How to Make Any Planet Our Home: Gotta-See Video
Most planets are barren wastelands, but if we can control the weather, we can create a planet on which we can survive. The process is called "terraforming," and it could open the door to human colonists spreading across the expanse of space.
Terraforming, at its essence, is altering a planet for the purpose of habitation by people. To do so would fundamentally change the planet, creating weather, adding nutrients to the soil, and so on. It's still science fiction, but the ideas are based on real scientific possibilities. via HowStuffWorks