Mercury is as cold as ice.

Indeed, Mercury, the closest planet to the sun, possesses a lot of ice, scientists working with NASA's Messenger spacecraft reported Thursday.

Sean C. Solomon, the principal investigator for Messenger, said there was enough ice there to encase Washington, D.C., in a frozen block 2½ miles deep.

That is a counterintuitive discovery for a place that also ranks among the hottest in the solar system. At noon at the equator on Mercury, the temperature can hit 800 degrees Fahrenheit.

But near Mercury's poles, deep within craters where the sun never shines, temperatures dip to as cold as minus 370.

The findings appear in a set of three papers published Thursday on the website of the journal Science. The ice could be an intriguing target for a future robotic lander or even a resource for astronauts in the far future.

The Messenger spacecraft swung into orbit around Mercury in March 2011 and has completed its primary mission.

The water could also be an intriguing resource for people. Between the scorched equator and the frozen poles, temperatures on Mercury can be temperate, especially a few feet below the surface - an ideal location to build a colony.

"People joke about it, but it's not so crazy, really," said David A. Paige, a professor of geology at UCLA who calculated the crater temperatures.