A spokesman for the Moscow-based Russian Institute of Medical and Biological Issues, which runs the project, said that four healthy men will be held in a chamber with the pressure equivalent to being five meters underwater.
"For the first six days, the decompression chamber will maintain a standard oxygen level, and then from the seventh to tenth day of their stay, the oxygen level will be lowered to the equivalent of the atmospheric level at an altitude of 3 km. The participants in the experiment will live in accordance with a special daily routine," he said.
The experiment will provide information on the physiological impact of a flight to the Mars and back, he said.
The test is one among several preparatory trials for the main experiment, expected to begin in late 2008 to simulate a space flight to Mars, including a 250-day journey to the Red Planet, a 30-day period on its surface, and a 240-day return flight.
Two Europeans and four Russians have been selected for the main flight simulation, which may last from 520 to 700 days.
During nearly two years of isolation, crew members will experience many of the conditions likely to be encountered by astronauts on a real space flight.
They will adhere to a strict daily regime of work, rest and exercise, and exactly follow the diet of crews aboard the International Space Station (ISS).
The first experiment of the project was conducted on November 15-29.