Six men have voluntarily accepted the challenge to live locked inside a windowless module for the next year and a half, simulating a manned space mission to Mars.
Last Thursday, the men began the Russian-led space experiment studying the effects of isolation and cramped spaces on the human body.
The endurance trial is designed to simulate the 250-day flight to Mars, a landing and surface stay of up to 30 days, and then the 240-day trip back to Earth.
Three Russians, two Europeans and one Chinese participant will follow a strict schedule conducting over a hundred experiments in the confined area during the test period.
"It just simulates real space flight and maybe it's no matter of death and life, but I think in some aspects it's much more," China's Yu Wang said.
"For me, it will be mainly my family and the sun and fresh air as this is a isolation study, we won't see them really," explained French engineer Romain Charles of the European Space Agency in his journal.
The experiment will tackle the psychological challenges of a real flight to the Red Planet -- like stress, claustrophobia and fatigue.
The Mars simulation is expected to last until November 2011 with the crew relying on supplies of food, equipment and other essentials packed inside their mock spaceship. Only electricity, water and some air will be supplied from the outside, ESA officials said.
*The Christian Science Monitor contributed to this report.