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This week at the AAAS : You can look but you can't touch...

点击量:   时间:2018-01-15 02:01:03

By Jeff Hecht NO MATTER how eager researchers are to get their hands on Martian soil, they will only be able to look, not touch, when NASA brings back the goods. “The sample will be considered hazardous until proven otherwise,” says Jonathan Richmond, director of the office of health and safety at the Centers for Disease Control and Prevention in Atlanta, Georgia. NASA plans to scoop up 500 grams of Martian soil on its fifth Mars lander mission, which sets off in 2005. When the mission returns to Earth, the samples will be rushed straight into a Class 3 biohazard glove box—a level of containment just one grade down from the type used to isolate lethal pathogens such as the Ebola virus. NASA decided on this level of protection after asking a panel of experts, including Richmond, how it might retrieve a sample without contaminating either Mars or Earth with each other’s organisms. Few specialists believe there is anything still living on Mars, but NASA has a legal obligation to consider the most serious outcome possible. To the public, the worst thing that could happen would be to bring back a deadly Martian disease (This Week, 6 April 1996, p 7), so NASA must show that nothing can escape. The agency must also take precautions to prevent contamination of Mars, which could lead to false conclusions about Martian life. The sample will return to Earth in a three-layered package. Once on the ground, researchers will open the package in stages, placing it inside a series of sealed glove boxes. After removing the outer layer of the package in the first glove box, they will send the package on to a second box. There, says Richmond, an instrument resembling a sophisticated version of an old-fashioned can opener would release Martian gas trapped inside. After scientists study the gas, the core of the package will travel along to later gloveboxes for analysis. It is a complicated precaution, but should convince people the mission is safe. “Back in 1985, we sort of went through this with the release of bioengineered organisms,