Every three and a half Earth days, the moon Europa rotates around Jupiter. It’s the sixth largest moon in the Solar System, but what makes it unique is that it’s one of the smoothest objects in the Solar Systems. No mountains jut from its surface, no canyons scar its face. It is a moon sheathed in ice, and underneath that ice, it may be far more like Earth than even our wildest guesses.
Scientists have suspected for a while that Europa’s ice has an ocean underneath, and that ocean might support life. The best analogy is that Europa has the pieces to the puzzle when it comes to supporting life. Radiation from Jupiter splits Europa’s icy surface at a molecular level, creating oxygen, while underneath the surface, the theoretical ocean combines with rocks to form new minerals, a process called serpentinization that happens to generate hydrogen.
What’s important here is the ratios. NASA’s latest computer model of Europa has determined that ten times as much oxygen is generated as hydrogen, which is exactly the ratio we see on Earth. Just as important, that ratio means the chemical energy needed for life is present in Europa’s oceans, even without volcanic activity, provided there’s any life that wants to take advantage of it. That may sound unlikely, but the place on Earth most similar to Europa is Antarctica, and we keep finding life deep underneath that ice.
Even if life isn’t taking advantage of it at the moment, that might potentially open the door to humans taking advantage of it. Depending on just how Earth-like it is, if Europa is devoid of life, we could, say, establish an undersea colony and ensure it’s got enough to eat by breeding sea creatures.
This is just a theory, of course. Europa might be ice all the way down to its core, or there may be something very different underneath that smooth surface. We won’t know for sure until we send a probe there and look. That’s going to happen in the next decade, though, so we may soon know for sure if alien life hides underneath Europa’s icy surface.