today - surfaces of the terrestrial planetsneffj.people.cofc.edu/astr129/notes/lec21.pdf ·...
TRANSCRIPT
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Lec 21: 14 November 2011 Chaps. 11 Terrestrial Planets. LAST TIME - Earth II. Our Changing Surface • Heat transfer through interior • Oceanic v. Continental Crust • Geological Activity & Plate Tectonics
TODAY - Surfaces of the Terrestrial Planets • Earth’s Plate Tectonics • Surface details & activity of Venus • Surface details & activity of Mars
NEXT - Water, Atmospheres, and Climate
Earth shows dramatic evidence of plate tectonics
Venus has continents and plains, but no plate tectonics
Mars has north-south asymmetry (flat northern lowlands and cratered southern highlands), but no plate tectonics
Venus
Surface Features of Venus • 2 “continents” (Ishtar & Aphrodite)
– e.g. Lakshmi: 11 km high; 5 km relief – cf. Himalayas 10 km high; 6 km relief – Rest of surface is low-lying & relatively flat
Surface Features of Venus (continued)
• Impact Craters – about 1000 of them from 2 to 280 km diameter – cf. Earth has 150; Moon has many more – very few are under 10 km (Why?) – nearly all are “pristine” – entire surface ~15% of Lunar maria density – entire surface is about 500 million years old
• Catastrophic or Steady State Resurfacing?
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Surface Features of Venus (continued)
• Volcanoes – 80% of surface is basaltic lava plains – would expect more modified/filled in
craters is volcanic activity was steady state than if it were catastrophic
– shield volcanoes – pancake domes – lava rivers (longest 7000 km; over 40 are >
100 km; Earth has some of 10 km or so) – It takes longer to cool/solidify on Venus!
Volcanic activity resurfaced Venus recently
(or resurfacing Venus currently)
Earth-based Radar Map Magellan Radar Map (Venus Orbit)
Lava Rivers longer than any on Earth or Moon
Magellan 3-D radar images
Surface Features of Venus (continued)
• Volcanoes – 80% of surface is basaltic lava plains – would expect more modified/filled in
craters is volcanic activity was steady state than if it were catastrophic
– shield volcanoes – pancake domes – lava rivers (longest 7000 km; over 40 are >
100 km; Earth has some of 10 km or so) – It takes longer to cool/solidify on Venus!
Surface Features of Venus (continued)
• Cracks, Ridges, “Coronae”, hot spots, but No Plates
Venera 13 Color Photos From Surface of Venus
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Best View of Mars from Earth (Hubble Space Telescope)
Surface Features of Mars
• Northern Hemisphere: mostly low-lying plains • Southern Hemisphere: mostly highlands
(appears much darker)
Surface Features of Mars (continued) • Craters and Impact
Basins – Hellas (1800 km
diameter; 6 km deep) – Argyre (700 km across) – crater counts indicate
ages: • Southern Highlands ~ 4
billion years • volcanoes very young
(<200 million years) • Northern Plains ~2 to 3
billion years
Southern Highlands
~ 4 GY old Northern Plains
2-3 GY old
Surface Features of Mars (continued)
• Valles Marineris – rift zone 4000 km
long, 500 km wide, 7 km deep
• Tharsis Bulge & Giant Shield Volcanoes – Olympus Mons is
700 km wide, 27 km tall, and 2 km across the peak
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Olympus Mons