Gullies and Dunes

2 June 2004
This 1.5 meters (5 ft.) per pixel Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image of gullies and dunes in a crater near Gorgonum Chaos was acquired in late May 2004. The gullies may have formed by a combination of processes. Many middle- and polar-latitude gullies such as these are thought to form both by mass movement of dry materials and action of liquid water. Some investigators suggest alternative fluids such as carbon dioxide. Still others make a case that no fluid was involved at all. Some gullies on Mars show clear association with subsurface layering and undermining of those layers; they also show banked channels; these kinds of observations are usually taken in support of the water hypothesis. The crater in which the landforms shown here occur is located at 37.5°S, 169.3°W. This image covers an area about 1.5 km (0.9 mi) across. The scene is illuminated by sunlight from the upper left.