Complex winds

A piece of Mars: My brain keeps seeing it as stuffed pillows, but it’s the other way around — the sun is coming from the upper left, so the centers of the little polygons are low and their edges are sharp-crested dunes. Or maybe ripples, we’re still not sure. Stare at it until your brain makes it work that way. The little ripples inside them were formed after the big ones. I can tell because their orientation is so strongly affected by the topography of the big ones. (HiRISE ESP_026599_1500)