`Titan looks a little bit like home'

WASHINGTON, OCT. 21. Clouds and rain may make Saturn's moon Titan look a little bit like home, but its spring showers would produce drops of methane, not water, scientists said.

They said yesterday images taken from the earth strongly suggest that Titan, the moon considered to be most like our planet, has clouds made of methane.

The clouds move about and disappear, which suggests that they produce rain, Caitlin Griffith of Northern Arizona university in Flagstaff and colleagues report in today's issue of the journal Science .

``Their short lives point to the presence of rain,'' the astronomers wrote. ``We propose that Titan's atmosphere resembles earth's, with clouds, rain and an active weather cycle.'' Except, instead of water, this weather is produced by the stuff of cow burps and swamp gas - methane. For their study, Griffith and colleagues analysed near-infrared light emitted by Titan. Such spectral analyses can show what elements and compounds are present, and in what amounts.

They found a lot of methane in the atmosphere, and found its presence waxed and waned. One big fluctuation looked like nothing so much as a hurricane-sized cloud system.

One mystery is how the clouds and weather systems form. Earth gets a lot of energy from the sun and spins quickly, both of which cause weather systems to move across its surface.

``Compared to earth, Titan's atmosphere is cooler, more massive and thus essentially more sluggish,'' the researchers wrote. ``Titan spins slowly, providing little vorticity to cloud systems. In addition, Titan receives about 100 times less power from the sun.'' And no one knows yet just what goes on at the surface of the moon. ``The local terrain, topography, winds and humidity on Titan are unknown,'' they wrote.

- Reuters

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