It’s a rock-eat-rock world

A Piece of Mars: This 738 x 415 m (0.46 x 0.26 mi) scene shows dark sand flowing down a channel bisected by a ~60 m (~200 ft) tall, thin “island”. That island, and many others around it (see the whole image), is what remains after windblown sand slowly carved away the rest of the rock, the same way rivers slowly cut through rock on Earth. The presence of the dark sand shows that the process is still active today. (HiRISE ESP_04400_1750, NASA/JPL/Univ. of Arizona)