Behind the scenes of Curiosity, NASA's latest mission to investigate the possibility of life on Mars. The agency aims to land a nuclear-powered rover vehicle, which cost $2.5billion to develop, on the surface of the planet by winching it down from a rocket-powered crane, then use it to explore the terrain. The programme also discovers the lessons experts have learned from previous expeditions, many of which ended in failure, and the project's chief scientist John Grotzinger discusses what he hopes the mission will reveal.