Bring an umbrella on Saturn's moon Titan

By Julie Steenhuysen

CHICAGO (Reuters) - The daily weather forecast on Saturn's largest moon Titan appears to be a steady drizzle of liquid methane, at least around the bright, exotically named region known as Xanadu, U.S. researchers said on Thursday.

But this is hardly the paradise romanticized by the Samuel Taylor Coleridge poem "Kubla Kahn."

New images from Hawaii's W.M. Keck Observatory and Chile's Very Large Telescope show nearly global cloud cover at high elevations and a dreary morning drizzle that seems to dissipate around midmorning local time -- which is about three Earth days after sunrise.

Scientists had expected rain in the atmosphere of this planet-sized moon, but these near-infrared images for the first time have revealed a persistent drizzle of methane off the western foothills of Xanadu.

"We expected that perhaps it was raining. It was reasonable that it could be raining. We just didn't know if it was raining right now," said Mate Adamkovics, a University of California, Berkeley researcher whose paper appears in the journal Science.

Titan is larger than the planet Mercury, but much, much colder, with surface temperatures of minus 297 degrees Fahrenheit (minus 183 degrees Celsius) -- cold enough to turn an explosive gas like methane into a liquid form.

It is well known for its hydrocarbon lakes and methane cloud cover. Radar images of Xanadu taken in 2006 showed deep channels that cut through plains and wind around hills.

And now it appears these moisture-laden clouds rain down on Xanadu.