Europa, the second moon of Jupiter, is encased in a thick crust of ice. Sitting far from the Sun, it's one of the last places you would expect to harbor life. But due to its elliptical orbit around Jupiter — it periodically swings closer and further from the giant planet — the differences in gravity flex and squeeze the core, heating it to molten temperatures.

The end result: Buried under 100 kilometers of rock-hard ice is a globe-spanning liquid water ocean. More liquid water than on the Earth. But is there life?

Why it matters: New simulations suggest the icy shell is broken into segments that shift, flex, and subduct, just like the Earth's crust. Essential nutrients on the surface could then make their way to the ocean, providing a possible pathway for life —permanently locked away from sunlight — to survive.