Titan's Enigmatic Infrared-Bright Spot is Surface Make-Up

TITAN'S ENIGMATIC INFRARED-BRIGHT SPOT IS SURFACE MAKE-UP
From Lori Stiles, University Communications, UA, 520-621-1877
October 06, 2005

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Contact information listed at end of release
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A 300-mile-wide patch that outshines everything else on Titan at long
infrared wavelengths appears not to be a mountain, a cloud or a
geologically
active hot spot, University of Arizona scientists and Cassini team
members
say.

"We must be looking at a difference in surface composition," said Jason
W.
Barnes, a postdoctoral researcher at UA's Lunar and Planetary Lab.
"That's
exciting because this is the first evidence that says not all of the
bright
areas on Titan are the same. Now we have to figure out what those
differences are, what might have caused them."

When NASA's Cassini spacecraft flew by Titan on March 31 and again on
April
16, its visual and infrared mapping spectrometer saw a feature that was
spectacularly bright at 5-micron wavelengths just southeast of the
continent-sized region called Xanadu.

The bright spot occurs where Cassini's visible-wavelength imaging
cameras
photographed a bright arc-shaped feature approximately the same size in
December 2004 and February 2005.

Cassini's radar instrument, operating in the "passive" mode that is
sensitive to microwaves emitted from a planetary surface, saw no
temperature
difference between the bright spot and surrounding region. That rules
out
the possibility that the 5-micron bright spot is a hot spot, such as a
geologically active ice volcano, Barnes said.

Cassini microwave radiometry also failed to detect a temperature drop
that
would show up if some two-mile high mountain rose from Titan's surface,
he
said.

And if the 5-micron bright spot is a cloud, it's a cloud that hasn't
moved
or changed shape for three years, according to ground-based
observations
made at the Keck Telescope and with Cassini's visual and infrared
mapping
spectrometer during five different flybys. "If this is a cloud," Barnes
said, "it would have to be a persistent ground fog, like San Francisco
on
steroids, always foggy, all the time."

"The bright spot must be a patch of surface with a composition
different
from anything we've seen yet. Titan's surface is primarily composed of
ice.
It could be that something is contaminating the ice here, but what this
might be is not clear," Barnes said.

"There's a lot left to explore about Titan. It's a very complex,
exciting
place. It's not obvious how it works. It's going to be a lot of fun
over the
next couple of years figuring out how Titan works," he said.

Barnes and 34 other scientists report the research in the Oct. 7 issue
of
Science. Authors include UA Lunar and Planetary Laboratory scientists
and
Cassini team members Robert H. Brown, head of Cassini's visual and
infrared
mapping spectrometer team; Elizabeth P. Turtle and Alfred S. McEwen of
the
Cassini imaging team; Ralph D. Lorenz of the Cassini radar team;
Caitlin
Griffith of the Cassini visual and infrared mapping team; and Jason
Perry
and Stephanie Fussner, who work with McEwen and Turtle on Cassini
imaging.

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, Calif.,
manages the mission for NASA's Science Mission Directorate, Washington,
D.C.
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. The Visual and Infrared Mapping Spectrometer team is
based
at The University of Arizona in Tucson.

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Contact Information
Robert H. Brown 520-626-9045
Jason Barnes 520-626-1356
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