Numerous craters have since been formed within the basin. In this image taken by Mariner 10, only half of the basin is visible. Earth L iquid water, wind and other erosional forces erase impact craters on the Earth. There are still many craters on Earth which are visible from space. The southern hemisphere is more heavily cratered than the northern hemisphere.
Winds are the main erosional force on Mars and windblown dust and soil erode craters over time.
The structure of some Martian impact craters, such as the one pictured here at left, provide evidence that suggests the presence of water or ice in the surface at the time the impact occurred. More about Martian craters. A steroids are rocky and usually heavily cratered due to a long history of impacts with other asteroids and possibly comets. Old impact craters on asteroids have beem deformed and erased by newer impact craters. Alternatively, impact events can disintegrate asteroids into smaller pieces.