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.

ID: ESP_044088_2640
date: 22 December 2015
altitude: 316 km

https://uahirise.org/hipod/ESP_044088_2640
NASA/JPL-Caltech/University of Arizona
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