Harrison "Jack" Schmitt is the only geologist to have gone prospecting on the moon. As a crew member of Apollo 17, he was also the last person to leave footprints in the lunar soil. In part one of a two-part interview with Astrobiology Magazine editor Leslie Mullen, he discusses his first-hand experience of exploring the Earth's planetary companion, and explains why future space explorers will likely face very different conditions.

Astrobiology Magazine (AM): I recently read a book called "Moondust," in which many of the astronauts who'd walked on the moon, including yourself, were interviewed. The author noted that the number one question asked of lunar astronauts is, "What was it like to walk on the moon?"

Harrison Schmitt (HS): You know what the number two question is? "What was it like to walk on the moon?" You can never answer that question to anyone's satisfaction.

AM: That's what it said in the book -- no one felt they could express it adequately.

HS: Well, you can't. Being there is an essential ingredient. It's the same as trying to describe to someone what it's like to stand on the rim of the Grand Canyon. Or to have your first child. Any meaningful event that you've had in your life is probably that kind of experience. It has a personal meaning, and it will be different for every individual.

But sometimes people just want a description of what it was like -- the black sky, the brilliantly illuminated slopes of the mountains, the bright sun, and then our Earth as a big blue marble hanging over one of the mountains. The physical feeling of walking on the moon is like walking on a giant trampoline, to some degree.

AM: That brings me to a question about the human physiological limitations in the moon environment, which we'll have to overcome if we want to develop a permanent base there. For instance, spacesuits are not very practical for daily use. You've said that the pressurized gloves of a spacesuit quickly exhaust the muscles of your forearms when you use them.

HS: Right. It's like squeezing a tennis ball continuously. But I think those limitations are temporary. I'm sure all of them have technological solutions. The broader questions of physiological adaptation also must be addressed, first by definitive research and then by specific countermeasures. And also, potentially, there are pharmaceutical solutions. We just haven't worked hard enough over the past 40 years, frankly, to develop countermeasures to the adverse consequences of space adaptation.

AM: The space suit has evolved over that time.

HS: But it's still basically the same concept. Although the suits are still being used on the shuttle and the space station, we have to get away from what we're doing now and start on a clean slate. Our technology base today is better than it was 40 years ago, so I hope we can stimulate some new thinking with this "Moon, Mars and Beyond" initiative.

AM: I read one account of an astronaut who strayed too far during a spacewalk, and the physical effort of getting back was so exhausting he almost didn't make it. And then to think of the effort people will expend on the moon, having to struggle in similar ways every day…

HS: Use of the suits takes physical strength that even an extremely well-conditioned person sometimes just doesn't have. Another problem right now, at least in the US program, is the suits are standard sizes. And the smallest suit is still too big for some people who are in the astronaut program, particularly for some of the women. If that doesn't change, they will never be able to experience EVA. But why do the suits have to be like that? We should see if we can come up with a better solution.

AM: As a geologist on the moon, did you use a rock hammer?

HS: I did a little, but not a lot. In our crew, it was principally the tool that Gene Cernan used. Even though I was responsible for the design of a lot of the equipment, or at least monitoring the design, the hammer handle was a little too big for my hand. I found that I could do almost everything I needed to do and get all the samples I wanted with a scoop. When I needed to break rocks, Gene broke them, although occasionally I had to show him how to do it.

The Apollo pilot astronauts hadn't grown up doing geological field work, and they often would try to break a rock by hitting it in the middle rather than on the edge, where it chips off very easily. For some reason, even though we'd spent several days in the field training them in geology, in the final analysis they just wanted to beat on the rock. That's not the best reason to take a geologist to the moon, but it's one of the reasons.

AM: Also because a geologist can recognize which rocks are the most scientifically interesting.

HS: That's right –- geologists have a life history of observational science. Now, in fairness, test pilots have their own history of observational science. They were all good observers, and we took advantage of that in the training. But just as I wouldn't try to compete with them as test pilots because they had 10 to 15 years advantage on me in that field, I had a similar advantage on them in field geology. And that's why you want to take professional people into space, to the moon, and to Mars –- you want people who have life experience that's relevant to what we need to do. So we need to always be thinking of how to mix and match crews so that we have the maximum necessary experience base. And then you cross-train between the various disciplines.

AM: That's one thing about astrobiology -- it's so interdisciplinary. When you give talks at astrobiology meetings, do you get a sense that your audience could likely contain the next people who will be going to the moon and Mars?

HS: Some of them are the right generation. I hope that they have a chance to join up, and that the selection process gives them the opportunity. The selection process doesn't need to be nearly as rigid as it was physically; it's going to be based more on intellectual competition than physical competition.

AM: I've read that when the space program first started, scientists really didn't know how the human body would respond to being in space.

HS: That was partly why the selection process was so hard. They were conservative because of the uncertainty about human physiology in space. And also, the Apollo spacecraft required everybody to be a pilot. There already was a physiological envelope you had to fit into in order to be a pilot -- your eyes, and heart, and things like that. And since all of the scientists had to become pilots, we had to pass through that filter as well.

AM: But you don't think physical qualifications are going to be an issue for future space travel?

HS: It already isn't an issue. As soon as the shuttle came along, it was no longer as much a concern.

AM: But that's low Earth orbit, versus going to the moon.