Across the surface of Mars ferocious winds constantly work at shaping and reshaping the sand-covered landscape. These gales hew "yardangs" out of the terrain of the Red Planet, leaving a layer of powdery sand in the passages between the features. Due to the thin atmosphere, the ridges and dunes created by these winds cast stark shadows. [See more images of Mars.]
(Image: © NASA/JPL-Caltech/University of Arizona)
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