Before we colonize anything outside of our own self-sustained gravity well, we kind of need to have a working model of a self-sustained /ecological system/. Wh

Before we colonize anything outside of our own self-sustained gravity well, we kind of need to have a working model of a self-sustained /ecological system/. Which we noticeably lack. Let's not forget that, under the criteria of self-sustainment, Biosphere II was a failure, yes? And that subsequent research in ecological systems indicate that we are, collectively, more ignorant than wise as to the mechanics necessary to sustain a fully functional off-world environment. Yes, we could be wiped out by a kilometer-radius asteroid at any moment. That doesn't mean we actually know what to do about it. Colonizing other planets necessitates /self-sustaining/ colonization - it's utterly pointless, after all, to have a Mars colony doomed to a slow and painful death if its ludicrously expensive supply line to Earth collapses. If that doesn't convince you, though, /you/ can be the first one to try out a Biosphere-3 on Mars. Go ahead - I won't take your place in line. I promise.