Vigormortis said:
Frankly, we should already have a moon base. I'm serious. The American moon landing program never should have stopped. Sadly, the combination of budgetary issues, governmental BS, and a general lack of interest on the world stage (i.e. the general public) stymied that endeavor. Had it continued, we would have likely had a research base on the moon by the late eighties or nineties and would already being using it as a launching station for mars missions today.
A moon base is no small thing, but I'd grant you it should be possible.
Why would it be useful for Mars missions, though? Now, a station orbiting the Earth would, IMHO, be a much better intermediate step for that than a moon base, unless you mean some sort of training/acclimitisation thing.