"But the liquid isn't water, and the mountains aren't rock," Lunine said. "Almost certainly, the liquid is methane and the mountains are water ice."
Intermixed with the peaks are dark, flat areas that might be lakes or playas (dry lake beds). "The radar doesn't tell us if it's liquid, but between the hills are some flat plains," Lunine said.
Some of the mountains form ridges, but again the similarity is to desert, because the ridges are relatively short and scattered.
"It's not like the Rocky Mountains, where you've got this huge chain that stretches for a very long distance," Lunine said.
It's still rugged terrain, though.
"I wouldn't want to drive a rover over that stuff," said fellow Titan researcher Ralph Lorenz via email.
"We expected from early low-resolution radar data that Xanadu had to be rough," added Lorenz, also of the Lunar and Planetary Laboratory.
"So for onceTitan has given us so many surpriseswe got something right."
Xanadu appears to rise above a dry surrounding lowland. On one side Xanadu is bounded by vast, spreading sand dunes, similar to those seen on other parts of Titan (read "Saturn Moon Has Seas of Sand, Images Reveal" [May 4, 2006]).
But the dunes don't resume on Xanadu's far side.
"It seems that Xanadu is interrupting the wind flow," Lunine said
The next radar-mapping flyby is scheduled for tomorrow, when Cassini will pass over Titan's far north, where scientists hope to find lakes of liquid methane.
All told, Cassini is scheduled to do radar flybys of about 20 to 25 percent of Titan's surfacea number that might be stretched to 30 percent if the orbiter doesn't suffer a major breakdown.
But don't expect Cassini to reveal all of Titan's secrets. "Every pass looks different," Lunine said. "If you covered only 30 percent of the Earth, think of all the things you would have missed."
"It really [shows] how varied Titan's landscape is," Lorenz said.
"You have these dark plains with sand dunes around much of the equator, and then on the leading face of Titan, you hit this 'continent' of rugged mountains. It really argues for further exploration by a balloon or other aircraft that can visit all these terrains."
Steve Wall of NASA added in a statement, "We have a newly discovered continent to explore, just like the early explorers of America."
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