Since earth’s oceans will be boiled away by the sun’s increasing luminosity, as I mentioned in my last post, we’ll eventually need to find other oceans elsewhere — or learn to do without water, which seems even less likely.
The news today is running a story about a subsurface ocean under Enceladus, a moon of Saturn. Here, in an obviously-photoshopped picture from one of those news stories, it’s shown in an impossible location, next to the U.K., for the purposes of size comparison. In addition to this moon, subsurface water is expected to exist on Titan, another moon of Saturn, as well as three of the four Galilean moons of Jupiter: Europa, Callisto, and Ganymede.
The Jovian system doesn’t get closer than 4.2 AUs from earth, and Saturn’s moons are further out still — but at least our descendants do have other places to go, once our oceans become too hot to stay liquid. They’re expected to be boiled away, by the sun’s increasing luminosity, in ~1.5 billion years.