Firstly, Mimas just looks like it could blow up Princess Leia’s home world of Alderaan, its indentation looks like the business end of the Death Star from “Star Wars, Episode IV: A New Hope,” hence it’s name. Depending on your age, it could even harken you back to this conversation of the 1970s/A long, long, time ago:
Obi-Wan Kenobi: That’s no moon… It’s a space station!
Han Solo: It’s too big to be a space station!…
Luke Skywalker: I have a very bad feeling about this.
Saturn’s Moon: “Star Wars” aside
A new study recently published in the journal Science, has taken the “Death Star” moon out of science fiction, and placed it firmly in just….science.
While the Herschel Crater on the surface of Mimas does beg Star Wars, it also has a massive wobble, that until recently, wasn’t explained given the size of the moon. The wobble is about twice as big as one might expect from a moon that size if it was a regular solid structure, turns out it might not be solid.
The researchers who penned the study suggest two reasons for the wobble, either it has a vast ocean beneath the surface or a core that is not so much spherical as rugby ball-shaped.
“After carefully examining Mimas, we found it librates – that is, it subtly wobbles – around the moon’s polar axis,” said lead author Dr Radwan Tajeddine, who works at Cornell University in the US. the others involved in the study are astronomers from both France and Belgium.
The scientists reached this conclusion through the study of high-res photos of Mimas that were taken by the Cassini spacecraft, which was launched in 1997 to explore Saturn and her moons.
While the Earth’s single moon also wobbles, Mimas, the innermost of Saturn’s major moons, swivels back and forth by six kilometers.
The team first took a look at the Herschel Crater, which is nearly a third of the six of the icy moon itself, as a reason for the wobble. However, the team determined that even a “huge mass anomaly” that is the crater couldn’t be responsible. As a result they started looking at “more exotic interior models”
It’s what’s inside that matters
They determined that the core of Mimas could be the aforementioned rugby ball, or a spherical core separated by a “global ocean” and that would allow “the shell to wobble more easily, because it’s not attached to another mass”.
“When we saw this wobbling, the first thing we thought of was an ocean,” Dr Tajeddine said reiterating his belief that there is an ocean beneath the surface.
It often seems that each new astronomical discovery invariably leads to a conversation about extraterrestrial life and Prof Chris Lintott, an astrophysicist at the University of Oxford, was happy to oblige in a conversation with the BBC.
“If you’d asked me before now, I would have said that Mimas is a boring, icy moon.
“If the ocean is really there, we’re getting to the point where it’s just completely standard for icy moons to have substantial bodies of water inside – and that could have interesting implications for how many of these things could support life.”