for National Geographic News
Scientists have confirmed the presence of a suspected big, black, glassy lake on Saturn's moon Titan, adding to the growing body of evidence that the giant satellite is oddly Earthlike.
Titan is thought to host mountains, desert-like flats, rivers, lakes and—possibly—an underground ocean.
Whereas water dominates climate cycles on Earth, weather on Titan—where surface temperatures can be -300 degrees Fahrenheit (about -200 degrees Celsius)—revolves around thick, dark hydrocarbons.
Methane and ethane fill the air with a dirty haze that rains down as ash, and rivers run with a gasoline-like liquid.
And now scientists know the hydrocarbons collect in black lakes with surfaces as smooth as glass—perhaps as many as a hundred lakes and seas in the north pole region alone.
An instrument aboard the Cassini orbiter, called the visual and infrared mapping spectrometer, or VIMS, confirmed the presence of the lake called Ontario Lacus when the craft detected ethane.
"Detection of liquid ethane in Ontario Lacus confirms a long-held idea that lakes and seas filled with methane and ethane exist on Titan," said Larry Soderblom, a study co-author from the U.S. Geological Survey in Flagstaff, Arizona.
The study, led by Robert Brown at the University of Arizona in Tucson, appears in today's issue of the journal Nature.
Murkier Than Mud
Cassini—along with its Huygens probe, which detached and landed on Titan's surface in 2005—is part of a cooperative mission of NASA, the European Space Agency, and the Italian Space Agency.
Previous observations of the lake with the Cassini radar imager, as far back as 2005, were unable to fully distinguish the lake's liquid hydrocarbons from the atmosphere's thick hydrocarbon haze. (See "First Space Lakes Found on Saturn Moon" [July 27, 2006].)
But Cassini's VIMS camera uses spectroscopy—a technique that identifies the chemical composition of objects by the way they reflect light.
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