they're not really "colonizing" it though, are they? that would imply some degree of self sufficiency which will never happen on mars, it's nothing but dead lifeless rock everywhere. they'd be completely dependent on us.
not to mention on such a small planet you'll probably lose bone density and muscle mass extremely fast and turn into some emaciated auschwitz survivor looking person due to lack of gravity. and no, working out doesn't help enough to reverse it. i was reading this article about how astronauts coming back from the space station sometimes couldn't even walk and needed rehab, despite their training equipment. they were even thinking of giving them HGH to help stop the deterioration.
I think they could be able to eventually terraform the planet.
you do realize we would need like, ALL of the resources on this planet and every country working together to do that, right? it's not at simple as sending a bunch of untrained petition signers over there with some barrels of hydrogen. hell, even that would be insanely expensive.
