Jane Poynter and Taber MacCallum kept their relationship alive inside Biosphere 2 and now they'd like to test their marriage on a long, risky flight to Mars.

The couple spent two years inside Biosphere 2, emerging from the Southern Arizona experiment in contained living in September 1993.

Now married, they are founders and officers of Paragon Space Development Corp., a Tucson firm that makes life-support systems for space travel.

They have signed on to an ambitious plan to send humans around Mars - a 501-day mission scheduled to blast off in January 2018.

One man and one woman will make the flight and Poynter said she and MacCallum would like to be the pair if they can survive a crew selection process described as "extremely rigorous" at a news conference announcing the plan Wednesday.

"Inspiration Mars," headed by pioneer space tourist Dennis Tito, is a plan to send a couple around Mars and return to Earth, using available private technology.

MacCallum, during a webcast of the news conference, said, "All the work to date shows the mission is possible - just barely."

"This is going to be a very austere mission, a Lewis and Clark trip to Mars," said MacCallum, who is the chief technology officer for the newly formed Inspiration Mars Foundation.

Tito, who in 2001 paid a reported $20 million to be flown in a Russian spacecraft to the International Space Station, has committed to fund the first two years of the five-year crash program and raise the money for the rest of it.

He wouldn't put a price tag on the mission but said it would be cheaper than NASA's robotic missions to the planet. The cost of NASA's current Mars mission, which landed the robotic science laboratory Curiosity, is estimated at $2.5 billion.

Poynter compared the flight to "a really long road trip in a small RV that goes 32,000 times around the Earth's equator and you can't get out for 501 days."

Having a couple as crew would be a plus, she said. She said she and MacCallum would like to be that couple.

"In the Biosphere, it was hugely helpful to have somebody I really trusted and was really close to, to share the struggles and the adventures and misadventures," she said.

The voyage would be physically debilitating, would subject the crew to medically dangerous amounts of radiation and would offer no hope of rescue if something went wrong.

"There is no question this is a risky and bold endeavor," said Dr. Jonathan Clark, a former NASA flight surgeon whose astronaut wife, Laurel, was killed when the Space Shuttle Columbia broke apart on re-entry in 2003.

Clark, the group's chief medical officer, said potential crew members would be fully screened physically and psychologically and possibly surveyed on a "genomic and proteomic" level to identify any potential problems.

Clark said he is working with other doctors to address risks. The crew, for instance, would be at 3-percent increased risk for death from cancer because of the radiation exposure outside the Earth's protective magnetosphere.

MacCallum said he is already working with NASA on radiation shielding and on the hazardous re-entry.

Space travel is risky, he said. "That's the kind of risk America used to take."

Poynter compared the radiation risk to smoking a pack of cigarettes a day for the 501-day flight.

But nobody will be smoking, or eating very well, on this trip.

Half the capsule's 1,200 cubic feet of space will be loaded with dehydrated food. The crew's urine and perspiration will be recycled. They will be drinking the same water every other day, said Poynter.

Peter Smith, the University of Arizona planetary scientist who headed NASA's Phoenix Mars Lander mission, suggested the new group consider an easier flight - a two-week jaunt around the moon perhaps.

"That way, you don't have the endurance problem and you can bring decent food and maybe a bottle of wine."

Smith called the plan "an exciting concept" but predicted the team would encounter problems it can't solve in the short time it has given itself.

"The problems tend to multiply as you penetrate into the details of a mission of this sort," he said.

Smith said he knows and likes MacCallum and Poynter and thinks they have the right stuff for space travel. "Those two go out and race motorcycles, for God's sake, the kind where your knee is scraping the ground."

Smith said he also likes the idea of "shaking things up" in an era when NASA has at least temporarily abandoned human missions.

Inspiration is the entire reason for the Mars trip, said Tito.

NASA has made great strides in robotic exploration and in astronomical projects such as the Hubble Space Telescope, he said.

"We have not made nearly the same progress in human spaceflight. We've been waiting 40 years. I think it's time to put an end to that lapse," Tito said.

Tito chose 2018 because the alignment of Mars and Earth will make it possible to "boomerang" a capsule around the Red Planet and back to Earth without added propulsion.

The next time that alignment occurs is in 2031, he said.

On StarNet: Read stories from the day the Biosphere 2 was sealed for its grand experiment and the day the Biosphere crew members emerged after two years at azstarnet.com/morguetales

Contact reporter Tom Beal at tbeal@azstarnet.com or 573-4158.