Media playback is unsupported on your device Media caption Watch millionaire Dennis Tito's journey from space tourist to mission head

A team led by millionaire and former space tourist Dennis Tito plans to send a "tested couple" to Mars and back in a privately funded mission.

The Inspiration Mars Foundation plans to start its one-and-a-half-year mission in January 2018.

The foundation has carried out a study which it says shows that it is feasible to achieve such a mission using existing technology.

The group still has to raise funding for their mission.

I can attest from personal experience that having somebody that you really deeply trust and care for was an extraordinary thing to have Jane Poynter, Paragon Space Development Corporation

Among those involved in the project is Jane Poynter, who spent two years locked away in a sealed ecosystem with seven other people in 1991 which she described as a "New Age Garden of Eden".

She told BBC News that the mission planners wanted the crew to consist of an older couple whose relationship would be able to withstand the stress of living in a confined environment for two years.

"I can attest from personal experience from living in Biosphere 2 that having somebody that you really deeply trusted and cared for was an extraordinary thing to have," Ms Poynter explained.

Ms Poynter, who ended up marrying one of those involved in the Biosphere 2 project, Taber Macallum, admitted that it could be "challenging" for the couple. But said that the selection process would attempt to find "resilient people that would be able to maintain a happy upbeat attitude in the face of adversity".

The plan was to choose a middle-aged couple because their health and fertility would be less affected by the radiation they would be exposed to during such a long space mission.

Media playback is unsupported on your device Media caption Dennis Tito: "It's been outstanding from a scientific standpoint. We have not made nearly the same progress in human space flight"

The couple would receive extensive training and would be able to draw on psychological support from mission control throughout the mission.

Ms Poynter's expectation is that a couple journeying to Mars would be "inspirational".

"We want the crew of vehicle to represent humanity," she said. "We want the youth of the world to be reflected in this crew and for girls as well as boys to have role models".

Space historian, Prof Christopher Riley of Lincoln University, believes that sending a couple to Mars might be a good idea.

"The idea of sending older astronauts on longer duration missions, after they have had children, has been around for a while. The reasoning is that such a long duration mission, outside of the protective magnetosphere of the Earth, could leave them infertile," he said.

"Married couples have occasionally flown in space before, on short flights, and it seemed to work well, so why not."

It takes mavericks like Tito to create pivot points in history where significant things happen Prof Christopher Riley, Lincoln University

However results emerging from the so-called Mars500 project suggests that even carefully screened individuals are likely to suffer from psychological problems from a prolonged space mission.

The mission will be a straightforward flight to the Red Planet and return without landing. This greatly reduces the cost of the mission. The Mars Inspiration team believe that it is technically possible to launch such a mission in five years' time.

The Mars Inspiration team is aiming for a January 2018 launch because it coincides with a close alignment of Mars and Earth, such that a round trip would take about a year-and-a half, or 501 days - whereas outside of this window such a trip might take two or three years .

Many believe that new technologies will need to be developed to deal with the extended periods of radiation such a trip would involve and to cope with supplying food and water for the crew.

The Mars Inspiration team says that it has carried out a feasibility study for the mission which it plans to release on Sunday. Anu Ojha, from the British National Space Centre in Leicester has seen the study.

He says that it is theoretically possible to go to Mars and back using the Dragon and Falcon Heavy systems manufactured by California-based firm SpaceX.

Loo roll crunch

But conditions would be squeezed and spartan, with no room for pressurised space suits. The report suggests that 1,360kg of dehydrated food will be enough to last the journey and the manifest includes 28kg of toilet paper for a crew of 2 for 500 days.

But the issue of radiation protection according to Mr Ojha is "glossed over" with the recognition that more work and "creative solutions" need to be explored. More work will also need to done to improve recycling technologies to convert urine into water.

The man leading the venture is Denis Tito, who paid 20 million dollars to become the first "tourist" in space. He spent six days on the International Space Station (ISS) in 2001.

The millionaire is financing part of the project but much more money needs to be raised. The organisers have not stated how much the mission will cost nor how much they need to raise, saying only that it is much cheaper than one would imagine a Mars mission to be. Ms Poynter did however confirm that a significant amount of money still needed to be raised.

Anu Ojha believes that unless the venture is 100% underwritten at this stage it won't get off the ground.

"If a bunch of billionaires have committed the approx $1-2bn required, then we could see history being made in under five years. If (at the) the press conference they say 'we have this fantastic concept but need the money - please give generously' then it's dead in the water," he told BBC News.

However Prof Riley is more optimistic. "There are lots of big ifs in trying to achieve this epic endeavour, but none which are totally insurmountable given enough money and assistance, and the will to do it," he said.

"It takes mavericks like Tito to create such pivot points in history where significant things happen, and such a trip would be as significant as Apollo 8's first circumnavigation of the Moon on Christmas Eve 1968, when the world listened in to the reflections of the first human beings to orbit another world.

"Perhaps fifty years later, on Christmas Eve 2018 we might be all tuning in to a similar broadcast from Mars. I hope so!"

The effort represents the latest development in private sector companies moving into space exploration. Last December, one of the last men on the Moon, Harrison Schmitt, told BBC News that he believed Nasa and other government run space agencies were "too inefficient" to be able to send astronauts back to the Moon.

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