Five years ago, astronauts who spent weeks in space reported a change in their eyesight. These astronauts were members of the crew on the International Space Station. Research showed a change in the shape of their eyes. Normally-round eyeballs had become flat during time in space. The research also showed that the right eye was affected more than the left, and that men were more affected than women. Scientists could not find an explanation for the differences.
Bone loss was one of the problems first reported by astronauts returning to Earth after longer stays in space. So scientists designed exercise machines to use on the space station. Tests showed that the exercise equipment helped space travelers keep their bones almost as strong as when they left Earth.
There are other health issues for astronauts who spend a long time in space. They may have problems eating and sleeping. But the biggest health issue is exposure to radiation. On Earth, human beings are protected by the atmosphere and the planets magnetic field. In outer space, there is no such protection.
For more than 50 years, the health of American astronauts has been a concern of NASA -- the National Aeronautics and Space Administration. NASA does not let the risk of cancer for its astronauts rise more than three percent during their lifetime. But there is more to be worried about than a possible increased risk of cancer.
On Long Island, New York, scientists have been studying the effect of cosmic rays on mice. The scientists say they have found possible brain damage to the animals.
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