[meteorite-list] Cassini Spies The Brightest Infrared Spot on Titan

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed May 25 17:48:51 2005
Message-ID: <200505252148.j4PLmBC21991_at_zagami.jpl.nasa.gov>

CASSINI SPIES THE BRIGHTEST INFRARED SPOT ON TITAN
>From University of Arizona News Services, 520-621-1877
May 25, 2005

* * *Image and contact information listed at end of release * * *


Something odd is happening on Titan just southeast of Xanadu.

When the Cassini spacecraft flew by Titan on March 31 and again on April
16, its Visual and Infrared Mapping Spectrometer (VIMS) saw a spectacular,
300-mile-wide (500 kilometer) bright spot at long infrared wavelengths. The
spot was just southeast of the continent-sized region called Xanadu.

At 5-micron wavelengths -- the longest, reddest wavelengths that VIMS sees
-- the red spot is the brightest area yet seen on Titan. The feature is the
size and shape of West Virginia and 50 percent brighter than bright Xanadu.

The bright spot appears to be at the same location where Cassini's Imaging
Science Subsystem (ISS) saw a bright, 345-mile (550-kilometer) wide
semi-circle at visible wavelengths in December 2004. ISS saw the arc-shaped
feature again at lower resolution during the February 2005 flyby.

VIMS and ISS scientists combined their results for a complementary look at
the infrared-bright feature on Saturn's moon, Titan.

"At first glance, I thought the feature looked strange, almost out of
place," said University of Arizona Professor Robert H. Brown of the Lunar
and Planetary Laboratory (LPL), head of the VIMS team. "After thinking a
bit, I speculated that it was a hot spot. In retrospect, that might not be
the best hypothesis, but the spot is no less intriguing."

"The spot is maybe only 10 percent brighter at shorter, or bluer, infrared
wavelengths," said Jason Barnes, a UA postdoctoral researcher who works with
Brown. "But at these longer infrared wavelengths, this is a whopping
difference in spectrum, or color. It's just the kind of thing we've been
looking for. Unfortunately, we don't know yet what it is."

The VIMS team suggests that the bright red spot is either a surface
coloration -- the strange reflection from an unusual patch of Titan's
surface -- or mountains, a cloud or a hot spot, Barnes said.

"It seems clear that ISS and VIMS are detecting the same basic feature on
or controlled by Titan's surface," said ISS team scientist Alfred S. McEwen,
who directs LPL's Planetary Imaging Research Laboratory. "This bright patch
may be due to an impact event, landslide, cryovolcanism or atmospheric
processes. Its distinct color and brightness suggests that it may have
formed relatively recently."

"The feature seen by ISS looks like it's on the surface," said LPL's
Elizabeth (Zibi) Turtle. Turtle is an associate on the Cassini imaging team,
which is headed by UA adjunct Professor Carolyn Porco of the Space Science
Institute in Boulder, Colo.

"It's possible that VIMS is seeing a cloud that is topographically
controlled by something on the surface, and that this weird, semi-circular
feature is causing this cloud," Turtle said.

Other bright spots have been seen on Titan, but all have been transient
features that move or disappear within hours, and they have different
spectral (color) properties than this feature has.

If the feature is a cloud, it reflects light in a way that is
uncharacteristic of clouds, Brown said.

Barnes checked VIMS images from previous Titan passes, in July and October
2004, and found a bright spot consistent with the size and shape with the
spot first identified by VIMS images from the March 2005 flyby. "If the spot
is a cloud, then its longevity and stability imply that it is controlled by
the surface," he said. "Such a cloud might result from airflow across low
mountains or outgassing caused by geologic activity."

The bright red spot could be reflections from a patch of terrain made up of
some exotic surface material. "Titan's surface seems to be mostly dirty ice.
The bright spot might be a region with different surface composition, or
maybe a thin surface deposit of non-icy material," Barnes said.

Scientists have also considered that the spot might be mountains. If so,
they'd have to be much higher than the 100-meter-high (300-foot) hills
Cassini's radar altimeter has so far seen. Scientists doubt that Titan's
crust could support such high mountains.

Another possibility is that the bright region is a "hot" spot, an area
warmed by a recent asteroid impact or warmed by a mixture of water ice and
ammonia oozing out of an ice volcano over the colder surrounding terrain.

The VIMS team will be able to test the hot spot hypothesis on the July 2,
2006 Titan flyby, when VIMS will take nighttime images of the area. If the
spot glows at night, researchers will know it's hot.

For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov . For additional images visit the VIMS page at
http://wwwvims.lpl.arizona.edu and the Cassini imaging team homepage
http://ciclops.org.

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 .

-------------------------------------------------------

Images online at:
VIMS -http://wwwvims.lpl.arizona.edu/
ISS - http://ciclops.org
Cassini - http://saturn.jpl.nasa.gov/

Science contacts
 Robert H. Brown 520-626-9045 rhb_at_lpl.arizona.edu
 Jason Barnes 520-626-1356 jbarnes_at_barnesos.net
 Alfred S. McEwen 520-621-4573 mcewen_at_lpl.arizona.edu
 Elizabeth (Zibi) Turtle 520-621-8284 turtle_at_lpl.arizona.edu

 Media contacts
 Lori Stiles UA News Services
     520-626-4402 lstiles_at_u.arizona.edu
 Preston Dyches CICLOPS/Space Science Institute
    720-974-5859 media_at_ciclops.org
 Carolina Martinez Jet Propulsion Laboratory Media Relations
    818-354-9382 Carolina.Martinez_at_jpl.nasa.gov
Received on Wed 25 May 2005 05:48:10 PM PDT