A1 09 Venus Mars Atmos
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A1 09 Venus Mars Atmos

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Prof. Miller's Astronomy 1 lecture notes on Venus and Mars's Atmosphere

Prof. Miller's Astronomy 1 lecture notes on Venus and Mars's Atmosphere

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    A1 09 Venus Mars Atmos A1 09 Venus Mars Atmos Presentation Transcript

    • Venus’s Atmosphere LACC: §9.3, 9.5, 9.6 • Venus’s surface environment • Venus’s atmospheric evolution = run-away greenhouse • Venus’s cloud cover An attempt to answer the “big questions”: what is out there? Are we alone? Thursday, March 11, 2010 1
    • Venus http://www.astrosurf.com/nunes/explor/explor_m10.htm Thursday, March 11, 2010 2
    • Venus: Atmosphere 90 bars surface Composition pressure • CO2 96% 850°F average • N2 3.5% surface temperature (hotter than • Ar 0.006% Mercury due to a • O2 0.003% 920°F greenhouse effect) • Ne 0.001% winds of a few mph Thursday, March 11, 2010 3
    • Venus: Greenhouse Effect http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap09/FG09_19.jpg Thursday, March 11, 2010 4
    • Venus: Runaway Greenhouse Effect Due to high temperatures, some (all?) of Venus’s H2O was in a gaseous state instead of a liquid state. As an atmospheric gas, the sun’s uv light broke the H2O molecules apart--photodissociation. The lighter H left the atmosphere--thermal escape; the heavier O is quite reactive and bonded with C (to make CO2), surface rocks (e.g. rust), or left the atmosphere via thermal escape. Less water in general means less liquid water for the CO2 to dissolve in to, so atmospheric CO2 levels increase. Higher atmospheric CO2 levels increase the surface temperature--greenhouse effect. Higher temperatures convert more liquid H2O into a gas. (Return to top and repeat.) Thursday, March 11, 2010 5
    • Venus: H2SO4 Clouds http://lasp.colorado.edu/~bagenal/3720/CLASS16/16EVM-Dyn2.html Thursday, March 11, 2010 6
    • Venus: Atmosphere Sulfuric acid, H2SO4, clouds! Sulfur dioxide SO2 and H2O can combine to make H2SO4. SO2 comes from volcanoes; but on Venus, SO2 becomes sulfuric acid clouds because there is no liquid water to dilute it. Thursday, March 11, 2010 7
    • Venus: Venera 13 & 14 Even though it’s covered by sulfuric acid clouds and has a surface air pressure of 90 bar, the Soviets managed several probe landings: Venera and Vega probes. http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-venus.html Thursday, March 11, 2010 8
    • Venus’s Atmosphere LACC: §9.3, 9.5, 9.6 • Venus’s surface environment: 96% CO2, 90 bars, 850°F (planet-wide), slow rotation so less wind/ erosion, constant cloud cover • Venus’s atmospheric evolution = run-away greenhouse: high temperatures result in H2O gas which photodissociates, less liquid water so less CO2 dissolves out, high CO2 levels raise the temperature because of greenhouse effect... • Venus’s cloud cover: sulfuric acid clouds An attempt to answer the “big questions”: what is out there? Are we alone? Thursday, March 11, 2010 9
    • LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed. • Ch. 9, pp. 219-220: 4. Due at the beginning of the next class period. Test covering chapters 6-9 next class period. Be thinking about the Solar System Project. Thursday, March 11, 2010 10
    • Mars’s Atmosphere LACC: §9.3, 9.5, 9.6 • Mars’s surface environment • Mars’s atmospheric evolution = run away refrigerator • Mars’s clouds An attempt to answer the “big questions”: what is out there? Are we alone? Thursday, March 11, 2010 11
    • Mars http://rosetta.jpl.nasa.gov/dsp_images.cfm?buttonSel=gallery&buttonSelL2=images&category=mars Thursday, March 11, 2010 12
    • Mars: Atmosphere Composition -67°F surface temperature • CO2 95.3% • 80°F hot day • N2 2.7% • -200°F cold night • Ar 1.6% (11°F greenhouse) • O2 0.15% • Ne 0.0003% winds of a few mph; 0.007 bar pressure massive dust storms Thursday, March 11, 2010 13
    • Mars’ Surface Polar caps of H2O and CO2 ice. Channels and gullies indicate liquid water flowed, but over 3 billion years ago. Wind erosion occurs. Thursday, March 11, 2010 14
    • Mars: Runaway Refrigerator Effect Mars’s lower surface gravity (0.38g) means it lost it’s atmospheric gases more readily--thermal escape. As the planet’s atmosphere thinned, the greenhouse effect became less significant, so Mars grew colder. Mars became so cold, even CO2 began to condense out of the atmosphere. As CO2 condensed out of the atmosphere, the greenhouse effect became less significant so Mars grew even colder... i.e. a runaway refrigerator effect. Eventually Mars became so cold and the air pressure too low for liquid H2O to exist on its surface. Thursday, March 11, 2010 15
    • Mars: Atmosphere Occasionally, clouds of dust, H2O, and/or CO2 form. The surface pressure is too low for liquid H2O, even when the temperature does get above freezing. CO2 freezes at about -190°F. Much of Martian polar ice-caps are frozen CO2 (a.k.a. dry ice). Thursday, March 11, 2010 16
    • Mars: Dust Storms http://antwrp.gsfc.nasa.gov/apod/ap030602.html http://abyss.uoregon.edu/~js/images/mars_dust_storm.gif http://www.nasa.gov/mov/330028main_close_720p_A.mov Because the martian atmosphere is thin--about 1% as dense as Earth's at sea level--only the smallest dust grains hang in the air. "Airborne dust on Mars is about as fine as cigarette smoke," says Bell. http://science.nasa.gov/headlines/y2003/09jul_marsdust.htm Thursday, March 11, 2010 17
    • Mars: Landslide http://photojournal.jpl.nasa.gov/catalog/PIA10245 Thursday, March 11, 2010 18
    • Mars: Landslide The scarp in this image is on the edge of the dome of layered deposits centered on Mars' north pole. From top to bottom this impressive cliff is over 700 meters (2300 feet) tall and reaches slopes over 60 degrees. The top part of the scarp, to the left of the images, is still covered with bright (white) carbon dioxide frost which is disappearing from the polar regions as spring progresses. The largest cloud (upper images) traces the path of the debris as it fell down the slope, hit the lower slope, and continues downhill, forming a billowing cloud front. This cloud is about 180 meters (590 feet) across and extends about 190 meters (625 feet) from the base of the steep cliff. http://photojournal.jpl.nasa.gov/catalog/PIA10245 Thursday, March 11, 2010 19
    • Mars: Liquid Water http://www.msss.com/mars_images/moc/2006/12/06/gullies/sirenum_crater/index.html Thursday, March 11, 2010 20
    • Mars: Faces On Mars http://stardate.org/resources/gallery/gallery_detail.php?id=71 http://apod.nasa.gov/apod/ap990315.html Thursday, March 11, 2010 21
    • Mars: Deep Holes On Mars In a close-up from the HiRISE instrument onboard the Mars Reconnaissance Orbiter, this mysterious dark pit, about 150 meters across....Lacking raised rims and other impact crater characteristics, this pit and others like it were originally identified in visible light and infrared images from the Mars Odyssey and Mars Global Surveyor spacecraft. While the visible light images showed only darkness within, infrared thermal signatures indicated that the openings penetrated deep under the martian surface and perhaps were skylights to underground caverns. In this later image, the pit wall is partially illuminated by sunlight and seen to be nearly vertical, though the bottom, at least 78 meters below, is still not visible. The dark martian pits are thought to be related to collapse pits in the lava flow, similar to Hawaiian volcano pit craters. http://apod.nasa.gov/apod/ap070928.html Thursday, March 11, 2010 22
    • Mars: Martian Meteorites Splotches of glassy material Comparison of Viking-measured contain trapped martian Mars atmosphere to trapped gases atmosphere. in EETA79001 Shergottite glass. Rock is 16 cm across. Figure is from Pepin, R. O., 1985, Evidence of Martian Origins, Nature, 317, p. 473-475. http://www.psrd.hawaii.edu/July99/EETA79001.html Thursday, March 11, 2010 23
    • Mars: Martian Meteorites http://www.aerospaceweb.org/question/astronomy/q0193.shtml Thursday, March 11, 2010 24
    • Mars: Martian Meteorites The most tantalizing clue found so far came from a meteorite discovered in Antarctica. Named ALH 84001, this hunk of space debris is believed to have been blasted off the surface of Mars about 16 million years ago. The rock survived the perils of space and a fiery trip through the Earth's atmosphere to land in Antarctica some 13,000 years ago. The meteorite was discovered in 1984, but it was not until 1996 that scientists announced evidence of life in the ancient rock. Though the findings are still controversial, the meteorite contains fossilized remains that could be a primitive form of bacteria. If so, ALH 84001 is the first hard evidence that life of any kind evolved on a planet other than Earth. http://www.aerospaceweb.org/question/astronomy/q0193.shtml Thursday, March 11, 2010 25
    • Mars’s Atmosphere LACC: §9.3, 9.5, 9.6 • Mars’s surface environment: 95% CO2, 0.007 bars, -67°F (±100+), winds of a few mph, massive (fine) dust storms, wispy clouds • Mars’s atmospheric evolution = run away refrigerator: low surface gravity (0.38g) means thermal escape of atmosphere; less atmosphere means less greenhouse effect, so temperatures fall; H2O, CO2 condense, so temperatures fall... • Mars’s clouds: H2O, CO2, fine dust An attempt to answer the “big questions”: what is out there? Are we alone? Thursday, March 11, 2010 26
    • LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed. • Ch. 9, pp. 219-220: 7. • Study for the test on the Inner Planets (Chapters 6-9) Due at the beginning of the next class period. Test covering chapters 6-9 next class period. Be thinking about the Solar System Project. Thursday, March 11, 2010 27
    • Review for the Test 2 of 5: The Terrestrial Planets [10 pts] Compare and contrast the physical properties of Mercury, [10 pts] Compare and contrast the atmospheric properties of Venus, Venus, Earth, Luna, and Mars. Earth, and Mars. • mass, size, density, notable surface features (Caloris Basin, • Composition and Surface Pressure: Venus--90-bar 850°F Chicxulub crater, maria, highlands, Tycho, Tharsis Bulge, CO2, Earth--1-bar 59°F N2 (and O2), Mars--0.007-bar Olympus Mons, Valles Marineris) -58°F CO2 • Interiors: core (inner/outer, (Mercury’s vs Luna’s). mantle, • Clouds: Venus--H2SO4 sulfuric acid (radar ranging), crust); seismic waves Earth--H2O water, Mars--H2O water, CO2 carbon dioxide, • orbits (distance from the sun, eccentricity, inclination, fine dust length of a year) and rotational properties (axial tilt, solar • Temperature--Mercury 797°F to -283°F, Venus 850°F vs. sidereal day, spin:orbit resonance, tide locking) (hotter than Mercury), Earth--59°F average, Moon--257°F to -283°F, Mars-- -67±100+°F [10 pts] Understand the processes that shaped the terrestrial planet’s surfaces. [10 pts] Understand the processes that shape the terrestrial planet’s • Collapse of solar nebula, Condensation (frost line), atmosphere. Accretion (planetesimals, differentiation), Heavy • How early atmospheres (CH4, NH3, H2O, CO2) become Bombardment, Cooling (don’t forget scarps), clearing an mature atmospheres (N2 w/ H2O oceans or CO2): orbit of debris outgassing by volcanoes, dissociation by solar uv, • Tectonic Activity: Core-Interior Heat (radioactive decay), thermal escape, liquid water?, condensation Mantel-Convection, Crust (coronae, ridges and cracks, • Greenhouse Effect (Venus--runaway greenhouse, Mars-- Plate Tectonics, maria, Valles Marineris) runaway refrigerator, Earth--just right) • Age of planetary surface: radiometric dating (Earth, Luna), • Evidence and effect of life on the planets (Martian number of impact craters, erosion, resurfacing--extensive meteorites, oldest fossils, extinction events, O2) volcanic activity or plate tectonics [10 pts] Identify objects from a picture. • Mercury, Venus, Earth, Luna, Mars, Phobos, and Deimos from space • Venus, Earth, Luna, Mars from the surface • Shield Volcanoes, “Pancake” Lava Domes, Scarps, impact craters, coronae Thursday, March 11, 2010 28