NASA Cassini Spots Global Ocean on Saturn's Icy Moon, Enceladus

Scientists have discovered a global ocean on Saturn's moon, Enceladus. The ocean, found by NASA's Cassini mission, may tell researchers a bit more about this icy world.

The moon has a very slightly wobble as it orbits Saturn. Yet scientists could only account for this wobble if Enceladus' outer shell was not frozen solid. Instead, an ocean must exist beneath an icy crust.

Previous analysis of Cassini data suggested the presence of a lens-shaped body of water underlying the moon's south polar region. However, gravity data collected during the spacecraft's several close passes over the south polar region lent support to the possibility that the sea might be global.

"This was a hard problem that required years of observations, and calculations involving a diverse collection of disciplines, but we are confident we finally got it right," said Peter Thomas, lead author of the new paper, in a news release.

Enceladus is not perfectly spherical and because it goes slightly faster and slower during different portions of its orbit around Saturn, Enceladus rocks back and forth as it rotates. By examining the wobble more closely, the researchers determined that, in fact, Enceladus must have a liquid sea of some kind.

"If the surface and core were rigidly connected, the core would provide so much dead weight the wobble would be far smaller than we observe it to be," said Matthew Tiscareno, co-author of the new paper. "This proves that there must be a global layer of liquid separating the surface from the core."

The findings reveal a bit more about the moon. More specifically, it shows what kind of discoveries can be made with long-lived orbiter missions to other planets.

The findings are published in the journal Icarus.

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