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General Features

General Features. Mass: M Earth = 6 x 10 27 g Radius: R Earth = 6378 km Density:  = 5.5 g/cm 3 Age: 4.6 billion years Orbital period = 365 days Rotation period = 1 day. Clicker Question:. A moon covered with numerous and very old craters created by meteorite impacts likely

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General Features

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  1. General Features Mass: MEarth = 6 x 1027 g Radius: REarth= 6378 km Density:  = 5.5 g/cm3 Age: 4.6 billion years Orbital period = 365 days Rotation period = 1 day

  2. Clicker Question: A moon covered with numerous and very old craters created by meteorite impacts likely A: has no ocean to cover the craters B: orbits a large Jupiter sized planet C: a cold, solid interior D: has no protective magnetic field

  3. Clicker Question: Volcanoes are usually found in places where A: the low pressure of the aptmosphere pulls the lava/magma to the surface B: earthquakes occur from oceanic plates colliding with continental plates C: deep-rooted mountains have cracked the Earth’s crust D: the Earth’s rotation has caused weak spots in its crust

  4. Clicker Question: The change in position of the continents over time is primarily caused by A: the continental plates floating on the ocean B: mantle material circulating inside the Earth C: the Earth’s slow shrinking as it cools D: global wind patterns and sustained ocean currents

  5. Terrestrial Planets' Spin, Habitability

  6. Mercury Mass = 3.3 x 1026 g = 0.055 MEarth = 2439 km = 0.38 REarth Radius Density = 5.4 g/cm3 (Earth 5.5 g/cm3) = 0.38 that of Earth Gravity Semimajor axis = 0.39 AU

  7. Discovery of Water Ice on Mercury Goldstone 70m radar received by the VLA Polar regions could be 125 K and never warmed by the Sun

  8. Orbit of Mercury 3:2 resonance with the sun Orbital period of 88 days Sidereal rotation of 59 days 1 “day” on mercury = 176 earth days Daytime temp = 500 K Nighttime temp = 100 K

  9. Structure of Mercury (from Mariner 10 and theoretical arguments) 1.Crust 100-200 km thick 2. Mantle 600 km thick 3. Core, 1800 km in radius And no atmosphere, so no wind or erosion. Surface reflects geologic history well.

  10. Messenger at Mercury in 2011

  11. Venus Mass = 0.82 MEarth Radius = 0.95 REarth Density = 5.2 g/cm3 Average distance from Sun = 0.72 AU Orbital period = 225 days Rotation period = 243 days (longer than orbital period, and retrograde!)

  12. Venus' Atmosphere - Pressure at surface is 90 x that of Earth's => much more gas in atmosphere. No oceans. - Consequence - meteoroids burn up easily. No impact craters less than ~3 km. - 96.5% CO2 - Yellowish color from sulfuric acid clouds and haze. - Hot at surface - 730 K! Almost hot enough to melt rock - Why so hot? Huge amount of CO2 leads to strong greenhouse effect.

  13. Early on, T may have been much lower (but still warmer than Earth). Oceans? But if warm enough, T would start to rise because of... Runaway Greenhouse Effect 1) Water and CO2 evaporate from oceans into atmosphere. 2) Greenhouse effect more efficient. 3) Temperature rises. 4) More evaporation (back to #1). => complete evaporation of oceans. Thick atmosphere.

  14. Missions to Venus Soviet Venera 4 -18 (1967 - 1983) Mariner 2, 5 and 10 (1962, 1967 and 1974) Pioneer Venus (1978) Magellan (1989) Venera 13 photo of surface. Rocks are basalt and granite. Color is due to atmosphere. Color corrected for atmosphere.

  15. "Radar Echo" technique measures altitude Magellan probe time for signal to return tells you the altitude of surface feature. Planet Surface

  16. Radar data (Pioneer Venus mission) reveal altitude variations on surface. Flatter than Earth, no evidence for plate boundaries => no large scale plate tectonics. But plenty of evidence of stresses and fractures on smaller scales => much small-scale shifting of crust 1 km

  17. Impact Craters Unlike Moon, larger impact craters distributed randomly over surface => all parts of surface have about same age. Paucity of large impact craters => surface is young, 200-500 million years?

  18. Volcanism Shield volcano elevation map from Magellan radar data. About 100 km across. Volcanism may be ongoing, based on sulfur dioxide variations in atmosphere. But very little resurfacing in past 200-500 million years.

  19. Volcanism Shield volcano elevation map from Magellan radar data. About 100 km across. Volcanism may be ongoing, based on sulfur dioxide variations in atmosphere. But very little resurfacing in past 200-500 million years. Venus surface flyover

  20. Clicker Question: Venus and the Earth are very similar (within 10%) in their: A: Amount of carbon dioxide in their atmospheres. B: Distance from the Sun. C: Surface gravity. D: Length of a day. E: All of the above.

  21. Clicker Question: It takes 8 minutes for light to travel 1 AU, how long does it take for a radar signal to travel from Earth to Mercury and back at its closest point to Earth in its orbit? A: 1 minute B: 10 minutes C: 2 hours D: 2 days E: 1 year

  22. Mars eccentricity = 0.093 Range in distance from Sun = 1.38 - 1.66 AU Rotation Period = 24.6 hours Orbital Period = 687 days Mass = 0.11 MEarth Radius = 0.53 REarth Density = 3.9 g/cm3 Average distance from Sun = 1.52 AU

  23. Mars' History Smaller than Earth, Mars cooled faster. Most volcanic activity ended two billion years ago. Differentiation less complete than on Earth. No evidence for plate tectonics. Atmosphere mostly froze out into subsurface ice, polar ice caps and surface rocks.

  24. Mars' History Smaller than Earth, Mars cooled faster. Most volcanic activity ended two billion years ago. Differentiation less complete than on Earth. No evidence for plate tectonics. Atmosphere mostly froze out into subsurface ice, polar ice caps and surface rocks. Valles Marineris flyover movie

  25. The Martian Atmosphere - 95% CO2 - Surface Pressure 0.006 that of Earth's atmosphere (thin air!) - Surface Temperature 250 K. - Dust storms sometimes envelop most of Mars, can last months. A "Reverse Runaway Greenhouse Effect" may have happened: during volcanic phase (first two billion years), thicker atmosphere, warmer surface, possibly oceans. But gradually most CO2 dissolved into surface water and combined with rocks, then atmospheric and surface water froze (creating ice caps and possible permafrost layer). Or: most atmosphere lost due to low gravity Or: most atmosphere lost due to heating by early impacts

  26. The Martian Surface OlympusMons Tharsis Bulge Valles Marineris Hellas Basin Southern Hemisphere~5 km higher elevation than Northern, and more heavily cratered. South is like lunar highlands, surface ~4 billion years old, North like maria, ~3 billion years old. Valles Marineris - 4000 km long, up to 7 km deep. Ancient crack in crust. Reasons not clear. (Mars Global Surveyor radar data) Tharsis Bulge - highest (10 km) and youngest (2-3 billion years) region. Olympus Mons - shield volcano, highest in Solar System, 3x Everest in height. 100 km across. Hellas Basin - large impact crater, ~4 billion years old.

  27. The View From the Surface Dry, desert-like. Red => high iron content. Mars didn't differentiate as completely as Earth. Sky has butterscotch hue due to dust. Sojourner robot from Pathfinder (1997) Viking 1 site (1976) “Endurance” crater from Opportunity rover (2004)

  28. Pathfinder site was an outflow channel Red arrows: rounded boulders indicating water erosion? White arrows: "conglomerate" rock, like in Earth's riverbeds? Blue arrows: sharp-edged boulders, volcanic rock?

  29. Spirit and Opportunity Rovers Scenes from “Roving Mars” (start at 20:27)

  30. Opportunity’s first pictures from Victoria Crater Deepest crater explored by far (230 feet, 10 times deeper than Endurance Crater) => more layers of geologic history. Will it go in? Will it ever get out?

  31. Mars Reconnaissance Orbiter view of Victoria Crater

  32. Evidence for Past Surface Water "runoff channels" or dry rivers "outflow channels" teardrop "islands" in outflow channels standing water erosion in craters?

  33. Did Mars once have a huge ocean? Long stretches along border are very even in elevation, like a coastline Ocean fed by outflow channels from higher elevation southern hemisphere?

  34. Clicker Question: Large scale motions of the crust (plate tectonics) are seen on which planets: A: Mercury and Venus B: Earth, Venus and Mars C: Only the Earth D: Mars and Venus E: All terrestrial planets - Mercury, Venus, Earth and Mars.

  35. Clicker Question: From Mars, Deimos has an angular diameter of 140 arcseconds. Would colonists on Mars ever see Deimos produce a total solar eclipse? A: Yes, every day on Mars B: Yes, every new moon C: Yes, but rarely D: Never

  36. Clicker Question: The largest mountain in our solar system is: A: Caloris Basin range on Mercury B: Gula Mons on Venus C: Mt. Everest on Earth D: Olympus Mons on Mars .

  37. Clicker Question: Where is the water that once flowed on the surface of Mars? A: In the atmosphere B: In the polar caps only C: In a layer of permafrost below the surface and in the polar caps D: It was diverted to Los Angeles

  38. Evidence for "Permafrost" layer beneath surface "Splosh" craters suggesting liquefied ejecta.

  39. Valles Marinaris flyover movie

  40. Mars' Moons Phobos and Deimos Phobos: 28 x 20 km Deimos: 16 x 10 km Properties similar to asteroids. They are probably asteroids captured into orbit by Mars' gravity.

  41. Next mission – Mars Science Laboratory – fall 2009 launch

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