If humans are going to be spending longer periods in space, on the Moon, or even on Mars, it's just a matter of time before they'll need surgery. Can delicate surgery even be done in the weightlessness? Doctors from NASA and the Canadian Space Agency think so. They're working out a series of experiments where surgeons will attempt procedures in weightless situations, like underwater or in a special aircraft that simulates weightlessness. They believe that future missions will have at least one surgeon and several of the crew will be trained in surgical techniques as well.