I don't think the statement is true, Man can do things no machine can do. But having said that, up to now, man has not been very productive in space, from a scientific point of view. The major success of manned missions has been the lunar rocks, which have altered our picture of how the solar system was formed. But for the cost of Apollo, we could have brought back tons of lunar material with robots.

I don't think this is due to any inherent shortcomings of manned missions, it's just that they haven't been planned well enough to exploit Man's capabilities, and because of cost, and because the perceived need for human intervention is premature. Granted, a human geologist can certainly outperform a robot, but for the cost of sending 1 human we could send a dozen different robots to many different sites, and we would be able to have a more successsful program even if half of them failed or malfunctioned. Think in terms of the outer planet missions, how many manned missions would it take to duplicate Pioneer, Voyager, Galileo, Cassini, etc. And we would still be waiting for the capability to launch them, we couldn't hope to match that record for perhaps another century.

A good example is from the science I'm most familiar with: astronomy. Before Apollo, I was enchanted with the idea of being able to operate a manned observatory from earth orbit. But Hubble and the other orbiting observatories have demonstrated that incredible astronomy can be done by remote control, and that the support staff need not be in close proximity to the telescopes. Granted, we couldn't have repaired Hubble without astronauts, but we could have always launched many others for the cost of shuttle development.

We need to maintain a manned capability in space, both as a space station and as a means of supplying it. We can do science there, as well as use it as a launch point. But the primary purpose of that activity is the systematic development of manned technology so it will be ready when the robots find something that will demand the human touch. The day will come when this capability will be ready to support multiple manned missions that can only be done by men. And that day will come! But right now, I am appalled at the number of programs that have had to be cancelled, cut back, or even prematurely shut down after years of successful operation because the shuttle and the space station are starved for cash.

My proposal would be to upgrade our earth to orbit manned capability and to complete the space station (we've got too much invested in it to shut it down now), but forget about manned missions to Mars, and certainly the moon. The ability to do things in orbit that cannot be done on earth or by robots was a staple of science fiction 50 years ago, but that's because we underestimated the capabilities of communications and computing technology, and overestimated the progress of propulsion systems.