A newly discovered affliction has some doctors wondering if astronauts traveling to Mars could be blind by the time they got there.A new study of astronauts shows that radiation and bone loss aren't the only health risks for long-duration stays in space. About one-third of the U.S. space station crew members return with impaired vision, a condition in which at least one case was permanent. The data has been slow in coming since astronauts can be disqualified from flying if they have serious ailments. "These are guys who really don't like to complain about physical issues because it may...