This observation shows a well-preserved impact crater on the rim of a much larger crater located in Terra Cimmeria, in the Southern highland region of Mars.
This crater, like many others on Mars, has several gullies which can you see in the subimage here. Gullies often occur on steep slopes and on crater walls, although their origin is still a point of ongoing investigation.
Another interesting aspect of this observation is the shape of the terrain near the center of the crater floor.
This caption is based on the original science rationale.
Written by: HiRISE Science Team (27 April 2011)
This is a stereo pair with ESP_021781_1440 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_021491_1440
Image: NASA/JPL/University of Arizona