How would a half terraformed planet effect people? How well would they be able to breath the air? In my universe, on un-livable rocks at least, colonies are created with their own oxygen supply and such but are only temporary as they try to terraform the planet with large terraforming machines (I have always imagined the terraformers from Aliens) An event occurred that caused inhabitants to flee certain planets and without constant looking after a lot of the terraformers would fail. My question is, what would become of the planet. Would there be enough air to breath for short times or would people need to continue to wearing oxygenated masks and such to live outside. And in the occurrence that people were stranded on the planet would they simply die or evolve/mutate to be better suited to breath the air? Anybody who knows me/of me on this board knows I have been creating an expansive universe for my book and more and this is something I have overlooked that I find interesting.