since we are talking 200-400 years from now anyway, industry will likely be 100% automated. i have to believe that pollution will be near zero. while we cant reverse the damage we've already done to earth, it is safe to say that if we inhabited a new planet, pollution would be of little concern.

also on the topic of technology and automation, i have to say that maybe using mars for things other than life might be practical... for example, certain industries could remain on mars?

im not trying to do a 180 on my point of view, i still believe what i believe however i feel if we must spend the money here, we should think more practically than starting life on an entirely new planet.