New radar images of Saturn's moon Titan reveal
dunes, hills, valleys and rivers that scientist say look a lot like home.
But on Titan, which is frigid and shrouded in
smog, the features are likely carved in ice rather than solid ground.
The detailed view is of a bright area on Titan
called Xanadu.
It's about the size of Australia and has been studied from afar for years. Now
scientists are getting a better look with NASA's Cassini spacecraft. Radar is bounced
off the surface to generate an image that cannot be made using visible-light
observations because the orbiting spacecraft can't see through the moon's thick
atmosphere.
The observations reveal mountains about as high
as the Appalachians.
"Surprisingly, this cold, faraway region
has geological features remarkably like Earth," said Jonathan Lunine, a
Cassini researcher at the University of Arizona.
The river channels are likely carved by liquid
methane or ethane, as the moon is too cold for water to be liquid.
"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.
Liquid methane might fall as rain or trickle
from springs to create the rivers, Lunine and his colleagues figure. Perhaps
the rivers carry grains of material that accumulate as dunes elsewhere.
"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. "Xanadu has been
washed clean. What is left underneath looks like very porous water ice, maybe
filled with caverns."
Image Gallery: Imagining Saturn and Titan
Image Gallery: Cassini's Latest Discoveries
Cassini Sees Xanadu on Saturn's Moon Titan