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Going to Mars? It'll be one wild trip

Mary Roach's book about how humans handle outer space, "Packing for Mars," tells you pretty much everything you always wanted to know about sex, poop and vomit on the final frontier. But Roach insists that extraterrestrial grossology isn't the point of her story.

Taking lighthearted looks at the science of bodily functions (or non-functions) is Roach's specialty: "Stiff" delved into the scientific contributions of cadavers. Roach recounts her global odyssey in search of evidence of the afterlife in "Spook." And in "Bonk," she takes a lighthearted look at the study of sexual physiology.

"All of the books are about the wonders and mysteries and strangenesses of the human body," Roach told me this week during a telephone interview.

She kicks those themes up to a higher level in "Packing for Mars," which is based on her encounters with scientists and spacefliers, mission planners and historians at space centers and laboratories around the globe. Here are just a few of the questions addressed in the book:

• Why do roughly half of all astronauts get sick in space? (Because of a mental disconnect between the brain's interpretation of visual and vestibular data.)

• Would it be fatal to throw up in your space helmet? (Maybe, but probably not.)

• Have any astronauts had sex in space? (Again, probably not, but Roach nevertheless delves into the theoretical mechanics of sexual congress in zero-G.)

• How do you go to the bathroom in space? (Verrry carefully.)

• How does recycled urine taste? ("Clear and sweet," Roach says.)

The subject matter can make for hilarious discussions, such as this one on "The Daily Show." But Roach says she isn't playing this merely for laughs, even though "the press tends to pick up on the s*** and vomit." For her, the bottom line is that exploring outer space forces us to rethink and re-engineer the most basic things that humans do. Why do it? At least in part, we explore, rethink and re-engineer precisely because those are among the basic things that humans do.

Roach discussed the big picture as well as the funny little details during our interview. Here are some edited excerpts from the Q&A:

Cosmic Log: There's been a lot of talk in the space community over which way NASA should go. Are we going to the moon or not? Maybe not, at least not in the time frame that was suggested five years ago. As an outsider who's now been inside the space effort, do you have any thoughts about how the mission should be framed?

Mary Roach: I would love to see a Mars mission be an international effort, in the same way that the International Space Station has been. People know it as a place to do science, but what it's also been is a 10-year exercise in global space cooperation. You have dozens of space agencies around the world cooperating, sending personnel, funding it, and really working together. The whole idea there was getting ready for Mars. The ISS has been long-term training for a Mars mission.

Packing for Mars

W.W. Norton

"Packing for Mars" surveys the curious science of life in the void.

So, for me, it would be sad for it all to just come grinding to a halt after all the years and all the work that's gone into studying how you deal with bone loss in space. [Bone loss is also a problem.] What are we going to do about radiation? How are we going to deal with the psychological challenges? To have all the research just pile up and then go nowhere would seem tragic to me.

I would love to see it be a global effort, also because that's a way to make it more fundable. I'd love to see private enterprise and a bunch of different international space agencies get together and make it an all-encompassing project. Not since the moon landing have we seen an event that has been watched by so many people. It would bring people together. Not to be all idealistic and dorky about it, but it would be a pretty amazing thing to happen. And I hope it does happen in my lifetime. …

The other thing to bear in mind is that the technology coming out of a Mars mission would be pretty extraordinary. Anything that you have on Earth has to be rethought for zero gravity, in a vacuum, so you have to think outside the box in terms of creative technologies that work. You have things that are lightweight, miniaturized, automated, fireproof, very strong. Those kinds of technologies get a boost from a mission. With Mars, you’re going to have extreme recycling and sustainability. You can't carry a lot of stuff. It’s just six people for a two-year mission. You've got weight restrictions. So a lot of new technologies would come out of that.

Q: A major theme in your book is how difficult it is for the human body to adapt to living in space. Is there anything you found during during your adventures that surprised you the most, or grossed you out, or that you found fascinating?

A: Well, all of it I found fascinating. I guess I was most fascinated by the extent to which zero gravity affects all the different parts of the body... The human bladder, for instance. It's designed for gravity. I didn't realize that the way that you know you have to go to the bathroom is that you have these things called stretch receptors. When the liquid builds up on the floor of the bladder, it starts to stretch it out, and that sends a signal to your brain.

But in zero gravity, the liquid clings by surface tension to the entire interior of the organ. They don't have that same signal. By the time you realize that you need to go, the bladder could be so full that you press the urethra shut. Then you use a catheter, and you've got a minor medical emergency. It's actually a fairly serious aspect of learning to deal with being in space. You almost have to toilet-train astronauts.

I was floored by the number of ways in which zero gravity affects almost everything about you. You're two to three inches taller, your spine flattens out, you have more fluid in the upper half of your body, and the body's blood volume sensors are up only in the top half of the body. Your body thinks you have too much fluid, so you end up shedding fluid, and so you end up losing weight. Also, your body thinks you have too much blood, so it slows down production of blood cells, and your immune system is compromised.

Q: That reminds me, there were some questions raised in the book where the scientific answers were a little unresolved. You mentioned fluid retention, and there was some discussion about what zero gravity does to penis size ...

A: Well, I think we did resolve that. I think that I got a pretty good explanation from [NASA physiologist] John Charles. There's something called the line of hydrostatic indifference, right around the diaphragm. The penis is below that. In zero gravity, you would have less blood, less body fluid down there, so I think that confirms what Buzz Aldrin and the Apollo astronauts have said. Some of the shuttle astronauts have a different view. I don't know, maybe they were just really excited about being in space.

Q: Another thing I was curious about was what happens if somebody dies in space. You address that issue in the book, saying that if someone died during a spacewalk, you would just have to cut that astronaut loose. But if someone were to die on the space station, or the shuttle?

A: There wouldn't be that much of an issue. They would bring the body back. The shuttle mission is usually just a couple of weeks. If someone died on the International Space Station, the shuttle would go up and bring the body back and return it to the family. But on a Mars mission, where you can't turn around and come back, that's where it becomes an issue.

Space itself is a very effective preservative. You put the body in the air lock and expose it to the vacuum of space, and it will be frozen. Then you could either do a burial in space, or you could bring it back if you're coming back, or you could bury it on the surface of Mars. Those are the options ... they talk about "Medcode Zero."

If the family was OK with burial in space, that would be a fitting end ... kind of like burial at sea. It wouldn't be a disrespectful thing to do to send the body out of the air lock.

Q: In the book, you say that being on a zero-gravity airplane flight was almost like doing heroin....

A: No, no, no! I've never done heroin.

Q: I understand. You're not a heroin addict ...

A: Some people have written that I compared zero gravity to being on heroin. No. I was making the point that I can imagine that people who do heroin immediately want to do it again. It was like that, in that I got back down from the zero-gravity ride and immediately wanted to do it again.

Q: I was just curious whether you have found that opportunity ...

A: Ah. No, I haven't had another fix. It's a little expensive, something around $5,000. That seems like a little much for me to be spending on something so frivolous as a few minutes in zero gravity. But believe me, I'd attempt it.

Q: Do you aspire to go into space yourself? If someone were to say, 'Mary, we'd like you to write this book about taking a flight on SpaceShipTwo,' would you do it?

A: I would love to go into space. Yes, of course. I wouldn't want to be on the first round trip. I'd be a little uncomfortable with the safety angle on the first flight. But eventually? Absolutely.

For another perspective on "Packing for Mars," check out former msnbc.com colleague Rob Merrill's review for The Associated Press. Join the Cosmic Log corps by signing up as my Facebook friend or hooking up on Twitter with @b0yle. And if you really want to be friendly, ask me about "The Case for Pluto."