NASA has worried that cosmic rays could undermine a human voyage to Mars. New simulations and calculations, though, suggest that such lengthy exposure to space radiation may pose only half the health risk that NASA had expected.
The best U.S. space radiation simulations take place at Brookhaven National Laboratory’s Booster accelerator, where a facility for space research opened in 2003. The device sends beams of protons, iron and other cosmic elements down a 100-meter-long tunnel to strike human cells, mice and rats. Biologists then assess DNA damage. The Booster has enabled NASA to conduct regular, more realistic experi-ments beyond the one-week-a-year timetable of the past.
One interesting preliminary finding, according to Brook-haven radiobiologist Betsy Sutherland, is that the lower a proton’s energy, the more damage it does. Apparently, lower-energy protons, which travel more slowly, have more time to interact with tissues. In lowering its assessment of risk, NASA also factored in astronauts’ better-than-average health and switched from “whole-body” radiosensitivity to organ-by-organ measurements, where new studies have found lower risks for lungs, breasts and the blood system.
Such analyses, if they prove correct, could mean that Mars mission astronauts might not need radioprotective drugs at all, says Francis Cucinotta, NASA’s chief scientist for human radiation research. For solar storms and other acute risks, he adds, “we might want to carry them just in case.” Possible drugs include retinoids—vitamins that work as antioxidants—and compounds that delay cell division long enough for damaged cells to repair themselves before they can propagate mutations.
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发表于 2008-10-26 20:24:00
