I think the purpose of going back is simply to establish a permanent presence on another world. That’s an important milestone, just as the first orbit or the first trip to the moon was. It will help us develop our in-space capabilities in a host of ways, such as docking, refueling in space, learning mining techniques (it’s a virtual certainty that we’ll be mining water ice), moving cargo back and forth to Earth, etc.
Better to prove out these technologies when spare parts and rescues are only 3 days away, rather than six months away.
There is still lots to learn on the Moon, btw. Radio astronomy on the dark side would be completely insulated from Earth’s radio noise. Lunar geology may yet have some surprises. We may even find tubes that we can seal and use as living space for thousands of people if we want. The lunar ‘rilles’ are collapsed lava tubes, There are plenty of uncollapsed ones left, and they are now totally stable and will last for millions of years.
If enough water ice is found on the moon, it’s actually possible that we could build a mostly self-sustaining colony there with at least hundreds of people in it within 50-75 years.
Like what? The Department of Education’s budget has been increased by more than NASA’s entire budget during the Bush administration. Where do you think the money would be better spent? Hell, I’ll bet NASA does more for science education in the U.S. than the entire Dept of Education, just by inspiring kids to study harder and to find science more interesting. A re-invogorated exploration program that actually expands the frontiers of space will do wonders for the country as a whole in terms of encouraging kids to stay in school, giving people a sense of pride in their country, and acting as an inspiration to the rest of the world. It also helps the U.S’s image to be doing big things that aren’t military.
Defining the value of the space program in terms of science is loading the deck in your favor. Robots are currently good for collecting scientific data. Great. Let’s keep doing that, or even doing more of it. But robots aren’t nearly as good as astronauts for engaging the public and expanding the boundaries of mankind. Eventually, you have to send people.
Actually, the way to get that is not to send a probe there, but to build freaking big telescope arrays in orbit. There is no theoretical reason why you couldn’t build an array big enough to image planets in other star systems the way we image Mars or even the Moon. The Terrestrial Planet Finder will be able to image features on Earth-sized planets around the nearest stars, and analyze their atmospheres for composition and signs of life.
Let’s do more of this. Hell, why don’t we just double NASA’s budget and just do it all? Even with the boondoggles and bad management, as far as I’m concerned NASA is one of the few government agencies that has delivered a reasonable bang for the buck. Doubling NASA’s budget would make it only about half the size of the Dept. of Education.