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  3. As NASA prepares to set twin robots loose on the Martian surface and makes plans to send another in 2007, the agency’s long term

As NASA prepares to set twin robots loose on the Martian surface and makes plans to send another in 2007, the agency’s long term

admin2014-02-20  31
问题     As NASA prepares to set twin robots loose on the Martian surface and makes plans to send another in 2007, the agency’s long term goal is clear: determine whether the red planet does or ever did harbor life.
    But the current search for life is necessarily limited to life as we know it, organisms dependent on liquid water. A SPACE, com reader recently suggested that "We as humans are arrogant, simply believing that any other form of life will be just like us. "     Researchers devoted to the search for extraterrestrial(ET)have a similar view. "Scientists’ approach to finding life is very Earth-centric," says Kenneth Nealson, a geobiologist at the University of Southern California. "Based on what we know about life on Earth, we set the limits for where we might look on other planets," Nealson said. Within that framework, however, there are extreme cases of life on Earth that suggest the range of places to look on frigid Mars.
    Nealson and his colleagues recently found the most extreme sort of organism in a salty liquid lake under the permafrost of Siberia. The organism, named cryopegella, can exist at colder temperatures than any previously discovered. Nealson’s team figures that if the ice at the polar caps of Mars warmed to liquid water, organisms like cryopegella could have awakened and repaired any damage that might have occurred to their various cellular components. That does not mean there are necessarily dormant microbes within the ice caps of Mars. But it does suggest a broader range of potential cradles for life.
    Other researchers agree, and a host of so-called "extremophile" discoveries on Earth in recent years indicate the polar regions of Mars might be prime hunting grounds. As on Earth, organisms there might be slathered in natural antifreeze or be able to go dormant for tens of thousands of years, waiting for a brief thaw, their moment in the Sun.
    Meanwhile, scientists recognize that there could indeed be life elsewhere in the universe that does not require water. And some astrobiologists are trying to explore the possibilities. But it is a tough problem to approach. In looking for "life as we don’t know it," it’s hard to even imagine what to expect.
    Life might or might not exist on Mars. If there are critters there, they might or might not be like bacteria on Earth. In laboratory conditions, scientists in 2001 were able to get one-celled organisms to incorporate an amino acid—a fundamental building block of life—that no other known life uses. The discovery borders on the creation of artificial life, experts said. It also suggests that ET might operate by entirely different rules than those we’re used to.
    If life on Mars is fundamentally different from what scientists understand life to be, then current spacecraft and others in the works may well not recognize what’s right under their mechanical noses.
Nealson’s team’s discovery of extreme cases of life on Earth suggests that______.
选项 A、there might be life on Mars that still remains dormant
B、there might be ET in the universe that is like human beings
C、there might be life that is beyond the range of our current search
D、there might be ET elsewhere in the universe that does not require water
答案C
解析 推断题。文章第四段讲到，纳尔森研究小组在西伯利亚冻土带下的一个盐水湖中发现了最为极端的生物组织，即cryopegella，这种生物体能存活的温度比以前所知道的都要低。他们认为，火星两极的冰帽如果变暖融化，类似cryopegella的生命体就可能复苏，它们各种细胞成分可能受到的损伤也可能修复。这虽然并不意味着火星冰帽中一定会有休眠微生物，但却暗示孕育生命的摇篮可能会更广泛，这也就是说可能超出了我们目前寻找的范围。因此C为正确答案，而A与这句话却相反，B和D都与这个意思不相符合，所以都不对。
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