The human body did not evolve to live in space. And how that alien environment changes the body is not a simple problem, nor is it easily solved.
Some problems, like the brittling of bone, may have been overcome already. Others have been identified — for example, astronauts have trouble eating and sleeping enough — and NASA is working to understand and solve them.
Then there are the health problems that still elude doctors more than 50 years after the first spaceflight. In a finding just five years ago, the eyeballs of at least some astronauts became somewhat squashed.
The biggest hurdle remains radiation. Without the protective cocoon of Earth’s magnetic field and atmosphere, astronauts receive substantially higher doses of radiation, heightening the chances that they will die of cancer. How much of a cancer risk later in life is acceptable?
By KENNETH CHANG JAN. 27, 2014