One of the questions about in the comments to my post on Apollo question asked “Why do we have a manned space program?
That's a fair question, but before I answer it, there are two things I want to talk about.
The first is to give credit where credit is due. A tremendous amount of really good science has been done by unmanned probes, and with the exception of the moon, virtually all our knowledge about the solar system has come from these missions.
The second is to be careful to define what we're discussing. When I talk about “a” manned program, I'm not necessaarily talking about the current manned program.
So, why should we have a manned space program. Well, you should be sure to go read some of the information written by NSS, but here's my opinion:
There is something about personal participation that fires the human imagination. Whether it's climbing Mt. Everest, travelling to the south pole, or flying higher than anybody else, people have always aspired to be the first to do something. Striving to accomplish that which is difficult is a defining human characteristic.
So that's the abstract reason. But there are also practical reasons.
The first reason is that space has the potential to provide nearly limitless resources. Whether it is possible to exploit them economically isn't yet clear, but if we could replace half of the world's coal-fired power plants with solar power satellites, we could make a tremendous reduction in the release of sulpher, radioactive elements, and greenhouse gasses. Clean power from space has a lot of appeal.
There are also opportunities around other resources. If we could mine asteroid iron, our reliance on environmentally-damaging mining on Earth would be reduced.
Given our continued population growth, the ability to spread out and get resources elsewhere is very interesting.
The final reason concerns the long-term survival of the species. We have good evidence to global catastrophe in the past, and without spreading out to other planets, it's fairly certain that such an event will happen again.
So, that's what I think, but those who are smarter and more informed than I am have written a lot on the subject.