Wind Action on Martian Sand Dunes

Key observations that appear to indicate that some Martian dunes are active today were captured by the Mars Global Surveyor in this August, 1998 image. The dark spots on these north polar dunes were areas where the seasonal frost coating had been removed--either by sublimation or by wind erosion. The dark material was presumed to be the sediment that composes the dunes. These dark streaks are interpreted to be the result of wind action. Gusts of wind have blown the dark sand out across the frost-covered dunes, creating a streak of deposited sand over the frost. Each streak indicates a different wind gust that moved in a different direction.