In about four billion years – roughly the time Earth has already been in existence – our sun will be close to exhausting its store of energy and begin to burn out. In this process, stars like our sun actually expand and grow much hotter in this terminal phase, and Earth itself will first become too hot to sustain life and then may actually become engulfed in the solar outreach.
Scientists now think that one place where life like ours might continue before the sun dies altogether is Titan, a moon orbiting the planet Saturn. Right now it is frozen solid, but as the sun expands, it will warm up. Probes sent to Titan suggest that right now it is quite similar to Earth four billion years ago. It is surrounded by clouds of methane and nitrogen and has great pools of hydrocarbons, just the kind of organic molecules needed to kick-start life.
We used to think Mars might be a good place to live, but analyses now suggests that the water has concentrations of minerals that would make life as we know it untenable.
The disadvantage of living on Titan is that it will eventually return to its deep freeze state once the sun burns itself out, and the solar system as we know it will cease to exist. On the other hand, as a temporary stopover, it’s a lot closer than the other nearest planet that might have possibilities for us. That one is about 5000 years away.