Glint of Sunlight Confirms Liquid in Northern Lake District of Titan

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
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Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jia-rui.c.cook@jpl.nasa.gov

Image advisory: 2009-199 Dec. 17, 2009

Glint of Sunlight Confirms Liquid in Northern Lake District of Titan

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2009-199&cid=kintera_advisory_2009-199

PASADENA, Calif. -- NASA's Cassini Spacecraft has captured the first flash of sunlight
reflected off a lake on Saturn's moon Titan, confirming the presence of liquid on the part of the
moon dotted with many large, lake-shaped basins.

Cassini scientists had been looking for the glint, also known as a specular reflection, since the
spacecraft began orbiting Saturn in 2004. But Saturn's northern hemisphere, which has more lakes
than the southern hemisphere, has been veiled in winter darkness. The sun only began to directly
illuminate the northern lakes recently as it approached the equinox of August 2008, the start of
spring in the northern hemisphere. Titan's hazy atmosphere also blocked out reflections of
sunlight in most wavelengths. This serendipitous image was captured on July 8, 2009, using
Cassini's visual and infrared mapping spectrometer.

The new infrared image is available online at: http://www.nasa.gov/cassini,
http://saturn.jpl.nasa.gov and http://wwwvims.lpl.arizona.edu.

This image will be presented Friday, Dec. 18, at the fall meeting of the American Geophysical
Union in San Francisco.

"This one image communicates so much about Titan -- thick atmosphere, surface lakes and an
otherworldliness," said Bob Pappalardo, Cassini project scientist, based at NASA's Jet
Propulsion Laboratory, Pasadena, Calif. "It's an unsettling combination of strangeness yet
similarity to Earth. This picture is one of Cassini's iconic images."

Titan, Saturn's largest moon, has captivated scientists because of its many similarities to Earth.
Scientists have theorized for 20 years that Titan's cold surface hosts seas or lakes of liquid
hydrocarbons, making it the only other planetary body besides Earth believed to harbor liquid on
its surface. While data from Cassini have not indicated any vast seas, they have revealed large
lakes near Titan's north and south poles.

In 2008, Cassini scientists using infrared data confirmed the presence of liquid in Ontario Lacus,
the largest lake in Titan's southern hemisphere. But they were still looking for the smoking gun to
confirm liquid in the northern hemisphere, where lakes are also larger.

Katrin Stephan, of the German Aerospace Center (DLR) in Berlin, an associate member of the
Cassini visual and infrared mapping spectrometer team, was processing the initial image and was
the first to see the glint on July 10th.

"I was instantly excited because the glint reminded me of an image of our own planet taken from
orbit around Earth, showing a reflection of sunlight on an ocean," Stephan said. "But we also had
to do more work to make sure the glint we were seeing wasn't lightning or an erupting volcano."

Team members at the University of Arizona, Tucson, processed the image further, and scientists
were able to compare the new image to radar and near-infrared-light images acquired from 2006
to 2008.

They were able to correlate the reflection to the southern shoreline of a lake called Kraken Mare.
The sprawling Kraken Mare covers about 400,000 square kilometers (150,000 square miles), an
area larger than the Caspian Sea, the largest lake on Earth. It is located around 71 degrees north
latitude and 337 degrees west latitude.

The finding shows that the shoreline of Kraken Mare has been stable over the last three years and
that Titan has an ongoing hydrological cycle that brings liquids to the surface, said Ralf Jaumann,
a visual and infrared mapping spectrometer team member who leads the scientists at the DLR
who work on Cassini. Of course, in this case, the liquid in the hydrological cycle is methane
rather than water, as it is on Earth.

"These results remind us how unique Titan is in the solar system," Jaumann said. "But they also
show us that liquid has a universal power to shape geological surfaces in the same way, no matter
what the liquid is."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and
the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate,
Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The visual
and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

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