The document discusses Venus and Mars, comparing their similarities to Earth but differences that make life impossible. Venus has a runaway greenhouse effect that led to extremely high temperatures. Its atmosphere is 96% carbon dioxide. Mars has a thin atmosphere that has lost lighter gases over time, leaving it mostly carbon dioxide. Both planets show evidence of past volcanic activity but lack plate tectonics and water on their surfaces today.

1. Venus and Mars 0

3. Venus Earth’s Twin

6. The Atmosphere of Venus UV image Extremely inhospitable: 96 % carbon dioxide (CO 2 ) 3.5 % nitrogen (N 2 ) Rest: water (H 2 O), hydrochloric acid (HCl), hydrofluoric acid (HF) 4 thick cloud layers ( -> surface invisible to us from Earth). Very stable circulation patterns with high-speed winds (up to 240 km/h) Extremely high surface temperature up to 745 K (= 880 o F) Very efficient “greenhouse”! 0

12. On earth, mantle plumes couple with plate movements to make island chains. What would be formed without the plate movement?

13. Venus is dominated by…volcanos Maat Mons

16. Shield Volcanoes Found above hot spots: Fluid magma chamber , from which lava erupts repeatedly through surface layers above. All volcanoes on Venus and Mars are shield volcanoes 0

17. Volcanic Features on Venus Baltis Vallis: 6800 km long lava flow channel (longest in the solar system!) Coronae: Circular bulges formed by volcanic activity Aine Corona Lava flows Pancake Domes: Associated with volcanic activity forming coronae Some lava flows collapsed after molten lava drained away 0

20. Crater Aurelia

21. Craters on Venus Nearly 1000 impact craters on Venus’ surface: -> Surface not very old. No water on the surface; thick, dense atmosphere -> No erosion -> Craters appear sharp and fresh 0

23. The Little Desert Planet 1

25. The Atmosphere of Mars Very thin: Only 1 % of pressure on Earth’s surface 95 % CO 2 Even thin Marsian atmosphere evident through haze and clouds covering the planet Occasionally: Strong dust storms that can enshroud the entire planet. 0

26. The Atmosphere of Mars (II) Most of the Oxygen bound in oxides in rocks -> Reddish color of the surface 0

28. The Atmospheric Temperature Structures of the Terrestrial Planets 0

29. Geology of Mars Northern Lowlands: Free of craters; probably re-surfaced a few billion years ago. Southern Highlands: Heavily cratered; probably 2 – 3 billion years old. Possibly once filled with water. 0

31. North vs. South

32. Typical N. hemisphere region

33. Typical S. hemisphere region

34. Olympus Mons Alba Patera (Volcanoes) Aligned Shield Volcanoes Valles Marineris

36. The main shield volcanoes on Mars are Olympus Mons, and the aligned shield volcanoes: Ascraeus Mons Parvonis Mons Arsia Mons 41

39. Olympus Mons 46

40. The other type of volcano is a patera – a huge crater with almost no slope around it. Larger, but lower, than shield volcanos. Apollinaris patera http://www.the-planet-mars.com/pictures/Apollinaris-Patera-volcano.jpg 49

41. Alba Patera – almost no slope, huge caldera 50

42. 51

44. www.astro.virginia.edu/class/oconnell/astr121/im/global-altim-hel-hem.jpg Hellas 53

45. Light-colored Hellas Planitia 54

47. 56

49. Hidden Water on Mars No liquid water on the surface: Would evaporate due to low pressure. But evidence for liquid water in the past: Outflow channels from sudden, massive floods Collapsed structures after withdrawal of sub-surface water Valleys resembling meandering river beds Gullies, possibly from debris flows Central channel in a valley suggests long-term flowing water 0

50. Hidden Water on Mars (II) Gusev Crater and Ma’adim Vallis: Giant lakes might have drained repeatedly through the Ma’adim Vallis into the crater. 0

51. Evidence for Water on Mars Large impacts may have ejected rocks into space. Galle, the “happy face crater” Meteorite ALH84001: Identified as ancient rock from Mars. Some minerals in this meteorite were deposited in water -> Martian crust must have been richer in water than it is today. 0

52. Ice in the Polar Cap Polar cap contains mostly CO 2 ice, but also water. Multiple ice regions separated by valleys free of ice. Boundaries of polar caps reveal multiple layers of dust, left behind by repeated growth and melting of polar-cap regions. 0

53. The Moons of Mars Phobos (Fear) Deimos (Demons) Two small moons: Phobos (diameter ~ 25 km) and Deimos (diameter = 12 km). Too small to pull themselves into spherical shape. Very close to Mars; orbits around Mars faster than Mars’ rotation. Typical of small, rocky bodies: Dark grey, low density. Probably captured from outer asteroid belt. 0

54. Terrestrial Planets Mercury Venus Earth Mars

55. Natural Climate Change When Good Planets go Bad What happened to them?

56. The Terrestrial Planets H2O and CO2 clouds, dust Winds, dust storm -81F 0.007bar 95% CO 2 2.7% N 2 Mars none none Day:260F Night: 280F 10 -14 bar He, Na, Ar Moon H2O clouds, pollution Winds, hurricanes, rain, snow 60F 1 bar 77% N 2 21% O 2 H 2 O Earth Sulfuric acid clouds Slow winds, acid rain 880F 90 bars 96% CO 2 3.5% N2 Venus none none Day: 800F Night: -280F 10 -14 bar He, Na, O Mercury Clouds, Hazes Winds, Weather Ave Surface Temp. Surface Pressure Atmos. Compsn. World

63. Venus Today

73. 26

74. The War of the Worlds www.cloudster.com/Sets&Vehicles/WarOfTheWorlds drzeus.best.vwh.net / wotw/illus/interior.html 27

75. www.retrocrush.com / 100monsters/70.html 28

76. “ This is Glub, sitting in for Tom Dunn on the ‘ Eleven O’Clock News,’ and I wish to announce that there has been a rather sudden and sweeping change in your government. 29

77. Gusev

78. Meridiani Planum