5 May 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the outer edge of the south polar residual cap of Mars during southern summer. The variability in brightness across the image would not be as apparent had the data been acquired during late winter or spring, owing to the presence of seasonally deposited, carbon dioxide frost. Over the spring and into early summer, the seasonal carbon dioxide is removed through sublimation, and then the thicker, older accumulations of carbon dioxide -- deposited hundreds or thousands of years ago -- erodes. As this occurs, some surfaces become darker, either because they are roughened by erosion, contain dark material such as mineral dust, or both.

Location near: 86.9°S, 111.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: upper left
Season: Southern Summer