This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pedestal crater superposed on the floor of the much larger Mellish Crater. When an impact crater of this type forms, material is thrown onto the adjacent terrain to form portions of the ejecta blanket we see today.
If the ejecta blanket is sufficiently rocky, it will protect the underlying terrain from wind erosion. Over time, much of the exposed material surrounding the ejecta blanket will be removed by wind, leaving behind the rocky ejecta and the material below it, resulting in the pedestal-like appearance seen here.
Location near: 73.0Â°S, 22.7Â°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer