ASSOCIATED PRESS Telescopes atop Mauna Kea have recorded for the first time clouds floating over Saturn's biggest moon, Titan. Features, like the small bright clouds near the south pole, can be seen at their highest resolution ever in this image taken with the W.M. Keck II telescope in December 2001 and February 2002.

Mauna Kea telescopes
spot clouds near Saturn

The clouds are floating over
Titan, Saturn's largest moon

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By David Briscoe
Associated Press

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 other body in the solar system, scientists reported yesterday.

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 are covered in clouds, most notably Jupiter, it is the first time an entire process of evaporation and cloud formation has been spotted in space, said Michael Brown of Caltech.

Brown and Henry Roe, of Berkeley, reported on the work of a team of astronomers in today's issue of Nature and tomorrow's issue of the Astrophysical Journal.

Titan may be in a stage similar to conditions on Earth before the atmosphere was able to support life, some scientists theorize, making it a good laboratory for examining Earth.

"This is the only place with an analog to the terrestrial hydrological cycle," Brown said. "We don't see raindrops, but I guarantee there are clouds, and they disappear on short time scales." It makes sense, he said, that it also rains on Titan.

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

Any precipitation that may be falling on Titan would be methane rain or hail, rather than water, Brown said. He added that many mysteries remain about the giant moon, including the nature of vast, dark regions that could be seas of ethane or tar-covered lowlands. Ethane and methane are both made up of carbon and hydrogen molecules, while water is hydrogen and oxygen.

Titan is larger than the planet Mercury and the biggest unexplored body in the solar system. A haze has prevented past attempts to more clearly view its surface.

The cloud discovery, however, opens new possibilities for observation. Clouds over the pole have varied in as little as a few hours, said Roe, lead author of the report.

The National Aeronautics and Space Administration's Cassini spacecraft, orbiting around Saturn on a multiyear mission, also is set to drop a probe named Huygens by parachute to Titan's surface in 2004. The cloud observations are based on views from atop Mauna Kea in late 2001 and earlier this year.

Roe continues to work at the Keck observatory, documenting information about the clouds. Brown plans to return to the mountaintop later this month.

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Nature
Astrophysical Journal
Keck Observatory Titan page
Gemini Observatory
NASA Titan page