Hills made by wind and ice

A Piece of Mars: A fluid is something that fills a container it’s put into, and it includes both gas and liquids. This 0.7×0.5 km (0.43×0.31 mi) scene shows hills of sediment left behind by two different fluids (wind and ice). The hill on the left is a rippled sand dune, which has been piled up by the wind as it drops its sandy load. On the right is a layered sinuous hill, leftover from when ice flowed down a slope offscreen to the right. The dune is slowly encroaching on the hill, and will eventually be disrupted by it. (HiRISE ESP_048913_1330, NASA/JPL/Univ. of Arizona)