A manned space mission to Mars should only include men aged over 60 in view of irreversible sterility that will afflict crew members on the flight, veteran Russian cosmonaut Valery Polyakov said in Moscow yesterday. Prolonged exposure to radiation, calcium deficit and muscular atrophy caused by weightlessness would make it “irrational and cruel” to send younger men, the qualified doctor said at a conference on the medical effects of long term space flight.