64-year-old Günther Reitz is an expert on cosmic rays. After working on NASA'sApollo program, he joined the German Aerospace Center (DLR) in Cologne in 1975 and still runs its Radiation Biology Unit. His latest project is NASA's Mars rover, Curiosity. A die-hard sci-fi fan, he dreams of a day when mankind will not only travel to Mars but will be able to journey through the entire solar system.