A piece of Mars: Yep, this is really Mars. It’s a tiny bit (600×450 m) of the southwestern side of a large dune in the southern midlatitudes. The dark lines are furrows that are thought to be carved by blocks of CO2 ice that slide down in the spring. The tiny stripes are ~4m wavelength windblown ripples that are just starting to get covered in seasonal frost. Both the furrows and ripples are likely to be active today. (ESP_034234_1255, NASA/JPL/Univ. of Arizona)