|Volume: 03, Issue: 11||06/01/2005|
Cassini Seeing Red... On TitanSeveral of Cassiniís instruments have highlighted an unusual bright red spot on Saturnís moon Titan that is mystifying scientists. The spot, approximately the size and shape of West Virginia, is just southeast of the bright region called Xanadu.
The 300-mile-wide 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.
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, 345-mile-wide 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 at the Lunar and Planetary Laboratory at 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 color properties than this feature. This spot is persistent in both its color and location.
"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 300-foot-high 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 is hot.
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