The new observations suggest water ice, mixed with organic molecules, is “widespread on the surface of the asteroid”, Humberto Campins of the University of Central Florida in Orlando reported at a meeting of the American Astronomical Society’s Division of Planetary Sciences in Fajardo, Puerto Rico, last week.

That is surprising, since the asteroid’s distance from the sun means it should lose about 1 metre of ice each year. “This ice is unstable, and therefore we need a process to explain why there is ice on the surface now,” Campins said at the meeting.

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