[TeMPOraL]

> There's also no reason to do it (given advances in robotics and autonomous systems) unless you subscribe to a kind of cultish belief in humanity's manifest destiny to become an interplanetary civilization.

Beyond other reasons given by the pro-colonization crowd, there is a simple reason. It's there, it's within reach, so why not?

> If there had been an intermediate destination between the Moon and Mars for us to work towards after Apollo, things might have gone differently, but you work with the Solar System you're dealt.

And yet people haven't been to the Moon since Apollo, so I feel the problem isn't with the lack of stepping stones.

[jblwps]

> It's there, it's within reach, so why not?

Opportunity cost, if nothing else? Think of the immediate, real impact we could have by throwing money at (to pull an example out of a hat) malaria. Not to say that there mightn't be real gains to be had by manned space missions (although I'm somewhat skeptical of the magnitude of those gains), but there's more uncertainty for sure.