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SCIENCE
-- Juliet Eilperin
  Pronghorn antelope trying to migrate between calving and wintering grounds have lost many of their routes to development. (By Julie Larsen Maher -- Copyright Wildlife Conservation Society) |
Cosmic Radiation and Bones
Astronauts traveling to the moon and beyond face an unexpectedly large risk of bone loss as a result of cosmic radiation, new research on mice suggests.
Space scientists have long known that weightlessness causes atrophy of bones and muscles, and researchers had suspected that radiation could also have an effect. But the mouse experiment found that even limited exposure to certain kinds of radiation caused a loss of 39 percent of the spongy portion of the inner bone.
"We were really surprised to find that degree of bone loss," said lead researcher Ted A. Bateman of Clemson University, whose findings appear in the online version of the Journal of Applied Physiology. He said that the radiation primarily degraded the spongy inner "trabecular" portion of the bone rather than the hard outer "cortical" area.
Bateman said that the results of a mouse study cannot be directly applied to people but that they are consistent with research findings that women who receive radiation treatment for cancer are substantially more likely to experience fractures because of bone loss. "I think this means that the combination of radiation and weightlessness pose some real biomedical problems for humans living for long periods in space," he said.
While astronauts have experienced some bone loss, it has not been dramatic. Bateman said this may be because, except for the moon missions, the astronauts remained inside Earth's magnetic field, which protects against the cosmic radiation that is likely to be most damaging -- protons and heavy ions.
Much of the U.S. scientific effort on the international space station is now focused on how to enable astronauts to stay in space for prolonged periods.
-- Marc Kaufman
