Sediment History

This Mars Global Surveyor image demonstrates the theme of erosion, deposition, and then more erosion. The circular feature is interpreted to be an ancient impact crater. This crater indicates that a layered rock surface was exposed to the atmosphere for some period of time before the next layer of material (the bright, almost white ridged rock that covers most of the upper half of this picture) was deposited. Further erosion created the ridge and gully pattern.