Radar reveals signs of seas on Titan

Newly discovered features that appear to be hydrocarbon seas on Saturn’s moon Titan are at least 10 times as large as any such features previously imaged there. Recent radar observations of Titan’s north pole taken with the Cassini spacecraft show that one of the putative oceans is larger than any of North America’s Great Lakes.

TITANIC OCEAN? Large dark patch in radar image (left) of Saturn’s moon Titan shows what may be a hydrocarbon sea bigger than Lake Superior. Goddard/NASA, JPL/NASA

The features’ darkness in radar images indicates smooth surfaces, and their outlines resemble shorelines. Scientists contend that the bodies are probably made of liquid ethane or methane. Methane is abundant in Titan’s thick atmosphere and cycles between the moon’s atmosphere and rigid surface, much as water cycles on Earth.

Some of the features are large enough for Cassini’s visible and infrared mapping spectrometer to perform a key test in the next year or two, when the sun climbs higher over Titan, says Cassini researcher Jonathan Lunine of the University of Arizona in Tucson. With stronger solar illumination, the instrument could obtain spectra indicating whether the bodies are indeed composed of liquid hydrocarbons.

“We couldn’t do that with the other lakes” previously discerned by Cassini’s radar (SN: 8/5/06, p. 83: Titan’s Lakes: Evidence of liquid on Saturn’s largest moon) because those areas were too small, Lunine adds. Cassini took the radar images during a Feb. 22 flyby, and NASA released them on March 13.

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