Astronomy: Evidence of an underground ocean on Saturn's moon Mimas | Nature | Nature wallet

One research paper suggests that there may be an ocean hiding under Saturn's moon Mimas, which features an icy, cratered surface.naturePublished in Analysis of observational data sent by Saturn's Cassini probe revealed that Mimas' underground ocean is relatively new and still evolving. Continuing to study Mimas may help us learn more about the formation of icy bodies.

Evidence of subsurface oceans is accumulating on some satellites, but discovering them is challenging. Mimas, one of Saturn's small moons, has different surface characteristics from other icy moons like Enceladus, making it a poor candidate for exploring underground oceans. This idea is disputed by Valerie Laini and colleagues, who evaluated Mimas observational data from the Cassini spacecraft.

Previous research has suggested two possibilities regarding Mimas' interior design. One is an elongated rocky core, the other a global ocean. Analysis by Linney et al reveals that Mimas' rotational motion and changes in orbit are affected by the interior of the small satellite. For Mimas to be a solid model, the core of the rock would have to be elongated, taking on an almost pancake-like shape, which is inconsistent with observations. Measurements of the Mimas site suggest that the orbital evolution of Mimas can be best explained by the influence of its inner ocean. According to calculations by Linyi and others, the underground ocean of Mimas lies beneath an ice crust 20 to 30 kilometers deep. Simulations also indicate that this ocean appeared between 25 million and 2 million years ago. Therefore, it is believed that signs of such an underground ocean did not have time to leave their mark on the surface.

Linney and his colleagues point out that these results suggest that the recent process at Mimas may be typical of the early stages of formation of other icy bodies. In accompanying news and views, Mateja Cook and Alyssa Rose Roden say: “The findings by Lenny and others will stimulate comprehensive investigation of medium-sized icy moons throughout the solar system.”

doi:10.1038/s41586-023-06975-9

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