A Piece of Mars: Along the right side of this 0.5×0.5 km (0.31×0.31 mi) scene is the rim of a crater – the stripes are layers exposed (and then perhaps draped by falling ejecta) as the crater formed. To the left is the crater’s interior wall, dropping downward. Deep gullies have been eroded into the crater walls, probably by water, carrying sediment downslope. Rivers and landslides are generally great sources of sand-sized sediment, and this place is no exception. The sediment piled up downslope, and then the wind came along and sculpted it into beautiful cross-hatched patterns (click on the image to see full resolution). (HiRISE ESP_015984_1335, NASA/JPL/Univ. of Arizona)