[meteorite-list] Odd Spot on Titan Baffles Scientists

[Ron Baalke]

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

Lori Stiles (520) 626-4402 
University of Arizona News Service, Tucson

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

News Release: 2005-086			May 25, 2005

Odd Spot on Titan Baffles Scientists 

Saturn's moon Titan shows an unusual bright spot that 
has scientists mystified.  The spot, approximately the 
size and shape of West Virginia, is just southeast of 
the bright region called Xanadu and is visible to 
multiple instruments on the Cassini spacecraft. 

The 483-kilometer-wide (300-mile) region may be a "hot" 
spot -- an area possibly warmed by a recent asteroid 
impact or by a mixture of water ice and ammonia from a 
warm interior, oozing out of an ice volcano onto colder 
surrounding terrain.  Other possibilities for the 
unusual bright spot include landscape features holding 
clouds in place or unusual materials on the surface.

"At first glance, I thought the feature looked strange, 
almost out of place," said Dr. Robert H. Brown, team 
leader of the Cassini visual and infrared mapping 
spectrometer and professor at the Lunar and Planetary 
Laboratory, University of Arizona, Tucson. "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 Cassini spacecraft flew by Titan on March 31 and 
April 16.  Its visual and infrared mapping spectrometer, 
using the longest, reddest wavelengths that the 
spectrometer sees, observed the spot, the brightest 
area ever observed on Titan.  

Cassini's imaging cameras saw a bright, 550-kilometer-wide 
(345-mile) semi-circle at visible wavelengths at this same 
location on Cassini's December 2004 and February 2005 Titan 
flybys.  

"It seems clear that both instruments are detecting the same 
basic feature on or controlled by Titan's surface," said 
Dr. Alfred S. McEwen, Cassini imaging team scientist, also 
of the University of Arizona. "This bright patch may be due 
to an impact event, landslide, cryovolcanism or atmospheric 
processes.  Its distinct color and brightness suggest that it 
may have formed relatively recently."

Other bright spots have been seen on Titan, but all have been 
transient features that move or disappear within hours, and 
have different spectral (color) properties than this feature.  
This spot is persistent in both its color and location.  "It's 
possible that the visual and infrared spectrometer is seeing a 
cloud that is topographically controlled by something on the 
surface, and that this weird, semi-circular feature is causing 
this cloud," said Dr. Elizabeth Turtle, Cassini imaging 
team associate, also from the Lunar and Planetary Laboratory.  

"If the spot is a cloud, then its longevity and stability imply 
that it is controlled by the surface.  Such a cloud might result 
from airflow across low mountains or outgassing caused by 
geologic activity," said Jason Barnes, a postdoctoral researcher 
working with the visual and infrared mapping spectrometer team 
at the University of Arizona.

The spot could be reflected light 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 added.

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 seen so far. 
Scientists doubt that Titan's crust could support such high 
mountains.

The visual and infrared mapping spectrometer team will be able 
to test the hot spot hypothesis on the July 2, 2006, Titan flyby, 
when they take nighttime images of the same 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 and http://www.nasa.gov/cassini . 
For additional images visit the visual and infrared mapping 
spectrometer 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, 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 visual and infrared mapping spectrometer 
team is based at the University of Arizona. The imaging team is 
based at the Space Science Institute in Boulder, Co.

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