Spring has recently come to the northern hemisphere of Mars. The increase of temperature led to a number of seasonal changes on the surface, one of which was photographed by the MRO spacecraft located in an areocentric orbit. It managed to capture the “defrosting” of the Martian dunes.
During winter, the dark sand dunes of the Red Planet are covered with a layer of white frost. But this is not ordinary water ice, but dry. It consists of carbon dioxide, which freezes out of the Martian atmosphere during a decrease in temperature in winter. With the coming of spring, the reverse process begins. Dry ice sublimates, and carbon dioxide gradually returns to the atmosphere.
That is what MRO captured. Using a HiRISE camera on board the spacecraft, scientists managed to get a picture of the dunes located inside the 207 km Kaiser crater. The photo shows dark streams flowing down the sunny side. They are formed as a result of sublimation of carbon dioxide frost. The dunes consist of sand, which is “raked” by the winds blowing along the bottom of the crater.