As expected, pioneering space tourist Dennis Tito and his foundation on Wednesday announced an ambitious plan to send humans to Mars in just five years, but with a twist—they're recruiting an astronaut couple to make the historic voyage.

Rumors popped up last week that Tito's non-profit Inspiration Mars Foundation was hoping to send the first humans on a flyby trip to Mars that would embark in January 2018, much sooner than other potential crewed missions to the planet being discussed by national space agencies and other private spaceflight enterprises.

Tito confirmed the basics of the mission in a press conference in Washington D.C. today. The trip to Mars and back is anticipated to take 501 days and the Jan. 5, 2018 was selected for the mission for two reasons. The Earth and its planetary neighbor will be in "rare planetary alignment" for the mission and won't be as close to each other again until 2031. What's more, the window for the mission "also coincides with the 11-year solar minimum providing the lowest solar radiation exposure" for the astronauts selected.

The "fast, free-return" mission would take the astronauts to within 100 miles of Mars before using a half-orbit around the planet to slingshot their spacecraft back towards Earth.

"When nations boldly follow opportunities, rooted in curiosity and guided by technological innovation, they grow, prosper, learn, and lead. And this is what makes a nation great," said Tito, who described the proposed journey to Mars as a "mission for America."

"With the support of NASA and an evolving team of industry partners, we intend to do everything possible to take advantage of this unique opportunity for America," the chairman and founder of the Inspiration Mars Foundation added in a statement.

"We are engaging the best minds in industry, government and academia to develop and integrate the space flight systems and to design innovative research, education, and outreach programs for the mission. This low-cost, collaborative, philanthropic approach to tackling this dynamic challenge will showcase U.S. innovation at its best and benefit all Americans in a variety of ways."

The foundation is seeking two private citizens for the mission. It's looking for a man and a woman because "having both sexes represented as the Earth's first ambassadors to deep space" would better reflect humanity, according to National Geographic.

Taber MacCallum, the Inspiration Mars Foundation's chief technology officer, explained that the selected pair would not necessarily have to be a couple. But given the length of the trip—it will be the longest space voyage by far if undertaken—in the claustrophobic conditions of a cramped spacecraft, the group will give priority to seeking astronauts in a relationship, preferably a married couple.

The foundation will also be seeking astronauts in their early 50s rather than a younger pair, because older voyagers "would be less likely to develop the cancers that radiation could bring," MaCallum, CEO of Paragon Space Development Corporation and a team member on the Biosphere 2 project, told National Geographic.

"In conditions like those going to Mars, you have to have a colleague who is also a companion of some kind, or else the pressure gets too great. We think a married couple would be ideal, but we haven't ruled out people who aren't a couple," he said.

The Inspiration Mars Foundation also clarified some information about its plans. It had been reported that the mission would utilize a deep-space version of the SpaceX Dragon capsule and its future-generation Falcon Heavy rocket, which the private spaceflight company is currently developing. In fact, SpaceX vehicles and capsules were "used as the baseline for the feasibility study the group conducted" but "have not been selected for use on the actual mission," a foundation spokesperson told PCMag.

"Foundation officials are in talks with several U.S. commercial aerospace companies about prospective launch and crew vehicles and systems," according to the group.

The feasibility study will be presented at the 2013 IEEE Aerospace Conference in early March.