After spending a year-and-a-half locked away in steel tubes, six astronauts are about to return to the real world.
The Mars500 project - undertaken at a Moscow institute - was intended to find out how the human mind and body would cope on a long-duration spaceflight.
The study included a pretend landing on Mars, where three of the crew donned real spacesuits and walked across an enclosed sandy yard.
The crew, comprised of three Russians, two Europeans and a Chinese national, have had only limited contact with the outside world since they were locked away on June 3 last year.
Their "spaceship" has no windows, and the protocols demanded their communications endure a similar time lag to that encountered by real messages as they travel the vast distance between Earth and Mars. The round travel time for a question to be sent and for an answer to be received was about 25 minutes.
