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Phoenix666 [soylentnews.org] writes:

Jupiter’s moon Europa is under a constant gravitational assault. As it orbits, its icy surface heaves and falls with the pull of Jupiter’s gravity. Scientists now believe that as it does so, it creates enough heat to support a salty ocean beneath the moon’s solid shell.

Now, experiments suggest that the process—called tidal dissipation—could create far more heat in Europa’s ice than scientists had previously thought [futurity.org]. The findings could ultimately help researchers to better estimate the thickness of moon’s outer shell.
...
“[Scientists] had expected to see cold, dead places, but right away they were blown away by their striking surfaces,” says Christine McCarthy, a faculty member at Columbia University who led the new research while a graduate student at Brown University. “There was clearly some sort of tectonic activity—things moving around and cracking. There were also places on Europa that look like melt-through or mushy ice.”

The only way to create enough heat for these active processes so far from the sun is through tidal dissipation. The effect is a bit like what happens when someone repeatedly bends a metal coat hanger, McCarthy says.

“If you bend it back and forth, you can feel it making heat at the junction. The way it does that is that internal defects within that metal are rubbing past each other, and it’s a similar process to how energy would be dissipated in ice.”

From "Tidal dissipation in creeping ice and the thermal evolution of Europa" [sciencedirect.com].

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