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Does Saturn's moon hide underground oceans?

Observations of how Titan warps as it orbits Saturn provides strong evidence for a liquid ocean buried under the surface of the gas giant's largest moon.

By Charles Q. / June 28, 2012

This diagram shows Saturn's largest moon Titan using data from gravity measurements by NASA's Cassini probe, which suggest an underground water ocean exists on the satellite.

A. Tavani


The best evidence yet for a liquid ocean buried under the surface of Saturn's moon Titan has been found, scientists report.

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New observations show that Titan warps during the gravitational tides it experiences, suggesting an ocean sloshes under its outer shell. This ocean has long been theorized but never confirmed.

Titan is the biggest of the more than 60 known moons orbiting Saturn, and is larger than the planet Mercury. Scientists have long suspected that an ocean might lurk under Titan's surface, as well as under Jupiter's moons Ganymede, Callisto and Europa. Previous observations have shown that the entire surface of Titan appears to be sliding around like cheese over tomato sauce on a pizza.

Now the way Titan flexes under Saturn's gravity suggests the moon is indeed home to a vast underground ocean of either water or a water-ammonia mix. [Photos: The Rings and Moons of Saturn]

"Liquid water elsewhere in the solar system is one of the main goals of planetary exploration for NASA," said study lead author Luciano Iess, a planetary geodesist at Università La Sapienza in Rome. "This discovery points to the fact that many satellites in the outer solar system hide large amounts of liquid water."

To get a glimpse into Titan's mysterious interior, scientists relied on NASA's Cassini spacecraft, which has orbited Saturn since 2004. They focused on the extraordinarily powerful tides the planet's gravitational pull causes its moons to experience — tides ferocious enough to have once ripped apart titanic chunks of ice to produce the world's rings. Titan itself faces tidal effects up to 400 times greater than our moon's draw on Earth.

By monitoring how Cassini's acceleration changed during six close flybys past Titan between 2006 and 2011, the researchers deduced the strength of the moon's gravity field. Since a body's gravity stems from its mass, these details helped reveal how matter is distributed within Titan and how this changed depending on how near or far the moon was from Saturn during its oval-shaped 16-day orbit around the planet.

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