Ice on Mercury?

Mercury was well named by the Romans-- the planet that moves the fastest through space is named for the fleet-footed messenger god in the Roman pantheon. The planet's orbital speed is due to its proximity to the Sun. One year on Mercury is only 88 Earth days long.

That proximity affects the very nature of Mercury. The planet is the smallest in the Solar System, likely because the Sun's gravity interfered with the coalescing process that builds planets. It has no atmosphere, largely because the Sun would boil any atmosphere away. The Mercurian day is roughly twice as long as its year because the Sun's gravity slows its rotation. Because of that slow rotation, temperatures on the surface have time to reach extremes-- 800 degrees on the sunlit side, -300 on the dark side. Offhand, Mercury may be among the last places in the Solar System to expect to find water on the surface. Yet, radar studies suggest precisely that.

Much as may exist on Earth's Moon, there seems to be deep craters in at least the north polar regions of Mercury where the crater floors are always in shadow. There, water ice seems to exist, either directly on the surface or under a thin layer of dust. Presumably, the ice was delivered by comets smacking into Mercury. How much ice is there is unclear, but the fact that any at all might be there reminds us of the fundamental quirkiness of the cosmos.