SATURN'S BIGGEST MOON DOTTED WITH METHANE LAKES,
TRIBUTARIES As scientists have predicted but have had a hard time proving,
the surface of Titan, Saturn's largest moon, appears to be dotted with lakes of liquid methane. The lakes are more intriguing evidence of the active phenomena at play on the only moon in the solar system with a dense atmosphere.
The discovery, reported on Wednesday by an international team of researchers, was made by a radar survey of Titan's high northern
latitudes by the Cassini spacecraft, which has been orbiting Saturn and its retinue of satellites since July 2004.
One of the mission's major objectives is the investigation of Titan's environment, thought to be a frigid version of conditions on the primordial Earth.
The radar imaging system detected more than 75 dark patches in the landscape near Titan's northern polar region, the scientists said in a detailed description of the find published in Thursday in Nature.
The patches, they said, indicated smooth surfaces in an otherwise rugged topography, suggesting lake beds either partly dry or filled with liquid.
These smooth surfaces, more or less circular and with diameters ranging from 2 miles to 40 miles, are associated with channels that appear to have been formed by flowing liquids, presumably
tributaries to the lakes.
Methane exists in Titan's atmosphere and, in the extreme cold of high latitudes, is expected to rain on the surface and be present as liquids in subsurface reservoirs.