Discover the Universe Week 6
Discover the Universe Week 6 AST 1002
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This 10 page Class Notes was uploaded by Jocelyn on Sunday October 4, 2015. The Class Notes belongs to AST 1002 at University of Florida taught by Reyes, Francisco J in Summer 2015. Since its upload, it has received 18 views. For similar materials see Discover the Universe in Science at University of Florida.
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Date Created: 10/04/15
Tuesday September 29 2015 Discover the Universe Week 6 The Ozone Layer The ozone layer is located at about 2 30 km above the surface It contains about 10 parts per million of ozone A group of chemicals known as CFCs choroflourocarbons Freon are efficient to combine with the ozone molecule 03 destroying the ozone molecule CFC contains carbon chlorine and fluorine HOW The CFC molecule dissociates in the upper atmosphere by solar radiation and releasers chlorine combining with ozone and forming molecular oxygen 02 The chlorine acts as a catalyst t participates in the reaction but is released at the end of the reaction Seismology How seismic waves travel through Earth s interior Earthquakes generate two types of seismic waves P and S waves P waves Pressure can travel through the liquid outer core but they are actually deflected by the core S waves Shear travel in the mantle but not through the liquid core Higher density material faster the waves travel Different densities force the waves to follow curved patterns The Earth s Interior Crust 15 km thick 8 km under ocean and 2050 km under continents Mantle 3000 km thick 80 planet volume Core inner core is solid outer core is fluid Density and temperature increase with depth High central density suggests the core is mostly nickel and iron Tuesday September 29 2015 Evolution of the Solid Earth Accretion The material that formed the Earth comes from the material accreted that first form the protoplanetary disk The material in the disk collapses and forms protoplanets This process happened about 46 million years ago age of Sun Earth was bombarded by interplanetary debris Left over from the formation of the Solar System As we will see later all the planets and satelittes were bombarded by debris The debris created impact crater such as those on the Moon The impacts contribute to an increase of the temperature Radioactive decay usually elements such as uranium and thorium will release heat when their nuclei break up into simpler lighter elements This also contributed to the increased temperature Once the melting occurred differentiation of the interior began Differentiation Earth was molten allowing higherdensity material to sink into the core The material in the core is still at a high temperature about 5000 K Crustal Formation cooling and thickening of the Earth s crust The Surface of the Earth is still active Seismic activity such as earthquakes volcanoes and plate tectonics Sites of activity outline surface plates Continental drift continents drift a few cmyear The technical term for continental drift is Plate Tectonics Plates collide head on mountains or shear past earthquakes Some plates are separating under Atlantic and new mantle material wells up between them What causes the forces that shift plates Convection Tuesday September 29 2015 Lunar Surface Lack of atmosphere and water preserves surface features Maria singular mare Younger areas mantle material maria means seas Few impact craters Maria darker areas resulting rom earlier lava flow Basaltic relatively iron rich high density 3300 kgmquot3 Highlands older areas crust material Many impact craters SEE SLIDE Lunar Erosion Lunar craters caused by meteoroid impacts The high speed of the impactor meteroid nucleus of comet causes an explosion at the point of impact Pressure to the lunar surface heats the rock and deforms the ground Explosion pushes rock layers up and out The ejecta blanket surrounds the crater It forms radial features around some craters These are called rayed craters In some cases the compressed material bounces back and forms a crater with a central peak Craters can be u to 100 km in diameter A new 10 km crater is formed every 10 million years A new 1 m crater is formed each month A new 1 cm crater is formed every few minutes Earth s Magnetosphere The space around the Earth influenced by Earth s magnetic field Magnetic poles are close to but not the same as rotational axis poles Thursday October 1 2015 The magnetic field is distorted by the solar wind The composition of the solar wind high speed charged particles electron protons ions Solar flares eject high energy charged particles that compress the magnetic field The compression induces currents in power lines and may cause a black out Van Allen belts named for Dr James Van Allen are two doughnutsshaped zones where high energy particles are trapped on the magnetic field What causes Earth s magnetic field The relatively fast rotation of the planet The electrically conducting metal core dynamo effect Aurora Borealis Charged particles are ejected from the Sun In a solar flare a large amount of these charged particles are ejected Formation of the Moon Theories Both the Earth and the Moon formed together from the same material of the photo planetary disk The moon formed somewhere else and was captured by the Earth Impact Theory The most accepted theory Glancing collision between a Marssized body Mars diameter is about half of Earth s diameter and the molten Earth The Mars sized body was formed somewhere else and there was an exchange of material Parts of the Earth mantle were ejected in the collision and later condensed and formed the moon Earth had already gone through the process of differentiation so little iron from the core was elected into the collision Most of the material ejected came from the mantle Chapter 6 The Terrestrial Planets Earth Venus Mars and Mercury The rotation and spin of the terrestrial planets Thursday October 1 2015 Mercury 59 days Venus 243 days Earth 1 day Mars 103 days Mercury and Venus are called interior planets because their orbits are inside Earth s orbit Only seen for a few hours before sunrise and after sunset Max angle between Mercury and the Sun is 28 degrees Max angle between Venus and the Sun is 47 degrees The angle is known as elongation Deoending on the position of the two planets in the ecliptic they can only be seen at a rather low angle above the eastern before sunrise or western horizon after sunseD Venus is the third brightest object in the Sky after the Sun and the moon Mercury Mass 0055 mass of the Earth Radius 038 radius of the Earth 2400 km Avg density 5400 kgmquot3 Earth 5500 kgmquot3 Escape speed 42 kms Surface temperature 100 700 K Surface gravity 038 Earth 1 Mercury is not tiday locked to the Sun How to obtain the rotational period of an object using the Doppler shift If the planet is rotation the wave reflected from the side approaching the observer will be blue shifted Mercury s Atmosphere Almost nonexistent 5 Thursday October 1 2015 All gases that may have existed in the atmosphere left the gravitational attraction of the planet The as molecules had large velocities due to the high surface temperature Due to the small mass it has a low escape velocity 42 kms There is no atmosphere to retain heat It means drastic temperature changes between day and night 700 K day 800 F 100 K night 280 F Near the poles the temperature remains cold 125 K all the time it has been found that is covered with thin ice sheets Mariner 10 found traces of what appears to be a thin atmosphere The traces of an atmosphere are atoms trapped by the planet from the solar wind Hydrogen and Helium H and He are trapped for a short time a few weeks but they escape into space Mercury s Surface Similar to the Moon with large amounts of impact craters Old Surface No indication of plate tectonics Craters have a flat bottom and have thinner ejecta rims than lunar craters This is due to the higher gravity on Mercury compared with the Moon Concentration of craters not as dense as on the Moon Not dark features like the maria on the Moon Cliffs scarp are seen on the surface features not seen on the Moon They appear to be about 4 billion years old and are not the result of plate tectonics Probably the result of surface cooling shrinking and splitting at this time Some cliffs are several hundred km long Venus Mass 082 mass of the Earth Radius 095 radius of the Earth Thursday October 1 2015 Density 5300 kgmquot3 Surface gravity 091 Earth gravity Escape velocity 10 kms Surface temperature 730 K around 850 F0 Atmospheric pressure 90 Earth 1 No sateittes Venus Rotation Rotation direction is retrograde 243 day rotation period Rotation measured using Radar signals and Doppler Effect The thick cloud cover doesn39t allow to see the surface and find a reference point to obtain the rotational penod Venus Atmosphere Much more massive atmosphere than Earth s about 90 times the pressure Composition C02 965 Nitrogen 35 Clouds are very thick not possible to see the surface No H2 the clouds are made of Sulfuric Acid H2SO4 Fast moving 400 kmhr clouds in upper atmosphere Clear sti air at the surface 730 K temperature on the surface Lead melting point 600 K Higher than Mercury due to the Greenhouse effect Venus Surface Elevated continents make up 8 of the surface 25 on Earth Largest volcano structures are called coronae upwelling in the mantle which causes the surface to bulge out Usually surrounded by other volcanoes Venus is thought to still be volcanicay active Thursday October 1 2015 Volcanic activity may explain the presence of sulfuric acid clouds Volcanoes resurface the planet every 300 years A Caldera crater is formed at the summit when lava withdraws Venera soviet spacecraft only survived an hour on Venus because of the heat Rocks are basaltic and granite lVlars Mass 011 mass of Earth Radius 053 radius of Earth Avg density 3900 kgmquot3 Surface gravity 038 of the Earth Escape speed 50 kms Rotation period 103 days Surface temperature 180270 K 273 K 32 F is freezing Atmospheric pressure 0007 earth 1 Axial tilt 24 degrees lVlars Overview Diameter about 12 of Earth Rotation period is 246 hoursclose to Earth s rotational period Equator inclined at 24 degrees Mars Telescopic Exploration Giovanni Schiaparelli 1877 Mapped bright and dark regions Saw polar caps with changed with seasons Surface colors appeared to change plants Thursday October 1 2015 Identified long narrow features called Canali grooves channels canals Percival Lowell 1855 to 1916 In 1894 he built an observatory in Flagstaff AZ to study Mars Lowell Observatory He purchased and used of this observations a 24th Alvan Clark refractor He thought that canals were used by a civilization to bring water from he poles to the equatorial desert Images taken by the Mariner and Viking space craft about a century later 1960s prove that there were no canals llars Spacecraft Exploration 1965 Mariner 4 6 and 7 fly by Mars 1971 Mariner 9 first to orbit the planet and maps Mars in detail 1976 Viking 1 lands on Mars llars Rovers Pathfinder and Sojourner robots 1997 was a highly successful mission which sent back lots of picots of the Martian land telescope perform soil and atmosphere analyses The analysis of rocks of Mars show that they are iron rich Iron and oxygen in the atmosphere combine to give Mars surface its famous red color Iron Oxide or Rust The next landing mission Mars Climate Orbiter in 1999 failed to reach the planet This was an error between two teams using two systems metric and english Mars rovers Opportunity and Spirit are currently on Mars to study water landed in January 2004 Mars Surface Polar icecaps mainly frozen carbon dioxide and minor component of water ice Northern Hemisphere rolling volcanic planes 9 Thursday October 1 2015 Like lunar maria but larger Few craters young 3 billion years old Southern Hemisphere heavily oratered highlands older 10