Researchers believe that Saturn’s Mimas moon, which brings to mind the famous “Death Star” from “Star Wars,” may have a global ocean lurking deep beneath its surface.
“When Mimas was first seen by a spacecraft, it was classified as a boring satellite due to its heavily cratered and geologically inactive surface. Hence it was suggested that the moon is cold and has no heating in it,” says Radwan Tajeddine, a research associate at Cornell University. But in a paper appearing today in Science, Tajeddine and his colleagues suggest that Mimas might not be so dull after all.
The team used images taken by NASA’s Cassini spacecraft to analyze the rotation of Mimas as it spins on its axis, as well as the moon’s orbit around Saturn. The team expected to see some rocking motion, because Mimas’s rotational and orbital periods influence one another. “The wobbling happens because the orbit of the moon is elliptic,” says Tajeddine. “So the moon is faster when close to the planet and slower when far from it.”
However, Cassini’s pictures revealed that the moon’s wobble was double what was expected. Conventional models of the moon, such as one that assumed the moon’s mass is evenly distributed on the inside, couldn’t explain the strong wobbling. So the team started investigating more exotic scenarios.