MOSCOW, October 26 (RIA Novosti) - The Russian Institute of Medical and Biological Problems continues to recruit volunteers for participation in a 520-day simulation of an expedition to Mars, the institute said Monday.

"The basic requirements for volunteer testers are the following: age 25-50, higher education, knowledge of the Russian and English languages ensuring professional and household communication," the institute said, adding the professions of doctors and engineers are required.

A 105-day experiment to simulate a flight to Mars ended in July. It involved four Russians - astronauts Oleg Artemyev and Sergei Ryazansky, oncologist Alexei Baranov, and sports physiologist Alexei Shpakov.

It also involved two members of the European Space Agency: French civilian pilot Cyrille Fournier and German mechanical engineer Oliver Knickel. The six people spent over three months in a lab that simulated life on board a spaceship.

Each participant was paid 15,500 euros ($20,000) and underwent a variety of physical, psychological and professional tests during the mission. The scientists also tested various life-support, communications and scientific equipment.

The 105-day trial was a continuation of a 14-day experiment in November 2007, and precedes the main event, a 520-day simulation flight due to start in late 2009-early 2010.

The 520-day experiment will simulate all aspects of a journey to the Red Planet, with a 250-day outward trip, a 30-day stay on its surface, and a 240-day return flight.

During nearly two years of isolation, crew members will experience many of the conditions likely to be encountered by astronauts on a real space flight.

They will stick to a rigid daily regime of work, rest and exercise, and follow the same diet as crews aboard the International Space Station.