Scientists involved in the study have calculated that this could be done by winds generated from seasonal changes as Titan and Saturn slowly circle the sun.
With no underground ocean, the winds would have to push against the inertia of the entire moon, which is about 3,200 miles (5,150 kilometers) in diameter.
"You would have to have really killer winds to have any effect," Stiles said.
But if there is an ocean 60 to 180 miles (100 to 300 kilometers) below the surface, it would be easy for such winds to push the crust around in the observed manner, Stiles said.
It's an exciting prospect, said the study's lead author, Ralph Lorenz, a planetary scientist at Johns Hopkins University in Baltimore, Maryland.
That's because the ocean is most likely comprised of water and ammonia, while the planet's surface contains large quantities of hydrocarbons and other organic molecules. (Related: "Saturn Moon Has Lakes, "Water" Cycle Like Earth's, Scientists Say" [January 5, 2007].)
"Mixing organics and water is a very appealing astrobiological recipe," Lorenz said by email.
Stiles added: "It gives us one more place to look for life."
This is a "very important finding," said Christophe Sotin, a geophysicist at NASA's Jet Propulsion Laboratory who was not involved in the study.
But it needs to be confirmed, he said, by watching what happens to Titan's rotation as the winds shift in upcoming years.
If the crust's drift doesn't slow down and reverse course as the wind pattern changes, something else is causing the deviation from the previously expected rotation.
But if the ocean does exist, it would raise to four the number of large moons of Saturn and Jupiter thought to have such subterranean seas.
"Large reservoirs of water, a condition for life to form and develop, [would thus be] a common feature in the solar system," a team led by Sotin wrote in a commentary article in tomorrow's issue of Science.
But even without that carrot, the prospect of an ocean simply adds to Titan's mystique.
"Titan is very Earthlike compared to other bodies," Stiles said. "We see lakes—not water, but liquid. We see dunes, like in the Sahara desert. We see mountains and channels that look like river channels. It's one of the few other bodies that has weather."
(Related: "Titan Forecast: Cold, Drizzly Mornings" [October 11, 2007].)
"There aren't too many other bodies in the solar system where you see all these things going on," he added. "This deep ocean just adds to it."
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