Glint of Sunlight Confirms Liquid in Northern Lake District of Titan

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Glint of Sunlight Confirms Liquid in Northern Lake District of Titan
Jet Propulsion Laboratory
December 17, 2009

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 Titan'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 2009, 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.

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jia-rui...@jpl.nasa.gov

2009-199