Undercover

3 June 2006
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dunes covered with a seasonally-deposited layer of solid carbon dioxide (CO₂) in the north polar region of Mars. The dark spots indicate areas where the CO₂ frost has begun to change, either by being sublimed away, or by becoming rougher or coarser-grained, such that it appears darker than surrounding frost. Over the course of the spring season, the frost will be completely removed and the dark sands that make up the dune field will be visible by summer.

Location near: 77.7°N, 41.7°W
Image width: ~3 km (~1.9 mi)
Illumination from: lower left
Season: Northern Spring