Powerful radar signals that bounced off the rocky, cratered surface of Mercury seem to confirm the unlikely: The planet that orbits closest to the sun has permanent ice deposits at its poles.

The discovery, said astronomer John Harmon, "is a surprise. I don't think anyone was thinking of ice" when they began radar observations of the planet, where surface temperatures go as high as 930 degrees Fahrenheit.

Scientists, who said it's a bit like finding snowballs in hell, say the discovery may mean ice also is hidden in permanently shadowed areas on Earth's moon.