China's Wang Yue, who is currently participating in a 520-day simulation of an expedition to Mars, is celebrating his 29th birthday on Monday.
He celebrated his previous birthday also on board of a "spacecraft" during the simulated expedition.
"His mother and father will come to extend best wishes to their sun. We will make a special video message that will be broadcast to the 'spacecraft' with a 10 minute delay that simulates the time necessary to reach the orbit of Mars," Oleg Voloshkin, a spokesman for the Russian Institute of Biomedical Problems, said
The would-be astronauts - three Russians, a Chinese, a Frenchman, and an Italian - have lived and worked to a strict timetable since they clambered into a cramped capsule in a Moscow car park on June 3, 2010.
The European Space Agency (Esa) and the Russian Institute of Biomedical Problems experiment, called Mars 500, is designed to test how humans can cope with the stress of a return trip to the Red Planet.
The crew, who spent 250 days working on maintenance and scientific experiments before a 30-day stint performing tasks on a simulated Martian surface, are currently on their "return trip" to Earth.
