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Space Radiation Could Be A Mars Mission-Killer
Paris (AFP) Feb 21, 2007 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." According to a tentative NASA estimate, a trip to Mars and back would give a 40-year-old non-smoking man a 40-percent risk of developing fatal cancer after he returned to Earth, twice the terrestrial risk. Glory would be certain; early death a strong probability. Shielding options include placing the spaceship in a large protective mass, such as huge sphere of water five metres (16.25 feet) thick, which would provide similar protection to standing at an altitude of 5,500 metres (18,000 feet) on Earth. Another theorised solution would be to generate a huge magnetic or electrostatic shield around the ship to repel the particles, although the energy expenditure would be huge and the solution itself may pose hazards to health. Cost alone is likely to make these ideas unfeasible, leaving mission deciders with the nightmarish task of determining what is an acceptable level of risk for the men and women who will go to Mars. "At the very least, a trans-Mars vehicle will require a shielded refuge area, a sort of lead-shielded safe into which astronauts could crawl in case a solar flare occurs," says Crawford.
Source: Agence France-Presse Email This Article
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Moffett Field CA (SPX) Feb 22, 2007NASA officials announced they have signed an agreement with a U.S. company, Virgin Galactic, to explore collaborations on development of future space systems and support to commercial human spaceflight activities. Under the terms of a Memorandum of Understanding (MOU), NASA Ames Research Center and Virgin Galactic will explore possible collaborations in several technical areas. |
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