Women are to be recruited to stay in bed for three months – in preparation for a possible human mission to Mars. However, rather than enjoying the ultimate lie-in, the 25 volunteers will have their heads tilted downwards and be subjected to a series of medical tests. The experiment, in France, follows a similar one on 25 men last year, each of whom emerged with pale skin and poor balance. The tests, which start at the Institute for Space Medicine, in Toulouse, next year, will simulate the effects of weightlessness in extended spaceflight.