Cassini Finds Lakes On Titan's Arctic Region

July 28, 2006

Dwayne Brown/Erica Hupp
Headquarters, Washington
202-358-1726/1237

Carolina Martinez
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-9382

RELEASE: 06-274

CASSINI FINDS LAKES ON TITAN'S ARCTIC REGION

NASA's Cassini spacecraft has found lakes on Saturn's moon Titan.

The lakes are most likely the source of hydrocarbon smog in the frigid
moon's atmosphere. Finding the source of the complex soup of
hydrocarbons in Titan's atmosphere has been a major goal for the
Cassini mission and is a significant accomplishment.

Numerous well-defined dark patches resembling lakes are present in
radar images of Titan's high latitudes taken during a July 22 flyby.
At Titan's frigid temperatures, about minus 180 degrees Celsius, the
liquids in the lakes are most likely methane or a combination of
methane and ethane.

"This is a big deal," said Steve Wall, deputy radar team leader at
NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We've now seen a
place other than Earth where lakes are present."

This area of Titan has been in winter's shadow since before Cassini
arrived, and the spacecraft had not flown over it before. During the
flyby, Cassini's radar spotted several dozen lakes as small as 0.6
miles wide, with some nearly 20 miles wide. The biggest lake is about
62 miles long and may be only partly wet.

"What we see is darker than anything we've ever seen elsewhere on
Titan. It was almost as though someone laid a bull's-eye around the
whole north pole of Titan, and Cassini sees these regions of lakes
just like those we see on Earth," said Larry Soderblom, Cassini
interdisciplinary scientist at the U.S. Geological Survey, Flagstaff,
Ariz. "Titan has turned out to be like a musical crescendo -- each
pass is more exciting than the last."

Titan has not yielded its secrets easily because the dense smoggy
atmosphere makes it very difficult to obtain good visible images.
Radar can penetrate the smog and obtain clear images.

Dark regions in radar images generally mean smoother terrain, while
bright regions mean a rougher surface. Some of the new radar images
show channels leading in or out of a variety of dark patches. The
shape of the channels also strongly implies they were carved by
liquid.

Some of the dark patches and connecting channels are completely black
-- they reflect back essentially no radar signal, which means they
must be extremely smooth and might contain liquid. In some cases
rimscan be seen around the dark patches, suggesting deposits that might

form as liquid evaporates.

Scientists had predicted, but had no confirmation until now, that
pools of liquid were contributing to the high concentration of
methane and other hydrocarbons in Titan's atmosphere.

"We've always believed Titan's methane had to be maintained by liquid
lakes or extensive underground 'methanofers,' the methane equivalent
of aquifers. We can't see methanofers but we can now say we've seen
lakes," said Jonathan Lunine, Cassini interdisciplinary scientist at
the University of Arizona, Tucson.

Since lakes come and go with the seasons, they wax and wane over time,
and winds might alter the roughness of their surfaces. Repeat
coverage of these areas is expected to provide more information on
these lakes. By passing over a lake in a different direction, Cassini
may see the effect of prevailing winds in the changing brightness of
the lake surface. On later passes toward the end of its prime
mission, Cassini might see changes in the shape or size of lakes as
winter yields to spring in the northern hemisphere.

Cassini's next flyby is on September 7. In October, Cassini's radar
will look even closer to the north pole, searching for more lakes and
mapping more of the polar region covered by these features.

The Cassini-Huygens mission is a cooperative project between NASA, the
European Space Agency and the Italian Space Agency. The Jet
Propulsion Laboratory manages the Cassini-Huygens mission for NASA's
Science Mission Directorate, Washington.

For images on the lakes and more information, visit:

http://www.nasa.gov/cassini


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