Possible ocean under Titan's crust

Cool! (literally)

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.

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Luckily, the group's model is testable. It predicts a quickening of Titan's rotation rate in the coming year or two followed by a slowdown—something that can be measured on succeeding Cassini flybys.

This last bit about the theory being testable makes this more interesting to me. It's a great example to share with students. My 6th grade class is beginning a unit on geology today after finishing a unit on astronomy. We'll be spending a good deal of time asking, "How do we know what is inside of Earth?" It's fascinating to observe scientists piecing together a model for another body in our solar system.