geology of mars cratering image
Crater Morphology
Ejecta Blankets
Crater Degradation

Crater Degradation
Similar to craters on other celestial bodies, Martian craters can also be degraded by slumping of crater rims (i.e., landslides), subsequent impacts, lava flows, and ejecta from nearby impacts. In addition, Martian craters may be weathered by water and the atmosphere.

 figure 3.1

Figure 3.4 is an image of the Argyre Basin, which is an ancient impact crater about 1,000 km in diameter. Notice that the original crater rim has been obliterated by numerous subsequent smaller impact events. This view was taken from an orbiter. Crater density on Mars is significantly lower than that of the Moon and Mercury. This is probably because: (a) the number of asteroids and meteorites decreases the further a planet is from the Sun, and (b) subsequent geological processes on Mars, such as hydro-processes, aeolian processes and volcanism, have significantly destroyed the earlier impact history of the planet.

More pictures of Martian craters obtained by the Global Surveyor in 1997 and 1998 are available on the JPL/NASA site.

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geology of mars