Changing a Planet's Environment

I am doing a project on building a settlement in space. Some day earth’s resources may not be enough to support the human population and we may need to live on other planets.
 This part is about changing a planets environment, this is called terraforming.
Even when there is a permanent base on another planet it will still be hard for humans to survive. For instance, you wouldn't be able to just run outside. You would have to put on your space suit whenever you wanted to go outside. Some scientists have suggested ways of terraforming planets.  Terraforming planets means changing planets so they are more like Earth and we could then be self sufficient there.  They think that maybe we might be able to use bacteria to turn carbon dioxide into gases that would make the atmosphere thicker.  If we built large mirrors orbiting a cold planet it might help us to reflect some of the sun’s heat and make it warmer on that planet. After several hundred years humans may be able to live on another planet without an oxygen mask.

Scientists believe that in the future humans might build big plastic domes (see illustration) to live in space.