Mysterious material found on Saturn moons

DENVER, Feb. 20 (UPI) -- U.S. space scientists are investigating an unidentified black material coating the surfaces of some of Saturn's moons.

Astronomers said there's mounting evidence some mechanism has spread the material found on several of the moons from one to another and the material might have a common cometary origin.

Roger Clark of the U.S. Geological Survey in Denver said the Cassini spacecraft found the same spectral signature on all the moons -- Phoebe, Iapetus, Hyperion, Epimetheus -- and Saturn's F-ring that have coatings of dark material.

But the scientists said they don't know where the material originated or what it is.

"It's a mystery, which makes it intriguing," said Clark. "The data keep getting better and better. We're ruling things out and figuring out pieces."

Cassini's next close study of a Saturn moon is a March 12 flyby of Enceladus at a distance of 31 miles at its point of closest approach.

The Cassini-Huygens mission is a cooperative project of the National Aeronautics and Space Administration, the European Space Agency and the Italian Space Agency.

A collection of 14 papers about Saturn's moons appears in the February issue of the journal Icarus.