An international crew of researchers have emerged from a gruelling 520-day simulation of a flight to Mars.

Pale but smiling, the all-male crew of three Russians, a Frenchman, an Italian-Colombian and a Chinese walked out of a set of windowless modules in Moscow.

The facility simulated the confinement, stress and fatigue of interplanetary travel - minus the weightlessness.

Dressed in blue track suits emblazoned with the mission emblem, they carefully walked down a metal ladder to a greeting crowd of officials and journalists.

"The crew has completed the experiment," team leader Alexey Sitev reported to Russian space officials. "The mission is accomplished, the crew is in good health and is ready for new missions."

Psychologists said long confinement put the team members under stress as they grow increasingly tired of each other's company.

They said that psychological conditions can even be more challenging on a mock mission than a real flight because the crew will not experience any of the euphoria or dangers of actual space travel.

Despite that, the crew showed no sign of stress as they walked to microphones to speak before cameras. "We hope that we can help in designing the future missions to Mars," Frenchman Romain Charles said with a smile.

The crew communicated with the organisers and their families via the internet, which was delayed and occasionally disrupted to imitate the effects of space travel. They ate canned food similar to that offered on the International Space Station.

The organisers said each crew member will be paid about 100,000 dollars (£60,000), except the Chinese researcher whose reward has not been revealed by Chinese officials.

A real flight to Mars is decades away because of huge costs and massive technological challenges, particularly the task of creating a compact and relatively lightweight shield that will protect the crew from deadly space radiation.

The American space agency Nasa is aiming for a nearby asteroid around 2025 and then on to Mars in the 2030s.