Mars Express beams back images of ice-filled Korolev crater

Trapped layer of cold air keeps water frozen in 50-mile-wide impact crater

The stunning Korolev crater in the northern lowlands of Mars is filled with ice all year round owing to a trapped layer of cold Martian air that keeps the water frozen.

The 50-mile-wide crater contains 530 cubic miles of water ice, as much as Great Bear Lake in northern Canada, and in the centre of the crater the ice is more than a mile thick.