ASTR 151 Unit 3 Study Guide
ASTR 151 Unit 3 Study Guide ASTR 151 001
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This 12 page Study Guide was uploaded by Wesley Fowler on Friday April 22, 2016. The Study Guide belongs to ASTR 151 001 at a university taught by Dr. Sean Lindsay in Spring 2016. Since its upload, it has received 44 views.
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Date Created: 04/22/16
Wesley Fowler ASTR Chapter 8 The Moon’s Interior 3 Average Density: 3300kg/m - Lower than Earth’s, but higher than the Moon’s surface. Thus an iron core. Total Radius: 1,738 km Layers: Solid iron inner core: 240km (small) Fluid outer core: 330Km Molten inner mantle Large, rocky outer mantle: Out to 1600Km Thin rocky crust No plate tectonics No electromagnetic ﬁeld Maria is believed to be made of lunar mantle material mixed with the crust Origins of the Moon Earth’s mantle and crust are very compositionally similar to the Moon. They are all made up of similar rocky and metallic materials. - The Moon lacks a substantial metal core 1. Co-formation (sister) Theory: Earth and Moon formed separately, but at the same time, out of the same material. - The moon’s deﬁciency of iron refutes this theory. 2. Capture Theory: Earth and Moon formed separately apart from each other, with the Moon being captured by the Earth’s gravitational force, causing it to orbit. - The physics required for the Earth to capture the Moon in its orbit are not possible. 3. Fission (Daughter) Theory: Earth and Moon form as single object, and the Earth and moon split up due to a very high rotation rate. - The physics required for this split are not possible 4. Giant Impact Theory: When the Earth was mostly molten and young, a grazing collision happened with a “Mars-sized” protoplanet caused a chunk to separate from Earth. - This physics required are possible, and the theory explains compositional similarities Evolution of the Moon Oldest rocks dated: 4.4 billion years ago (age of highlands) - Crust must have formed by this time Shortly after formation, the Moon’s surface was entirely molten, it was covered by what is called the lunar magma ocean. Lunar Magma Ocean Sequence: 1) Formation result of hot accretion 2) Light material (anorthosite) ﬂoats -> Crust, such that thinner crust formed on near-side 3) Dense materials sink 4) Large impacts form huge basins during Late Heavy Bombardment – Precursors to maria 5) Volcanism over next several hundred million years (3.9 – 3.2 Gya) ﬁlled impact basins to form maria with mantle compositions 6) No signiﬁcant geologic activity after 3.2 Gya; Surface evolution dominated by the steady of impacts (generating new craters and regolith) Near-side crust is thinner than the far-side, and thus can ﬂood with lava. Wesley Fowler ASTR Chapter 8 Introduction to Mercury Distance from Sun: 0.4 AU Radius: 2,440 k23(slightly larger than the Moon) Mass: 3.3 x 10 kg Average Density: 5,400 kg/m (Very high) Orbital Period: 88.0 days Rotational Period: 58.6 days Axial Tilt: 0.034o - (Don’t need to memorize these) Has an extreme variation in temperature due to lack of atmosphere and very long Solar Days Does have a magnetic ﬁeld Does not have a permanent atmosphere Mercury’s Orbit Mercury has the highest eccentricity of all the planets Mercury always appears close to the sun when observed from Earth. It’s very hard to observe. Mercury, unlike the moon, does not have a synchronous orbit. Its orbital period is 88 days while its rotational period is 58.6 days. - This was discovered via sending radio pulses and analyzing them with the Doppler Effect Mercury is tidally locked even though its orbit is not synchronous. For every two orbits around the sun, mercury rotates three times. Thus, Mercury has a 3:2 spin-orbit resonance (ratio of relating periods) - The Moon has a 1:1 spin-orbit resonance This is caused by the tidal force between the Sun and Mercury. - 17x stronger than the force between the Sun and Earth - Tidal bulge aligns with perihelion and aphelion in 3:2 ratio 3:2 spin-orbit ration gives Mercury a solar day of 176 days, which is two Mercury years. The solar day is very strange on Mercury. The Sun rises in the east, goes back east and sets, then rises again to eventually set in the west. Mercury’s Surface Has a highly cratered surface that are less densely packed than the Moon’s surface. - Has gently rolling intercrater plains that cover 40% of the surface. The oldest surface. Scarps/Rupes: Very long and high cliffs that stretch across the surface Scarps/Rupes: Very long and high cliffs that stretch across the surface - Named after ships - Formed from the planet’s shrinkage Hollows: Deep pits with very steep walls that occur inside or near crater rims and ﬂoors. Most likely caused by being so close to the sun, solar erosion. - Unique to Mercury. Caloris Basin: 1400 km basin thought to be caused by an impact. Ringed by mountains 3 km high - Weird Terrain: Rippled territory on the opposite side of the impact zone, most likely caused by the shockwave from the impact. Just like the Moon, Mercury has permanently shadowed craters craters at the poles, which most likely contain water ice. Mercury’s Interior - Extraordinarily large iron core: 2100 km (~80% of diameter) - Thin and iron-poor mantle and crust: Top 400km Rotational inertia indicates an iron-sulﬁde layer outside the liquid iron core. Evolution of Mercury 1. After forming, Mercury melted and separated into layers. 2. Cooled down slower than the Moon, and thus has a thinner crust. This lead to molten ﬂooding, and the formation of intercrater plains 3. Mercury shrank as it cooled, causing Scarps/Rupes to form across the surface. Wesley Fowler ASTR Chapter 9 Venus Distance from Sun: 0.72 AU (2 planet from the Sun) Radius: 6,052 km 24.95 Earth radii) Mass: 4.87 x 10 kg (0.815 Earth Masses) Average Density: 5,250 kg/m (Implies differentiated) Rotational Period: -243.0 days Venus rotates CLOCKWISE Solar Day (Noon-to-Noon Day): 117 days o o Axial Tilt: 177.4 (to orbit, or 2o64 and retoograde rot.) Mean Temperature: 740 K (464 C or 870 F) Surface Pressure: 92 bar (Earth is 1 bar) Has an atmosphere Does not have a global magnetic ﬁeld: Very slow rotation Venus has an albedo of 0.7 Albedo: The amount of light reﬂected by an object (0-1) - 0 would be a perfect black body - 1 would perfectly reﬂect all light Venus’Orbit Orbits close to the sun, always appearing close to the Sun from Earth. Maximum distance is 47° - 3 brightest object in the sky next to the Sun and Moon - Has a full set of phases, observed by Galileo - Appears bigger in the sky when it orbits close to Earth Venus is the only planet with retrograde rotation - Axial Tilt of 177.4° Day is longer than the year. Rotational Period: 243.0 days Solar Day: 117 days (noon-to-noon) Orbital Period: 222 days Covered by very thick atmosphere, mostly comprised of CO 2 - Surface temperature of ~740K - Super-rotating atmosphere: Encircles Venus in about 4 days Venus’Surface Very young surface, about 300-600 million years old. Doesn’t have many impact craters - Crater counting dates Venus’surface as very young, from 300 million years to just under a billion years. - Two continent-sized highlands: Ishtar Terra and Aphrodite Terra. Cover 8% of surface - Mostly ﬂat lowlands - No plate tectonics, but has 167 volcanoes surface - Mostly ﬂat lowlands - No plate tectonics, but has 167 volcanoes - Can only be observed by using Radio or Infrared wavelengths Lakshmi Planum: Most prominent feature on Ishtar Terra, large plateau 1500 km across. Ovda Regio: The dominate feature of Aphrodite Terra, two ridges running in different directions. Maxell Monvccc s: Largest mountain/volcano on Venus, a shield volcano Venus’Volcanism Shield Volcanoes: Low proﬁle, wide based volcanoes. - Calderas: Impressions on the top of shield volcanoes - All of Venus’volcanoes are shield volcanoes The cracks on Venus, often associated with lava ﬂow, are indicative of a convective mantle. Lava Domes: Circular impression on Venus, formed by the collapse of domes formed by lava - Unique to Venus - Usually located near coronae Coronae: Venus’largest volcanic features, they are super lava domes. Huge circular lava regions. (100s- 1000s km in diameter) Likely produced by mantle convection. Volcanism is still presently active on Venus. 1. Large ﬂuctuation of sulfur dioxide above Venus’s clouds 2. Bursts of radio activity are similar to bursts have been observed on Earth 3. Large surface temperature variations on the order of days associated with known volcanic rift zones. Almost certainly active lava ﬂows on the surface. Venus’Atmosphere 90x the mass of Earth’s atmosphere, and has a much simpler design. - Troposphere goes up to 100km above the surface - Highly reﬂective sulfuric clouds between 50-70 km - Has no asthenosphere Super-rotating wind: 300-400 km/hr “jet stream” - Faster than the planet’s orbital rotation Below the haze are clear skies, sluggish air. Composition: CO (Carbon Dioxide) 96.5% 2 N 2Nitrogen) 3.5% - Top layer of clouds is made of sulfuric N 2Nitrogen) 3.5% - Top layer of clouds is made of sulfuric acid The high amount of carbon dioxide causes the atmosphere to absorb and reradiate around 99% of all infrared radiation released from the surface. This causes an extreme greenhouse effect on Venus. Earth and Venus shared a similar secondary atmosphere: Carbon dioxide, sulfur dioxide, water, and nitrogen compounds. - If Earth didn’t have oceans, it would probably have Venus’s atmosphere. Venus receives twice as much energy from the Sun because it’s 30% closer to it. - Causes oceans to ﬁrst evaporate, thus atmosphere thickens, thus temperature increases. Runaway Greenhouse Effect: The process of a planet’s surface temperature and atmospheric opacity contributing to the increase in the greenhouse effect. Wesley Fowler ASTR Chapter 10 Mars th Distance from Sun: 1.52 AU (4 planet from the Sun) Radius: 3,390 km (0.52 Earth radii) 23 Mass: 6.4 x 10 kg (0.11 Earth Masses) Average Density: 3,900 kg/m (LOW density) *Average density of surface rocks: 2,500kg/m 3 o Mean Temperature: 210 K (81.4 F) Max Temperature about 300 K Does have an atmosphere: Very thin (6% of Earth’s) Does not have a magnetic ﬁeld: No longer exists Mars’Orbit Orbital Period: 1.88 years (~687 days) Rotational Period (Sidereal Day): 24 hrs 37 min Semimajor Axis: 1.52 AU Eccentricity: 0.094 - Closest Opposition: 0.37 AU (Distance between Mars and Earth when closest to Earth) - Opposition to opposition roughly every 780 days. This is Mars’synodic period. Martian days are called sols Mars’axial tilt (obliquity) changes from 10 to 60 over very long periods of time Mars’Surface Has polar ice caps that show seasonal variability - Lowland Northern hemisphere: Smooth volcanic plains - Highland Southern hemisphere: Dark mountains Crater counting dates volcanic activity around 100 million years ago Surface Features Tharsis bulge: Contains four huge volcanoes - Size of North America, 10km above surface Tharsis bulge: Contains four huge volcanoes - Size of North America, 10km above surface Olympus Mons: The largest volcano on Mars, being 700 km across it covers a surface area equal to the size of Arizona. - Sticks out of atmosphere Hellas Basin: Large impact basin in the southern hemisphere. Valles Marineris: Huge canyon, the biggest in the solar system - 4000km long, deepest at 7km Water on Mars Runoff channels: Large, ancient river bed systems - Mostly in southern highlands - Active 4 billion years ago, which is the same as Mars’ atmosphere - Formation of clays - Suggest a wet period 4 billion years ago when the atmosphere was thick enough to support liquid water Outﬂow channels: Young areas characterized by a catastrophic ﬂood - Only appear in equatorial regions, closer to northern lowlands - Have tear-drop shaped “islands” - 3 billion years old - Suggest a wet period about 3.7-3 billion years ago by a catastrophic period of ﬂooding, possibly caused by the melting of ice on Mars. Water-ice currently exists on the surface of Mars. The higher latitudes have permafrost layers. - Supported by ﬂuidized ejecta features: Water underneath the surface ejecting out from an impact Recurring Slope Lineae (RSLs): Long dark streaks associated with hydrated salts. These disappear in colder temperatures. Where did the water go? 1. Into the subsurface where it remains frozen 2. Lost to space via the photodisassociation of H 2 into H a2d O . H2ving so little mass, the H 2an easily escape the low Martian gravity and escape to space, and the oxygen reacted with surface 3. Some locked in permanent North Polar Cap Martian Polar Caps Mars’ice caps are predominantly made of dry ice (CO ice), however residual North Polar Cap is 2 made of water-ice. - Mars’eccentricity leads the southern cap to generally be larger than the northern cap The seasonal caps grow and shrink each year - Composed of almost entirely carbon dioxide with temperatures lower than 150K - Southern ~4,000km Northern ~3,000km - Growth and shrinkage alters atmospheric pressure by around 30% The residual cap remains permanently frozen - Brighter and smaller than seasonal caps, The residual cap remains permanently frozen - Brighter and smaller than seasonal caps, - Southern ~350km almost all CO 2 - Northern ~1000km almost all water ice Mars’Atmosphere With no magnetic ﬁeld to protect itself, Mars’atmosphere was eroded away by solar wind - Mars lost its global magnetic ﬁeld 4 billion years ago - Mars’troposphere disappears at night because it’s too cold Composition: 95.3% CO 2 2.7% N 2 0.13% O 2 0.07% CO 0.03% water vapor Dust Storms: - Global dust storms once ever 5.5 years - 1-3 continent sized dust storm per Martian year Dust Devils: - Low wind speeds, bigger than Earth’s tornados Mars’Interior Core believed to be between 1,500 and 2,103km in radius. - Average density = 3900 kg/m (made of iron sulﬁde) Crust is about 50km thick Volcanos indicate Mars having a convective mantle Mars’ Moons Phobos and Deimos (fear and panic) - Only other terrestrial planet to have a moon - Moons are small compared to the Earth’s - Origin highly debated: possibly captured asteroids - Irregular in shape, look like asteroids - Very dark, albedo is ~0.06 Phobos’most distinct feature is the 10km wide Stickney Crater. The impact should have destroyed Phobos. Deimos is the smaller one. Wesley Fowler ASTR Chapter 11 Jupiter th Semimajor Axis is 5.2 AU (5 planet from the Sun) Orbital Period is 11.86 years Jupiter has 67 known moons Has three rings (all gas giants have rings) Synodic period is 398.9 days 4 brightest object in Earth’s sky Mean Radius: 69,900 km (~11 Earths wide) – Equatorial Radius: 71,492 km (11.21 E. Radii) – Polar Radius: 66,854 km (10.52 E. Radii) 27 Mass: 1.9 x 10 kg (318 Earth Masses) 3 Average Density: 1,300 kg/m 2 Surface Gravity: 24.8 m/s (2.53 g) Jupiter has the fastest rotation in the Solar System, making a complete rotation in 10 hours. Jupiter has a differentiated rotation, as in that it has different rotation rates at different latitudes. This is true for all gas giants Rotational Period: Equatorial: 9 hrs 50 min Polar: 9 hrs 55 min Magnetic Field: 9 hrs 55 min Jupiter has a differential radius, shaped as an Oblate Spheriod. This is caused by the planet’s very fast rotation rate. Jupiter has an atmosphere, and a magnetic field that is 20,000 times stronger than Earth’s Composition: Hydrogen (H ): 26.1% Helium (He): 13.8% Heavier Elements: 0.1% - Represents the primary composition of the entire universe, and our ancient solar nebula Jupiter’s Surface Features Banded structure of bright zones, and dark reddish belts - The zonal flow of each band is determined by eastward and westward wind Dark Belts: Eastward flow - Brownish-red - High-pressure, lower altitude Light Zones: Westward flow - Whitish - Low-pressure, high altitude Storms: Come in white ovals, red spots, and brown ovals - The Great Red Spot is a hurricane like storm, and can can fit three Earth’s inside it. Was first observed 300 years ago. Currently shrinking. - Brown Ovals are holes in the atmosphere, revealing the deepest layers of Jupiter Stratosphere: (Below the “surface”) Troposphere (Above the “surface”) - Top: Ammonia Ice Clouds [-40 km] - Mid [-60 km]: Ammonium hydrosulfide ice [maybe the red coloring agent] - Bottom [-80 km]: Water Ice (too deep to see) Jupiter has its own internal heat source leftover from its formation. - It is so hot below Jupiter’s “surface” that hydrogen exists purely as a liquid - Liquid metallic hydrogen: Hydrogen becomes an excellent conductor of electricity as it begins to liquidate and behave more like a metal. Being highly convective, the mantle creates an immensely strong dynamo effect, and thus a massive electromagnetic field. - Underneath the liquid metallic hydrogen is what is believed to be a rocky core (20,000K)
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