Escaping gravity wells is so inefficient and costly, which combines with the effects of microgravity on earth animals to make planetoid and planetary colonization unappealing. Meteoroids and asteroids have a higher content in volatiles and contain water-ice necessary to support settlements almost anywhere in the solar-system outside of Earth. O'Neill cylinders could provide standard earth gravity and open space would allow for solar power to provide for much of a station's energy needs. The colonists could trade produce with scavengers and sickly zero-g asteroid clinger-on-to's in exchange for water-ice and other minerals, perform microgravity industry and research in the non-spinning central node, and interface with Earth media and information industries via the Web. And with an initial stockpile of biomass enriched soil from Earth, through composting they could their agriculture going for years - new dirt to mix the enriching mass with readily available from the same asteroid-clingers.
I could see an underground city on the moon populated with people biomodded or cybernetically assisted to deal with the microgravity long-term, using the materials on the moon to build up their industry and infrastructure rather than trading them with earth (once again, having to fly ships off the planetoid over and over again is incredibly wasteful in terms of precious energy), but farther out the feasibility and desirability seems limited. The moon would be close enough that materials cheaply shuttled up from Earth via a beanstalk space-elevator of some kind could be flown by ships constructed and housed that same orbital station to Luna and then dropped via guided pods without the ship ever having to enter the planetoid's cruel grip.
The best use for Mars would be to not terraform it, but aresform it to recreate and enhance the conditions that let micro-organisms (perhaps the very ones we are descended from) live there long ago. To use gengineering and frozen samples extracted from that world to recreate those organisms and seed them back onto the world while we repair it's atmosphere and induce a greenhouse effect. We could play parent to the very lifeforms that we might have been seeded from by a chance meteorite (if it was'nt instead the random interplay of chemicals) and even if our race and civilization died out would it be too arrogant to hope that we would be able to buy them enough time to evolve into sapients themselves and be able to deal with the gradual atmosphere-killing effect of their world's location in the Solar System? I dub these beings not Martians but, instead, the Nergal; after the god attributed to the red planet by Earth's first great civilization.
- Excerpts from "The Cult of Asherah" #4