Does Saturn’s Moon Mimas Have a Hidden Ocean?
A study published in Nature on February 7th may have just found evidence that Saturn’s moon Mimas has an ocean under its surface. Researchers believe that if this distant world contains an ocean, it is hidden 12 to 19 miles beneath the surface and is relatively young.
Evidence in Mimas’ Rotation and Orbit
This is not the first time astronomers have suggested an underground ocean on Mimas. In 2014, a look at data from NASA’s Cassini probe showed that the moon has a wobble in its rotation. While a slight wobble is normal (our own Moon wobbles slightly during its orbit), the 2014 paper found that Mimas’ wobble was twice as much as it should have been. These findings were consistent with a subsurface ocean or an elongated core.
The new 2024 research paper doesn’t just account for wobbles in Mimas’ rotation; it also looks at its orbit. Analyzing Cassini data from flybys of Saturn and Mimas, the team found that Mimas’ orbit had shifted, with the point of Mimas’ closet approach to the planet changing by about 6 miles. Simulations of Mimas with an elongated core suggested that it should’ve shifted by 12 miles instead. This discrepancy, given Mimas small size, is notable enough to suggest that the moon’s wobble is most likely not due to an elongated core.
