If humans ever make it to Mars, here鈥檚 a prime piece of real estate for a base 鈥� an alluring patch of water ice on the floor of a crater near the Martian north pole.
The frozen 鈥渓ake鈥� was captured by a high-resolution camera on board the European Space Agency鈥檚 Mars Express spacecraft, which is orbiting the Red Planet. The ice rises 200 metres above the floor of an impact crater located on Vastitas Borealis, a broad plain that covers much of the planet鈥檚 far northern latitudes. The unnamed crater is 35 kilometres wide and has a maximum depth of 2 kilometres below its rim.
ESA scientists have ruled out a lake of frozen carbon dioxide, since CO2 had already disappeared from the north polar cap by the time the image was taken in northern Mars鈥檚 late summer.
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Fortunately for any future Mars explorers, the water ice is present all year round. Atmospheric pressure and temperature around the icy patch are such that the ice cannot either melt into liquid water or sublimate directly into water vapour.
Faint traces of water ice can also be seen along the rim of the crater and on its walls. There is no ice along the north-west rim and walls: this might be because Mars鈥檚 orientation to the sun means that this area is warmed by sunlight more than the rest of the crater.
