Sand
dunes slowly migrate across the Chasma Boreale region of Mars, as seen by the
Mars Reconnaissance Orbiter.
Individual
sand grains can get driven by the wind and bounce forward in short hops, a
process called "saltation." Somehow the sheets of saltating sand
grains manage to organize themselves into sand dunes. Entire sand dunes move
when wind pushes sand grains up and over the top of the dune, so that they
slide down the steep dune face.
This
image shows that steep dune slopes, known as slip-faces, point almost directly
to the left side. However, darker streaks seen in the bottom left of the larger
image leading away from the dunes represent sand grains getting blown off the
dunes without being replaced by sand upwind of the dunes. This suggests that
the dunes are eroding away.
— University of Arizona and SPACE.com
Staff
Credit: NASA/JPL/University
of Arizona
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