And the wind blew on

A piece of Mars: Small dunes (or possibly ripples) are likely no longer moving in today’s winds. Or are they? Dark splotches on their upper (northern) sides suggest some kind of wind scour has recently occurred. Winds blow, create dunes, then stop blowing, only to later strengthen and reactivate, destroy, bury, or overwrite older dunes.

Wind shadow, wind shadow

A piece of Mars: When the wind blows sand up against obstacles like this bright little hill, the sand is swept around to the sides. This leaves a wind shadow in the wake of the hill. It’s one of the easiest ways to determine the main wind direction on Mars. (ESP_028235_1785)