Mimas’s ocean appears to be relatively young, forming in the past 25m years when powerful tidal forces exerted by Saturn deformed Mimas’s core, warming it like a massaged squash ball. The heated core then melted overlying ice, creating an ocean inside the Saturnian moon.

we think of glacier water as pure, the water on Mimas is brand new and never been touched

This is the best summary I could come up with:

The unexpected discovery means Mimas, an ice ball 250 miles wide, becomes the latest member of an exclusive club, joining Saturn’s Titan and Enceladus and Jupiter’s Europa and Ganymede as moons known to harbour subterranean oceans.

By analysing thousands of images from Nasa’s Cassini mission to Saturn, Lainey and his colleagues reconstructed the precise spin and orbital motion of Mimas as it looped around the gas giant.

Their calculations suggest an ocean 45 miles deep lurks beneath Mimas’s 15-mile-thick icy shell, with temperatures near the sea floor reaching tens of degrees celsius.

The discovery of global oceans in moons around Saturn and Jupiter has prompted a flurry of interest from space agencies eager to explore their potential for harbouring life.

If life ever evolved on the tiny moon, the plumes could propel extraterrestrial microbes out into space where they could be detected by visiting missions.

David Rothery, a professor of planetary geosciences at the Open University, said that even if Mimas did harbour a subsurface ocean, there were easier places to search for life beyond Earth.

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