you hear (from Science Fiction novels/films) of planets being terraformed, this means readying a planet's atmosphere and a planet's biosphere for HUMAN INVASION/OCCUPATION.Sorry to put it in such blunt terms.
I'm not even going to go into all the clever engineering processes and global warming (ironically) solutions that have been suggested for how to terraform Mars.
I'm just going to say, "Mars' eleven-mile-high atmosphere consists of 95% CO2 and trees, plants and veggies LOOOOOOVE CO2."
Done.
