These shapes certainly look familiar to Star Trek fans, and even the Shat. This is a picture of sand dunes on the surface of Mars, in an image taken by the HiRISE camera on board the Mars Reconnaissance Orbiter.
Technically, they’re called barchan dunes. They can form when the wind blows predominantly from one direction. If there’s an obstacle, like a big rock or small hill, the wind will blow around the obstacle, the same way water flows around a rock. Sand will pile up on the leading edge and also be swept around to the backside. Eddies in the wind create circular currents on the downwind side, building up walls of sand on the sides and creating that horseshoe crab-like appearance.
Phil Plait explains more about barchan dunes at Bad Astronomy.
(Image credit: NASA/JPL-Caltech/Univ. of Arizona)
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