European Space Agency scientists are looking for volunteers willing to spend three months in bed to help them study the physiological effects of weightlessness.

"This is the biggest experiment of this kind in Europe," Mr Didier Schmitt, head of the agency's Life Sciences and Appliances department, recently told journalists.

It is designed to look into the effects of weightlessness that astronauts may encounter on the International Space Station or during a long manned journey to Mars.

The volunteers will lie at an angle with their feet slightly above their heads to simulate weightlessness, in which the head and chest fill with body fluids because of lack of gravity.

The Americans and Russians have conducted similar experiments. The Russians hold the record with two volunteers in bed for a year, but the ESA project will be the largest with 24 volunteers.