[In Depth] Sandy ripples point to Mars's past
Investigators with NASA's Curiosity rover are exploring dark sand dunes on Mars and have discovered structures thought to be unlike any on Earth: ripples spaced about 3 meters apart, intermediate in size between the little ripples and big dunes found on both planets. Scientists aren't sure how they form, but they think the density of the thin martian atmosphere plays a role in shaping them. If they can find the fossilized ripples in rocks hardened from ancient dunes, they could glean clues about the thicker atmosphere of early Mars. The result is one of the highlights of a campaign to investigate the dunes in Gale Crater that gird the mountain the rover is trying to get to. For several weeks this past December and January, the rover stopped to take pictures, make wind measurements, and sift sand into its chemical analysis instrument. Author: Eric Hand