8 May 2004
This March 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a gullied crater wall at southern mid-latitude near 35.5°S, 223.0°W. Formation of such gullies might have involved flowing liquid water. The Mars science community has been debating, since they were first reported in June 2000, whether such gullies were carved by water, carbon dioxide, or perhaps formed in completely dry, granular material without the influence of a fluid. The scientists have also debated whether the water--if it was water--started out in the form of ground ice, a snow pack, or liquid groundwater. Since June 2000, many hundreds of new gully locations--and tens of thousands of individual gullies--have been identified. Their relative youth suggests to some the possibility that Mars today has water or ice within less than 1 kilometer of the surface--a depth that may be readily accessible to future explorers. This picture is illuminated by sunlight from the upper left and covers an area about 3 km (1.9 mi) across.