[meteorite-list] Cassini Reveals Titan's Xanadu Region To Be An Earth-Like Land

[Ron Baalke]

July 19, 2006

Dwayne Brown/Erica Hupp
Headquarters, Washington 
202-358-1726/1237 

Carolina Martinez 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-9382
RELEASE: 06-281

CASSINI REVEALS TITAN'S XANADU REGION TO BE AN EARTH-LIKE LAND

New radar images from NASA's Cassini spacecraft revealed geological 
features similar to Earth on Xanadu, an Australia-sized, bright 
region on Saturn's moon Titan. 

These radar images, from a strip more than 2,796 miles long, show 
Xanadu is surrounded by darker terrain, reminiscent of a 
free-standing landmass. At the region's western edge, dark sand dunes 
give way to land cut by river networks, hills and valleys. These 
narrow river networks flow onto darker areas, which may be lakes. A 
crater formed by the impact of an asteroid or by water volcanism is 
also visible. More channels snake through the eastern part of Xanadu, 
ending on a dark plain where dunes, abundant elsewhere, seem absent. 
Appalachian-sized mountains crisscross the region. 

"We could only speculate about the nature of this mysterious bright 
country, too far from us for details to be revealed by Earth-based 
and space-based telescopes. Now, under Cassini's powerful radar eyes, 
facts are replacing speculation," said Jonathan Lunine, Cassini 
interdisciplinary scientist at the University of Arizona, Tucson. 
"Surprisingly, this cold, faraway region has geological features 
remarkably like Earth."

Titan is a place of twilight, dimmed by a haze of hydrocarbons 
surrounding it. Cassini's radar instrument can see through the haze 
by bouncing radio signals off the surface and timing their return. In 
the radar images bright regions indicate rough or scattering 
material, while a dark region might be smoother or more absorbing 
material, possibly liquid.

Xanadu was first discovered by NASA's Hubble Space Telescope in 1994 
as a striking bright spot seen in infrared imaging. When Cassini's 
radar system viewed Xanadu on April 30, 2006, it found a surface 
modified by winds, rain, and the flow of liquids. At Titan's frigid 
temperatures, the liquid cannot be water; it is almost certainly 
methane or ethane. 

"Although Titan gets far less sunlight and is much smaller and colder 
than Earth, Xanadu is no longer just a mere bright spot, but a land 
where rivers flow down to a sunless sea," Lunine said. 

Observations by the European Space Agency's Huygens probe, that 
Cassini carried to Titan, and by NASA's Voyager spacecraft strongly 
hint that both methane rain and dark orange hydrocarbon solids fall 
like soot from the moon's dark skies. 

On Xanadu, liquid methane might fall as rain or trickle from springs. 
Rivers of methane might carve the channels and carry off grains of 
material to accumulate as sand dunes elsewhere on Titan. 

"This land is heavily tortured, convoluted and filled with hills and 
mountains," said Steve Wall, the Cassini radar team's deputy leader 
at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "There appear 
to be faults, deeply cut channels and valleys. Also, it appears to be 
the only vast area not covered by organic dirt. Xanadu has been 
washed clean. What is left underneath looks like very porous water 
ice, maybe filled with caverns.

"In the 1980s, it took the shuttle imaging radar to discover 
subsurface rivers in the Sahara. Similarly, if it hadn't been for the 
Cassini radar, we would have missed all of this. We have a newly 
discovered continent to explore," Wall said.

Cassini will view Titan again on Saturday, July 22, exploring the high 
northern latitudes. In the next two years the orbiter will fly by 
Titan 29 times, nearly twice as many encounters as in the first half 
of Cassini's four-year prime mission. Twelve of the planned flybys 
will use radar. 

For Cassini images and information, visit: 

http://www.nasa.gov/cassini

The Cassini-Huygens mission is a cooperative project between NASA, the 
European Space Agency and the Italian Space Agency. The Jet 
Propulsion Laboratory manages the Cassini-Huygens mission for NASA's 
Science Mission Directorate, Washington.
	
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