An Ocean Might Be Inside Saturn’s Moon Mimas

One of Saturn’s smallest moons ­– Mimas – could be secretly bubbling something underneath its surface: an ocean of water, according to a new study in the journal Science.

“After carefully examining Mimas, we found it librates — that is, it subtly wobbles — around the moon’s polar axis,” Radwan Tajeddine, a Cornell research associate in astronomy and lead author said in a university news release.

Studied by the Cassini spacecraft, the wobble contains about twice the surface displacement that researchers anticipated, indicating that the moon has a more dynamic interior than previously thought.

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

Mimas’ wobble suggests there could be something going on below the surface—conceivably an ocean. The idea is similar to spinning a raw egg versus a hard-boiled egg: the raw egg will spin more unevenly and at a reduced rate as its liquid insides move around.

But, then again, maybe not, as Tajeddine and his colleagues believe a “weirdly shaped” rocky core could also create the same wobble movement.

If Mimas is home to an ocean, the scientists suspect it’s between 15 miles and 18 miles beneath the moon’s glacial surface.

In the past, Mimas was mostly recognized due to its massive Herschel Crater that made it resemble the Death Star of the Star Wars movies; while many scientists believed the moon was made up of solid rock—nothing more.

“People thought that this was a boring moon,” Tajeddine told New Scientist.

Tajeddine’s study places Mimas on the map for a moon that could possibly house life within the solar system, though some scientists are saying not so fast.

“It’s really hard to understand how an ocean could survive for billions of years inside something as small as Mimas,” Francis Nimmo of the University of California, Santa Cruz, told New Scientist.

Although an ocean discovery would be exciting, Nimmo presumes the moon simply has a rocky interior.