Six volunteers on Friday stepped out into the outside world after spending the last one-and-a-half-years locked away in an isolation module in Moscow to simulate the effects of a return trip to Mars.

The multi-national crew showed no ill effects after emerging from the capsule where they had lived and slept for the last 520 days but were clearly delighted they completed their earth-bound "journey" to the Red Planet.

A researcher broke the seal and then opened the door of the capsule and all six crew members, dressed in blue overalls, walked out one-by-one in good health to cheers from scientists and family who had gathered.

"The international crew has completed the 520 day mission," commander Alexei Sityov, one of three Russian participants in the experiment, told Russia's space bosses in formal military style after exiting the capsule.

"The programme has been fully carried out. All the crew members are in good health. We are now ready for further tests," he added in comments broadcast by Russian television and the European Space Agency.

Italian crewmember Diego Urbina, who clenched his fists with delight as he finally stepped out of the capsule, said it had been an honour to have been involved in the programme.

He said he hoped that the experiment would help "humankind one day greet new dreams" on the Red Planet.

Chinese participant Wang Yue put it simply: "After 520 days, we are finally back."

The crew of one Chinese, one Italian, one Frenchman and three Russians were each presented with a flower by young female researchers in white coats as a reward for their endeavours.

But they were then immediately ushered away by researchers from Moscow Institute of Biomedical Problems (IMBP) for several days of medical tests. They are next due to appear in public for a news conference on Tuesday.

The unprecedented experiment has simulated the duration and isolation of a return journey to the Red Planet, even including "walks" on a replica of the Martian surface and 20-minute time gaps in communication with outside.

Yet ever since the crew were first locked up back on June 3, 2010 their module has stayed firmly rooted to the earth in a car park outside the Moscow research facility.

While there were some titters when the volunteers donned space suits for their "space walk" in a glorified sandpit at the halfway point, scientists insist the experiment was vital preparation for an eventual manned trip to Mars.

"Yes, the crew can survive the inevitable isolation that is for a mission to Mars and back. Psychologically, we can do it," said Patrik Sundblad, the human life sciences specialist at the European Space Agency.

He said that the crew had performed well despite occasional ups and downs. "August was the mental low point: it was the most monotonous phase of the mission."

Controversially, the experiment did not include a woman, with researchers clearly wanting to avoid it degenerating into a scientific version of television's sexual tension-filled "Big Brother".

"Spending 520 days with people from different groups, different nationalities, different mentalities is not simple at all. They have behaved very worthily," Mark Belakovsky, the project's deputy director told AFP.

Each of the participants is receiving 3 million rubles (around $100,000) for their work, the Interfax news agency quoted the head of the project Boris Morukov as saying.

Initially, the Russians were to receive less but the sum was increased once ESA revealed how much its two volunteers were receiving, Interfax said.

ESA and the US space agency NASA have separately sketched dates in around three decades from now for a manned flight to Mars.