for National Geographic News
Rivers of methane are likely flowing on Titan, Saturn's largest moon, according to observations made by the Huygens space probe, which landed on Titan in January.
But what are methane rivers like? One scientist suggests the answer may be found right here on Earth.
"If we know the underlying physics of how rivers operate on Earth, the same generalized laws ought to work on Titan," said Gary Parker, a geologist and civil engineer at the University of Illinois at Urbana-Champaign.
According to Parker, the methane rivers on Titan may be wider and deeper than Earth's rivers of water, but they might flow much the same way that Earth's rivers do.
Surface images of Titan taken by the Huygens probe show gravel-size pieces of ice resembling rounded stones in a dry riverbed.
"The differences are noticeable, but they are not so overwhelming that a gravel-based river on Titan should be unrecognizable to [people] on Earth," Parker said.
He presented his findings this week at the annual meeting of the American Geophysical Union in San Francisco.
Titan is extremely cold. The moon is about minus 290ºF (179ºC) on its surface. It has a dense atmosphere of nitrogen, methane, and hydrocarbon. At these temperatures, the rain is liquid methane.
Data from the Huygens space probe and NASA's Cassini satellite show a world with Earthlike features, including the appearance of volcanoes, mountains, and shorelines.
Although he is not a planetary researcher, Parker became interested in Titan four years ago because of speculation that there might be rivers there.
His expertise is in rivers and ocean currents on Earth, and he has collected data from rivers all over the world.
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