Introductory AstrSolar System
Introductory AstrSolar System ASTR 111
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This 18 page Class Notes was uploaded by Khalil Sawayn on Monday September 28, 2015. The Class Notes belongs to ASTR 111 at George Mason University taught by Jie Zhang in Fall. Since its upload, it has received 23 views. For similar materials see /class/215141/astr-111-george-mason-university in Astronomy at George Mason University.
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Date Created: 09/28/15
ASTR111 003 Lecture 11 Nov 13 2006 Fall 2006 Introduction To Modern Astronomy Introducing Astronomy Chap 16 Planets and Moons Chap 717 Ch7 Comparative Planetology I Ch8 Comparative Planetology II Ch9 The Living Earth Cth Our Barren Moon Chl 1 SunScorched Mercury Ch12 Cloudcovered Venus Ch13 Red Planet Mars Ch14 Jupiter and Saturn Ch15 Satellites of Jup amp Saturn Chl6 Outer World Chl7 Vagabonds of Solar System Venus Data Gilles Guiding Questions What makes Venus such a brilliant morning star or evening star What is strange about the rotation of Venus In what ways does Venus s atmosphere differ radically from our own Why do astronomers suspect that there are active volcanoes on Venus Why is there almost no water on Venus today Why do astronomers think that water was once very common on Venus Does Venus have the same kind of active surface geology as the Earth Brilliant Morning Star and Evening Star At its greatest eastern and western elongations Venus is about 47 from the Sun Earth39s orbit Morning Star Us at greatest at greatest western elongation eastern elongation rises nearly 3 hours before the Eanh 19quot 1 Sun High in the eastern sky at dawn Evening Star At greatest eastern elongation High above the western horizon after sunset Brilliant Morning Star and Evening Star It is the brightest object in the sky except the Sun and the Moon Venus is relatively large Close to the Sun Close to the Earth Strongly reflect the Sunlight by its cloudy atmosphere Thick Cloud Cover of Venus Venus is similar to the Earth in its size mass average density and surface gravity It is covered by unbroken highly reflective clouds that conceal its other features from Earthbased observers Crescent Venus The ring indicates atmosphere Cloudy Venus Peculiar Rotation Rotation is retrograde rotation is opposite of the direction of orbital motion Orbit motion around the Sun counterclockwise Venus s rotation on its axis clockwise Planets and satellites have prograde rotation except Venus Uranus and Pluto Venus exhibits retrograde Most planets exhibit I rotatlon ItS rotatlon around its axis is the V opposite of the direction I of orbital motion prograde rotation the direction of the planet39s rotation around its axis 39 is the same as the direction of orbital motion a Prograde rotation b Retrograde rotation Atmosphere Measured by Spacecraft and their landing probes Composition Mostly carbon dioxide 965 Remaining is Nitrogen 35 Temperature C 100 200 300 400 Surface Temperature 460 C in both dayside and nightside Density Very high 90 atm at the surface Both temperature and pressure decrease as altitude increases Altitude km o L1lLJIi txl 200 300 400 500 600 700 Temperature K 00001 0001 001 01 Pressure atm Atmosphere Dense greenhouse gas 002 raises the surface temperature by more than 400 C Venus has three layers of highaltitude clouds from 48 km to 68 km Venus s clouds consist of droplets of concentrated sulfuric acid H2804 highly corrosive Temperature C 100 O 100 200 300 400 iPularvriiggjcloudsV V fea ur39e 39 Middlemloudnlayer LowewdoudJayer r 1 quotii Altitude km Pressure atm 200 300 400 500 600 700 Temperature K Venus s Clouds Sulfuric acid in the clouds come from the sulfurous gas injected into the atmosphere by volcano Hotspot volcanism a hot region beneath the planet s surface extrudes molten rock over a long period of time eg the Havaiian volcanoes Ongoing volcanic activity Unexpected high level of sulfuric acid in 1978 and steadily declined over the next years Clouds may be replenished by active volcanoes Mount St Helens Earth 1980 Venus s Clouds Relatively young lava flows are seen from volcanoes The lack of craters on the surface suggests that the entire surface of Venus is no more than a few hundred million years old Maat Mons volcano Young lava flows from Maat Mons Venusian Volcano by Radar Climate Evolution Venus versus Earth Similarities Venus and Earth are similar in size mass density and surface gravity The early atmospheres of both Venus and Earth were similar in content water vapor H20 carbon dioxide 002 and Sulfur dioxide 802 that have outgassed from volcanism Venus versus Earth Disparities now The Earth has abundant water in its oceans and little carbon dioxide in its relatively thin atmosphere The Venus is very dry and its thick atmosphere is mostly carbon dioxide Climate Evolution On the Earth H20 and 002 are recycled Water Vapor falls as rain forming the oceans 002 dissolves in the water falling into the ocean 002 and H20 are incorporated into sedimentary rocks As a result most 002 is removed from the atmosphere and locked into the Earth s rocks 1 H20 C02 and 502 are outgassed from volcanoes 2 H20 falls as rain co2 and so2 dissolve in the oceans 3C02 SOZand smieillzio are 7 incorporated into sedimentary rocks 4The sedimentary rocks are eventually subducted to great depths where heat liberates the gases a EarthH OCO and SO are recycled 2 2 2 Climate Evolution On the Venus the atmosphere experienced a runaway greenhouse effect In the early history it may also have liquid ocean But temperature is relatively higher the atmosphere has relatively more water vapor The greenhouse effect of the water vapor raised the temperature and more liquid water evaporated This further intensified the greenhouse effect and raised the temperature even higher This runaway process continued until oceans disappeared Almost all of the water vapor was eventually lost by the action of ultraviolet radiation on the upper atmosphere Climate Evolution Without ocean to dissolve in the outgassed CO2 would accumulate in the Venus s atmosphere The Earth has roughly as much carbon dioxide as Venus but it has been dissolved in the Earth s oceans and chemically bound into its rocks A 2With no oceans to dissolve in C02 becomes part of the atmosphere 1 H20 C02 and from volcanoes SO2 are outgassed 3 Some H20 and 502 combine to form HZSO4 sulfuric acid in Venus s clouds b Venus H20C02and 02 are NOT recycled l C 4 Remaining H20 molecules break apart due to ultraviolet radiation from the Sun 5 Remaining 02 molecules are locked up in minerals gt Atmosphere Clouds Surface The surface of Venus is surprisingly flat with only a few major highlands and several large volcanoes The surface of Venus shows no evidence of plate tectonics or the motion of large crustal plates No long chain of volcanic mountains 39t39 39 Tethus ISHTAR TERM Regio 1 Metis 39 I Lakshmi 7 Planum Fo rtuna PHRQDIT E o t a a Thetis Regio ch 39 ta 0 D Regio Interior No seismic data available to give a definite answer The presence of volcanisms suggests a molten interior Venus has no planetwide magnetic field possibly due to the fact that Venus rotates too slow Venus has no plate tectonics possibly due to that the crust is too hot and soft to move in rigid plates Extension volcanoes over upwellings Compression andquotpileupquot over downwellings Hot plastic crust Convecting mantle b VenuszThe crust may be too hot and soft to move in rigid platesThe absence of water may limit motions beneath the crust
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