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

Sean C. Solomon, the principal investigator for Messenger, said there was enough ice there to encase Washington, D.C., in a frozen block two and a half 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.

“In these planetary bodies, there are hidden places, as it were, that can have interesting things going on,” said David J. Lawrence, a senior scientist at the Johns Hopkins University Applied Physics Laboratory working on the Messenger mission.

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

Planetary scientists had strong hints of the ice a couple of decades ago when telescopes bounced radio waves off Mercury and the reflections were surprisingly bright. But some researchers suggested the craters could be lined with silicate compounds or sulfur, which might also be highly reflective, and not water ice.