NASA has a serious health concern to resolve before it fires up a manned mission to Mars or some other way-off locale: Astronauts might not be able to see anything once they get there. As the Orlando Sentinel explains, the space agency is seeing more cases of astronauts reporting blurred vision after months on the International Space Station. Vision generally returns to normal once the astronauts are back home, but the concern is that a three-year mission to Mars could be a different story.
"No one has been in space long enough to know how bad this papilledema can get," says one neurosurgeon. "When they start going (to) long-distance (destinations) like Mars, you can't end up having a bunch of blind astronauts." NASA acknowledges that the problem has "the potential for causing mission impact," and has enlisted scores of researchers to study it. The agency even has special eyeglasses on the space station for astronauts to use in the meantime. (Read more astronauts stories.)