NASA’s Curiosity Mars rover, partway through the first up-close study ever conducted of extraterrestrial sand dunes, is providing dramatic views of a dune’s steep face, where cascading sand has sculpted very different textures than the wavy ripples visible on the dune’s windward slope. (…)
Researchers are using Curiosity to examine examples of the Bagnold Dunes, a band of dark sand dunes lining the northwestern flank of Mt. Sharp, the layered mountain the rover is climbing. A characteristic that sets true dunes apart from other wind-shaped bodies of sand, such as drifts and ripples previously visited by Mars rovers, is a steep, downwind slope known as the slip face. Here, sand blowing across the windward side of the dune suddenly becomes sheltered from the wind by the dune itself. The sand falls out of the air and builds up on the slope until it becomes steepened and flows in mini-avalanches down the face. [More at link]