Urine Shakes, Sweat Lettuce, Fecal Wheat Bread Sandwiches

The steel door swings shut on the chamber, sealing off the outside world. They feel no fear or regret, the four of them, just eagerness to get on with their new lives. After a stretch of hard work, Nigel Packham showers in filtered urine. Vickie Kloeris downs shots of distilled sweat. Laura Supra swallows a heat-sensing pill that relays her core body temperature to a transmitter strapped around her shoulder like a purse. She later fetches the pill from her feces. So does John Lewis. Not that their waste is going to waste. Quite the opposite: It is keeping them alive.

Outside the chamber, a team of scientists and engineers scrutinizes this gang of four. The observers are just a few feet away from the chamber around the clock, kibitzing, observing, learning, analyzing urine, blood, and saliva samples. Inside, the crew - that's what they call themselves, a "crew" - is kept on a strict exercise regimen to ward off bone disintegration and muscle loss. The support team can be spoken to (over the audio system) and seen (via video link) and corresponded with (through email), but neither they - nor the crew's loved ones - can be touched. Not for 91 days. There is one ground rule for this endeavor, as clear and inescapable as the law of gravity: Nobody is to enter or leave the chamber. The chamber gives life. The chamber is life.

Consider it the new Biosphere - but a Biosphere with meaning. There are no designer jumpsuits, no zoolike tours for the paying public. It is sponsored not by a reclusive New Age renegade, but by the United States government. The airtight chamber sits in Building 7 of NASA's Johnson Space Center, near Houston. This is hard science, and if it works, Homo sapiens will be a step closer to visiting Mars. If it fails, our species will likely experience Mars only vicariously, through robotic probes.

Nigel Packham and his colleagues refuse to give up on humanity's right to interplanetary exploration. I first meet Nigel, commander of the chamber crew, two weeks before the door swings shut on September 19. He gives me a quick tour of his home-to-be and says he cannot wait for the "mission" to begin.

Nigel is a slight man, thin and intense and thoughtful, in the manner of a master safecracker. He has a PhD in chemistry and devoted some of his doctoral research to cold fusion. He helped design the chamber's life-support system, and he got involved in the project because he wants to put human beings - including himself - on the Red Planet. Along with almost everyone else around, he is wearing a pin that reads "Mars or Bust."

The Mars Underground is surfacing. Encouraged by public enthusiasm over Pathfinder and our resurgent curiosity about life on the fourth planet from the Sun, renegades at NASA are developing everything from interplanetary propulsion systems to flexible spacesuits for Martian extra-vehicular activity. Their funding is very modest, but these rebels are laying the groundwork for a human mission to Mars. The 91-day chamber experiment is a milestone in a series of NASA tests known as the Lunar-Mars Life Support Test Project. It is a key component of what its backers believe will end up being a manned mission to Mars in a decade or two. "I have no doubt," says Nigel Packham, "that in my working lifetime we will get there."

__I__n 1989, the White House asked NASA to draw up a long-range plan for space exploration. This was one of those moments when opportunity and funding are akin to ripe pieces of low-hanging fruit. NASA devised a program for a human mission to Mars that included building a huge station in space, another on the Moon, and, finally, a massive spaceship. The probable cost: US$450 billion.

The program was DOA. NASA had blown it.

The problem was simple. Nourished by Reagan-era "Star Wars" fantasies, NASA had become a bureaucratic gargoyle, light-years removed from the gung-ho days of Mercury, Gemini, and Apollo. Critics had long complained about the billions spent on a bloated, scientifically questionable space shuttle program. By 1989, no one was willing to trust the agency with another megabudget project.

The rebuff reflected the end of NASA's big-project era. The small-is-beautiful approach came into vogue. If the '80s were a decade of mainframe projects, the '90s would be a decade of laptop undertakings. No waste, no frills - just innovation and efficacy. The great leaps forward in space exploration would be taken not by the government, but by the people - people like Robert Zubrin.

As NASA sank under its own weight in the late '80s, Zubrin, then a space engineer at Martin Marietta, promoted Mars Direct, the Macintosh of space-exploration ideas: If you want to reach Mars, he said, you don't need a lunar base, a space station, or a big spaceship. You can fly to Mars in two easy steps for $20 billion or so.

The nut of Zubrin's idea is known as In Situ Resource Utilization. Instead of bringing a massive fuel payload to Mars, his scheme calls for producing fuel on Mars by converting carbon dioxide from the planet's atmosphere into methane and oxygen, which can be used to fuel not only rovers, but the return trip. The conversion process also produces oxygen and water for backup life-support supplies.

Zubrin (who now heads his own aeronautics firm near Denver) had found the holy grail of interplanetary travel - and NASA's "reference mission" for flying to Mars now embraces his ideas.

The space agency is developing a three-launch mission manned by six astronauts that could cost only $30 billion, if unofficial estimates hold - $12 billion less than the fleet of B-2 bombers Congress has authorized. "The notion of living off the land is key to putting people on Mars in a cost-effective way," says John Connolly, an engineer in NASA's Exploration Office. "You have to break this bond with Earth."

NASA's mission to Mars begins with the launch of an unmanned cargo craft, which will land with equipment for converting carbon dioxide to methane and oxygen and will contain a small ascent module. Second to go will be another automated flight, a return craft that will settle into orbit around Mars. The third launch, the transit craft, will carry the astronauts and serve as their living quarters on the ground, expanded with resources from the cargo vehicle. Their journey will take about six months; they will then live on Mars for 18 months or so, investigating whether life there exists or once existed. When the time comes to leave, the astronauts will board the ascent vehicle and blast off to a rendezvous with the orbiting return craft, and they will be home in another six months.

It's a good plan, but it has problems. NASA administrator Daniel Goldin is having a hard enough time raising funds to underwrite the shuttle and the agency's $20 billion contribution to the International Space Station program, whose costs have steadily grown. Pushing a high-profile Mars program is impolitic, so the idea has been shuffled off to a bureaucratic attic like an unruly child whose presence might upset sensitive visitors. Until better times come along, NASA is keeping the manned Mars mission alive with a few million dollars of research funds every year, a sliver of the agency's annual budget of $13.5 billion.

With their funding, the renegades at NASA are trying to provide small-is-beautiful answers to every technological question, so that when the White House becomes interested in flying humans to our planetary neighbor, a ready-to-execute program is available. NASA scientists and engineers - especially at the Johnson Space Center, the Ames Research Center, and the Jet Propulsion Laboratory - have cooked up a gumbo of research projects. Among them is a life-support experiment. How do you supply astronauts with air and water and food for three years if you're financially unable to build a spaceship big enough to carry all the provisions? What's needed is both simple to outline and devilishly difficult to accomplish: the ability to recycle every drop of water, every bit of organic and inorganic waste, and every breath of air with a system that doesn't need a continuous supply of stockpiled chemical purifiers and filters.

This is why NASA started the Lunar-Mars Life Support Test Project, which operates under the umbrella of the Advanced Life Support program at the Johnson Space Center. It is evolving into an ambitious program known as BIO-Plex, which will place four humans inside interconnected, self-supporting chambers at a construction cost of $6 million to $8 million. The "chambernauts" will live in their compartments for periods ranging from 120 days in 2001 to 425 days starting in 2005. Each successive test will draw the life-support loop closer to completion: During the first test, half of their food will be grown in the chambers and 25 percent of the human and plant waste will be recycled; five years later 95 percent of the food will be grown "locally," as the jargon goes, and all but 5 percent of the waste will be recycled.

But a great leap, as a certain astronaut once said, starts with a small step. Which is why Nigel Packham (who in an earlier test spent two weeks in an airtight chamber with 22,000 oxygen-producing wheat plants) and three colleagues volunteered to spend 91 days in an airtight chamber, drinking their own urine, probing their own feces, and washing their garden lettuce with recycled sweat.

I am at the Johnson Space Center, and the door to Building 7 swings open, revealing a superclean, brightly lit warehouse that contains the 20-Foot Chamber, named unimaginatively after its diameter. The crew calls it the Can. It's three stories tall, a cream-colored barrel of steel that would seem an appropriate place to house petroleum, not people. I approach the chamber through a side airlock, which is used during the test as an exercise room. A step ahead, I enter the first level of the chamber, which serves as the crew's work and rest area. Each floor is bedroom sized, though each is filled with far more than a bedroom's worth of stuff.

The first level contains a conference table and chairs, a refrigerator, two microwave ovens, a hot plate, a small kitchen sink, and a washing machine. A TV is in one corner, and a pair of computer screens are mounted on the wall. The room has the confined feel of a racing sloop's galley, except that there are no views, no sea breeze, just circular walls hugging you like a parka and artificial light that never dims. Two posters hang over the conference table - a panoramic view of the Martian landscape around Pathfinder and a photograph of an astronaut on the Moon. Nigel nods at the pictures and says, "They give us an idea of where we're heading."

Up a steel ladder, like something out of a submarine movie, the second floor is crammed full of life-support machinery, the heart and lungs of this beast. The third level holds a tiny bathroom and closet-sized sleeping cabins, each of which contains a narrow bed, a desk, and a stack of drawers for personal belongings. Sliding doors can be shut for privacy, but the doors and walls are thin, and privacy is an illusion: Unless you are speaking in a whisper, your neighbor can hear you on the phone and in your sleep. This is your universe. No sun, no fresh air, no privacy. Three months now - three years later.

What kind of people do you put into this environment? Until three years ago, when US astronauts began flying long-duration missions on Mir, NASA - which had always been concerned about astronauts' ability to handle stress, danger, and emergencies - had paid little attention to a different psychological issue: adaptation to long missions. The advent of the International Space Station and the prospect of flying to Mars have forced NASA to focus on this psychological realm, and that means figuring out which sorts of people do well in confinement and which combinations of personalities make the best crews.

Those are the considerations Albert Holland, a NASA chief psychologist, brought to bear when he helped select the four residents of the Can from among the engineers and scientists, most involved with the ALS program, who applied. The right stuff that NASA looked for in the chambernauts - and looks for in astronauts - is broader than the right stuff of the '60s. Astronauts then were drawn from the ranks of hotshot pilots, who lived for the thrill of blasting into the cosmos atop an aeronautic roman candle and returning home a hero. Those aren't the people who would do well on long-duration missions, where not much happens beyond tending to zero-gravity gardens and the like. The people Holland sought for the chamber crew were the kind who gain quiet satisfaction from doing a job well, no matter how routine that job might be or how long it might take.

Written exams posed a panoply of innocent-sounding questions, jigsaw-puzzle pieces that, put together, depicted a person's psychology. Applicants were asked to grade, on a five-point scale, various statements, including: "I'm pretty good about pacing myself so as to get things done on time"; "I like to have a lot of people around me"; "I sometimes fail to assert myself as much as I should"; "I'm pretty set in my ways"; "Without strong emotions, life would be uninteresting to me."

Kent Joosten, the chief engineer of NASA's Exploration Office, was selected to command the chamber crew, but a medical hiccup knocked him out at the last minute, and he was replaced by Supra. When Holland offered to tell him what the psych tests showed about his personality, Joosten jumped at the chance, thinking it would be amusing to know how ludicrously off-base the results were. Joosten, who has a rather healthy disrespect for authority, was surprised to hear Holland say that the tests showed he has a rather healthy disrespect for authority. "That was a real wake-up call," Joosten laughs.

The applicants also had several hours of face-to-face interviews with Holland. These weren't interrogations, but lengthy discussions in which Holland tried to tweeze as much as possible about the candidates' psychological wiring. Some areas of exploration were obvious. To discover how an applicant would hold up in times of stress, Holland asked questions about difficult times the candidate had gone through in his or her life and how the applicant dealt with those difficulties - and then analyzed the respondent's solution: Was it calm? Impulsive? Creative? But NASA also probed for other, less-obvious character traits. Holland looked closely for a sense of humor - not just any sense of humor, but a self-deprecating one. During a long mission, the ability to laugh at oneself is a crucial way of relaxing and warding off stress. The wrong sort of humor - particularly, needling or sarcasm - can destroy a crew. (Would you want to spend three months in a chamber with David Letterman? Think about it.)

A sense of modesty was also vital, because the psychologists see it as a crucial indication of a candidate's willingness to team. The last thing you want, in a space station crew or a ground chamber team, is a blowhard who thinks he's the best thing since Neil Armstrong - the type most likely to create friction with crewmates and resist advice from Ground Control. To identify such people, Holland studied small things. If the candidate seized an opportunity to mention he'd finished first in his class at the Naval Academy, Holland was on guard; if the applicant shied away from self-promotion even when offered the chance, Holland was impressed.

Working with a committee composed largely of managers and engineers from the ALS program, Holland helped narrow the initial batch of 45 applicants to eight. They were put through two days of team-building exercises, including rock climbing, in which the finalists were linked in pairs and told to climb a wall. The link broke if they moved too far apart; every step had to be planned and taken in unison.

A final crew was chosen - Packham, Lewis, Kloeris, and Supra - and another round of team-building exercises was held, including a three-day stay in an underwater chamber in Florida. The goal was to see how the crew functioned in confinement; if serious problems cropped up, changes could still be made.

"I have done 80 percent of my work before the doors close," Holland said. "Once you close the door, you should have people inside who are ready, able, and willing."

__T__hey are of temperate mood, strong intelligence, and high reliability. They are the kind of people who, if you left them in your home during the day, would take excellent care of the children, repair the car's busted gasket, delete the virus about to fry your hard drive, mop the kitchen floor, and then tell you they had a really good time - and mean it.

But they are not clones. Some are out-of-the-box thinkers; others are methodical problem solvers. And their backgrounds are so different, one can imagine a sitcom developed around them.

Nigel Packham, the commander, is 37 years old and divorced. He hails from the United Kingdom, which he left more than a decade ago in his quest to become an astronaut. He retains a light accent from his homeland - as does John Lewis, 31, though his homeland is Houston. Physically, these guys couldn't be more different; John seems almost twice as tall as the wiry Nigel. John is also a life-of-the-party fellow, while Nigel is quiet, internal. They are best friends.

Vickie Kloeris, at 42 the elder of the group, is married and the only crew member not directly tied to the Advanced Life Support division. Rather, she comes from the NASA division that prepares astronauts' meals, a job that sounds deceptively lowly. (If you want an unhappy and ill-performing crew, just serve them bad food for three months.) At the agency, food prep is an important science, and Vickie has coauthored papers with titles like "Folic Acid Content in Thermostabilized and Freeze-Dried Space Shuttle Foods."

Laura Supra, 29, is the crew's youngster, a Californian and University of Colorado grad who lived in France while studying for a master's degree in aerospace engineering. She plies that trade at NASA contractor AlliedSignal, where, her résumé says, her work included developing an "advanced regenerable extravehicular-activity carbon-dioxide removal system for portable life-support systems that utilizes metal-oxide adsorbent to revitalize the astronaut's air."

They share a passion for their work. Nigel, who has 17 plaques and letters of commendation on the wall behind his desk, reads electrochemistry textbooks in his spare time. For him, 60-hour workweeks are the norm. "The thought of the test slipping because of something I haven't done or that I had the ability to change is the worst nightmare I could possibly ever have," he tells me.

But he and his project colleagues also know how to relax - a crucial trait for any astronaut on a three-month mission. I join several of them at Molly's, a beer-stained Houston dive and favorite watering hole for the Mars crowd.

Amid the loud music and the shouts of patrons, they share the latest gossip about David Wolf, an astronaut freshly returned from a sojourn on Mir. I start chatting with a woman, who introduces herself as Beth Caplan from the Exploration Office. She sees the look on my face and anticipates the question in my mind. "You're wondering," she laughs, "what's a nice Jewish girl from New York doing in a place like this?" Her answer, over the blast of an old Madonna tune, is succinct: "Space."

__I__t begins on September 19. The crew settles into a busy routine. Dress is casual; T-shirts and shorts are the norm in the chamber, where the temperature stays between 68 and 72 degrees. Each morning begins with a 7:30 conference call with managers, engineers, and coordinators, though crew members wake whenever they wish. (Nigel and Vickie are habitual early risers.) During the call everyone, inside and outside the Can, is updated on how things are going and on the plans for the day. Then crew members set about their chores. They must exercise for approximately 90 minutes a day, 13 days out of every 14. A computer keeps track of the time and energy they expend exercising.

The most time-consuming chore is the care of the life-support system - actually three systems: one for recycling oxygen, another for processing water, and a third for treating solid waste. In conventional life-support systems, oxygen and water are replenished from stockpiles on hand (think of a submarine), or they are cleansed and recycled with chemicals and filters. The cutting-edge aspect of the 20-Foot Chamber's life-support system - indeed, the reason for the 91-day test - is that NASA is using biological material, notably microbes and plants, for much of the recycling.

The life-support system's most revolutionary feature is the Biological Water Processor, or BWP. The BWP has the look of conjoined mainframes and has two biological subsystems through which waste water flows. The first and most innovative subsystem is a cylinder the size of a water heater called the Immobilized Cell Bioreactor, which contains row after row of microbe-inoculated foam pads. Waste water, which includes urine, condensed sweat, and kitchen and bathroom runoff, is pumped through the pads, and the microbes consume the organic pollutants - mostly urea and soap. Filled with a nauseating brown slime, this bioreactor is, to put it mildly, loathsome. But Nigel uses the word "beautiful" to describe it. "To an engineer, it's like, 'What the hell is it? That's the stuff that gums up my pumps,'" he says. "But it cleans your water perfectly."

After passing through the ICB, water is fed through another cylinder, the Trickling Filter Bioreactor, filled with microbes that convert ammonium into nitrite and nitrate compounds. The water's journey then comes to a purifying end after flowing through the Reverse Osmosis System, which eliminates inorganic pollutants, such as chloride, sodium, potassium, sulfate, and phosphate.

Every day the Biological Water Processor cleanses 30 gallons of liquid - enough to fulfill the crew's drinking, cooking, laundry, and washing needs - which has fewer impurities than the water in Houston's municipal system. In a blind taste test, the chamber's water would win out over the stuff that flows from the tap in most US cities, according to the crew.

The Can's air-recycling system is looped into the solid-waste system. Crew members put their fecal matter into 14-ounce plastic bottles, store the bottles in a refrigerator until the end of the day, and then transfer them to the outside world through a parcel-sized airlock at the back of the chamber's first level. NASA engineers then mix the contents of the bottles with water transpired from 22,000 wheat plants growing in a nearby chamber and pour the slurry into a small incinerator that is fired up to 1,400 degrees Fahrenheit. The carbon dioxide and water vapor emitted from the incinerator are fed to the wheat plants, and the oxygen produced by the plants - accounting for 25 percent of the crew's recycled oxygen, is piped back into the Can.

Although the incinerator breaks down and is offline for seven weeks, the test is far from a failure. The principle - that carbon dioxide can be isolated from fecal matter and used in a spaceship's life-support system - holds up. Even when the life-support machines are working smoothly, the crew fiddles with them to figure out their weaknesses. What would happen if the flow of water at a certain valve declined? What if the purity of carbon dioxide increased at another gauge? This process is a bit like taking the first nuclear submarine on a shakedown voyage: There is no end to the checking and tightening of screws that must be done.

The chamber's coziness precludes storing enough food for the entire mission, so edibles are passed inside through the small airlock. The fare is simple - microwave meals, processed cheese, Sara Lee pies. Fresh fruit and vegetables are occasional treats, but in general the goal is to approximate an astronaut's bland diet. The chamber has a small greenhouse for growing lettuce - about four heads harvested every 10 days for salads. The "garden" provides mental relief, too: Space psychologists have learned that astronauts enjoy experimenting with plants because the greenery provides a bit of color and life in the unchanging routine of spaceflight.

But the days are not long enough. Aside from monitoring the valves and pumps and tubes and microbes that keep them alive, the crew members carry out an array of experiments on themselves, including an elaborate series of sleeping tests for about two days every two weeks. Sleep is a big deal at NASA because astronauts have trouble sleeping well; the agency wants to know why and what to do about it. The problems relate to microgravity, but constant confinement, unvarying diet, and repetitive work may also be factors. By putting the chamber crew through a rigorous test, NASA is trying to hone its methodology for measuring sleep patterns.

For the test, the chambernauts wear an Actilume, a device the size of a microcassette recorder that is worn on each crew member's nondominant wrist and records movement (mass acceleration, in NASA-speak) and light levels. During the test period, the Can's inhabitants take hourly saliva samples, which scientists analyze for melatonin levels. Logs are kept on sleep duration and the number, if any, of sleep interruptions. The most inconvenient part of the test is disposing of an ingestible pill that measures core body temperature. The pill winds its way through each crew member's bowels, and each person has to fish it from their feces because NASA does not want the pills vaporized in the incinerator.

The Can's residents also engage in something ingrained at the new NASA - public relations - participating in outreach programs with visiting tourists, speaking with schoolchildren linked to them via classroom computers, and even communicating with astronauts aboard an orbiting shuttle. Occasionally, VIPs and celebrities like Alan Alda stop by and chat them up through the video link. The crew members also reply to a stream of queries to their Web site. A frequent question: "Do you really drink your urine?" They also do their best to stay in touch with family and friends through phone calls and email.

Vickie Kloeris sends a diary to friends every week or so, keeping them updated on life in the Can, including bathing etiquette. "Showers are limited to 14 pounds of water per day," she wrote. "You can do two 7-pound showers or one 14-pound shower. The 14-pound shower is 1.7 gallons of water and lasts less than one minute, so showering is an art form."

Although quarters are tight, crew members, so busy attending to their own experiments, do not bump into each other around every corner, but they try to gather each day for lunch and dinner, the few times when all are likely to be in the same place at once. During these periods, they engage in the easy banter of close friends. The television is used sparingly, though the crew watches The X-Files and The Simpsons. In general, they do their best to maintain a sense of normalcy in this abnormal environment. They even hold a surprise baby shower for John Lewis and his wife, who is entering the final trimester of her pregnancy when the test begins. (She gives birth a few weeks after it ends.) While John's wife opens gifts in the control room, relayed to the chamber via video, he unwraps presents the control-room gang has secreted inside the chamber via the parcel airlock.

By the end of each day, the crew is more than ready for bed. Nigel doesn't have time to finish the Tom Clancy novel he brought into the chamber. John brought nearly a dozen books, including a collection of J. D. Salinger short stories and Tom Wolfe's The Electric Kool-Aid Acid Test, but he gets through only one or two. Vickie is out cold the moment her head hits her pillow.

__I__t is December 18 - the last night in the Can. The crew is 12 hours away from freedom, 12 hours away from returning to the delights of fresh food and fresh air and long baths and loved ones and the simple pleasure of doing as they please and going where they want. I call Nigel Packham, expecting to hear excitement or impatience in his voice, perhaps a story or two about the times he wanted to strangle his crewmates. But Nigel has enjoyed himself, thank you very much.

"We know so much about each other," he says about his fellow chambernauts. "We know way too much about each other in some areas. We know how much each other urinates. We know how frequently we go to the bathroom. We know what each other likes to eat. There are things we learned about each other that will never be shared with anyone else. These are not bad things, but absolutely amazing things, things that you'd never expect when we first closed the door."

They haven't merely bonded with each other. They have bonded, physically and emotionally, with their environment. Their chamber. Their Can. "It's almost like the chamber is a living, breathing entity," Nigel says. "It's providing oxygen for us and it's providing drinking water, and when you turn the systems off, it's like it stops breathing for you."

The power of this feeling is apparent even a month after he leaves the chamber to cheers from the scores of scientists and engineers who worked on the $1.5 million project. Nigel leads me to the Can's third level and shows me his cabin, which is much as he'd left it in December. The books he hadn't read are still there; so are some of his clothes. He finds a poem he'd written during the test and shows it to me. "A View of Life from Within," it is called, and it begins with these lines: "So long, just so long, to arrive / This day goes like the wind / With another to follow / The high of the past."

Nigel tells me he fell into a funk basically the first morning he woke up in his own bed at home, a free man again. This is not much different from a syndrome noted among astronauts, who occasionally have a hard time adjusting to life on Earth after the rush of living in space.

"I was just in the blues," Nigel says. "I didn't enjoy life very much for about a week or two weeks, and I'm not really enjoying it right now. It's not as much fun. You may say to yourself, 'This is stupid. This was a ground test. You were not looking down on Earth from however many miles up.' But you have been on a journey - you really have - and it's one that you really can't describe to anyone else, not in words."

I don't quite understand how the crew members could think they were on a "journey" when all they had to do was look through the porthole in the chamber door to realize they hadn't budged an inch. But then I remember that the porthole had been covered up. Just a few hours after the door swung shut, the crew placed a mission patch over their window to the outside world.

After egress, Nigel continued to visit his cabin almost every workday, sometimes during weekends, puttering around on the computer and taking care of email. There was no need for him to do this - he shares office space with other life-support scientists in a nearby building - but he became attached to the chamber. Being inside it takes him back to the test, the grand and wonderful test. "It was a high," he says. "It was higher than the highest kite you'd ever want to fly."

But not as high as the one he hopes - no, expects - to feel in a decade or two. For as he told his cheering colleagues after the steel door opened on December 19 and he emerged from the Can after 91 days, "You've changed the question. The question was, Can we keep people alive on the surface of Mars for long durations with biological life-support systems? It's not the question anymore. The question is: When?"