TITAN'S HIDDEN OCEAN: A strange shift in the position of mountains and lakes on the surface of Saturn's moon Titan can best be explained, researchers say, by positing a layer of liquid water (blue) some 100 kilometers below the surface.NASA-JPL

Astronomers’ mental image of Titan, the solar system’s second-largest moon, used to be that of a vast swimming pool. But maybe they should have imagined a water bed instead.

Last year, researchers reported that radar mapping of Titan by the Cassini spacecraft had found a peculiar shift in landmarks on the moon’s surface of up to 19 miles (30 kilometers) between October 2004 and May 2007.

Now investigators say the best explanation is a moon-wide underground ocean that disconnects Titan’s icy crust from its rocky interior.

“We think the structure is about 100 kilometers of ice sitting atop a global layer of water … maybe hundreds of kilometers thick,” says Cassini scientist Ralph Lorenz of Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

If confirmed, Titan would be the fourth moon in the solar system thought to contain such an internal water ocean, joining Jupiter’s satellites Ganymede, Callisto and Europa. Researchers believe that heat from radioactivity in a moon’s core or gravitational squeezing may melt a layer of frozen water.
read on