For centuries, the icy moons of the outer solar system hovered beyond Earth’s grasp. These were cold, sterile worlds – small, frozen spheres with brittle surfaces that didn’t do much except reflect shards of distant sunlight.

Now, of course, we know those moons are anything but dead. One of them – Jupiter’s moon Europa – harbors a rather Earthlike feature, scientists reported this week in Nature Geoscience. Like Earth’s, Europa’s crust might be broken up into a patchwork of tectonic plates. On Earth, the shifting of tectonic plates is responsible for the movement of continents, violent earthquakes, and volcanic eruptions.

Europa is the only other body in the solar system that shows strong evidence for plate tectonic activity –