MGS MOC Release No. MOC2-399, 22 June 2003

When spring comes to the southern hemisphere of Mars, dark spots begin to form on sand dunes covered with carbon dioxide frost. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dune field near 61.8°S, 160.5°W in early spring. The processes that form the dark spots remain mysterious. The spots might form at the locations of the thinnest frost, the coarsest sand grains, or at interfaces between two different types of material surfaces (e.g., between dune and surrounding plain). The area shown here is illuminated from the upper left and covers an area 3 km (1.9 mi) wide.