Along with the rest of the criteria that make for a good astronaut--some heavy degrees in science or technology, a tolerance for cramped spaces and freeze-dried food--let's add another one. The ideal astronaut should have narrow hands to prevent his or her fingernails from falling off. National Geographic reports that the design of astronauts' space suit gloves can lead to hand and finger injuries, including an icky condition called fingernail delamination in which the nail completely detaches from the nailbed. While missing nails do grow back in time, if the nail falls off in the middle of a spacewalk it can snag inside the glove, and moisture inside the glove can lead to bacterial or fungal infections in the exposed nailbed. MIT astronautics professor Dava Newman told National Geographic that astronauts take this medical prospect seriously: