its mars

Indeed!

:3 actually, you don't need to add water. The addition of greenhouse gasses would warm the planet sufficiently to liquify the immense amounts of water at it's poles.

Shame Mars' lack of a magnetosphere would allow any sort of thick atmosphere to just be blown off by solar winds... ...if only there was a way to kickstart the core again...

The addition of man-made water sources would speed up the process. And I didn't know its atmosphere could just get blown away. o.o

lol yup :3

Am I the only one who realises you need plants to get oxygen in the first place?

Not really. A catalytic converter would do the job just as easily.
Or you could use hydrolysis to create gaseous oxygen from the water, while simultaneously producing hydrogen gas useful for fueling manned outposts.

Of course if you REALLY wanted to go the bioterraforming route, your best bet would be O2-producing microbes that could withstand the harsh martian conditions. Genetically modified archaeobacteria ought to do the trick if you can warm the place up enough for liquid water.
Plants are far too sensitive and needy to be good for early-stage terraforming. Even the hardiest of earth's grasses and weeds would wither and die within hours of exposure to the martian surface. Shit, most microbes would even succumb, unless they were capable of forming endospores. You'd need extremophiles like those found in the Archea domain.

What an interesting concept.

Thank you!