Mars 500 mission to nowhere ends where it began. Reuters

After a gruelling 520-day mission cut off from loved ones, sunshine and fresh air, six pioneering astronauts left their cramped capsule on Friday – and emerged in a Moscow car park.

They looked tired and pale, but above all relieved, after giving 18 months of their lives to a bizarre experiment designed to simulate a voyage to Mars and back.

There was no dramatic end to the experiment – no spaceship landing, no parachute to Earth, no guts or glory involved.

Simply, at 2pm, a Russian scientist approached the capsule's shoddy metal door, turned a handle, broke a flimsy string seal, and opened the hatch. Just like that, 18 months of uninterrupted isolation, total lack of sunlight, monotony and voluntary hardship were over.

The humdrum nature of the event was no reason to forego an outpouring of lofty rhetoric hailing the achievements of the Mars500 experiment: "We have achieved on Earth the longest space voyage ever, so that humankind can one day greet a new dawn on the surface of a distant but reachable planet," Italian volunteer Diego Urbina said, with no apparent irony.

Friends and family gathered at a hangar in the car park of Moscow's Institute for Medical and Biological Problems to welcome back the six-man crew, breaking into applause as they emerged one by one.

Blue jumpsuits hung baggily from the men's thinned frames and sagged around their skeletal wrists as they waved hello to the friends and family who awaited their "return to Earth".

Video presented by the European Space Agency showed the men's last moments inside the 180-square-metre capsule that they have called home for the past year and a half as they became human guinea pigs for a potential mission to Mars.

The six men – three Russian, one Italian, one French and one Chinese – paced nervously on parquet floors, visibly anxious to step out into the real world.

"The longest night in the world is about to finish," Urbina tweeted on the eve of the exit ceremony. "Amazingly intense and VERY surreal hours: packing, sending data, stowing experiments, preparing to enter the most alien of worlds."

Wang Yue was more matter-of-fact: "After 520 days, we are finally back."

The unprecedented experiment saw the six men locked up in June 2010 as Russia and the European Space Agency sought to come as close as possible to recreating the long, isolated voyage to the red planet. The crew was free to communicate with "mission control", as well as with family and friends – but with 20-minute gaps to recreate conditions in space. Their physical and psychological health was closely monitored, and they were put through stress tests such as a total communication blackout.

The crew has now been taken to a Moscow hospital for a three-day quarantine. They will be shown to the public at a press conference on Tuesday. Psychologists are hoping the men will easily reintegrate into society, and doctors will check that their immune systems haven't been compromised after 18 months "away".

"I would like to thank very very much the six crew members who have dedicated two years of their life to make that simulation," said Jean Jacques Dordain, the director general of the ESA, in a video message. "I am convinced that this experience is the starting point of a much bigger adventure, which will be the flight to Mars."

That day is probably a long way off, Russian and European space officials admit. While the Mars500 experiment aimed to recreate the long voyage, several important factors were left out: the results of weightlessness, potential radiation poisoning, and the fact they spent just a short amount of time in a dusty sandpit that bears little resemblance to Mars.

Vitaly Davydov, deputy head of the Russian space agency, told Itar-Tass news agency that a manned trip to Mars was not being considered for at least 20 years. "In our plans, Mars [will happen] after 2030, in the mid-30s," he said. "So there's a chance that many here will live until that momentous event."

The Mars500 volunteers said they were ready to take part.

"Today, after a motionless trip of 520 days, I'm proud to prove, with my international crewmates, that a human journey to the red planet is feasible," said Frenchman Romain Charles.

Each crew member was paid 3m roubles (£61,000) for their work, project chief Boris Morukov told Interfax.

Each of the six also each received bouquets of flowers from young Russian women upon emerging. It was their first sight of a woman for 18 months.

Russian scientists chose an all-male crew after an attempt at a similar experiment in 2000 went horribly wrong when a Russian astronaut tried to forcibly french kiss Canadian Judith Lapierre. Scientists have yet to report any conflicts inside Mars500.