Should astronauts risk their health for Mars mission?
1 June 2013 Last updated at 00:01 BST
Scientists have confirmed that astronauts sent on missions to Mars would have an increased risk of developing cancer because of high levels of radiation.
The findings came from a study by Nasa's unmanned Curiosity Rover mission which counted the number of high-energy space particles striking it on its eight-month journey to the planet.
The data suggested humans would experience radiation doses that go beyond what is currently deemed acceptable for a career astronaut.
Dr Kevin Fong, a former Nasa scientist and director of the Centre for Space Medicine at University College London, said a manned mission should not be ruled out but there would be "health penalties".
Rebecca Morelle reports.