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雅思真题听力场景精练 第54期:科技类讲座 地质与考古(3)

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And the possibility of living organisms on Mars could still not be ruled out. Now, you should realize that it is a lot easier to prove that something exists than it is to prove that something doesn’t exist. Once you’ve discovered something, you’ve got it in the bag——but it’s harder to prove that something is not there, because no matter how much you look without finding it, it could still be hiding under the next rock. So scientists continue to look under the Martian rocks. The Viking mission in 1976 included three biological experiments——the Labelled Release experiment, the Pyrolytic Release experiment, and the Gas Exchange experiment. None of these experiments were successful. That is, none of them produced clear results detecting life forms. Most scientists now agree that the experiments were flawed——all of the results can be explained as purely chemical processes that do not require the presence of life. However, there is now evidence, as I said, that Mars once had significantly more water, and now scientists are considering the possibility that the planet once had life——but that it went extinct when conditions on Mars got worse.

重点单词   查看全部解释    
evidence ['evidəns]

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n. 根据,证据
v. 证实,证明

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release [ri'li:s]

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n. 释放,让渡,发行
vt. 释放,让与,准

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extinct [iks'tiŋkt]

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adj. 灭绝的,熄灭的,耗尽的

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flawed [flɔ:d]

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adj. 有缺陷的;有瑕疵的;有裂纹的

 
exchange [iks'tʃeindʒ]

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n. 交换,兑换,交易所
v. 交换,兑换,交

 
presence ['prezns]

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n. 出席,到场,存在
n. 仪态,风度

 
planet ['plænit]

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n. 行星

 

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