Gullies With Bright Material

29 March 2004
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a set of south middle-latitude gullies in a crater wall. Some of the gullies and the erosional alcoves that formed above them have cut and exposed a light-toned material. In the larger gully, this material has been transported down the slope, through the channel, to give the debris apron a lighter tone, as well. The origin of middle-and polar-latitude gullies on Mars remains an area of active debate and discussion within the Mars science community. Mass movement of debris, everyone agrees, has occurred. Unclear are the relative roles of water, ice, and carbon dioxide, if any, in the processes that created the gullies. The light-toned material exposed by the gullies is bedrock, not ice. These features occur near 38.8°S, 40.3°W. This February 2004 image covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.