Two spacesuited crew members on a mission from the European Space Agency clambered into a large sandpit and planted flags in the ground.
For an hour and 12 minutes, the pair walked around and performed experiments on the surface of Mars – or, at least, a rudimentary mock-up on a patch of ground the size of a tennis court, in an elaborate simulation of a landing on the red planet.
The exercise was the highlight and halfway point of the Mars500 project, which aims to find out how humans would cope with the psychological ordeal of a real trip to Mars. Instead of launching the six volunteer crewmen into space, the agency has sealed them for 520 days inside a pretend spaceship built from interconnected modules at a research centre in Moscow.
The crew blasted off, in an imaginary sense, in June last year and have been monitored every minute of the day since. Throughout the mission they are expected to take urine, blood and other samples for scientists to analyse. They have a gym for exercise and a small cabin each. To alleviate the boredom, they have books, DVDs and computer games. On Saturday, three of the crew simulated a descent on to the surface of Mars in a "lander" module. On Monday Russian Alexandr Smoleevskiy and Italian Diego Urbina ventured into the sandpit for their first simulated "Marswalk".
"Europe has for centuries explored Earth, led by people like Columbus and Magellan," Urbina said at the start of his expedition. "I can feel how inspiring it will be to look through the eyes of the first human to set foot on Mars." During the walk, the crew planted flags for Russia, China and the European Space Agency.
The next walk, by Smoleevskiy and a Chinese crew member, Wang Yue, is scheduled for Friday, followed by another four days later.
The landscape is covered with reddish sand and built to resemble the surface of the Gusev crater on Mars, a potential landing spot for a future mission to the planet.
The crew members will begin the toughest part of their journey, the eight-month return trip, on 1 March.
