NASA Confirms Liquid Lake on Saturn Moon

MEDIA RELATIONS OFFICE
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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http://www.jpl.nasa.gov

Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

Lori Stiles 520-360-0574
University of Arizona, Tucson
lstiles@u.arizona.edu

NEWS RELEASE: 2008-152 July 30, 2008

NASA Confirms Liquid Lake on Saturn Moon

PASADENA, Calif. -- NASA scientists have concluded that at least one of the large lakes observed
on Saturn's moon Titan contains liquid hydrocarbons, and have positively identified the presence of
ethane. This makes Titan the only body in our solar system beyond Earth known to have liquid on its
surface.

Scientists made the discovery using data from an instrument aboard the Cassini spacecraft. The
instrument identified chemically different materials based on the way they absorb and reflect infrared
light. Before Cassini, scientists thought Titan would have global oceans of methane, ethane and other
light hydrocarbons. More than 40 close flybys of Titan by Cassini show no such global oceans exist,
but hundreds of dark, lake-like features are present. Until now, it was not known whether these
features were liquid or simply dark, solid material.

"This is the first observation that really pins down that Titan has a surface lake filled with liquid,"
said Bob Brown of the University of Arizona, Tucson. Brown is the team leader of Cassini's visual
and mapping instrument. The results will be published in the July 31 issue of the journal Nature.

Ethane and several other simple hydrocarbons have been identified in Titan's atmosphere, which
consists of 95 percent nitrogen, with methane making up the other fiver percent. Ethane and other
hydrocarbons are products from atmospheric chemistry caused by the breakdown of methane by
sunlight.

Some of the hydrocarbons react further and form fine aerosol particles. All of these things in Titan's
atmosphere make detecting and identifying materials on the surface difficult, because these particles
form a ubiquitous hydrocarbon haze that hinders the view. Liquid ethane was identified using a
technique that removed the interference from the atmospheric hydrocarbons.

The visual and mapping instrument observed a lake, Ontario Lacus, in Titan's south polar region
during a close Cassini flyby in December 2007. The lake is roughly 20,000 square miles (7,800
square miles) in area, slightly larger than North America's Lake Ontario.

"Detection of liquid ethane confirms a long-held idea that lakes and seas filled with methane and
ethane exist on Titan," said Larry Soderblom, a Cassini interdisciplinary scientist with the U.S.
Geological Survey in Flagstaff, Ariz. "The fact we could detect the ethane spectral signatures of the
lake even when it was so dimly illuminated, and at a slanted viewing path through Titan's
atmosphere, raises expectations for exciting future lake discoveries by our instrument."

The ethane is in a liquid solution with methane, other hydrocarbons and nitrogen. At Titan's surface
temperatures, approximately 300 degrees Fahrenheit below zero, these substances can exist as both
liquid and gas. Titan shows overwhelming evidence of evaporation, rain, and fluid-carved channels
draining into what, in this case, is a liquid hydrocarbon lake.

Earth has a hydrological cycle based on water and Titan has a cycle based on methane. Scientists
ruled out the presence of water ice, ammonia, ammonia hydrate and carbon dioxide in Ontario Lacus.
The observations also suggest the lake is evaporating. It is ringed by a dark beach, where the black
lake merges with the bright shoreline. Cassini also observed a shelf and beach being exposed as the
lake evaporates.

"During the next few years, the vast array of lakes and seas on Titan's north pole mapped with
Cassini's radar instrument will emerge from polar darkness into sunlight, giving the infrared
instrument rich opportunities to watch for seasonal changes of Titan's lakes," Soderblom said.

More information is available at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and
http://wwwvims.lpl.arizona.edu .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the
Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of
Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission
Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The
Visual and Infrared Mapping Spectrometer team is based at the University of Arizona.

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