Dec. 16, 2008

Rachel Prucey 
Ames Research Center, Moffett Field, Calif.
650-604-0643
rachel.l.prucey@nasa.gov 

Carolina Martinez
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-9382
carolina.martinez@jpl.nasa.govRELEASE: 08-110AR

TITAN’S VOLCANOES GIVE NASA SPACECRAFT CHILLY RECEPTION

MOFFETT FIELD, Calif. -- Data collected during several recent flybys 
of Titan by NASA's Cassini spacecraft have put another arrow in the 
quiver of scientists who think the Saturnian moon contains active 
cryovolcanoes spewing a super-chilled liquid into its atmosphere. The 
information was released today during a meeting of the American 
Geophysical Union in San Francisco. 

"Cryovolcanoes are some of the most intriguing features in the solar 
system," said Rosaly Lopes, a Cassini radar team investigation 
scientist from NASA's Jet Propulsion Laboratory in Pasadena, Calif. 
"To put them in perspective -- if Mount Vesuvius had been a 
cryovolcano, its lava would have frozen the residents of Pompeii." 

Rather than erupting molten rock, it is theorized that the 
cryovolcanoes of Titan would erupt volatiles such as water, ammonia 
and methane. Scientists have suspected cryovolcanoes might inhabit 
Titan, and the Cassini mission has collected data on several previous 
passes of the moon that suggest their existence. Imagery of the moon 
has included a suspect haze hovering over flow-like surface 
formations. Scientists point to these as signs of cryovolcanism 
there. 

"Cassini data have raised the possibility that Titan's surface is 
active," said Jonathan Lunine, a Cassini interdisciplinary scientist 
from the Lunar and Planetary Laboratory, University of Arizona, 
Tucson. "This is based on evidence that changes have occurred on the 
surface of Titan, between flybys of Cassini, in regions where radar 
images suggest a kind of volcanism has taken place." 

What led some Cassini scientists to believe that things are happening 
now were changes in brightness and reflectance detected at two 
separate and distinct regions of Titan. Reflectance is the ratio of 
light that radiates onto a surface to the amount reflected back. 
These changes were documented by Visible and Infrared Mapping 
Spectrometer data collected on Titan flybys from July 2004 to March 
2006. In one of the two regions, the reflectance of the surface 
surged upward and remained higher than expected. In the other region, 
the reflectance shot up but then trended downward. There is also 
evidence that ammonia frost is present at one of the two changing 
sites. The ammonia was evident only at times when the region was 
inferred to be active. 

"Ammonia is widely believed to be present only beneath the surface of 
Titan," said Robert M. Nelson of JPL, a scientist for Cassini's 
Visual and Infrared Mapping Spectrometer team. "The fact that we 
found it appearing at times when the surface brightened strongly 
suggests that material was being transported from Titan's interior to 
its surface." Some Cassini scientists indicate that such volcanism 
could release methane from Titan's interior, which explains Titan's 
seemingly continuous supply of fresh methane. Without replenishment, 
scientists say, Titan's original atmospheric methane should have been 
exhausted long ago. 

But other scientists familiar with the spectrometer data argue that 
the ammonia identification is not certain, and that the purported 
brightness changes might not be associated with changes on Titan's 
surface. Instead they might result from the transient appearances of 
ground "fogs" of ethane droplets very near Titan's surface, driven by 
atmospheric rather than geophysical processes. Nelson has considered 
the ground fog option, stating, "There remains the possibility that 
the effect is caused by a local fog, but if so, we would expect it to 
change in size over time due to wind activity, which is not what we 
see." 

The chilly volcanoes of Titan are not a fait accompli. An alternative 
hypothesis to an active Titan suggests the Saturnian moon could be 
taking its landform evolution cues from a moon of Jupiter. 

"Like Callisto, Titan may have formed as a relatively cold body, and 
may have never undergone enough tidal heating for volcanism to 
occur," said Jeffrey Moore, a planetary geologist at the NASA Ames 
Research Center, Moffett Field, Calif. "The flow-like features we see 
on the surface may just be icy debris that has been lubricated by 
methane rain and transported downslope into sinuous piles like 
mudflows." 

More revelations may be forthcoming. Scientists are still analyzing 
the data from Cassini's most recent flyby on Dec. 5, 2008. Cassini's 
next Titan flyby is scheduled in 11 days, when the spacecraft will 
come within 970 kilometers (603 miles) of its cloud-shrouded surface. 


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 
mission for NASA's Science Mission Directorate in Washington, D.C. 
The Cassini orbiter was designed, developed and assembled at JPL. The 
radar instrument was built by JPL and the Italian Space Agency, 
working with team members from the United States and several European 
countries. The Visual and Infrared Mapping Spectrometer team is based 
at the University of Arizona. 

For more information about the Cassini-Huygens mission, visit: 

http://www.nasa.gov/cassinil

	
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