Download Surface Features of Venus

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
Venus
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
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?
1
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 >
Earth-based Radar Map
Magellan Radar Map (Venus Orbit)
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)
Surface Features of Venus (continued)
Lava Rivers longer than any
on Earth or Moon
Magellan 3-D radar images
•  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)
Venera 13 Color Photos From Surface of Venus
•  Cracks, Ridges,
“Coronae”, hot spots,
but No Plates
2
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
3
Olympus Mons
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