Planetary Surfaces: Discussion

One common confusion involved age. All planets in our solar system are the same age -- about 4.6 billion years old. However, ages of surfaces can be very much less than this figure.

Another confusion involved effects of atmosphere on number of impact craters. Our atmosphere protects us from small stuff, but even the thick atmosphere of Venus can't protect that planet from large impacts! The difference in crater density on Venus, Earth, and Mars indicates relative age of surface, not effect of atmosphere.

  Venus Earth Mars
Few -- young surface
Few -- young surface
Manicouagan, Barringer
Many -- old surface
Schiaparelli, Huygens
Hellas (impact basin)
Very extensive;
planet resurfaced
Maat Mons
Maxwell Montes
Common at plate edges,
hotspots within plates
Rainier (strato)
Mauna Loa (shield)
Many in some areas
Olympus Mons
One plate (thick?),
two `continents':
Ishtar, Aphrodite
Mobile plates -> drift,
rifting, subduction
Mt. Everest
San Andreas fault
No active plates
Tharsis bulge (uplift)
Valles Marineris
Erosion Limited; no water,
stagnant atmosphere
Extensive water erosion,
active weather systems
Grand Canyon
Ancient water erosion,
violent dust storms
Ares Vallis (outflow)
Joshua E. Barnes (
Last modified: September 26, 2006
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