Among the many physical risks facing astronauts sent to the Moon or Mars, the biggest danger will also be the least visible: radiation.This is nuclear particles that are spewed out by the Sun -- and which in storms called solar flares can be potentially lethal -- or arrive at almost light speed from beyond the Solar System, a phenomenon called cosmic rays.The particles slice through strands of DNA, boosting the risk of cancer and other ailments.Manned missions in low orbit, such as the US space shuttle, the Soviet-era Mir and the International Space Station (ISS), are mostly protected by Earth's magnetic field, the magnetosphere.The Apollo trips to the Moon, beyond this shield, took a calculated risk, for the missions were of short duration, of up to 12 days.But some of the astronauts reported seeing flashes in their eyes, a sign of cosmic-ray damage to retinas.A 2001 NASA study found that at least 39 former astronauts suffered cataracts after flying in space, 36 of whom took part in high-radiation missions such as the Apollo landings.Some cataracts took 10 years or more to show up, but others developed in as little as four years.Ian Crawford, of the School of Earth Sciences at University College London's Birkbeck College, says a Moon colony could be shielded by simply burying it under a metre (yard) or so of lunar soil and limiting exposure on trips on the surface."But if you are going to Mars, this is a much bigger problem because convenient shielding materials are not just lying around. So your spacecraft has to be launched with shielding and shielding is massive. Therefore you need a bigger rocket, and the cost goes up."Copyright (c) 2007 Agence France Presse.Fair Use Notice: This page contains copyrighted material the use of which has not been specifically authorized by the copyright owner. This website distributes this material without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. We believe this constitutes a fair use of any such copyrighted material as provided for in 17 U.S.C SS 107.
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