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Title: How young is Mimas's hidden ocean, and how did it form?
Plain: Mimas, a small cratered moon of Saturn, wobbles slightly as it spins, and its orbit slowly turns, in ways that point to an ocean under 20 to 30 km of ice, though its surface shows no sign of activity. The ocean must therefore be very young, and why it formed so recently is unknown.
Precise: Given libration and periapsis-precession constraints indicating a global ocean beneath a 20 to 30 km ice shell that formed within the last roughly 25 Myr, determine the ocean's age and the cause of its recent formation (an eccentricity pumping event from passage through a resonance with another moon, or ring-moon tidal evolution) and whether the ocean is still growing. An answer is an age with uncertainty and a consistent orbital-thermal history.
Settled by: Coupled orbital-thermal evolution models of the Saturnian moons reproducing Mimas's eccentricity and ocean depth, tested by future measurements of its tidal response or heat flow.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: Lainey et al. 2024 (Nature) inferred the ocean formed between about 25 and 2 Myr ago.
Posed since: 2024