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Astronomers think subsurface oceans exist on the Saturn moons Enceladus and Titan; the Jovian satellites Europa, Ganymede and Callisto; and a number of other solar system bodies. Indeed, such buried water may be abundant in the Kuiper Belt, the ring of frigid objects beyond Neptune's orbit, Nimmo said.

"My guess is that, on big Kuiper Belt objects, these kinds of oceans are pretty common," Nimmo said. "One of the lessons of the last 20 years is that oceans pop up in all kinds of unexpected places."