Spring is already starting to show its influence at the Russell Crater field of sand dunes. Channels down the face of the largest dune show dark spots where the sublimation of the seasonal carbon dioxide ice cap has begun.

This active process (where ice evaporates directly to gas) dislodges loose material, leaving dark streaks down steep slopes. The process starts when the sun peeks above the horizon at the end of antarctic night. Bright streaks may be loose frost cascading down steep slopes.

Written by: Candy Hansen   (12 November 2008)

More info and image formats at http://hirise.lpl.arizona.edu/PSP_010090_1255

Image: NASA/JPL/University of Arizona