In the film Aliens Lt Ellen Ripley (Sigourney Weaver) returns to the planet, LV4-26 where she first encountered the "Alien". In the first film the planet's atmosphere was toxic and they had to wear space suits. In the second they had terraformed the planet using a facility built by Weyland-Utani. Why am I mentioning Aliens? Because it's freaking cool!
The thing is, man hasn't even reached our nearest planet yet leave alone the outer reaches of space. As global warming increases is it possible that the terraforming sci-fi of Aliens could be something we need to apply to our own planet? Some people think so - read more on treehugger.