My opinion, first of all, is that many Mars direct people fail to understand a simple point: Mars isn't the ONLY goal for human exploration. The moon IS a goal too. The asteroids are goals. I'd even venture to say Mercury is a goal for human explorers. These MD guys almost always frame their arguments as if Mars were the only goal. "Dear Senators, we shouldn't go to the moon because Mars is the goal and the Moon will slow us down blah blah blah." While I'll readily agree Mars is the most exciting, it is not the only destination out there for human explorers.

Second, it's plain nuts to think about going directly on a 2-3 year voyage to Mars without ever giving astronauts the opportunity to learn how to live off world (other than a few individuals who have lived on space stations for 6 months). The Moon is the obvious place to practice, even if it is not an analagous environment. We simply need PRACTICE living off world for extended periods of time. Once we have an astronaut corps of say 20 -40 men and women who have lived on the Moon for 1-2 years at a time, then we will have individuals who are fully prepared for the ultimate exploration mission in all human history.