"It’s the next essential step in human development," an impassioned NASA researcher tells host Alan Alda in this season’s second episode of SCIENTIFIC AMERICAN FRONTIERS. He’s talking about mankind’s second steppingstone into the cosmic pond -- Mars. Wednesday, November 11 on public television (see local listings), SAF devotes an entire episode to the quest for the Red Planet.

The technology is all but there for such an endeavor, but right now there’s no official Mars program. So what’s stopping us? Money, of course. A NASA proposal ten years ago for a Mars mission named a cost of four hundred billion dollars. The agency insisted that a giant platform had to be built in space for a giant ship -- and it would have to lug two years’ worth of air, food, equipment and fuel to Mars and back.

Or would it? Alan takes us to a small laboratory outside Denver. Working in a ramshackle metal garage is a classic American type -- the Maverick Brainstormer. On a machine that looks like an Appalachian moonshine still, Bob Zubrin has concocted a process that could make a mission to the Red Planet possible -- and affordable. Zubrin’s contraption would vacuum in a bit of Mars’ volatile atmosphere and create methane, an ideal rocket fuel. If it works, the ship would only have to carry enough fuel to get there--making its size, logistics and price tag a tenth of what NASA envisioned.

So how do the "real" rocket scientists feel about this outsider’s better idea? As Alan shows us at the Johnson Space Center in Houston, NASA likes Zubrin just fine -- in fact, they’re now funding him. "He is very helpful to us, it’s always healthy to have people out there pushing you," says Doug Cooke of NASA’s Planetary Exploration Group. Cooke shows Alan just how Zubrin’s gadget could get us to Mars for a coach-fare price. The trick isn’t one big spacecraft, but three smaller ones -- each launchable with existing space shuttle technology. An unmanned "return vehicle" lands on Mars first and distills fuel; eventually this ship will take the astronauts back to Earth. A second human-free craft lands near it with all the scientific and living supplies. The third leaves Earth a year later -- with the crew.

But before spending a dime of the taxpayer’s hard-earned, one big question remains: Why go? Elsewhere on the NASA campus, Alan looks for answers with biologists like Kathy Thomas-Keprta and reports, "Mars is full of features that could only be created by running water." Within this mundane-sounding fact could lie the story of the next century. Anywhere on our planet where there is liquid water, there is life -- and once life takes hold in an environment it’s all but impossible to blot it out. It’s a question of odds. If astronauts find a history of life on the planet next door to our own, then it’s a virtual certainty on countless planets orbiting countless stars. The implications of this are, of course, beyond human imagination.

There’s one big problem with putting humans in space for two and a half years: the body itself. Alan explains that, without the constant resistance of gravity, "Bones, muscles, heart -- all are dramatically weaker" after extended sorties in space. Andy Thomas, an American astronaut doing a stint on Russia’s Mir space station, shows Alan a variety of exercise strategies used to combat this ongoing danger. Down on Earth (Mountain View, California to be exact), NASA is working on it too: our intrepid host test-drives an ingenious pedal-powered centrifuge that spins him around like a big turntable. "The idea is to force the blood out toward the feet, as gravity does," Alan says, "So the heart has to pump harder and more naturally."

Back in Houston, they’re trying this out -- and more. Alan checks in on a crew of four that’s been sealed for weeks in a habitat similar to the one that will someday perch on Mars. There’s exercise gear, and something else just as vital: a garden that gives the crew fresh fruits, vegetables and oxygen. In the spirit of this, there’s also a "bioreactor" gizmo that uses microbes to recycle the crew’s waste water -- all kinds of it, let’s just say -- into pure drinking water. "Natural life-support systems are light and efficient, and they’re new thinking for NASA," reports Alan.

If there’s one thing Mars-bound astronauts must expect, it’s the unexpected. The mission never goes exactly the way you planned it; something, somewhere will go wrong. A few miles up Interstate 45, the University of Houston’s Tim Saito leads Alan through what may soon be a front-line weapon against technical difficulties: virtual reality. On board the Mars craft will be a computerized replication of every system on the ship. "The idea is that a Mars mission will take along a complete virtual version of itself. When things go wrong, the crew can learn and work out the fixes before they do them," Alan says.

A journey to Mars? It’s science, but it isn’t fiction. Not anymore.

SCIENTIFIC AMERICAN FRONTIERS, now in its ninth season, is produced by the Chedd-Angier Production Company in association with Scientific American magazine. The series is underwritten solely by GTE Corporation. "Science in Paradise" is written, produced and directed by John Angier and Andrew Liebman. The series is presented on PBS by Connecticut Public Television.

Successful explorers -- Lewis and Clark, Marco Polo, you name them -- all had one thing in common. They didn’t try to bring home with them; they lived off what they found on their journey. When venturing into the unknown, one must adapt or perish. Bob Zubrin grasped this before NASA did. "Lewis and Clark crossed the American continent, twenty-five men, hunting as they went," he tells SAF host Alan Alda. Imagine what they would have had to take with them if they’d tried to bring along their food, water and air -- for themselves and their horses. Hundreds of wagons and supplies. If they had tried to do the expedition that way, it would have exhausted the economic resources of Thomas Jefferson’s America."

Impractical as all this sounds, it’s just how NASA proposed to put Americans on Mars ten years ago. Huge platforms in space for building a huge spaceship -- with a window sticker of four hundred billion dollars. It was all but laughed out of Congress. "Today there’s no official manned Mars program, but the idea is very much alive," says Alan. "If any one person can claim credit for this, it’s Bob Zubrin."

So who is this guy? As Alda puts it, "Bob’s an aerospace engineer by training, but an explorer by heart." We meet him on the Wednesday, November 11 episode of SCIENTIFIC AMERICAN FRONTIERS on public television (see local listings). Zubrin contacted NASA some years ago with a very big idea. The space agency gets countless such letters from outsiders -- most of them outright cranks who have taped too many episodes of Babylon 5. But this letter was from Dr. Robert Zubrin, president of a company called Pioneer Astronautics. It’s only a small garage outside Denver, but inside it is a machine that may be the key to a Mars mission America can afford.

Bob calls it his "General purpose Martian still," and it makes rocket propellant out of thin air -- literally. It’s a chemical processor that would take a bit of the Red Planet’s atmosphere and convert it to methane -- rocket fuel. The staggering cost of NASA’s plan was based on taking enough fuel to get to Mars and back. A one-way-only ship is smaller, you don’t have to build a new rocket to carry it (space shuttles will do fine), and it costs a bare tenth of the NASA plan.

For Zubrin, one good idea led to another. The Martian-methane breakthrough spawned a revolutionary mission strategy he calls "Mars Direct." You don’t send one big rocket -- you send three smaller ones. "The first shoots out to Mars, it’s the Earth Return Vehicle," Zubrin explains. "There’s no one in it. It lands on Mars and begins making fuel. Now you’ve got a fully fueled return vehicle sitting there. Once that’s done, then you shoot the crew out in the Habitat Vehicle." A third rocket -- unmanned -- will carry crew supplies and equipment. This and the "Hab" stay behind on Mars; future missions will use them and leave ships of their own for storage and living use. Eventually they’ll form a cluster of living quarters that will support an entire colony, like so many Martian Motel 6's.

"As we started looking at Bob’s ideas, we found that more and more of them are credible. Bob is an idea guy, and you can’t ignore the ideas he comes up with," says NASA’s Doug Cooke. The space agency likes Bob’s ideas so much they’ve put him on their payroll. Cooke heads up a project called the Planetary Exploration group that is utilizing Bob’s ideas to make a Mars mission a reality. NASA is also coming up with ideas of their own: lightweight, inflatable shelters made of fabrics that can stop a meteorite hitting them at a speed of four miles a second; "bioreactors" that harness microbes to recycle waste water into pure drinking water; exercise gadgets that will combat the degenerative effects of weightlessness on the human body; and spacesuits an astronaut can live and work in comfortably.

So will the day come when the Red Planet will be a Carnival Cruises destination? Alan poses this question to a group of NASA scientists, and the answer from these very serious thinkers is startling. "The answer is emphatically yes, but the question is when," replies one. "‘When’ is the only issue. We will go to Mars. We will explore Mars, and humanity will expand. It’s the ‘when’ question that is the perplexing one."

But with so many problems here on Earth, many Americans will not like the prospect of tax dollars going to problems off it. Just what’s in a Mars mission for us? Potentially, everything. There is overwhelming evidence that water once ran across the now-desolate planet. Almost without exception of Earth, wherever there is liquefied water, some life exists. As with so many other critical questions, Bob Zubrin offers rare insight into the mammoth implications of finding the same on Mars. "It’s not just that Mars once had bacteria or something," he tells Alan. "What you will show is that the processes that lead to life have a high probability. And what that means is, when you look up into the night sky, and see a million stars, you see a million inhabited worlds. It’s a question of immense philosophical importance, and one that completely justifies the Mars mission, as far as I’m concerned."

Our own world has been changed more than once by dreamers originally dismissed as kooks. Perhaps it’s about to happen again. As Bob says, "People do a lot of things for themselves, but the most important things they do are for their future." Thanks to "idea guys" like him, Americans have a future on Mars -- and beyond.

SCIENTIFIC AMERICAN FRONTIERS is produced by The Chedd_Angier Production Company. Graham Chedd and John Angier are executive producers. The series is presented on PBS by Connecticut Public Television. The underwriter, GTE Corporation, also funds an extensive educational outreach program to junior high school and high school classrooms throughout America.