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Mars mission may be postponed on doctor's orders

发布时间:2019-02-27 04:13:03来源:未知点击:

By Vincent Kiernan Washington DC THE first human expedition to Mars will have to wait for at least two decades, if NASA does not step up its efforts to assess the dangers to astronauts posed by cosmic rays, says an expert panel convened by the US National Research Council. At NASA’s current rate of research, it will take at least 20 years to find out how much shielding is needed for astronauts on the 15-month round trip to the Red Planet, says the NRC panel. With no atmosphere to protect them, spacefarers are bombarded with high-energy particles that can easily penetrate the thin skin of a spacecraft. If NASA were to embark on an expedition to Mars before the health risks were assessed, says the NRC panel, it would have to err on the side of caution. This would mean shielding the craft with large amounts of material that can absorb cosmic rays, such as lithium hydride. That could add as much as $30 billion to the cost of the mission, says the NRC report, which was commissioned by NASA. “When I first saw those figures, I was horrified,” says Richard Setlow, associate director for life sciences at the Brookhaven National Laboratory in Upton, New York, who chaired the NRC committee. The cost could torpedo the entire project. Many scientists fear that cosmic radiation could cause cancer, cataracts, sterility and lead to irreversible neurological damage. These fears may be exaggerated, Setlow’s panel notes, but it adds that NASA must increase its effort in the area if it wants to put humans on Mars in the forseeable future. The necessary experiments require the use of particle accelerators, which can produce radiation dosages high enough to simulate, over a short period of time, the cumulative effect of cosmic radiation during an interplanetary voyage. To assess the risks and work out cheaper ways of blocking the cosmic rays, laboratory animals will have to be exposed to particle beams for about 3000 hours, the committee estimates. At present, NASA uses particle accelerators for only 100 hours or so each year. To speed up the research, the NRC report urges the space agency to consider building its own particle accelerator. This would cost some $20 million, with the experiments themselves costing a few tens of millions more. This is a pittance compared to the enormous cost of shielding a Mars craft for a worst-case scenario, says Setlow. “Obviously, it would be cheaper to do the experiments.” Frank Sulzman, acting deputy director in NASA’s life sciences division, says that tight budgets may make it difficult to find the money needed for cosmic ray safety experiments. “Doing more in one area probably means doing less in another,