After 230 days in isolation, an international team is about to 'land' on Mars.
The six men - Diego Urbina and Romain Charles from Europe, Sukhrob Kamolov, Alexey Sitev, Alexandr Smoleevskiy and Mikhail Sinelnikov from Russia and Wang Yue from China - have been locked in a steel capsule in Moscow in a simulation of a 520-day Mars mission.
They will next week reach 'Mars orbit', with the landing scheduled for February 12. Two days later, Smoleevsky and Urbina will take their first steps on the 'Martian surface' - an enclosed simulation, naturally.
They will simulate various experiments over the two-day landing, before beginning the long journey back home - which will be livened up a little with a few mock emergencies for the crew to deal with. They've already experienced a 20-hour loss of water, electricity and ventilation, just to keep them on their toes.
And the boys have found other ways to keep themselves busy on the trip, celebrating Christmas with the help of a cardboard Christmas tree and some balloons.
"On 25 December we opened our presents just before lunch," says Mars500 crew member Romain Charles on the crew blog.
"It was a real pleasure to discover all the gifts falling, little by little, from the socks: metallic bottles from Russia, small glasses from Colombia, cards from China and chocolates from France."
The aim of the experiment is to see how a crew could stand up to such a long mission. The men have been through all the standard astronaut selection procedures, and have been living on canned food, with only a single shower per week.