Six volunteers Friday will emerge blinking into the outside world after spending almost one-and-a-half-years in isolation at a Russian research centre to test the effects on humans of a flight to Mars.
The six men, who have spent 520 days in a capsule in a car park outside the Moscow institute, will at 1000 GMT open the hatch of their module that slammed shut on June 3, 2010, before being taken for a barrage of medical tests.
The experiment simulated blast off in June last year and landing on Mars in February, with volunteers carrying out spacewalks in full space gear in a sand-filled enclosure before setting off on the long journey back to Earth.
"I think they're in a period of expectation," said Mark Belakovsky, the project's deputy director, said Tuesday.
"I would say the guys have a very positive mood. They know that they have done something really big."
The all-male team is made up of three Russians, two doctors and one engineer; a Chinese astronaut trainer; and French and Italian engineers, who were sent by the European Space Agency.
"Spending 520 days with people from different groups, different nationalities, different mentalities is not simple at all. They have behaved very worthily," Belakovsky told AFP.
The project has prompted some ridicule for its earth-bound nature, without the weightlessness of a real flight. But the organisers have strictly followed real rules of space travel -- even down to a 20-minute delay in communications.
And the space agencies that are partners in the Mars 500 project have said it played an important role proving that people would be able to endure the solitude and frustration of a long-haul flight to Mars and back.
"Yes, the crew can survive the inevitable isolation ... for a mission to Mars and back," Patrik Sundblad, the human life sciences specialist at the European Space Agency (ESA), is quoted as saying on its website.
"Pyschologically, we can do it."
The blue-overalled volunteers have spent all the time except for the Mars landing in a hermetically sealed complex of narrow rooms, following orders from the project leaders and relying on food stores.
In the last few days of the experiment, the volunteers are simulating a "spiral trajectory towards the Earth's field of gravity," the experiment's website says.
They will stay in quarantine until November 8, Belakovsky said, as researchers are worried they could be vulnerable to winter bugs after isolation, despite tests showing they are in good health.
They are then due to give a news conference along with the project leaders from Moscow's Institute of Biomedical Problems on November 8 at 0800 GMT.
After that, they will be allowed out and will stay in Moscow, while continuing to visit the institute for medical tests until December 4, the formal end of the project, Belakovsky said.
In the most noticeable change since blast-off, team's commander, Russian engineer Alexei Sityov, has had time to grow a long beard while in the complex, as a video blog posted last week on the ESA's website showed.
It also showed France's Romain Charles strumming a guitar while Italy's Diego Urbina sang "I'm on my way home, sweet home."
Belakovsky was confident the men would be able to adapt to life outside.
"I don't think it will be difficult for them to adapt because our psychologists worked with them very intensively. I think they will find adaptation quite easy."
Russia and the European Space Agency hope to make the trip to Mars for real by 2040.
Explore further: Russia locks up six for Mars experiment