I think Mars has a lot of long term potential as another world for Humanity, but it needs some serious clean up and, honestly, we need the fusion rocket engines to make it happen.  That way we can redirect kuiper belt objects to Mars to provide the volatiles it needs: turns out the locked in CO2 is only enough for the equivalent of 61k ft here on earth if released.  

So, let's say you did drop lots of Quaoar or some other kuiper belt object on Mars.  You'd have a good century of cleaning up from there.  Dropping in raw sodium and the proper microbes to sequester all that nasty chemicals from the volatiles mixing with the perchlorates and everything else.  

It would be beautiful, in the end.   Just keep your hands off of Elysium Mons.  It's MINE!  ;)