“The idea of sending older astronauts on longer duration missions, after they have had children, has been around for a while. The reasoning is that such a long duration mission, outside of the protective magnetosphere of the Earth, could leave them infertile. http://www.bbc.co.uk/news/science-environment-21603490 “However results emerging from the so-called Mars500 project suggests that even carefully screened individuals are likely to suffer from psychological problems from a prolonged space mission. Mission planners wanted the crew to consist of an older couple whose relationship would be able to withstand the stress of living in a confined environment for two years.