It seemed more like a bizarre reality TV show than high-tech international space travel experiment: Six men lived in cramped, windowless compartments for more than 17 months to simulate a mission to Mars.
When they emerged from their claustrophobic capsules Friday in western Moscow, the researchers in blue jumpsuits looked haggard but were all smiles _ dreaming of lying in the sun at the beach, taking long strolls and driving fast cars.
Organizers said the 520-day experiment was the longest mock space mission ever, measuring human responses to the confinement, stress and fatigue of a round trip to Mars _ minus the weightlessness, of course. They describe it as a vital part of preparations for a future mission to the Red Planet, even though it may be decades away because of huge costs and daunting technological challenges.
The facility at Moscow's Institute for Medical and Biological Problems, Russia's premier space medicine center, included living compartments the size of a bus, connected with several other similarly sized modules for experiments and exercise.
There have been other confinement experiments, including Biosphere 2, a giant glass-and-steel facility in Arizona in the 1990s that housed four men and four women in self-sustaining two-year isolation. That project was dogged by controversy and technical problems.
Scientists who organized the mock Mars mission said it differed from the other experiments by relying on the latest achievements in space medicine and human biology.
Emerging from their isolation, the crew of three Russians, one Frenchman, an Italian-Colombian and a Chinese carefully descended a metal ladder to a greeting from crowd of officials and journalists Friday.
"The international crew has completed the 520-day experiment," team leader Alexey Sitev told Russian space officials. "The mission is accomplished. The crew is in good health and is ready for new missions."
Organizers said each crew member will be paid about $100,000, except for the Chinese researcher, whose compensation hasn't been revealed by officials from his country.
The crew will spend three days in quarantine before holding a news conference. They spoke to relatives and friends from behind a glass panel to minimize the risk of infection.
Sitev, who led the team into the quarters in June 2010 _ just a few weeks after getting married _ said he dreams of going to the beach.
"I want to go somewhere to the warm sea as we have missed two summers here," he said in remarks carried by RIA Novosti news agency shortly before wrapping up the mission. "My thoughts are drifting toward swimming at sea and basking on warm sand."
His Italian-Colombian crewmate Diego Urbina told RIA Novosti that he would also like to have a vacation in the Caribbean and would spend his earnings on a sports car and a pilot training course.
Sukhrob Kamolov, the Russian mission doctor, said he thought the $100,000 was a lot of money when they went in, but after a year and a half in the confined space, it didn't sound so big.
During the simulation, the crew members were under constant surveillance by scientists and communicated with their families and space officials via the Internet, which was delayed and occasionally disrupted intentionally to imitate the effects of space travel. They showered only several times per month _ once every 10 days or so _ pretending to conserve water. Their food was similar to what is on the International Space Station.
Midway through the mission, the crew even conducted a mock landing, venturing from their quarters in heavy space suits to trudge into a sand-covered room and plant the flags of Russia, China and the European Space Agency on a simulated Martian surface.
Scientists say that long confinement without daylight and fresh air put team members under stress as they grew increasingly tired of each other's company.
Psychological conditions can be even more challenging on a mock mission than a real one because there would be none of the euphoria or danger of space travel.
"If anything, the make-believe nature of this exercise's goal _ a simulated Mars walk _ would have made it even harder psychologically than a real mission," said James Oberg, a space consultant and NASA veteran. "So the team's success is even more impressive, not less so, because it was 'only a game.'"
In an email to The Associated Press, Oberg said he was particularly impressed with the crew's ability to overcome the language barrier, but added that the absence of women in the experiment was a major flaw.
"Aside from the absence of physiological factors such as weightlessness and cosmic radiation, the most glaring shortcoming of this exercise was the all-male composition of the crew," he said. "Psychological studies of frontier life and extended expeditions suggest that aside from specific skills they contribute, the presence of women in an isolated group is a positive, 'civilizing' effect, not a stress-inducing distracting influence."
The organizers said they had considered women for the experiment but left them out for various reasons. They denied deliberately forming an all-male crew because of the failure of a similar simulation in the past.
A 1999-2000 experiment ended in acrimony after a Canadian woman complained of being forcibly kissed by a Russian team captain following a fistfight between two Russian crew members. Russian officials attributed the incidents to cultural gaps and stress.
There was no sign of strain Friday as the crew flanked each other, smiling and waving to cameras.
"We hope that we can help in designing the future missions to Mars," Frenchman Romain Charles said.
Urbina said the crew was proud to complete the longest space flight simulation so that "humankind can one day greet a new dawn on the surface of distant but reachable planet."
A real flight to Mars is a distant prospect due to challenges such as creating a compact and relatively lightweight spacecraft that would shield the crew from deadly cosmic radiation.
Vitaly Davydov, a deputy head of the Russian space agency, said the simulation will help pave the way for a real Mars mission. He added that it's not expected until the mid-2030s and should be done in close international cooperation.
NASA is aiming for a landing on an asteroid around 2025 and Mars in the 2030s.