Mars’ permanent North Polar cap is ringed by sand dunes. In the winter and spring the dunes are covered by a seasonal cap of dry ice.
Here, we see the dark dunes in the summer, bare of seasonal frost. Two classic barchan dunes march across the rugged terrain. The long dark dune is crossing transverse aeolian ridges probably formed in a previous climate regime.
Written by: Candy Hansen (audio: Tre Gibbs) (24 February 2016)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_044088_2640
Image: NASA/JPL/University of Arizona