Cassini Reveals Lake-Like Feature on Titan

http://ciclops.org/view.php?id=1194

NASA'S CASSINI REVEALS LAKE-LIKE FEATURE ON TITAN

MEDIA RELATIONS OFFICE
CASSINI IMAGING CENTRAL LABORATORY FOR OPERATIONS (CICLOPS)
SPACE SCIENCE INSTITUTE, BOULDER, COLORADO
http://ciclops.org



Preston Dyches (720) 974-5859
Cassini Imaging Central Laboratory for Operations
Space Science Institute, Boulder, Colo.

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

Erica Hupp/Dolores Beasley (202) 358-1237/1753
NASA Headquarters, Washington

For Immediate Release: June 28, 2005


NASA'S CASSINI REVEALS LAKE-LIKE FEATURE ON TITAN

Scientists are fascinated by a dark, lake-like feature recently
observed on Saturn's moon Titan.

NASA's Cassini spacecraft captured a series of images, released today,
showing a marking, darker than anything else around it. It is
remarkably lake-like, with smooth, shore-like boundaries unlike any
seen previously on Titan.

"I'd say this is definitely the best candidate we've seen so far for a
liquid hydrocarbon lake on Titan," said Dr. Alfred McEwen, imaging
team member and a professor at the University of Arizona, Tucson. The
putative lake measures 230 kilometers by 70 kilometers (145 miles long
by 45 miles) wide, about the size of Lake Ontario, on the U.S.
Canadian border.

The feature lies in Titan's cloudiest region, which is presumably the
most likely site of recent methane rainfall. This, coupled with the
shore-like smoothness of the feature's perimeter makes it hard for
imaging scientists to resist some speculation about what might be
filling the lake, if it indeed is one.

Cassini imaging team member Dr. Tony DelGenio of NASA's Goddard
Institute for Space Studies in New York, said, "It's possible that
some of the storms in this region are strong enough to make methane
rain that reaches the surface. Given Titan's cold temperatures, it
might take a long time for any liquid methane collecting on the
surface to evaporate. So it might not be surprising for a
methane-filled lake to persist for a long time."

A computer-enhanced image of the feature and a three-frame movie
showing the evolution of nearby clouds can be seen at:
http://ciclops.org, http://saturn.jpl.nasa.gov and
http://www.nasa.gov/cassini.

Despite earlier predictions, no definitive evidence for open bodies of
liquid has yet been found on Titan. Cassini has not yet been in a
favorable position for using the camera to check for glints from
possible surface liquids in the south polar region.

"This feature is unique in our exploration of Titan so far," said Dr.
Elizabeth Turtle, Cassini imaging team associate at the University of
Arizona. "Its perimeter is intriguingly reminiscent of the shorelines
of lakes on Earth, which are smoothed by water erosion and deposition."

An alternate explanation is that this feature was once a lake, but has
since dried up, leaving behind dark deposits, Turtle said. Yet another
possibility is that the lake is simply a broad depression filled by
dark, solid hydrocarbons falling from the atmosphere onto Titan's
surface. In this case, the smooth outline might be the result of a
process unrelated to rainfall, such as a sinkhole or a volcanic
caldera.

Dr. Torrence Johnson, an imaging team member at NASA's Jet Propulsion
Laboratory (JPL) in Pasadena, Calif., said, "It reminds me of the lava
lakes seen on Jupiter's moon, Io."

"Eventually, as the seasons change over a few years, the convective
clouds may migrate northward to lower latitudes," said DelGenio, "If
so, it will be interesting to see whether the Cassini cameras record
changes in the appearance of the surface as well."

"It is already clear that whatever this lake-like feature turns out to
be, it is only one of many puzzles that Titan will throw at us as we
continue our reconnaissance of the surface over the next few years,"
said Dr. Carolyn Porco, imaging team leader at the Space Science
Institute in Boulder, Colo.

Thirty-nine more Titan flybys are planned for Cassini's prime mission.
In future flybys the science teams will search for opportunities to
observe the lake feature again and to look for mirror-like reflections
from smooth surfaces elsewhere on Titan. Such reflections would
strongly support the presence of liquids.

The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. JPL, a division of
the California Institute of Technology in Pasadena, manages the
Cassini mission for NASA's Science Mission Directorate, Washington.
The Cassini orbiter and its two onboard cameras were designed,
developed and assembled at JPL. The imaging team is based at the Space
Science Institute in Boulder, Colo.