A piece of Mars: The surface in this 960×540 m (0.6×0.34 mi) scene has a distinct fabric to it that runs from the upper left to lower right. Are these old lithified dunes? And what makes the tiny filamentary lines that run from upper right to lower left, are those ripples? I’m not convinced either way, but I suspect the wind has had a hand in shaping them, one way or another. (HiRISE ESP_040297_1605, NASA/JPL/Univ. of Arizona)