This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) wide angle view of the martian south polar region was acquired on September 12, 2001, four years to the day after MGS first began to orbit the Red Planet. The bright area at the center of the image is the permanent south polar cap---the part of the cap that will remain through the coming summer. The bright areas that surround the center make up the seasonal frost cap that was deposited during southern winter, which ended June 17, 2001. The dark area in the lower right corner results from two phenomena--the seasonal frost is subliming away much faster in this region, and the area is darker because it is closer to the night side of the planet. The fuzzy or hazy zone that covers most of the left side of the image consists of afternoon clouds and fog. The polar frosts contain both water and carbon dioxide ices. Clouds of condensing water ice crystals are common over parts of the polar cap at this time of year. For scale, the permanent cap at the center of the image is about 420 km (260 mi) across. Sunlight illuminates the scene from the upper left. For a summertime view of the cap, see http://www.msss.com/mars_images/moc/4_27_00_spcap/. Summer in the southern hemisphere will begin in mid-November 2001.

Photo Credit: NASA/JPL/Malin Space Science Systems