ALL THESE WORLDS ARE YOURS EXCEPT… MIMAS? Saturn’s Moon Mimas Harbors Global Ocean beneath Its Icy Shell, Study Suggests.

Evidence that some moons may have oceans beneath their surface is growing, but the detection of such watery worlds is challenging.

Mimas — the innermost, and smallest (radius = 198.2 km, or 123 miles), regular moon of Saturn — is an unlikely candidate, owing to differences in its surface properties compared with other icy moons, such as Enceladus.

This theory is challenged by Sorbonne Université researcher Valery Lainey and colleagues, who assess observations of the small moon made by Cassini.

Previous research suggested two possibilities for Mimas’ interior: either an elongated rocky core or a global ocean.

The new study reveals changes to the rotational motion and orbit of the small moon that are affected by its interior.

Applying the solid-body model would require the rocky core to be elongated, almost pancake-shaped, which does not match the observations.

Instead, the measurements of Mimas’ position suggest that the evolution of its orbit is better explained as being influenced by an internal ocean.

The more water we find out there, the better.