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Inside a moon of Saturn lies a sea of water

4 APR 2014


In 2005, NASA’s Cassini spacecraft sent pictures back to Earth depicting an icy moon of Saturn spewing water vapor and ice from its fractures. It was big news that the tiny moon, Enceladus, only 500 kilometers in diameter, was such an active place. Using gravity measurements collected by Cassini, scientists have now confirmed that Enceladus does in fact harbor a large pool of water under its icy surface. The New York Times explain:

“Using atomic clocks on Earth, the scientists measured the radio frequency with enough precision that they could discern changes in the velocity of Cassini, hundreds of millions of miles away, as minuscule as 14 inches an hour. They found that the moon’s gravity was weaker at the south pole. At first glance, that is not so surprising; there is a depression at the pole, and lower mass means less gravity. But the depression is so large that the gravity should actually have been weaker. Liquid water is 8 percent denser than ice, so the presence of a sea 20 to 25 miles below the surface fits the gravity measurements. The underground sea is up to six miles thick, much deeper than a lake.

It makes Enceladus a more attractive destination for a future mission, especially one that would collect samples and return them to Earth to see if they contain any microbes.The discussion on the possibility of extraterrestrial life in the solar system centers on four bodies: Mars; Enceladus; Europa, a moon of Jupiter; and Titan, another moon of Saturn.

Dr. McKay, who was not involved with gravity measurements, noted that only Enceladus was known to possess the four essential ingredients for life, at least as it exists on Earth: liquid water, energy, carbon and nitrogen.”

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