Man has the stomach, but not the legs, for Mars

The first person to walk on Mars would break a leg, research published today reveals.

The first person to walk on Mars would break a leg, research published today reveals.

Although there are still several technical problems to be solved before anyone visits the Red Planet, keeping space travellers fit enough during the voyage to take that first step could be one of the trickiest.

The trouble lies with the skeleton and its capacity to withstand a two to three-year journey in zero gravity. When bones are left unused - not bearing any weight - they leak calcium and weaken.

When the travellers to Mars step out of the spacecraft, like stooped elderly ladies with osteoporosis, they will be at high risk of fractures. A study published in The Lancet, of 15 Russian cosmonauts on the space station Mir, found all had suffered bone loss from their legs. In those who spent longest in space - six months - the losses ranged up to 23 per cent.

One cosmonaut had bones that were similar to those of paraplegics. Yet the one who had made the most space "walks" - and had spent longest in space - showed no bone loss at all.

The researchers from St Etienne University in France found the arms of the cosmonauts were unaffected - possibly because they had taken the role of the legs. In space, cosmonauts don't walk - they pull themselves along.

The findings show in-flight exercises to keep the legs in peak condition do not work. And once the cosmonauts returned to Earth, their bones improved but were still significantly weaker six months later than before their mission.

Michael Holick, of the Bone Research Laboratory at Boston University in the US, says in The Lancet that the problem, unsuccessfully investigated since the 1970s, could "substantially affect plans for long distance space travel."