Clouds On Saturn's Biggest Moon

Telescopes atop Mauna Kea have recorded for the first time clouds floating over Saturn's biggest moon - considered by some astronomers to be the most earth-like body in the solar system, scientists reported Wednesday.

Peering across 808 million miles, scientists from the California Institute of Technology and the University of California, Berkeley, used telescopes at the Keck and Gemini observatories atop the dormant volcano on the Big Island to photograph methane clouds near the south pole of the moon Titan.

Although some planets, most notably Jupiter, are covered in clouds, it's the first time the process of evaporation and cloud formation has been spotted in space, said Caltech scientist Michael Brown.

Brown and Henry Roe, of Berkeley, report on the work of a team of astronomers in Thursday's issue of Nature and Friday's issue of the Astrophysical Journal.

Titan may be in a stage similar to Earth before the atmosphere was able to support life, some scientists theorize. "We don't see raindrops," said Brown in a telephone interview from California. "But I guarantee there are clouds and they disappear on short time scales."

Any precipitation falling on Titan would be methane rain or hail, rather than water, he added.

The distant moon could not support life. It has an atmosphere of methane, ethane and hydrogen cyanide with no oxygen. It would also be too cold: minus 297 degrees Fahrenheit on the surface.

The cloud observations are based on views from atop Mauna Kea in late 2001 and earlier this year. Titan, one of 30 moons orbiting Saturn, is a little less than half the size of Earth, and much larger than Earth's moon.

A haze has hindered past attempts to more clearly view the surface of Titan. Previous observations of the body had indicated an unchanging surface and no clouds.

Brown said improvements in the resolution of telescopes will aid the study of Titan.

"We're suddenly at the point where we can learn all these new things," he said. The National Aeronautics and Space Administration's Cassini spacecraft, orbiting around Saturn on a multiyear mission, also is set to parachute a probe named Huygens to Titan's surface in 2004.

By David Briscoe