in a water molecule Free oxygen doesn t exist well anywhere besides Earth Suppose we found a solar system with the property described These are not real discoveries In light of what you39ve learned about the formation of our own solar system decide whether the discovery should be considered reasonable or surprising Explain your reasoning 20 A solar system has five terrestrial planets in its inner solar system and three jovian planets in its outer solar system This would probably be false A majority of the material in a solar nebula is hydrogen and helium and this material can condense only belong the frost line Because there s more material beyond the frost line it would make more sense that there d be more jovian planets than terrestrial planets 21 A solar system has four large jovian planets in its inner solar system and seven small terrestrial planets in its outer solar system False The inner solar system is closer to the sun therefore containing higher temperatures Only rock and metal condense at higher temperatures so the planets formed in the inner solar system must be terrestrial The outer solar system contains colder temperatures Only helium and hydrogen compounds can condense at such low temperatures so the outer solar system must contain jovian planets 22 A solar system has ten planets that all orbit the star in approximately the same plane However five planets orbit in one direction eg counterclockwise while the other five orbit in the opposite direction eg clockwise This is not possible If the planets are orbiting a star in approximately the same plane they will all orbit in the same direction Apparent retrogration may occur though 23 A solar system has 12 planets that all orbit the star in the same direction and in nearly the same plane The largest moons in this solar system orbit their planets in nearly the same direction and plane as well However several smaller moons have highly inclined orbits around their planets This isn39t possible either The smaller moons would be bound to their planets on approximately the same plane due to their masses 24 A solar system has six terrestrial planets and four jovian planets Each of the six terrestrial planets has at least five moons while the jovian planets have no moons at all This is very unusual because Jovian planets have a much larger mass and lots of gas which makes it easier for them to create moons with accretion and capture smaller moons in their orbit 25 A solar system has four Earthsize terrestrial planets Each of the four planets has a single moon that is nearly identical in size to Earth s Moon This is unusual because the size of our own moon relative to the size of our planet is very large Our planet is not large enough to capture a moon our size in our gravity therefore our moon had to have been created when an asteroid collided into Earth 26 A solar system has many rocky asteroids and many icy comets This is not surprising Our own solar system has many rocky asteroids and many icy comits 27 However most of the comets orbit in the inner solar system while the asteroids orbit in far ung regions much like the Kuiper belt and Oort cloud of our solar system This would be very surprising considering the fact that the farther into the solar system you go the colder it is Comets are largely made up of ice because they are formed in the cold regions of the solar system Asteroids are made of metal and rock because they are formed much closer to the star 28 A solar system has several planets similar in composition to the jovian planets of our solar system but similar in mass to the terrestrial planets of our solar system This is not possible The j ovian planets have their composition because of how large they are If they were smaller their densities and compositions would be different 29 A solar system has several terrestrial planets and several larger planets made mostly of ice This is possible It is more likely that planets that are made of ice would be larger 30 Radiometric dating of meteorites from another solar system shows that they are a billion years younger than rocks from the terrestrial planets of the same system This is true They have remained unchanged since then Ch 9 1 What is planetary geology Brie y summarize the different geological appearances of the ve terrestrial worlds Planetary geology is the extension of the study of Earth s surface and interior to apply to other solid bodies in the solar system such as terrestrial planets and jovian planet moons Both Mercury and the Moon are densely covered by craters except in areas that appear to be volcanic plains Bizarre bulges and odd volcanoes dot the surface of Venus Mars is home to the solar system s largest volcanoes and a huge canyon cutting across its surface Additionally it has numerous features that appear to have been shaped by running water Earth possesses surface features similar to all of these and more including a unique layer of living organisms that covers almost the entire surface of the planet 2 For the terrestrial objects how does the pressure and temperature change from the surface to the center Both temperature and pressure increase as you go from the surface down to the center of the terrestrial object 3 Why does the Earth have both a solid and liquid core Because temperature increases with depth in a planet it may seem surprising that Earth s inner core is both solid and liquid However the inner core is kept solid by the higher pressure at its greater depth even though the temperature is also higher 4 What is the structure of the moons core The structure of the Moon s core is surprisingly small and it is assumed to have formed from debris blasted out of Earth s rocky outer layersPartially molten layer kind of like the earth Solid inner core uid outer core partial melt mantle 5 What is differentiation and how did it lead to the coremantlecrust structures of the terrestrial worlds Differentiation is the process by which gravity separates materials according to density with highdensity materials sinking and lowdensity materials rising Gravity pulls denser material to the bottom driving the less dense material to the top forming the core mantlecrust structure 6 What do we mean by the lithosphere How does lithospheric thickness vary among the ve terrestrial worlds The lithosphere is the relatively rigid outer layer of a planet that generally encompasses the crust and the uppermost portion of the mantle Smaller worlds tend to have thicker lithospheres Earth and Venus the largest terrestrial planets have thin lithospheres that extend only a short way into their upper mantles The smaller planets 7 Mars Mercury and the Moon 7 have thick lithospheres that extend nearly to their cores 7 Summarize the processes by which planetary interiors get hot There are three different sources of energy that explain the interior heat of the different terrestrial worlds Heat of accretion is when accretion deposits energy brought in from a far by colliding planetesimals The gravitational potential energy of a planetesimal is converted into kinetic energy as it approaches a forming planet causing it to accelerate Upon impact the kinetic energy is then converted into heat Second is heat of differentiation When a world undergoes differentiation the sinking of dense material and rising of lessdense material means that mass moves inward losing gravitational potential energy The energy is converted to thermal energy by friction that is generated as materials separate by density There is also heat from radioactive decay The rock and metal that built the terrestrial worlds contained radioactive isotopes of different elements such as uranium When radioactive nuclei decay subatomic particles y off at high speeds colliding with nearby atoms and heating them 8 Summarize the processes by which planetary interiors cool off Just as there are three basic heating processes there are three basic cooling processes Convection is the process by which hot material expands and rises while cooler material contracts and falls Conduction is the transfer of heat from hot material to cooler material through contact It occurs through the microscopic collisions of individual atoms and molecules Finally there is radiation which is ultimately how planets lose heat to space Objects emit thermal radiation characteristic of their temperatures and this radiation carries energy away and therefore cools the object 9 Why do large planets retain internal heat longer than smaller planets Just as the inside of a hot potato remains hotter longer than the inside of a hot pea larger planets retain internal heat longer than smaller planets The extra rock acts as insulation so it takes much longer for interior heat to reach the surface Also the bigger planets will start out hotter because of a deeper core with higher temperatures and pressure 10 Describe the interiors of the five terrestrial objects and tell why there is a difference The small sizes of the Moon and Mercury allowed their interiors to cool within a billion years or so after they formed As they cooled their lithospheres thickened and mantle convection was con ned to deeper and deeper layers They are now both geologically dead meaning they have no more heatdriven geological activity The much larger size of Earth allows it to stay quite hot inside as mantle convection keeps interior rock in motion and the heat keeps the lithosphere thin Because of this Earth is very geologically active Venus remains nearly as active as Earth due to its similar size Mars with a size in between the rest of the terrestrial planets has cooled signi cantly during its history but it probably still retains enough internal heat for some geological activity There are differences in interiors of the planets due to differences in size 11 Why does Earth have a global magnetic eld Why don t the other terrestrial worlds have similarly strong magnetic elds There are three basic requirements for a global magnetic eld 1 An interior region of electrically conducting uid liquid or gas such as molten metal 2 Convection in that layer of uid 3 At least moderately rapid rotation Earth is the only terrestrial world that meets all three requirements which is why it is the only terrestrial world with a strong magnetic eld 12 Suggest how you might turn on or turn off the terrestrial magnetic elds To remove the internal heat that causes the liquid metal to risefall convection l3 De ne each of the four major geological processes and give examples of features shaped by each process Do not con ne your examples to one planet Impact cratering is the creation of bowlshaped impact craters by asteroids or comets striking a planet s surface An example would be the scarred faces of Mercury and the Moon Volcanism is the eruption of molten rock or lava from a planet s interior onto its surface An example of this would be the formationmountains of Hawaii on Earth and the gas that makes up the atmospheres of Venus Earth and Mars Tectonics is the disruption of a planet s surface by internal stresses An example of this would be the valleys on Venus Mars and Earth and the earthquakes on earth Erosion is the wearing down or building up of geological features by wind water ice and other phenomena of planetary weather An example of this would be the formation of the Grand Canyon and the buildup of sand dunes 14 What is outgassing and why is it so important to our existence Outgassing is the process of releasing gases from a planetary interior usually through volcanic eruptions Virtually all the gas that made the atmospheres of Venus Earth and mars 7 and the water vapor that rained down to form Earth s oceans 7 originally were released from the planetary interiors by outgassing 15 Why is the Moon so much more heavily cratered than Earth Because the impacts of the heavy bombardment must have affected all worlds similarly regardless of their size or distance from the Sun Earth and the Moon must both have been battered by impacts in their early histories Therefore the relative lack of impact craters on Earth today tells us that most of Earth s impact craters have been erased over time by other geological processes such as volcanic eruptions and erosion while most of the Moon s impact craters remain undisturbed l6 Explain how crater counts tell us the age of a surface We can estimate the geological age of any surface region from its number of impact craters with more craters indicating an older surface The degree of crater crowding allows us to estimate the geological age of a planetary surface to within a few hundred million years 17 Summarize the ways in which a terrestrial world s size distance from the Sun and rotation rate each affect its relative level of impact cratering volcanism tectonics and erosion The geological processes operate differently on the different terrestrial planets due to three fundamental planetary properties size distance from the Sun and rotation rate Volcanism and tectonics both require internal heat which means they depend on planetary size Larger planets have more internal heat and therefore more volcanic and tectonic activity Erosion arises from weather phenomena and therefore has links with all three fundamental planetary properties Planetary size is important because erosion requires an atmosphere and a terrestrial world can have an atmosphere only if it is large enough to have had significant volcanic outgassing and if its gravity is strong enough to have prevented the gas from escaping to space Distance from the Sun is important because of its role in temperature The higher temperatures on a world closer to the Sun will make it easier for atmospheric gases to escape into space while the colder temperatures on a world farther from the Sun may cause atmospheric gases to freeze out Distance is also important because water erosion is much more effective with liquid water than with water vapor or ice and therefore is strongest when moderate temperature allows water vapor to condense into liquid form Rotation rate is important because it is the primary driver of winds and other weather Faster rotation means stronger winds and storms 18 Brie y summarize the geological history of the Moon How did the lunar maria form In the lunar highlands craters are so crowded that we see craters on top of other craters IN the lunar maria we see only a few craters on top of generally smooth volcanic plains The lunar highlands are about 44 billion years old telling us that the heavy cratering occurred early in the solar system s history Rocks from the maria date to 3039 billion years ago telling us that the lava ows that made these volcanic plains had occurred by that time The small size of the Moon means that it long ago lost its internal heat leaving it without ongoing volcanism and tectonics this is why you can still see all the craters on it The Moon also lacks a significant atmosphere and erosion due to its small size Nevertheless it still has a few volcanic and tectonic features indicating that at one point it had geological activity The maria are essentially molten ooded craters 19 What is regolith Regolith is a layer of loose heterogeneous material covering solid rock It includes dust soil broken rock and other related materials and is present on Earth the Moon some asteroids and other terrestrial planets and moons 19 What is regolith Regolith is a layer of loose heterogeneous material covering solid rock It includes dust soil broken rock and other related materials and is present on Earth the Moon some asteroids and other terrestrial planets and moons 20 Name four consequences of not having an atmosphere on the moon and how lack of an atmosphere brings them about No weather No erosion Black sky No water because of lack of pressure No temperature regulation No sound 21 Brie y summarize the geological history of Mercury How are Mercury39s great cliffs thought to have formed The small size of Mercury means that it long ago lost its internal heat leaving it without ongoing volcanism and tectonics this is why you can still see all the craters on it Mercury also lacks a signi cant atmosphere and erosion due to its small size Nevertheless it still has a few volcanic and tectonic features indicating that at one point it had geological activity The most surprising features of Mercury are its many tremendous cliffs 7 evidence of a type of tectonics quite different from anything we have found on any other terrestrial world They probably formed when tectonic forces compressed the crust causing the surface to crumple 22 Choose ve features on a global map of Mars and explain the nature and likely origin of each The Tharsis Bulge where the Olympus Mons and several other large volcanoes are concentrated is some 4000 kilometers across and most of it rises several kilometers above the average Martian surface level It was probably created by a longlived plume of rising mantle material that bulged the surface upward and provided the molten rock for the eruptions that built the giant volcanoes The most prominent tectonic feature is the long deep system of valleys called VallesMarineris which extends almost a fifth of the way along the planet s equator It is as long as the United States is wide and almost four times as deep as Earth s Grand Canyon No one knows exactly how VallesMarineris formed parts of the canyon are completely enclosed by high cliffs on all sides so neither owing lava nor water could have been responsible It s believed that it may have formed through tectonic stresses accompanying the uplift of material that created Tharsis cracking the surface and leaving the tall cliff walls of the valleys 23 Why isn39t liquid water stable on Mars today and why do we nonetheless think it owed on Mars in the distant past Current surface conditions do not allow liquid water to remain stable on Mars In most places and at most times Mars is so cold that any liquid water would immediately freeze into ice We nonetheless think water once owed on Mars due to features that look very much like dry riverbeds These channels were almost certainly carved by running water forcing us to conclude that Mars must once have had very different surface conditions such as warmer temperatures and greater air pressure 24 Choose at least three major geological features of Venus and explain how we think each one formed 25 What evidence tells us that Venus was quotrepavedquot about 750 million years ago Venus s relatively few impact craters are distributed fairly uniformly over the entire planet suggesting that the surface is about the same age everywhere crater counts suggest a surface age of about 750 million years We therefore conclude that the entire surface of Venus was somehow repaved at that time erasing all craters that fonned earlier 26 What might account for the lack of plate tectonics on Venus How did Earth and Venus get to be so different geologically The lack of plate tectonics on Venus suggests either that it has weaker mantle convection or that its lithosphere somehow resists fracturing The first possibility seems unlikely due to Earth and Venus s similar size therefore scientists suspect that Venus s lithosphere resists fracturing into places because it is thicker and stronger than Earth s lithosphere Earth and Venus got to be so different geologically due to their differences in their lithospheres 27 Describe the conveyorlike action of plate tectonics on Earth How does this action explain the differences between sea oor crust and continental crust 28 Brie y explain how each of the following geological features of Earth is formed sea oors continents islands mountain ranges rift valleys and faults 29 Contrast the surfaces of the five terrestrial objects Name the types of features and give reasons for the differences The Earth is the only planet covered with water because we have an atmosphere We also have continents with many mountain ranges volcanoes and valleys all created by tectonic plates Mars has impact craters and polar caps with a very dry dusty surface marked with river valleys and lake beds that were probably once filled with running water Earth s Moon and Mercury have very similar surfaces with tons of impact craters with no volcanism or tectonic plates Venus has a relatively small amount of impact craters many volcanoes and a searing hot surface covered by a thick cloudy atmosphere 30 Contrast the impact cratering on all of the terrestrial objects refer to ages of surfaces and crater forming modifying and destroying processes Earth s impact craters have been erased from view by erosion Venus has a few impact craters that are all very similar in age which means its entire surface was fonned around the same time The moon and Mercury have many impact craters all over their surfaces because they have no atmosphere and no means of erosion Mars has a numerous large impact craters in its southern hemisphere but very few in the northern because the southern highlands are an older surface 31 Brie y describe the geology of the terrestrial objects 25 billion years ago Moon and Mercury have a few more craters but they look a lot like they did Mars probably had water on it It would be warmer too Venus probably still had volcanic features on it but no water erosion It has been repaved Earth would look the same but the maps would look different because the continents have moved 32 To what extent do we think the geologies of the terrestrial worlds were destined from their birth Explain We believe that the terrestrial planets were destined from birth by the fundamental properties of their size distance from the sun and rate of rotation Therefore we can approximately guess the geology of terrestrial planets we nd in the future 33 Suppose Mars had turned out to be significantly smaller than its current sizesay the size of our Moon How would this have affected the number of geological features due to each of the four major geological processes Do you think Mars would be a better or worse candidate for harboring extraterrestrial life Mars would have cooled inside much more quickly and probably would not be big enough to have an atmosphere This would make it look much more like the Moon and Mercury Its impact craters would still be present Because of the lack of atmosphere it probably never would have had running water therefore would not have the dry riverbeds and canyons that it has today It also wouldn t have volcanism or tectonic plates 34 Based on what we can see on the surface of Mars does it seem possible that Mars once had a civilization with cities on the surface but that the evidence has now been erased or buried underground Explain There is evidence that there once running water so it is possible that there once was a city However Mars is a dead enough planet that at least in the Southern Hemisphere that we would have been able to see remnants of cities still today if they had ever existed 35 Consider Earth39s size and distance from the Sun Choose one property and suppose that it had been different for example smaller size or greater distance Describe how this change might have affected Earth39s subsequent geological history and the possibility of our existence today on Earth The combination of our planet s size and distance from the Sun impacts the rampant erosion by water and wind Earth is large enough for volcanism and outgassing to have produced an atmosphere while our distance from the Sun allowed water and vapor to condense and fall to the surface as rain Without either one of these properties our Earth would be very different today If it weren t for the Earth s size we wouldn t have an atmosphere and therefore would not be able to live on the planet 36 Suppose another star system has a rocky terrestrial planet twice as large as Earth but at the same distance from its star which is just like our Sun and with a similar rotation rate Describe the type of geology you would expect it to have Most everything would be similar to Earth however due to its larger size it would retain far more internal heat and remain far more volcanically and tectonically active 37 It39s the year 2098 and you are designing a robotic mission to a newly discovered planet around a nearby star that is nearly identical to our Sun The planet is as large in radius as Venus rotates with the same daily period as Mars and lies 12 AU from its star Your spacecraft will orbit but not land on the planet a Some of your colleagues believe that the planet has no metallic core How could you support or refute their hypothesis b Other colleagues suspect that the planet has no atmosphere but the instruments designed to study the planet s atmosphere fail because of a software error However the spacecraft can still photograph geological features How could you use the spacecraft39s photos of geological features to determine whether a significant atmosphere is or was present on this planet a If you see any sign of mountain ranges or volcanism on the planet it must have some sort of metallic core These geological features are caused by molten lava rising up b You could look for liquid water or signs of liquid water in the past The only way to keep water on the surface of a planet is if that planet has an atmosphere Signs of liquid water could include dry river beds valleys or lakes Suppose we were to make the following discoveries These are not real discoveries In light of your understanding of planetary geology decide whether the discovery should be considered reasonable or surprising In some cases both views can be defended Explain your answer if possible tracing your logic back to the terrestrial worlds fundamental properties of size distance from the Sun and rotation rate 38 New closeup photographs reveal vast fields of sand dunes on Mercury This discovery would be surprising because Mercury is now geologically dead possessing no more heatdriven geological activity 39 Seismographs placed on the surface of Mercury record frequent and violent earthquakes Again this discovery would be surprising because Mercury is considered to be geologically dead 40 A new orbiter observes a volcanic eruption on Venus This discovery would be reasonable because Venus s surface is covered by bizarre bugles and odd volcanoes 41 A Venus radar mapper discovers extensive regions of layered sedimentary rocks similar to those found on Earth This discovery would be surprising because sedimentary rock is formed through erosion and Venus has little erosion due to its slow rotation rate 42 Radiometric dating of rocks brought back from one lunar crater shows that the crater was formed only a few tens of millions of years ago This is pretty likely since our Moon has no atmosphere to prevent impacts so it continues to be impacted by space objects 43 New highresolution orbital photographs of Mars show many crater bottoms filled with pools of liquid This is unlikely because of the high temperatures on Mars Liquid water could occasionally melt and flow along the surface for a short time but it would most likely be evaporated or frozen 44 Drilling into the surface a robotic spacecraft discovers liquid water beneath the slopes of a Martian volcano This is likely because abundant water still exists on Mars in the form of ice in the polar caps and underground It is possible that some liquid water exists underground near sources of volcanic heat 45 Clearcutting in the Amazon rain forest on Earth exposes vast regions of ancient terrain that is as heavily cratered as the lunar highlands This discovery would be reasonable because Earth was once believed to be as cratered as the Moon However over time geological processes such erosion have worn down the craters 46 Seismic studies on Earth reveal a quotlost continentquot that held great human cities just a few thousand years ago but that is now buried deep under water off the western coast of Europe This isn39t possible because the sea levels haven t risen enough for the water to engulf an entire city within the past few thousand years 47 We find a planet in another solar system that has Earthlike plate tectonics the planet is the size of the Moon and orbits 1 AU from its star This is unlikely unless the planet was very young If the planet was the same age as Earth the core would be cooled and it would be geologically dead 48 We find a planet in another solar system that is as large as Earth but as heavily cratered as the Moon This is unlikely unless the planet is much farther from its star Larger planets like Earth that are close to the Sun are usually very geologically active and therefore easily erase their impact craters 49 We find a planet in another solar system with Earthlike sea oor crust and continental crust but that apparently lacks plate tectonics or any other kind of crystal motion The theory of plate tectonics explains the existence of two different types of crust Without the movement of the planet s lithosphere sea oor crust and continental crust would not exist Chapter 10 Questions 1 Brie y summarize the atmospheric properties of the five terrestrial worlds How do they differ in surface temperature pressure and composition Mars is the coldest of the terrestial planets with an average surface temperature of 50C though the Moon and Mercury both have temperatures of l75C at night Earth is the next coldest with an average surface temperature of 15C The Moon is next with a daytime average temperature of 125C Mercury has a daytime average temperature of 425C and Venus is the hottest of the terrestial worlds with an average surface temperature of 470C Mercury and the Moon have the least pressure at 10014 bar Mars follows with 00007 bar then Earth with 1 bar and Venus has the most pressure with 90 bars Mercury is composed of helium sodium and oxygen Venus is composed of mostly carbon dioxide and a little nitrogen Earth is mostly nitrogen as well as oxygen It also has some argon and variable amounts of water The moon is composed to helium sodium and argon and Mars is composed of mostly carbon dioxide and a little nitrogen and argon 2 What do we mean by atmospheric pressure Why does pressure decrease with altitude What is 1 bar of pressure Atmospheric pressure is the surface pressure resulting from the overlying weight of an atmopshere Pressure decreases with altitude because the higher you go in an atmosphere the less the weight ofthe gas above you and less weight means less pressure 1 bar of pressure is roughly equival to the pressure at sea level on Earth It is also equivalent to 103 kilograms per square centimeter or 147 pounds per square inch 3 Is there any atmosphere at the orbital altitude of the Space Station above Earth Explain The Space Shuttle orbits Earth within the outer reaches of the atomosphere where there is still some gas present above 60 kilometers The lowdensity gas may be barely noticeable under most conditions but it still exerts drag on orbiting spacecraft That is why satellites in lowEarth orbit slowly spiral downward eventually burning up as they reenter the denser layers of the atmosphere The Space Station would suffer the same fate without periodic boosts from the Space Shuttle or other rockets 4 What is the greenhouse effect Describe how it warms a planet The greenhouse effect is the process by which greenhouse gases in an atmosphere make a planet s surface temperature warmer than it would be in the absence of the atmosphere Visible light passes through the atmosphere Some visible light is re ected by clouds haze and the surface The surface absorbs visible light and emits thermal radiation in infrared Greenhouse gases absorb and reemit infrared radiation thereby heating the lower atmosphere A greenhouse gas molecule that absorbs an infrared photon does not retain this energy for long instead it quickly reemits it as another infrared photon which may head off in any random direction This photon can then be absorbed by another greenhouse molecule which does the same thing The net result is that greenhouse gases tend to slow the escape of infrared radiation from the lower atmosphere while their molecular motions heat the surrounding air In this way the greenhouse effect makes the surface in the lower atmosphere warmer than they would be from sunlight alone The more greenhouse gases present the greater the degree of surface wamiing 5 Ifthere were no greenhouse effect what factors would determine a planet s surface temperature How do the quotno greenhousequot temperatures of the terrestrial planets compare to their actual temperatures and why The planet39s distance from the sun which determines the amount of energy received from sunlight is one factor that would determine a planet s surface temperature without the greenhouse effect The closer a planet is to the sun the greater the intensity of the incoming sunlight The second factor is the planet s overall re ectivity which determines the relative proportions of incoming sunlight that the planet re ects and absorbs The higher the re ectivity the less light absorbed and the cooler the planet The quotno greenhousequot temperatures of the terrestrial planets are much lower than their actual temperatures This is because as previously stated the greenhouse effect warms the lower atmosphere of the terrestrial planets Without it temperatures would be lower 6 Describe Earth39s basic atmospheric structure from the ground up How do interactions of sunlight and gases explain the existence of each of the atmospheric layers The troposphere is the lowest layer Temperature drops with altitude in the troposphere The stratosphere begins where the temeperature stops dropping and instead begins to rise with altitude High in the statosphere the temperature falls again The thermosphere begins where the temperature again starts to rise at high altitude The exosphere is the uppermost region in which the atmosphere gradually fades away into space X rays have enough energy to ionize knock electrons from almost any atom or molecule They can therefore be absorbed by virtually all atmospheric gases UV photons generally do not have enough energy to cause ionization but they can sometimes break apart molecules For example ultraviolet photons can split water molecules and are even more likely to be absorbed by weakly bonded molecules such as ozone which split apart in the process Visible light photons generally pass through atmospheric gases without being absorbed but some are scattered so that their direction changes As already discussed infrared photons can be absorbed by greenhouse gases which are molecules that easily begin rotating and vibrating The exosphere is heated by xrays and UV where fastmoving gas molecules can escape to space The thermosphere is where xrays and UV heat and ionize gases The stratosphere is heated by UV light and there is no convection In the troposphere greenhouse gases trap infrared radiation from the ground convection is important 7 Why are these temperature profiles different The temperature profiles are all different because the temperature depends on the altitude as well as the amount of greenhouse gases in the atmosphere It appears that Venus has signi cantly more greenhouse gases present in its lower atmosphere It is then followed by Earth and then Mars 8 Why is the sky blue Why are sunrises and sunsets red Visible light consists of all the colors of the rainbow but not all the colors are scattered equally Gas molecules scatter blue light higher energy much more effectively than red light lower energy The difference in scattering is so great that for practical purposes we can imagine that only the blue light gets scattered When the sun is overhead this scattered blue light reaches our eyes from all directions and the sky appears blue At sunset or sunrise the sunlight must pass through a greater amount of atmosphere on its way to us Most of the blue light is scattered away leaving only red light to color the sky 9 Why does convection occur in the troposphere leading to active weather bth not in the stratosphere The ground returns the energy it absorbs from visible light by radiating in the infrared Greenhouse gases absorb this infrared light and warm the troposphere Because the infrared light comes from the surface more is absorbed closer to the ground than at higher altitudes which is why the temperature drops with altitude in the troposphere This drop in temperature combined with the relatively high density of the air in the troposphere explains why the troposphere is the only layer of the atmosphere with storms The primary cause of storms is the chuming of air by convection in which warm air rises and cool air falls Convection only occurs when there is a strong heating from below in the troposphere the heating from the ground can drive convection The stratosphere is too far from the ground for convection to occur 10 What is ozone How does the absence of ozone on Venus and Mars explain why these planets lack a stratosphere Ozone is the molecule 03 which is a particularly good absorber of ultraviolet light A planet can have a stratosphere only if its atmosphere contains molecules that are particularly good at absorbing ultraviolet photons Ozone plays this role on Earth but the lack of oxygen in the atmospheres of the other terrestrial worlds means that they also lack ozone As a result Earth is the only terrestrial world with a stratosphere at least in our solar system 11 What is a magnetosphere Describe its role in protecting any atmosphere from the solar wind and in creating auroras A magnetosphere is the region surrounding a planet in which charged particles are trapped by the planet39s magnetic eld The magnetosphere still allows a few solar wind particles to get through especially near the magnetic poles Once inside the magnetosphere these particles move along magnetic eld lines collecting in charged particle belts that encircle our planet The high energies of the particles in these belts can be 39 39 to I f and passing through them Charged particles trapped in the magnetosphere also create the beautiful spectacle of light we call the aurora Variations in the solar wind can buffet the magnetosphere and give energy to particles trapped there If a trapped particle gains enough energy it can follow the magnetic field all the way down to Earth s atmosphere where it collides with atmospheric atoms and molecules These collisions cause the atoms and molecules to radiate and produce the moving lights of the aurora Because the charged particles follow the magnetic field auroras are most common near the magnetic poles and are best viewed from high altitudes 12 What causes seasons How and why do seasons on Mars differ from seasons on Earth This is review The tilt of the Earth39s axis causes seasons Though the tilt of Mars and Earth are similar Mars is more than 20 closer to the sun during its Southern Hemisphere summer than its Northern Hemisphere summer This gives its Southern Hemisphere much more extreme seasons than its Northern Hemisphere even though Mars has nearly the same axis tilt as Earth 13 Describe Earth39s global wind patterns and the role of circulation cells How does rotation affect these cells Earth39s highlatitude winds located nearest the poles and the equatorial winds located near the equator both blow from east to west Earth s midlatitude winds located between the highlatitude winds and the equatorial winds blow from west to east Circulation cells are largescale cells similar to convection cells in a planet s atmosphere that transport heat between the equator and the poles Therefore these cells make Earth39s polar regions much warmer than they would be in the absence of circulation The Coriolis effect is the effect due to rotation that causes air or objects on a rotating surface or planet to deviate from straightline trajectories Earth39s equatorial regions travel faster than polar regions which are closer to the rotation axis Air moving away from the equator therefore has quotextraquot speed that causes it to move ahead of Earth s rotation to the east while air moving toward the equator lags behind Earth s rotation to the west In either case moving air turns to the right in the Northern Hemisphere and to the left in the Southern Hemisphere which explains why storms circulate in opposite directions in the two hemispheres The Coriolis effect plays an even more important role in shaping Earth s global wind patterns it splits each of the two huge circulation cells The three resulting cells circulate air somewhat like three interlocking gears These motions explain the global wind directions notice that surface air moves toward the equator in the cells near the equator and near the poles so the Coriolis effect diverts this air into westward winds In contrast surface air moves toward the poles in the midlatitude cells so the Coriolis effect diverts it into winds that blow eastward In essence the Coriolis effect on a rotating planet tends to divert air moving north or south into eastwest winds 14 Describe each of the four factors that can lead to longterm climate change 1 solar brightening the sun has grown gradually brighter with time increasing the amount of solar energy reaching the planets 2 changes in axis tilt the tilt of a planet s axis may change over long periods of time 3 changes in re ectivity an increase in a planet39s re ectivity means a decrease in the amount of sunlight that it absorbs and vice versa 4 changes in 39 as 39 J more 39 gases tend to make a planet warmer and less make it cooler 15 Describe each process by which atmospheres gain or lose gas What factors control thermal escape Which loss processes are permanent Which are temporary Atmospheres can gain gas by l outgassing volcanic outgassing has been the primary source of gases for the atmospheres of Venus Bart and Mars The terrestrial worlds were built primarily of metal and rock but impacts of icerich planetesimals from beyond the frost line brought in water and gas that became trapped in their interiors Studies of volcanic eruptions show that the most common gases released by outgassing are water carbon dioxide nitrogen and sulfurbearing gases 2 39 39 quot ion after creates an atmosphere some atmospheric gases may condense to become surface liquids or ices The subsequent evaporation or sublimation of these surface liquids and ices therefore represents a secondary source of atmospheric gas For example if a planet warms the rates of evaporation and sublimation will increase adding gas to the atmosphere 3 surface ejection the tiny impacts of micrometeorites solar wind particles and high energy solar photons can knock individual atoms or molecules free from the surface This surface ejection process explains the small amounts of gas that surround the moon and Mercury It is not a source process for planets that already have substantial atmospheres because the atmospheres prevent small particles and high energy solar photons from reaching the surface Planets can lose atmospheric gas through four different processes Two of these processes simply recycle gas from the atmosphere to the planet s surface or interior 1 condensation the process in which gases condense and fall as rain hail or snow essentially reversing the release of gas by evaporation or sublimation On Mars for example it is cold enough for carbon dioxide to condense into dry ice frozen carbon dioxide especially at the poles 2 chemical reactions that incoporate gas into surface metal or rock Rusting is a familiar example iron rusts when it reacts with oxygen thereby removing the oxygen from the atmosphere and incorporating it into the metal This process is so ef cient that it could remove all the oxygen in Earth39s atmosphere in just a few million years Earth retains atmospheric oxygen only because oxygen is continually resupplied by plants and other photosynthetic organisms Gas removed by condensation or chemical reactions can potentially return to the atmosphere at a later time In contrast the other two loss processes are always permanent 1 solar wind stripping for any world without a protective magnetosphere particles from the solar wind can gradually strip away gas particles into space 2 thermal escape if an atom or a molecule of gas in a planet s exosphere achieves escape velocity it will y off into space The relative importance of thermal escape on any world depends on its size distance from the sun and atmospheric composition In general more thermal escape will occur if a planet is small so that is has a low escape velocity or close to the sun which makes it hotter so that atoms and molecules of atmospheric gas are moving faster Lightweight gases such as hydrogen and helium escape more easily than heavier gases such carbon dioxide nitrogen and oxygen 16 Why do the Moon and Mercury have so little atmospheric gas How is it possible that they might nonetheless have water ice in polar craters The moon and Mercury39s gas densities are far too low for sunlight to be scattered or absorbed The lack of scattering means that even in broad daylight you would see a pitchblack sky surrounding the bright sun The lack of absorption means their atmospheres do not have a troposphere stratosphere or thermosphere In essence the moon and Mercury have only extremely lowdensity exospheres without any other atmospheric layers The total amount of gas in the exospheres of the moon and Mercury is very small If you could condense the entire atmosphere of either the moon or Mercury into solid form you would have so little material that you could almost store it in a dorm room The low density of the gas means that collisions between atoms or molecules are rare The gas particles therefore can rise as high as their speeds allowsometimes even escaping into space As a result the exospheres of the moon and Mercury extend thousands of kilometers into space It is possible that the moon and Mercury could have modest amounts of water ice frozen in craters near their poles The bottoms of some polar craters near their poles The bottoms of some polar craters lie in nearly perpetual shadow keeping them quite cold so water from the impacts of icerich comets may have condense and accumulated as ice in these craters 17 How do we think that Mars lost atmospheric gas What basic planetary property size distance from the Sun or rotation rate would have had to be different for Mars to have retained a thicker atmosphere Thre precise way in which Mars lost its carbon dioxide gas is not clear but recent data suggest a close link to a change in Mars s magnetic eld Early in its history history Mars probably had molten convecting metals in its core much like Earth today The combination of this convecting metal with Mars39s rotation should have produced a magnetic eld and protective magnetosphere However the magnetic eld would have weakened as the small planet cooled and core convection ceased leaving atmospheric gases vulnerable to being stripped into space by solar wind particles Had Mars kept its magnetic eld it might have retained much of its atmosphere and have a more moderate climate today Mars changed primarily because of its relatively small size It was big enough for volcanism and outgassing to release plenty of water and atmospheric gas early in its history but too small to maintain the internal heat needed to prevent the loss of this water and gas As its interior cooled its volcanoes quieted and released far less gas into the atmosphere while its relatively while its relatively weak gravity and the loss of its magnetic eld allowed existing gas to be stripped away to space Mars s distance from the sun helped seal its fate even with its small size Mars might still have some owing water if it were signi cantly closer to the sun where the extra warmth could melt the water that remains frozen underground and at the polar caps 18 What do we mean by a runaway greenhouse effect Explain why this process occurred on Venus but not on Earth A runaway greenhouse effect is a positive feedback cycle in which heating caused by the greenhouse effect causes more greenhouse gases to enter the atmosphere which further enhances the greenhouse effect Even though Venus is only about 30 closer to the sun than Earth is this difference was critical On Earth it was cool enough for water to rain down to make oceans The oceans then dissolved carbon dioxide and chemical reactions locked it away in carbonate rocks leaving our atmosphere with only enough greenhouse gases to make our planet pleasantly warm On Venus the greater intensity of sunlight made it just warm enough that oceans either never formed or soon evaporated leaving Venus with a thick atmosphere full of greenhouse gases 19 Describe several ways in which Earth s atmosphere is unique among the terrestrial worlds and how each unique feature is important to our existence 1 Why did Earth retain most of its outgassed water Earth retained its outgassed water because temperatures were low enough for water vapor to condense into rain and form oceans We need water to live 2 Why does Earth have so little carbon dioxide in its atmosphere compared to Venus when Earth should have outgassed about as much as Venus Evidence from tiny mineral grains suggests that Earth had oceans as early as 4344 billion years ago The oceans in turn explain the low level of carbon dioxide in our atmosphere Most of the carbon dioxide outgassed by volcanism on Earth dissolved in the oceans where chemical reactions turned it into carbonate rocks If we had more carbon dioxide than we do now the greenhouse effect would be much stronger and we wouldn t be able to live 3 Why is Earth39s atmosphere composed primarily of nitrogen and oxygen when these gases are only trace constituents in the atmospheres of Venus and Mars Nitrogen is the third most common gas released by outgassing after water vapor and carbon dioxide Because most of Earth39s water ended up in the oceans and most of the carbon dioxide ended up in rocks our atmosphere was left with nitrogen as its dominant ingredient The answer to oxygen mystery is life Plants and many microorganisms release oxygen through photosynthesis Photosynthesis takes in carbon dioxide and through a complex chain of chemical reactions releases oxygen Because chemical reactions can remove oxygen from the atmosphere it took a long time for oxygen to accumulate in Earth39s atmosphere According to present evidence it took at least a billion years of photosynthesis before the buildup of atmospheric oxygen began and Earth39s atmosphere probably has had enough oxygen for us to breathe only for the past few hundred million years Today plants and singlecelled photosynthetic organisms return oxygen to the atmosphere in approximate balance with the rate at which animals and chemical reactions consume oxygen keeping the oxygen levels relatively steady 4 Why does Earth have an ultravioletabsorbing stratosphere while Venus and Mars do not Life and oxygen also explain the presence of Earth s ultravioletabsorbing stratosphere In the upper atmosphere chemical reactions involving solar ultraviolet light transform some of the oxygen into molecules of ozone The ozone molecule is more weakly bound than the oxygen molecule which allows it to absorb solar ultraviolet energy even better The absorption of solar energy by ozone heats the upper atmosphere creating the stratosphere This ozone layer prevents harmful ultraviolet radiation from reaching the surface Mars and Venus lack photosynthetic life and therefore have too little oxygen and consequently too little ozone to form a stratosphere 20 What is the carbon dioxide cycle and why is it so crucial to life on Earth The carbon dioxide cycle is the process that cycles carbon dioxide between Earth39s atmosphere and surface rocks Atmospheric carbon dioxide dissolves in rainwater creating a mild acid The mildly acidic rainfall erodes rocks on Earth39s continents and rivers carry the brokendown minerals to the minerals to the oceans In the oceans calcium from the brokendown minerals combines with dissolved carbon dioxde and falls to the ocean oor making carbonate rocks such as limestone Over millions of years the conveyor belt of plate tectonics carries the carbonate rocks to subduction zones where they are carried downward As they are pushed deeper into the mantle some of the subducted carbonate rock melts and releases its carbon dioxide which then outgasses back into the atmosphere through volcanoes This cycle acts as a longterm thermostat for Earth because it has a builtin form of negative feedback that retums Ear39th s temperature toward quotnormalquot whenever it warms up or cools down The higher the temperature the higher the rate at which carbon dioxide is removed Without this cycle the temperatures on Earth would be extremely extreme 21 Brie y summarize the evidence linking human activity to global warming What are its potential consequences 1 The greenhouse effect is a simple and wellunderstood scientific model We can be confident in our understanding of it because it so successfully explains the observed surface temperatures of other planets Given this basic model there is no doubt that a rising concentration of greenhouse gases would make our planet warm up more than it would otherwise the only debate is about how soon and how much 2 The burning of fossil fuels and other human activity is clearly increasing the amounts of greenhouse gases in the atmosphere Observations show that the atmospheric concentration of carbon dioxide is currently significantly higher about 30 than it has been at any time during the past million years and it is rising rapidly 3 Climate models that ignore human activity fail to match the observed rise in global temperatures In contrast climate models that include the enhanced greenhouse effect from human production of greenhouse gases match the observed temperature trend quite well Comparisons between observations and models therefore clearly indicate that global warming results from human activity Some of the consequences include a rising sea level an increase in the severity of storms and dramatic changes in local climates 22 This table shows that Venus39s surface temperature in the absence of the greenhouse effect is lower than Earth s even though Venus is closer to the Sun Explain this unexpected result in one or two sentences This is because Venus has much more carbon dioxide in its atmosphere than Earth does Because Venus has more greenhouse gases than Earth without them it would be cooler 23 Suppose we could magically give Mercury the same atmosphere as Earth Assuming this magical intervention happened only once would Mercury be able to keep its new atmosphere Explain No Mercury would not be able to keep its new atmosphere This is because its distance to the sun and orbital path is much different than that of Earth s Eventually Mercury would return to its original state 24 As the Sun gradually brightens in the future how can the CO2 cycle respond to reduce the warming effect Which parts of the cycle will be affected Is this an example of positive or negative feedback The cycle will occur at a faster rate The negative feedback occurs because the overall rate at which carbon dioxide is pulled from the atmosphere is very sensitive to temperature the higher the temperature the higher the rate at which carbon dioxide is removed Decide whether the statement makes sense or is clearly true or does not make sense or is clearly false Explain clearly not all these have definitive answers so your explanation is more important than your chosen answer 25 If Earth s atmosphere did not contain molecular nitrogen X rays from the Sun would reach the surface This may be true X rays have enough energy to ionize almost any atom or molecule meaning that they can be absorbed by virtually all atmospheric gases If Earth s atmosphere did not have its most abundant element nitrogen X rays would have a chance to reach the surface 26 If the molecular oxygen content of Earth s atmosphere increases it will cause our planet to warm up False Oxygen is not a greenhouse gas and therefore would not cause our planet to warm up if the abundance were to increase 27 Earth s oceans must have formed at a time when no greenhouse effect operated on Earth This isn39t necessarily true Though the greenhouse effect may have been minimal it was most likely still existent The oceans are a large part of regulating the carbon dioxide cycle today 28 In the distant past when Mars had a thicker atmosphere it also had a stratosphere This is possible but not likely Mars s thicker atmosphere consisted of a troposphere but not necessarily a stratosphere 29 If Earth rotated faster hurricanes would be more common and more severe This is true If the Earth were to spin more quickly the strength of the Coriolis effect would increase as well causing hurricans to be more common and severe 30 Mars would still have seasons even if its orbit around the Sun were perfectly circular rather than elliptical This is true Seasons occur due to the tilt of the planet on its axis not because of its orbit Mars would still have seasons though they would be less extreme in the Southern Hemisphere because of its equal distance from the sun 31 Mars once may have been warmer than it is today but it could never have been warmer than Earth because it is farther from the Sun than Earth is This is false Though Mars is further from the sun than the Earth is its greenhouse effect may have been stronger causing it to have higher temperatures 32 If the solar wind were much stronger Mercury might develop a carbon dioxide atmosphere This is not true The solar wind can not help a planet develop a new type of atmosphere 33 learth had as much carbon dioxide in its atmosphere as Venus our planet would be too hot for liquid water to exist on the surface This may be true Earth still may have enough water on it to compensate for the amount of carbon dioxide in the atmosphere though the surface temperature would likely increase signfrcantly 34 A planet in another solar system has no life but has an Earthlike atmosphere with plentiful oxygen This isn39t possibly If it has plenty of oxygen and an Earthlike atmosphere the planet would have life Ch 11 N E Brie y describe how differences in composition among the jovian planets can be traced to their formation It is traced back to their origins Recall that the Jovian planets are thought to have formed in a very different way from the terrestrial planets which accreted from plantesimals containing only rock and metal Because rock and metal made up less thanl of the solar nebula the terrestrial planets never grew massive enough for their gravity to hold much of the abundant hydrogen and helium gas that made up the nebula The Jovian planets formed in the outer solar system where it was cold enough for hydrogen compounds to condense into ices Because hydrogen compounds were so much more abundant than metal and rock some of the ice rich plantesimals of the outer solar system grew to great size Once these plantesimals became sufficiently massive their gravity allowed them to draw in the hydrogen and helium gas that surrounded them All four Jovian planets are thought to have grown from icerich plantesimals of about the same massi roughly 10x the mass of Earth Thus their differences in composition stem from the amount of hydrogen and helium gas that they captured Jupiter and Saturn pulled in a lot more hydrogen and helium than Neptune and Uranus did Why is Jupiter so much more dense than Saturn Could a planet be smaller in size than Jupiter but greater in mass Building a planet of hydrogen and helium is a bit like making one out of uffy pillows Imagine assembling a planet pillow by pillow As each new pillow is added those compress those on the bottom more above As the lower layers are forced closer together their mutual gravitational stack grows substantially with each pillow but eventually the growth slows until adding pillows barely increases the height of the stack This analogy explains why Jupiter is only slightly larger than Saturn in radius even though it is more than three times as massive The extra mass of Jupiter compresses its interior to a much higher density More precise calculations show that Jupiter s radius is almost that maximum possible radius for a Jovian planet Ifmuch more gas were added to Jupiter its weight would actually compress the interior enough to make the planet smaller in size In fact the smallest stars are significantly smaller in radius than Jupiter even though they are 80x as massive Brie y describe the interior structure of Jupiter and why it is layered in this way How do the interiors of the other jovian planets compare to Jupiter Jupiter s interior has a layers that consist of gaseous hydrogen on the outside followed by liquid hydrogen then metallic hydrogen and finally a core of rock metals and hydrogen compounds As these layers get deeper they get hotter under more pressure and increase in density The interior or most of the Jovian planets are relatively similar but they differ mainly in the hydrogenhelium layers that surround their cores Satum s is the exact same except for you would have to travel deeper to find the inner layers due to Satum s less mass than Jupiter Uranus and Neptune s pressures are not high enough to form liquid or metallic hydrogen at all Each of these two planets has only a thick layer of gaseous hydrogen surrounding its core of rock metals and hydrogen compounds 4 Why does Jupiter have so much internal heat What generates internal heat on other jovian planets Jupiter s large size means it loses internal heat very slowly but calculations show that the remaining heat of accretion and differentiation is not enough to explain Jupiter s presentday heat loss Radioactive decay also adds heat but still not enough to account for all the internal heat The most likely explanation for Jupiter s excess hear is that the planet is still slowly contracting Contraction converts gravitational potential energy to thermal energy so continued contraction would be ongoing source of internal heat Although we have not measured any such contraction theoretical models show that it is probably occurring Moreover calculations tell us that contraction could easily explain Jupiter s internal hear even if the contraction is so gradual that we have little hope of ever measuring it directly Satum s pressure and its lower interior temperatures may allow helium to condense into liquid form at relatively high levels within the interior The helium droplets slowly rain down to the deeper interior This gradual helium rain represents a sort of ongoing differentiation because it means that higherdensity material is still sinking inside the planet Uranus and Neptune both don t have internal conditions that would allow helium rain to form and most of the original heat from accretion should have escaped long ago This explains why Uranus emits virtually no excess internal energy Neptune however emits nearly twice as much energy as it receives from the Sun The only reasonable explanation for this is somehow still contracting somewhat like Jupiter thereby converting gravitational potential energy into thermal energy Brie y describe Jupiter s atmospheric structure and cloud layers It has a troposphere stratosphere and thermosphere The temperature decreases as you go up in the troposphere but then increases again in the stratosphere and the thermosphere It has several gases that can condense into clouds Each of these gases condenses at a different temperature leading to distinctive cloud layers at different altitudes Jupiter has three primary cloud layers We can understand them imagining that we could watch gases rising through the troposphere with convection Deep in the troposphere the gases include three ingredients that will condense when temperatures are low enough water ammonium hydrosulfide and ammonia The rising had first encounters temperature cool enough for water vapor to condense Thus the lowest layer of clouds contains water droplets As the remaining gas continues to rise it next reaches an altitude at which ammonium hydrosulfide condenses to make the second cloud layer Then the next cloud layer is made of the cooler ammonium 6 How do the structures and clouds differ on the other jovian planets Data from telescopic and spacecraft observations tell us that the atmospheric structures of the other three jovian planets are quite similar to that of Jupiter The primary difference among them is that the atmospheres get progressively cooler with increasing distance from the Sun just as we would expect These temperature differences lead the planets to have their cloud layers at different altitudes Saturn has the same cloud structure as Jupiter but because of the lower temperatures these cloud lie much closer to the core of planet Saturn s cloud layers are also separated by greater ve1tical distances than Jupiter39s because Satum s weaker gravity causes less atmospheric compression We do V39 not know for sure about Neptune and Uranus because of the cool temperatures It would probably be the same but they are too far deep into the planet for us to see However high in the atmospheres of these two planets we can see clouds made from akes of methane snow Methane can condense in the very cold upper tropospheres of Uranus and Neptune but not in the warmer tropospheres of Jupiter and Saturn 7 How do the cloud layers help explain Jupiter s colors Water clouds on Jupiter probably re ect white light as do the upperlayer clouds made of ammonium In contrast the midlayer of ammonium hydrosulfide re ects brown and red light although no one knows why Most likely the colors in these clouds come from as yetunidenti ed compounds that are produced by chemical reactions deeper in the atmosphere and are then carried upward by convection 8 Why are Saturn39s colors more subdued than Jupiter Saturn colors are more subdued than J upiter s because they are closer to the surface of the planet This means that less light penetrates to the depths at which Satum s clouds are found and the light they re ect is more obscured by the atmosphere above them 9 Why are Uranus and Neptune blue The blue colors of Uranus and Neptune come from methane gas which is at least 20x more abundant by percentage on these planets than on Jupiter or Saturn Methane gas in the upper atmospheres of Uranus and Neptune absorbs red light allowing only blue light to penetrate to the level at which the methane clouds exist The methane clouds re ect this blue light upward giving the planets their blue color Uranus has a lighter blue color than Neptuen probably because it has more smog like hazer to scatter sunlight before it reaches the level of the methane clouds The extra haze is probably a result of Uranus s quotsidewaysquot axis tilt which leads to extreme seasons With one hemisphere remaining sunlit for decades gases have plenty of time to interact with solar ultraviolet light and to make the chemical ingredients of haze Continuous sunlight may also explain why Uranus has a surprisingly hot thermosphere that extends thousands of kilometers above its cloudtops 10 How would the appearance of Neptune change if you moved it to the same distance from the Sun as Jupiter It would probably be a lot bluer because the methane cloud would be much higher in the atmosphere thus able to re ect more blue light It would most likely be a much brighter blue because it will be closer to the sun and therefore the UV rays from the sun will interact much stronger with the methane cloud than before 11 Brie y describe Jupiter s weather patterns What is the Great Red Spot Jupiter has planetwide circulation cells similar to those on Earth As on Earth solar heat causes equatorial air to expand and spill toward the poles while cooler polar air ows toward the equator Also as on Earth the Coriolis effect splits the large equatortopole circulation cells into smaller cells However Jupiter s great size and faster rotation make the Coriolis effect much stronger on Jupiter than on Earth Jupiter39s circulation cells split into many alternating bands of rising and falling air These bands are visible as the stripes of alternating color in the photographs or Jupiter The alternating bands of rising and falling air shape Jupiter39s global wind patterns As on Earth the rising and falling air drives slow winds that are directed north or south but Jupiter39s strong Coriolis effect diverts these winds into far east or west winds The eastwest winds have peak speeds above 400 kmhr making hurricane winds on Earth seem mild by comparison The winds are generally strongest at the equator and at the boundaries between bands of rising and falling air Jupiter s global wind patterns are sometimes interrupted by powerful storms much as storms can interrupt Earth s global wind patterns Of course Jupiter s storms dwarf those that we see on Earth The Great Red Spot is a giant storm more then twice as wide as all of planet Earth It is somewhat like a hurricane except that its winds circulate around a highpressure region rather than a lowpressure region It is also extremely long lived Astronomers have seen it throughout the three centuries during which telescopes have been powerful enough to detect it Other smaller storms are constantly brewing in J upiter s atmosphere Brown ovals are lowpressure storms with their cloudtops deeper in Jupiter s atmosphere and white ovals are highpressure storms topped with ammonia clouds 12 Based on the infrared and visible images is Jupiter s Great Red Spot warmer or cooler than nearby clouds Is it is higher or lower in altitude than the nearby clouds Explain The bright colors of the Great Red Spot also pose a mystery We might expect its high altitude clouds to be white like the highaltitude ammonia clouds elsewhere but instead of course they are red The colors may be the result of chemicals formed by interactions between the storm s highaltitude gas and solar ultraviolet light but no one really knows for sure Jupiter does not have seasons because it has no appreciable to its equatorial temperatures presumably because heat from Jupiter s interior keeps the planet uniformly warm The Red spot circulates up in cyclonic forms to get higher so it s cooler 13 Suppose the jovian planets atmospheres were composed only of hydrogen and helium with no hydrogen compounds at all How would the atmospheres be different in terms of clouds color and weather Explain There would not be any clouds which means that the planets would probably just be white from re ecting whatever light was coming in from the Sun They would also be a lot colder towards the center of the core because there would be no greenhouse effect in the troposphere or anywhere in the atmosphere If Jupiter was composed of only hydrogen and helium then the atmosphere would be clear down to the lower layers of liquid hydrogen But because there are other elements included compounds would naturally happen like ammonia H28 H20 CH4 etc Given the enormous mass of this planet these compounds would reveal themselves as colored layers in various depths of Jupiter s atmosphere 14 Why does Jupiter have such a strong magnetic field Describe a few features of Jupiter s magnetosphere and compare it to the magnetospheres of the other jovian planets 1 its have an interior region of electrically conducting uid 2 convection in that layer of uid 3 at least moderately rapid rotation In Jupiter s case the electrically conducting uid region is a think layer of metallic hydrogen The great extent of this region combined with Jupiter s rapid rotation explains Jupiter s strong magnetic eld Jupiter s magnetic eld is by far the strongest of the four jovian planets it is some 20000 times as strong as Earth39s magnetic eld Satum s magnetic eld is weaker than Jupiter s because it has a thinner layer of electrically conducting metallic hydrogen Uranus and Neptune smaller still have no metallic hydrogen at all Their relatively weak magnetic elds must be generated in their core quotoceansquot of hydrogen compounds rock and metals The size of a planet39s magnetosphere depends not only on the magnetic eld strength bt also on the pressure of the solar wind against it The pressure of the solar wind is weaker at greater distances from the sun so the magnetospheric quotbubblesquot surrounding more distant planets are larger than they would be i f these planets were closer to the sun Thus Uranus and Neptune have moderatesize magnetospheres despite their weak magnetic elds No other magnetosphere is as full of charged particles as Jupiter s primarily because no other jovian planet has a satellite like Io Because trapped particles generate auroras Jupiter has the brightest auroras while those of the more distant jovian planets are progressively weaker 15 Describe the consequences of the Jovian planets magnetic elds We still have much to learn about he Jovian magnetic elds and magnetospheres For example we generally expect magnetic elds to be closely aligned with planetary rotation because the magnetic elds are generated with the rotating interiors of the planets However while this is the case for Jupiter and Saturn this is not the case for Uranus and Neptune The Voyager showed that the magnetic eld of Uranus is tipped by a whopping 60 degrees relative to its rotation axis and the magnetic eld s center is also signi cantly offset from the planet s center Neptune39s magnetic eld is inclined by 46 to its rotation axis No one has yet explained these surprising observations 16 Brie y describe how we categorize jovian moons by size What is the origin of most of the mediumsize and large moons What is the origin of many of the small moons We now know of 150 moons orbiting the Jovian planets Jupiter has the most with more than 60 moons known to date It s helpful to organize these moons into three groups by size small moons less than about 300 kilometers in diameter mediumsize moons ranging from about 300 to 1500 kilometers in diameter and large moons more than 1500 kilometers in diameter Large moons show evidence of active and ongoing geology and most of the mediumsize moons seem to have had geological activity in the past Medium sized moons probably formed by accretion within the disks of gas surrounding individual Jovian planets That explains why their orbits are almost circular and lie close to the equatorial plane of their parent planet and also why these moons orbit in the same direction in which their planet rotates Nearly all these moons also share an uncanny trait they always keep the same face turned toward their planet sychronus rotation The small moons are probably just small chunks of rock and ice that were pulled in by the gravitational pull of the planet itself Many small moons are probably captured asteroids or comets and thus do not follow any particular orbital patterns The small moons39 shapes are irregular much like potatoes because their gravities are too weak to force their rigid material into spheres 17 What are the key features of Jupiter s four Galilean moons Explain the role of tidal heating and orbital resonances in shaping these features The key features of Jupiter s Galilean moons are that they are all having volcanic activity that creates tectonics This is because of tidal heating and orbital resonance two other key factors of Jupiter s moons Tidal heating is a source of internal heating created by tidal friction It is particularly important for satellites with eccentric orbits such as lo and Europa Just like Earth exerts a tidal force that causes the Moon to keep the same face toward us at all times a tidal force from Jupiter makes To keep the same face toward Jupiter as its orbits But Jupiter39s mass makes this tidal force far larger than that which Earth exerts on the moon Moreover Io39s orbit is slightly elliptical so its orbital speed and distance from Jupiter may vary This variation means that the strength and direction of the tidal force change slightly as 10 moves through each orbit which in turn changes the size 18 Scientists strongly suspect that Europa has a subsurface ocean even though we cannot see through the surface ice Brie y explain why scientists think the ocean exists Scientists suspect that water is the agent of change on Europa s surface either liquid water rising up from beneath the icy crust or interior ice that is just warm enough to undergo convection that allows some of it to rise up and ow across the surface Closeup photos of the surface support the scientists theory Some photos show what would appear to be jumbled icebergs suspended in a region where liquid or slushy water has frozen Other photos show doubleridged cracks on the surface where tides force parts of the icy crust to scrape past each other warming and possibly melting the ice along the fault The rocky mantle and the metallic core would cause for the planet to be hot enough for there to be liquid water underneath the frozen ice which would be about 525 kilometers thick 19 Look up the densities of Jupiter s four Galilean moons in Appendix E3 and notice that they follow a trend with distance from Jupiter Based on what you39ve learned about condensation in the solar nebula can you suggest a reason for this trend among the Galilean moons Next compare the densities of the moons with the planetary densities in Table E 1 Based on the comparison do you think it was as hot toward the center of the nebula surrounding Jupiter as it was at the center of the solar nebula Explain The further the moons are from Jupiter the less dense they are This is because as the solar nebula condensed the more dense material such as rock stayed more central and less dense material such as ice managed to be further out The same concept applies to J upiter s moons No I don t think it was as hot toward the center of the nebular surrounding Jupiter as it was at the center of the solar nebula because the densities of the jovial planets don t follow the same pattern as the densities of the terrestrial planets 20 Describe the atmosphere of Titan What did the CassiniHuygens mission learn about Titan39s surface Titan has a very thick atmosphere 7 so thick that it hides the surface from view except at a few speci c wavelengths of light Titan39s color comes from chemicals in its atmosphere much like those that make smog over cities on Earth It s made up of about 90 molecular nitrogen with the remaining atmosphere consisting of argon methane ethane and other hydrogen compounds Its complex atmospheric chemistry probably produces numerous organic chemicalsthe chemicals that are the basis of life And although it is far too cold for liquid water to exist on Titan39s surface conditions are right for methane or ethane rain perhaps making rivers that feed into lakes or oceans The Cassini Huygens mission discovered that the surface has a hard crust but is a bit squishy below 7 like sand with liquid mixed in Photos showed quotice bouldersquot rounded by erosion These results support the idea of a wet climate with liquid methane Cassini observations of Titan have also taught us a lot The brighter regions in the photographs are icy hills perhaps made byice volcanoes The dark valleys were probably created when methane rain carried down quotsmog particlesquot that concentrate on river bottoms The vast plains into which the valleys appear to empty are probably also covered in smog particles carried there by rivers The polar regions are very different with numerous lakes of liquid methane or ethane Almost all the lakes were at high northern latitudes during winter perhaps the cooler winter temperatures favor condensation The occasional presence of polar storm clouds and the appearance of rivers owing into the lakes together suggest that Titan has a methaneetheane cycle resembling the water cycle on Earth Evidently the similarities between the physical processes that occur on Titan and Earth are far more important in shpaing the landscapes than the fact that the two worlds have very different compositions and temperatures 21 What is Titan39s atmosphere like How does Titan manage to have erosion Titan s atmospheric condition is unlike any other world in our solar system It has an icy composition which supplies methane and ammonia gas through evaporation sublimation and possibly volcanic eruptions Solar ultraviolet light breaks down some of those molecules releasing hydrogen atoms and leaving highly reactive compounds containing carbon and nitrogen The hydrogen atoms can leave Titan forever by thermal escape while the remaining molecular fragments can react to make the other ingredients of Titan39s atmosphere For example the abundant molecular nitrogen is made after ultraviolet light breaks down ammonia molecules and ethane is made from methane The methane and ethane in Titan39s atmopshere are both greenhouse gases and therefore give Titan an appreciable greenhouse effect that makes it warmer than it would be otherwise Still because of its great distance from the sun its surface temperature is a frigid 180C The surface pressure on Titan is about 15 times the sea level pressure on Earth which would be fairly comfortable if not for the lack of oxygen and the cold temperatures 22 What is Enceladus doing to create the E ring The particles that make up the E ring are bright and re ective like those on Enceladus Either particles from the ring are falling down onto Enceladus or Enceladus is supplying the ring with particles Though a definite answer is not known evidence point to Enceladus as the source for the ring particles The E ring is being disrupted by the solar wind and is losing particles It must therefore be getting replenished from somewhere Secondly there are not many craters on the surface of Enceladus and that suggests that something covers the craters up soon after impact Volcanoes are the most likely culprit Voyager spacecraft images of Enceladus show what look like lava ows except that in this moon s case it would be icy water ows No geysers or active volcanos have been found but they are probably the only answer that makes sense to the question of Enceladus surface and the E ring particles 23 What is Iapetus strange equatorial ridge and how do we explain it It is not clear how the ridge formed One difficulty is to explain why it follows the equator almost perfectly There are at least three current hypotheses but none of them explains why the ridge is confined to Cassini Regio l A team of scientists associated with the Cassini mission have argued that the ridge could be a remnant of the oblate shape of the young Iapetus when it was rotating more rapidly than it does today The height of the ridge suggests a maximum rotational period of 17 hours Iflapetus cooled fast enough to preserve the ridge but remained plastic long enough for the tides raised by Saturn to have slowed the rotation to its current tidally locked 79 days Iapetus must have been heated by the radioactive decay of aluminium26 This isotope appears to have been abundant in the solar nebula from which Saturn formed but has since all decayed The quantities of aluminium26 needed to heat Iapetus to the required temperature give a tentative date to its formation relative to the rest of the Solar System Iapetus must have come together earlier than expected only two million years after the asteroids started to form 2 The ridge could be icy material that welled up from beneath the surface and then solidified If it had formed away from the position of the equator at the time this hypothesis requires that the rotational axis would have been driven to its current position by the ridge 3 It has also been suggested that Iapetus could have had a ring system during its formation due to its large Hill sphere and that the equatorial ridge was then produced by collisional accretion of this ring However the ridge appears too solid to be the result of a collapsed ring Also recent images show tectonic faults running through the ridge apparently inconsistent with the collapsed ring hypothesis 24 What is the difference between a regular satellite and an irregular satellite A regular moon is a natural satellite following a relatively close and generally prograde orbit with little orbital inclination or eccentricity They are believed to have formed in orbit about their primary as opposed to irregular moons which were captured An irregular moon is a natural satellite following a distant inclined and often eccentric and retrograde orbit They are believed to have been captured by their parent planet unlike regular satellites which formed in situ 25 Why do we think Triton is a captured moon Triton may appear to be a typical moon but it is not It orbits Neptune quotbackwardquot opposite to Neptune39s rotation and at a high inclination to Neptune39s equator These are telltale signs of a moon that was captured rather than having formed in the disk of gas around its planet No one knows how a moon as large as Triton could have been captured but models suggest one possible mechanism Triton may have once been a member of a binary Kuiper belt object that passed so close to Neptune that Triton lost energy and was captured while its companion gained energy and was ung off at high speed 26 Why are the four Galilean satellites and Titan and Triton so much different Compare the interiors and atmospheres Io is believed to have a dense core composed of iron and iron sul de The radius of the core is approximately 900 km 560 miles which extends about halfway to the surface It is likely that the core formed either from internal heating processes during the early stages of the moon39s formation or as a result of the ongoing tidal heating that drives the volcanic activity at the surface Surrounding the core is a mantle of partially molten rock which is overlain by a relatively thin rock crust In Io s atmosphere there are no clouds and lightning The atmosphere of lo is very thin and does not remain bound to 10 for very long Even so it has an important impact on the Jupiter system Io39s atmosphere comes from its volcanoes then disperses because as a small moon Io does not have substantial gravity It is suggested that Europa has a metallic core and a rocky mantle Above the rocky mantle Europa has enough water to make a layer of ice about 100 km thick According to computer models the upper 525 km should be solidly frozen but beneath this icy crust tidal heating provides enough warmth to create a lyaer of either liquid water or realtively warm convecting ice Europa has its own atmosphere although it is very very thin Europa has its own atmosphere although it is very very thin Ganymede39s interior is a small core of metal overlain with some rocky material overlain still further with ice Ganymede may have a thin saltyslushy layer near the surface where electric currents are found Ice cannot support electric current but water can Ganymede39s atmosphere is very very thin The atmosphere is created when molecules from the magnetosphere moving very fast hit the surface and knock out a water molecule Because there is a magnetosphere the atmosphere of Ganymede does not simply oat away like the atmosphere of Europa does Callisto seems to have a strange interior that is not entirely uniform and does not vary dramatically Prior to Galileo scientists believed that Callisto s interior was totally undifferentiated but Galileo data suggests that the interior is composed of compressed rock and ice with the percentage of rock increasing as depth increases Callisto seems to have its own atmosphere although it is very very thin and may come and go with time The atmosphere is created when molecules from the magnetosphere moving very fast hit the surface and knock out a water molecule Titan39s interior is primarily composed of water ice of different phases with mountains of ice exposed at its suraface Deep inside Titan are to be found the more heavier rocky and metal elements such as silicates and iron These form the core of Titan Titan39s atmosphere is roughly 90 Nitrogen and 10 other complex molecules such as methane and is extremely thick The composition of Triton is mostly ice therefore there is probably a small core of some rocky material buried inside overlain with mantles of ice of various phases Triton s atmosphere is very very thin The air pressure on Earth is more than 50000 times higher than on the surface of Triton Most of the air on Triton is the gas nitrogen just like on Earth Most of the nitrogen on Triton is frozen It is on the ground in the form of frost Some of the nitrogen frost warmed up just a little and evaporated That s what makes Triton s thin atmosphere Triton39s atmosphere has a troposphere a thermosphere and an exosphere It does not have a stratosphere The top of the atmosphere is about 800 km 500 miles above Triton39s surface 27 Is there a chance for life in the j ovian systems There is a chance for life in the jovain systems if not presently then at least at some point in history Some of the moons have manageable pressure and either ice or water present both signs that life may exist in some form 28 Brie y explain why icy moons can have active geology at much smaller sizes than rocky worlds We can trace the answer to a crucial difference between the jovian moons and the terrestrial worlds composition The jovian moons by virtue of their formation in the cold outer solar system conatin large propotion of ices Because ices can melt or deform at much lower temperatures than rock icy worlds can experience geological activity at lower temperatures than rocky worlds Indeed most of the volcanism that has occured in the outer solar system except on Io probably didn t produce any hot lava at all Instead it produced icy lava that was essentially liquid water perhaps mixed with methane and ammonia Thus the major lesson of our study of j ovian moons is that quotice geologyquot is possibly at much lower temperatures than quotrock geologyquot This fact combined in some cases with tidal heating explains how the jovian moons have had such interesting geological histories despite their small sizes In essence the same physical properties that allowed hydrogen compounds to condense as ices in the outer solar system also allowed the worlds made from these ices to stay geologically active for long periods of time 29 What are planetary rings made of and how do they differ among the four jovian planets Spectroscopy reveals that Satum s ring particles are made of relatively refective water ice The rings look bright where they contain enough particles to intercept sunlight and scatter it back toward us We see gaps in places where there are few particles to re ect sunlgiht Satum s rings are incredibly thin The rings of Jupiter Uranus and Neptune are so much fainter than Saturn s that it took almost four centuries longer to discover them Ring particles in these three systems are far less numerous generally smaller and much darker All rings lie in their planet39s equatorial plane Particle orbits are nearly circular with small orbital tilts relative to the equator Individual rings and gaps are probably shaped by gap moons shepherd moons and orbital resonances 30 Explain the different brightnesses of rings The changes in brightness between the jovian planets rings deals with the amount of re ectivity that each of the planets rings possess Satum s rings are the most re ective of the sun39s light and are therefore the brightest It also deals with the amount of particles in the rings the more particles that are present the brighter that they are 31 Brie y describe the effects of gap moons and orbital resonances on ring systems Rings and gaps are caused by particles bunching up at some orbital distances and being forced out at others This bunching happens when gravity nudges the orbits of ring particles in some particular way one source of nudging comes from small moons located within gaps in the rings themselves sometimes called gap moons The gravity of a gap moon can effectively keep the gap clear of smaller ring particles while creating ripples in the ring edges The ripples appear to move in opposite directions on the two sides of the gap because ring particles on the inner side orbit Saturn slightly faster than the gap moon while those on the outer side orbit slightly slower than the gap moon Ring particles also may be nudged by the gravity from larger more distant moons For example a ring particle orbiting about 120000 km from Saturn s center will circle the planet in exactly half the time it takes the moon Mimas to orbit Every time Mimas returns to a certain location the ring particle will also be at its original location and therefore will experience the same gravitational nudge from Mimas The periodic nudges are reinforce one another and clear a gap in the ringsin this case the large gap visible from Earth the Cassini division This type of reinforcement due to repeated gravitational tugs is another example of orbital resonance much like the orbital resonances that make Io39s orbit elliptical Some resonances create vast numbers of ripples and waves that travel great distances through the rings Other orbital resonances caused by moons both within the rings and farther out from Saturn probably explain most of the intricate structures visible in ring photos 32 What are propeller moons and what are they doing Properlller moons clear ring material from the rings of the jovian planets Disturbed ring material closer to the moon re ects sunlight brightly and appears like a white airplane propeller hence the reason they get their name 33 Explain why we think that ring particles must be replenished over time Will the jovian planet rings always look the same These new particles must come from a source that lies in each planet s equatorial plane The most likely source is numerous small moons that formed in the disks of material orbiting the young jovian planets The small moons contribute ring particles in two ways First each tiny impact releases particles from a small moon39s surface and these released particles become new dustsize ring particles Ongoing impacts ensure that some ring particles are present at all times Second occasional larger impacts can shatter a small moon completely creating a supply of bouldersize ring particles The frequent tiny impacts then slowly grind these boulders into smaller ring particles some of which are quotrecycledquot by forming into small clumps that come apart again later on In summary the dust to bouldersize particles in rings all ultimately come from the gradual dismantling of small moons that formed during the birth of the solar system No the rings will not always look the same The collision that shatter small moons and generate large particles must occur only occasionally and at essentially random times which means that the numbers and sizes of particles in any particular ring system may vary dramatically over millions and billions of years Suppose someone claimed to make the discoveries described below These are not real discoveries Decide whether each discovery should be considered reasonable or surprising More than one right answer may be possible so explain your answer clearly 34 Satum s core is pockmarked with impact craters and dotted with volcanoes erupting basaltic lava This is not possible Satum s atmosphere is extremely thick and deep so any meteor would burn up before getting close to the core As for the second one there is a very veryvery slight possiblity it could be volcanicly active do to the large gravity acting on it but it39s much more likely that it is some sort of liqui ed metal do to the immense heat or extremely compressed super heated gas 35 Neptune39s deep blue color is not due to methane as previously thought but instead is due to its surface being covered with an ocean of liquid water This is not possible due to Neptune39s extreme cold temperatures 36 A jovian planet in another star system has a moon as big as Mars This is possible due to the relative sizes of the moons on Saturn and Jupiter 37 An extrasolar planet is made primarily of hydrogen and helium It has approximately the same mass as Jupiter but is the same size as Neptune This is not possible If it was as massive as Jupiter and the same size of Neptune the hydrogen and helium would condense 38 A new small moon orbits Jupiter outside the orbits of other known moons It is smaller than Jupiter s other moons but has several large active volcanoes This is not plausible Tidal forces are too weak on objects so far away and they are not forced into elliptical orbits by resonances which means that tidal heating isn39t an option It would also be too small to have volcanoes from radioactive heating and an object that small wouldn t retain the heat of accretion very long Last of all our formation theories say that small moons should not be the furthest away to begin with 39 A new moon orbits Neptune in the planet s equatorial plane and in the same direction that Neptune rotates but it is made almost entirely of metals such as iron and nickel This is not possible if it was made of metals it would be extremely dense and would not be a part of the jovial system 40 An icy mediumsize moon orbits a jovian planet in a star system that is only a few hundred million years old The moon shows evidence of active tectonics This is possible because the moon is so young if it were older it may not show evidence of plate tectonics 41 A jovian planet is discovered in a star system that is much older than our solar system The planet has no moons but has a system of rings as spectacular as the rings of Satum This is not possible without moons the rings of the planet would be lost either by decreasing size slowing in their orbits which causes them to spiral to their planet or other ways The moons are what keep the rings present 42 Radar measurements of Titan indicate that most of the moon is heavily cratered This is not possible because erosion exists on Titan Ch 12 1 Brie y describe the general characteristics of asteroidsincluding sizes masses densities and compositionsand how we measure them
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