By Paul Rincon
Science reporter, BBC News, Paris Air Show
The European Space Agency (Esa) is seeking volunteers for a simulated human trip to Mars, in which six crew spend 17 months in an isolation tank.
The Aurora programme envisages Europeans on Mars
They will live and work in a series of interlocked modules at a research institute in Moscow.
Once the hatches are closed, the crew's only contact with the outside world is a radio link to "Earth" with a realistic delay of many minutes.
It sounds like Big Brother, but there are no plans to televise the test.
The modular "spacecraft" measures some 550 cubic metres (19,250 cubic feet), the equivalent of nine truck containers. It is based at the Russian Institute for Biomedical Problems in the Russian capital.
The goal is to gain insight into human behaviour and group dynamics under the kinds of conditions astronauts would experience on a journey to Mars.
With the exception of weightlessness and radiation, the crew will experience most other aspects of long-haul space travel, such as cramped conditions, a high workload, lack of privacy, and limited supplies.
The volunteers will be put through a number of scenarios, such as a simulated launch, outward journey of up to 250 days, an excursion on the Martian surface, followed by the return home.
The 500-day duration is close to the minimum estimated timescale needed for a human trip to the Red Planet.
The Earthbound astronauts will have to deal with simulated emergencies and perhaps even real ones.
But, while Esa says it will do nothing that puts the lives of the simulation crew at unnecessary risk, officials running the experiment have made it clear they would need a convincing reason to let someone out of the modules once the experiment had begun.
"The idea behind this experiment is simply to put six people in a very close environment and see how they behave," Bruno Gardini, project manager for Esa's Aurora space exploration programme, told BBC News.
In all, 12 European volunteers will be needed. They must be aged 25-50, be in good health, have "high motivation" and stand up to 185cm tall. Smokers, or those with other addictions, to alcohol or illicit drugs, for example, will be rejected.
Esa is also looking for a working knowledge of both English and Russian.
"We will do pre-selection, medical tests, psychological tests, etc. But at the end, you really have to see how they react in as close to a real situation as possible on Earth," explained Mr Gardini.
He added that the results would help define the selection criteria for a future Mars mission.
"This is the beginning; it will be a long time before we go to Mars," the Esa official said.
"But this is a field which is difficult to quantify. It's human behaviour, so there's no method. The Russians have done lots of study in the past and we will be sharing some data.
"We have to look at the mix of people; at the end of the day, we want a team."
Marc Heppener, of Esa's Science and Application Division, said the crewmembers would get paid 120 euros (158 dollars) a day.
Viktor Baranov, of Russia's Institute of Biomedical Problems, said his organisation had received about 150 applications, only 19 of which had come from women.
A precursor 105-day study is scheduled to start by mid-2008, possibly followed by another 105-day study, before the full 520-day project begins in late 2008 or early 2009.
European scientists have been asked to submit proposals for experiments in the areas of psychology, medicine, physiology and mission operations.
Mounting a mission to Mars would face many other hurdles, not least of which would be shielding the crew against the potentially deadly dose of radiation they would receive on the journey.
Esa's Aurora programme has already begun preparations to land a rover - called ExoMars - on the Red Planet. It has the stated aim, however, of trying to get European astronauts to Mars at some time in the future.