Ripley: Van Leuwin, why don't you just check out LV426?
Van Leuwin: Because I don't have to. There have been people living there for 20 years and they've never complained about any hostile organisms.
Ripley: What do you mean? What people?
Van Leuwin: Terraformers, planet engineers. They go in, set up these big atmosphere processors to make the air breathable. Takes decades. It's what we call a shake-n-bake colony.