Saturn's Wobbling Moon, Mimas, May Have a Sub-Surface Ocean Beneath Icy Crust

It turns out that the closest of Saturn's regular moons may have an extraordinary feature--a sub-surface ocean sloshing beneath its icy surface. Scientists have used instruments aboard the Cassini spacecraft the measure the wobbles of Mimas and have found that this wobble could hint at a sea.

"After carefully examining Mimas, we found it liberates-that is, it subtly wobbles-around the moon's polar axis," said Radwan Tajeddine, lead author of the new study, in a news release. "In physical terms, the back-and-forth wobble should produce about 3kilometers of surface displacement. Instead we observed an unexpected 6 kilometers of surface displacement."

In order to better examine this moon, the researchers used a method called stereo-photogrammetry. This allowed them to interpret the images taken by Cassini to measure the libration. More specifically, the scientists used the photographs of Mimas to build precise 3D computer models of the locations of hundreds of surface reference points. From these, the researchers could not Mimas' shape and see how it wobbled over time.

"We're very excited about this measurement because it may indicate much about the satellite's insides," said Tajeddine. "Nature is essentially allowing us to do the same thing that a child does when she takes a wrapped gift in hopes of figuring out what's hidden inside."

Mimas is about 400 kilometers in diameter. Now with these latest findings, scientists can say that it's possible that its internal global ocean is located under an icy crust ranging in thickness between 25 and 30 kilometers. That said, the researchers will have to conduct further studies before they can definitively say that this moon holds an ocean. It's also possible that it merely has an odd-shaped core. That said, the latest study does reveal the possibility that Mimas has an ocean, and may actually be able to support some semblance of life beneath its icy crust.

The findings are published in the journal Science.