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万物简史 第349期:孤独的行星(14)

发表时间:2018-01-12内容来源:VOA英语学习网
The figures have since been refined and made a little more generous, 自那以后,这两个数字被更精确地测算了一遍,放宽了一点, 5 percent nearer and 15 percent farther are thought to be more accurate assessments for our zone of habitability—but that is still a narrow belt. 再近5%,再远15%,但仍是个窄带。 The discovery of extremophiles in the boiling mudpots of Yellowstone and similar organisms found elsewhere (由于在黄石公园沸腾的泥潭里发现了极端微生物和在别处发现了类似的微生物, made scientists realize that actually life of a type could range much farther than that-even, perhaps, beneath the icy skin of Pluto. 科学家们认识到,某种真正的生命的分布范围要比这广得多——甚至可能出现在冥王星的冰面底下。 What we are talking about here are the conditions that would produce reasonably complex surface creatures.) 我们在这里讨论的只是能产生比较复杂的地表生物的条件。) To appreciate just how narrow, you have only to look at Venus. 若要了解幅度为何很小,你只要望一眼金星。 Venus is only twenty-five million miles closer to the Sun than we are. 金星离太阳只比我们近2 500万公里。 The Sun's warmth reaches it just two minutes before it touches us. 太阳的热量射到那里只比我们早两分钟。 In size and composition, Venus is very like Earth, but the small difference in orbital distance made all the difference to how it turned out. 金星的大小和结构很像地球,但是,轨道距离上的小小差别,产生了全然不同的结果。 It appears that during the early years of the solar system Venus was only slightly warmer than Earth and probably had oceans. 看来,只是在太阳系形成之初,金星才比地球稍稍暖和一点,而且很可能有海洋。 But those few degrees of extra warmth meant that Venus could not hold on to its surface water, with disastrous consequences for its climate. 但是,热这么几摄氏度就意味着金星无法留住表面的水,结果对气候造成了灾难性的后果。 As its water evaporated, the hydrogen atoms escaped into space, 随着水分的蒸发,氢原子逸入太空, and the oxygen atoms combined with carbon to form a dense atmosphere of the greenhouse gas CO2. 氧原子与碳在大气里形成了厚厚的一层温室气体一氧化碳。 Venus became stifling. 金星变得令人窒息。 Although people of my age will recall a time when astronomers hoped that Venus might harbor life beneath its padded clouds, possibly even a kind of tropical verdure, 我这样年龄的人还记得起,天文学家们曾一度希望,在密密的云层下面,甚至可能是在郁郁葱葱的热带植物下面, we now know that it is much too fierce an environment for any kind of life that we can reasonably conceive of. 金星上存在着生命,但我们现在知道,那里的环境过于恶劣,不适与我们所能想象的任何生命。 来自:VOA英语网 文章地址: http://www.tingvoa.com/html/20180112/527675.html
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