"Defrosting dunes in the north. In northern winter a seasonal polar cap composed of carbon dioxide ice (dry ice) forms in the north polar region. This cap covers a vast sea of dunes at high northern latitudes. In the spring the ice sublimates (evaporates directly from ice to gas) and this active process loosens and moves tiny dust particles. - Since 2006, NASA's Mars Reconnaissance Orbiter (MRO) has been orbiting Mars, currently circling approximately 300 km (187 mi) above the Martian surface. [...]
Gee... these photos are dazzling !