A Russian and an Italian have climbed out of their craft and walked on the surface of Mars. But while the men know it is merely a sandpit near Moscow, their bodies might not be so sure.

The pair are among six men in their 20s and 30s who are taking part in a global experiment to track the psychological and physical challenges that would face a manned mission to the Red Planet.

In a project run by European, Russian and Chinese space agencies, the group will spend a total of 520 days locked in a set of windowless metal tubes designed to simulate a spacecraft. Why 520 days? That’s the estimated time it would take to fly to Mars and back.

In return for a payoff just short of $100,000, the men must go through a routine designed to mirror that of real astronauts. They must each work five days a week on maintenance and experiments and are limited to one shower a week. As would be expected on a real mission, the craft includes both a gym and a greenhouse for producing fresh vegetables.

In an effort to make the experiment more realistic, all communication between the “craft” and the outside world comes with a 20 minute delay, and officials have already experimented by introducing “technical glitches” to the feed.

Today two of the crew, Alexander Smoleyevsky and Diego Urbina became the “first men on Mars.” They and another crew member will spend a total of 10 days on the bogus planet, leaving the remaining three to experience what it would be like to be the 21st century Michael Collins.

In setting up the experiment, officials decided not to include any females on the trip, working on the basis that the on group dynamics would be so strong as to make it difficult to isolate the specific influences of the journey itself and the gender balance.

As it happens, last week NASA researchers concluded that were a woman to become pregnant in space, the craft might struggle to protect her from the effects of ionizing radiation that would be strong enough to leave a female fetus sterile from birth. However, once on the planet, potential parents might want to take a trip to nearby moon Phobos where a crater would obstruct around 90% of rays.