The highest professional level, resistance to stress and an inborn high radiation protection will be the main criteria to choose candidates for the Mars expedition, director of the Russian Medical and Biological Problems Institute academician Anatoly Grigoryev told RIA Novosti. He is one of the leaders of the project preparing the piloted expedition to the Mars. “Alongside high requirements to professional skills, physical and psychological health, significant attention will be paid to choosing people with a maximum ability to adjust to extreme pressure and high resistance to stress,” he pointed out.