One of the oldest questions facing humanity is whether we are alone in the universe. Now, thanks to a richer understanding of the conditions that support life in our own ocean, we have an opportunity to answer that question, and to do so within the lifetime of the current human generation.

For decades, planetary scientists looked to the “Goldilocks Zone”—the not-too-hot, not-too-cold region around a star where liquid water can exist on the surface of a planetary body—as the place where life would most likely be found. That meant exoplanets—planets orbiting distant stars—were our only hope for finding extraterrestrial life, but exploring there would require faster-than-light travel. NASA’s Galileo mission to Jupiter, followed by the Cassini mission to Saturn, changed everything when they showed there was another, hidden habitable zone right under our noses: We now know that at least half a dozen planetary bodies here in our own solar system host salt water oceans beneath a thick cover of ice, some in contact with a rocky seafloor.

To people like WHOI geochemist Chris German, that description sounds anything but alien. In fact, it is so familiar that it offers a tantalizing promise of what else might be there. “Seafloor hot springs occur in every ocean basin on Earth—even in ice-covered oceans like the Arctic” said German. “And we already know there’s chemically fueled life at those.”