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venus and mars
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  • 1. Venus and Mars 0
  • 2. Venus and Mars Two most similar planets to Earth:
    • Similar in size and mass
    • Atmosphere
    • Similar interior structure
    • Same part of the solar system
    Yet, no life possible on either one of them. 0
  • 3. Venus Earth’s Twin
  • 4. Venus The Rotation of Venus Almost all planets rotate counterclockwise, i.e. in the same sense as orbital motion. Exceptions: Venus, Uranus and Pluto Venus rotates clockwise, with period slightly longer than orbital period. Possible reason:
    • Off-center collision with massive protoplanet
    0
  • 5.  
  • 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
  • 7.
    • Venus has a runaway greenhouse effect
    • because its atmosphere is rich in CO 2
  • 8. The Surface of Venus
    • Early radar images from Earth and satellites revealed mountains, plains, craters. However the surface is DOMINATED BY VOLOCANISM
    Venera 13 photograph of surface of Venus : Colors modified by clouds in Venus’ atmosphere
    • More details was obtained from orbiting and landing spacecraft:
    After correction for atmospheric color effect: 0
  • 9. Radar Map of Venus’ Surface Surface features shown in artificial colors.
    • Scattered impact craters
    • Volcanic regions
    • Smooth lava flows
    0
  • 10. “ Blob” or Hot-Spot Tectonics
    • Rather than plate tectonics, Venus appears to have many mantle hot spots (upwelling mantle currents or plumes).
    • What might this mean about the crust of Venus?
  • 11.  
  • 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
  • 14.  
  • 15. Coronae or Arachnoids
    • Enormous circular structures with raised rims and lowered floors.
      • resemble volcanic calderas.
      • have a sunken “moat” just inside the rim
  • 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
  • 18. What’s Missing? Craters
    • Venus has few craters. Craters tend to be larger than 5 km in diameter. Why?
    • Venus has few craters for 2 reasons:
      • lava flows have covered many
      • small meteors have difficulty making it to the surface.
  • 19.  
  • 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
  • 22. Venus Magnetic Field
    • Complicated history; still poorly understood.
    • Very similar to Earth in mass, size, composition, density, but no magnetic field -> Core solid?
    • Solar wind interacts directly with the atmosphere, forming a bow shock and a long ion tail.
    • CO 2 produced during outgassing remained in atmosphere (on Earth: dissolved in water).
    • Any water present on the surface rapidly evaporated -> feedback through enhancement of greenhouse effect
    0
  • 23. The Little Desert Planet 1
  • 24. Mars
    • Diameter ≈ ½ Earth’s diameter
    • Very thin atmosphere, mostly CO 2
    • Rotation period = 24 h, 40 min.
    • Axis tilted against orbital plane by 25 o , similar to Earth’s inclination (23.5 o )
    • Seasons similar to Earth -> Growth and shrinking of polar ice cap
    • Crust not broken into tectonic plates
    • Volcanic activity (including highest volcano in the solar system)
    0
    • Orbital period
    • around the sun = 687 days
  • 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
  • 27. History of Mars’ Atmosphere
    • Initial atmosphere from outgassing.
    • Small mass of Mars; moderate temperatures
    • Lighter gasses:
    • Molecule velocity greater than escape velocity: -> gasses escape into space .
    • Mars has lost all lighter gasses; retained only heavier gasses (CO 2 ).
    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
  • 30. Surface Features Overview
    • N vs. S differences
    • Tharsis Plateau
    • Volcanoes
      • Shield Volcanoes
      • Patera Volcanoes
    • Planitia
    • Valles Marineris
      • Outflow Channels
    • Polar Ice Caps
    • Canals?
    • Evidence of Past Water
  • 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
  • 35. Volcanoes on Mars
    • 2 types of volcanoes: shields and pateras.
    • Shield volcanoes are wide and low. Because of the low viscosity of lava on Mars.
  • 36. The main shield volcanoes on Mars are Olympus Mons, and the aligned shield volcanoes: Ascraeus Mons Parvonis Mons Arsia Mons 41
  • 37. Olympus Mons
    • If one edge were in Lancaster, the opposite edge would be in Chicago!
    • At 15 miles or 80,000 feet, the crater is above Mars’ thin atmosphere.
    • You could stand on Mars’ surface and be in space at the same time!
    43
  • 38. Olympus Mons
    • 27 kilometers above mean datum.
      • 3x higher than Mt. Everest
      • 2.6x taller than Mauna Kea (from sea floor base to caldera)
    • Slope is only 2.5 o .
    • Surrounded by an escarpment up to 6 km high.
    • Caldera is 85 km x 60 km.
    44
  • 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
  • 43. From high to low – the Planitia
    • Hellas Planitia
      • 9 km deep
      • 2100 km across
      • rim is 1.25 km high
      • impact debris thrown out to a distance of 4000 km
    • Argyre Planitia
      • 5 km deep
      • 1800
      • several deep channels flow into it from surrounding terrain
    52
  • 44. www.astro.virginia.edu/class/oconnell/astr121/im/global-altim-hel-hem.jpg Hellas 53
  • 45. Light-colored Hellas Planitia 54
  • 46. Valles Marineris
    • Huge canyon system
      • 4000 km long
      • up to 600 km wide
      • up to 10 km deep (6-7 times deeper than our Grand Canyon)
      • NOT formed by flowing water! (but possibly modified by water)
      • How was it formed?
    55
  • 47. 56
  • 48. 63
    • Near the eastern end of the Valles Marineris are huge canyons called “outflow channels”.
  • 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
  • 57. Atmosphere Origins
    • Outgassing
    • Volcanoes.
    • CO 2 and H 2 O main gases.
    • Mt. St. Helens
  • 58. Atmosphere Loss
    • Thermal escape “boiling away” by temperature.
    • “ Knocking away” by solar wind particles.
    • UV-rays break molecules into smaller atoms.
      • Lighter atoms boil away.
    • Absorbed by surface
    • “ Blasted away” by impacts
  • 59. Thermal Escape
    • Atoms have mass.
    • Attracted to planet by gravity.
    • Temperature is measure of atoms motion.
    • High temperature = high velocity: escape velocity if too light.
  • 60. Knocking away
    • Sun blows off solar wind:
      • Protons
      • Electrons
      • Neutrons
    • Billiards with atmosphere (if no magnetosphere).
  • 61. Dissociation
    • Atoms held together in molecules by electromagnetic forces.
    • UV-rays source of energy.
    • Break molecular bonds.
    • Light elements (H) can boil away.
    • Importance of protective ozone layer.
  • 62. Absorption
    • Chemical reactions.
      • Rust for O 2 .
      • Carbonate rocks for CO 2 (when H 2 0 is present)
  • 63. Venus Today
  • 64. Venus Today
    • Pressure = 90 bars.
    • Temperature = 880 F.
    • No pole/equator temperature difference.
    • No day/night temperature difference.
    • No seasonal temperature difference.
    • No rain hits surface.
    • No storms.
    • Little wind.
  • 65. Venera Landers
    • Venera 13 and 14 color images from red, green and blue filters.
    Copyright: Don P. Mitchell – Mentallandscape.com
  • 66.  
  • 67.  
  • 68.  
  • 69. What went wrong on Venus?
    • Same size as Earth.
    • Same outgassing as Earth.
      • Same CO 2 content.
      • What happened to atmospheric H 2 O?
    • Higher initial temperature.
  • 70. What went wrong on Venus?
    • Higher initial temperature.
    • More water evaporates.
    • Atmosphere can hold more H 2 O before rains.
    • H 2 O is greenhouse gas – increases temp.
    • More water evaporates.
    • Feedback mechanism.
    • All H 2 O evaporates.
    • No oceans, seas or lakes.
  • 71. … it gets worse on Venus.
    • No water for CO 2 to react.
    • Increases greenhouse effect further.
    • UV-rays dissociate H 2 O.
    • H lost to space.
    • Result, 100% of CO 2 in atmosphere.
    • Runaway greenhouse effect.
    • Hot, dry, Venus today.
    • Good scientific theory?
    • Venus once like Earth?
  • 72. Mars Today
    • Pressure just below triple point of water:
      • 0.01 bar
    • Temperature below freezing:
      • -50 C
    • No rain, some clouds, dust, ice caps.
  • 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
  • 79. What went wrong on Mars?
    • Size.
    • Too small – core cools
    • Core cools – magnetic field stops (not magnetosphere).
    • Atmosphere CO 2 stripped by solar winds.
    • UV-rays dissociate H 2 O
    • H boils away
    • O rusts rocks
    • No CO 2 or H 2 O, no greenhouse effect.
    • Cold, dry Mars today.
    • Good scientific theory?