A Martian ice mound

This past December marked the 15th anniversary of the arrival of the European Space Agency’s Mars Express at the red planet. Although the orbiter’s original mission was to last only 687 days, or one Martian year, it has been extended multiple times—currently through the end of 2020. Mars Express is the longest ESA mission still in operation.

This overhead, natural-color composite view of the Korolev crater was assembled from observations by the spacecraft’s High Resolution Stereo Camera taken during five different orbits. At a latitude of 73° N, the crater is located in the northern lowlands just south of a broad dune field that partially encircles the north polar ice cap. It has a diameter of 82 km and is filled with a mound of water ice some 1.8 km thick, comparable in volume to Canada’s Great Bear Lake. Despite lying outside the ice cap, the deposit is stable year-round because the crater acts as a natural cold trap: It retains a layer of cold air that insulates the ice below it. (Image 412943 © ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO , cropped from original.)

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