Plans for a manned Mars landing have moved a step closer as Russian space scientists announced an ambitious experiment into the stresses the crew of a mission would be put under.

"Mars 500" is scheduled for next year. It will seek to replicate the physical and psychological pressures on a crew of six astronauts of an 18-month, 485 million-km space flight, including long-term weightlessness, exposure to potentially dangerous belts of radiation, hypermagnetic fields and the critical lack of instantaneous communication with an Earth-bound command centre.

Project head Anatoly Grigoriev, director of Moscow's Institute for Biomedical Problems and a full member of the Russian Academy of Sciences, said the international experiment, which will take place in purpose-built steel cylinders kitted out like a space station, would cost at least £15 million.

Once locked inside the cylinders, the crew would be sealed off from contact with the outside world other than strictly controlled communication with those carrying out the experiment.

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"Psychological preparation of the crew for a mission that will take a minimum of 500 days is essential," Professor Grigoriev said. "We must create a crew that is able to address any issue in space - medical, technological, scientific, emotional - without immediate advice from Earth."

He believes that only an international crew that brings together the differences in experience and temperament that characterise different cultures could successfully undertake such a mission.

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"The crew must be made up of 'renaissance men' - and that expression includes women," said Professor Grigoriev, who was recently criticised for suggesting that a mixed-sex crew would put men under intolerable pressure.