It was not always smooth sailing for the six young men who huddled in uncomfortably close quarters on a 520-day fake mission to Mars, a Russian scientist has revealed.

The multinational crew emerged blinking from its Moscow isolation module on Friday and was quickly bundled away for further observation after being briefly presented to the world's press.

But a scientist who was one of the brains behind the Mars-500 mission -- an unusual experiment designed to test the long-term effects of stress and isolation -- revealed that nerves had frayed on a few occasions.

"The psychologists witnessed conflicts emerge between crew members and the command team because the work load was not always being evenly distributed," scientific programme director Alexander Suvorov told the Gazeta.ru website.

"Some of the crew members had to do a lot of the work while others tended to play a more passive role," the scientist told the site.

Mars-500 is one of several experiments being staged around the world in preparation for a trip to Mars that Russia hopes to try in about 25 years.

The Moscow test was not conducted in weightless conditions and was designed primarily as a marathon study of what happens when a group of people get stuck in tight quarters for a long time.

The Russian programme director said that no one's physical health suffered.

But Suvorov admitted that natural jealousies emerged over who received more messages from their loved ones -- a problem similar to what young draftees experiences in their first months away from home.

"At different times, some of the crew members received more news from their loved ones, and others -- less. This created a light sense of jealousy," Suvorov said.

He quickly added that doctors were always on the ready to massage hurt egos and douse any explosive disputes.

"We preserved a single team. It did not break up into groups," the Mars-500 programme director said.

The crew's three Russian "Marsonauts" were accompanied by a volunteer from China and crew members from Italy and France.

The group controversially included no women -- a blow to those who hoped to see a scientific version of the sexual tension-filled TV show "Big Brother".

The journey was staged inside a series of interconnected metal tubes that were set up on the parking lot of a local research facility.

Each of the participants received three million rubles (around $100,000) for his troubles and messages of congratulations from around the world.