05-19-2010, 12:59 PM
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#31 (permalink)
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Eat your vegetables
Super Moderator
Location: Arabidopsis-ville
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Cassini strikes again - there's a liquid sea on Titan!
Quote:
New Evidence of a Fluid Sea on Saturn’s Moon Titan
By WILLIAM J. BROAD
Last July, a glint of sunlight from Saturn’s moon Titan sped through space and fell upon the sensors of the Cassini spacecraft, starting a process of discovery that is now strengthening the idea that the icy moon harbors liquid seas.
If confirmed, the finding means that Titan is the only body in the solar system other than Earth whose surface is known to hold stable fluids in a liquid state. The reflective sea — larger than the Caspian — is no vacation spot. The scientists calculate that its fluids are probably a mix of ethane and methane, with perhaps some liquid nitrogen thrown in for good measure. The temperature? About minus 300 degrees Fahrenheit.
The chilly sea is known as Kraken Mare, after the legendary sea monsters. It sprawls over an area of about 150,000 square miles.
A team of 15 scientists, writing on April 7 in Geophysical Research Letters, reported that the glint of sunlight bouncing off Kraken Mare, near Titan’s north pole, was a special type known as a specular reflection.
By definition, such mirrorlike reflections occur when the incoming and reflected rays have the same angle with respect to the reflective surface — in other words, the angle of incidence equals the angle of reflection. On Earth, glass, liquids and polished metals often produce specular reflections.
The scientists, in a four-page analysis, said the reflection captured by Cassini in July was clearly specular, “strongly suggesting” that Kraken Mare exists in a liquid state.
The Cassini mission to Saturn was launched in 1997 by the National Aeronautics and Space Administration, began orbiting the giant planet in 2004 and soon found radar evidence of seas and lakes on Titan.
Since Cassini’s arrival, the northern polar regions of Titan have been shrouded in winter darkness. But the recent onset of spring in the northern hemisphere and the beginning of direct illumination by the sun have allowed scientists to begin the hunt for specular reflections. The moon’s northern hemisphere has more lakes and seas than the southern hemisphere, and the bodies there are larger.
The paper’s lead author is Katrin Stephan of the Institute of Planetary Research in Berlin. Her 14 co-authors are from the Free University of Berlin, the University of Arizona, the University of Idaho, Cornell University, the United States Geological Survey and the Jet Propulsion Laboratory of the California Institute of Technology.
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