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Mercury is the closest planet to the Sun, orbiting at an average distance of just 57.9 million km. It takes 88 days to complete an orbit, and 58.6 days just to complete one day. Mercury’s day is almost as long as its year. And whatever side of Mercury facing the Sun can reach temperatures of 700 Kelvin. So is it possible that there’s ice on Mercury?
With temperatures so high, you would think that any ice would melt almost instantly. And then the water would boil away in the vacuum of space and be blown away by the Sun’s intense solar wind. Well, you might be surprised to know that scientists do think that there’s ice on Mercury. In fact, they’re almost certain it’s there.
Just like the Moon, Mercury surface is pounded by numerous impact craters; both large and small. Some of these craters are right at Mercury’s north and south pole so that there are small regions of Mercury which are hidden in eternal shadow. While the side of Mercury facing the Sun can reach 700 Kelvin, the side facing away can dip down to just 80 Kelvin at the planet’s north pole. So it stays cold enough for ice to form if you could find enough water.
But where could you find the water? Scientists think that Mercury, and all of the inner planets, were bombarded by comets throughout their history. Any comets that struck in these permanently shadowed regions of Mercury might have left behind deposits of ice that have never seen sunlight, and so have never melted.
Future spacecraft might be able to travel to Mercury and land within these shadowed craters and draw upon water ice as a resource. NASA’s MESSENGER spacecraft is expected to go into orbit around Mercury in 2011, and should help provide more evidence about whether this water ice on Mercury actually exists.
We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.
We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.
Is There Ice on Mercury?
NASA: Ice on Mercury