Frost-covered dunes

Frost-covered dunes

. A giant trough in the north polar cap shows dark sand emerging from beneath a veneer of bright frost leftover from the northern winter. This image of dunes in the Chasma Boreale was taken from the Mars Global Surveyor in September 1998. It is about 1.8 kilometers wide. (Courtesy of NASA, JPL and Malin Space Science Systems.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University