Elorza is a 45-kilometer crater located a bit east of Valles Marineris. Its floor contains several deposits of material with heavily cratered surfaces, overlying a less-cratered substrate. The heavily cratered material is more resistant to erosion and better able to preserve impact craters than the more easily eroded material that it lies on top of.
This photo was taken by the Context Camera on Mars Reconnaissance Orbiter. Photo D02_027907_1712_XN_08S055W.