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

The couple spent two years inside Biosphere 2, emerging from the experiment in contained living in September 1993. Now married, they are officers and owners of Paragon Space Development Corporation, 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 flight scheduled to blast off in January 2018.

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

"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 today's press 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 Mars," he said.

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.