for National Geographic News
Radar images of Titan, Saturn's largest moon, reveal a continent-size region of river valleys, hills, plains, and mountains. The area looks remarkably similar to terrain here on Earth, scientists say.
Mapping the region, called Xanadu, was one of the primary goals of the Cassini probe, now orbiting Saturn (Saturn wallpaper). The images were taken on an April 30 flyby that used radar to map a 2,800-mile-long (4,500-kilometer-long) strip of the area.
Xanadu has enticed scientists since 1994, when infrared images from the Hubble Space Telescope found a large, Australia-size bright spot on one side of Titan.
The bright spot, Xanadu, is so big it covers a tenth of the moon's surface.
"It is the only part of Titan that was named before Cassini got there, because it was such a strikingly large feature," said Jonathan Lunine, a planetary scientist from the Lunar and Planetary Laboratory at the University of Arizona in Tucson.
The name Xanadu comes from Samuel Taylor Coleridge's famous poem "Kubla Khan," about a mysterious realm where a river runs to a sunless sea.
Dense clouds shroud Titan's surface, making it mysterious and sunless as well. And the name turns out to be prescient, because Xanadu is chock full of river channels.
Xanadu also looks remarkably familiar.
"The images look much like radar images of Earth," Lunine said in a telephone interview. "I'm staring at an image of Arizona on my wall, and it doesn't look a lot different."
The pictures reveal a convoluted land of hills, river channels, and mountains that might be several thousand feet (one kilometer) tallroughly the height of the U.S. Appalachian Mountains.
But the area more closely resembles the U.S. Southwest. That's because the river networks look like those found in deserts, where tributary systems are simpler than in wetter areas.
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