Shadows behind boulders

A Piece of Mars: Bright material (either dust or sand) has accumulated in the lee of wagon- to car-sized boulders in this 0.96×0.54 km (0.6×0.34 mi) scene. It’s perhaps something like the Rocknest sand shadow that Curiosity visited a few years back. The wind blows from lower right to upper left, carrying along sediment that occasionally gets trapped in the protected areas behind the boulders. These sand shadows aren’t very thick, as the underlying texture (polygonal terrain!) is visible through them. (HiRISE ESP_047798_1150, NASA/JPL/Univ. of Arizona)