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SSS 2009-04-13

时间:2010-05-17 07:53来源:互联网 提供网友:木渐浅。   字体: [ ]
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    (单词翻译:双击或拖选)

This is Scientific American's 60-Second Science. I'm Cynthia Graber. This will just take a minute.

The Earth’s original atmosphere would have been unpleasant—deadly in fact—to any organisms that breathe oxygen. There wasn’t any. Not until about 2.4 billion years ago anyway. That’s the time of what scientists call the Great Oxidation Event. Now researchers believe they’ve found clues as to what may have caused the change. They published their report in the April 9 edition of the journal Nature.

Researchers analyzed1 trace elements in sedimentary rock from dozens of sites. Turns out nickel was 400 times more abundant in primordial2 oceans than in today’s waters. Microorganisms called methanogens love nickel-rich water, and they release methane3 into the atmosphere. Methane prevents a buildup of oxygen.

Scientists testing the rocks saw that around 2.7 to 2.4 billion years ago, ocean-dissolved nickel dropped off. This corresponds to the Great Oxidation Event. Lack of nickel could have killed off methanogens and left room for algae4 and other life forms that release oxygen during photosynthesis5.

Researchers don’t know exactly why nickel decreased—possibly because of the cooling and solidifying6 of the Earth’s mantle7. But the nickel disappearance8 is one more clue about how the planet went from suffocating9 to a place where a terrestrial tetrapod could take a deep breath.

 

Thanks for the minute for Scientific American's 60-Second Science. I'm Cynthia Graber.

 


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1 analyzed 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
参考例句:
  • The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
2 primordial 11PzK     
adj.原始的;最初的
参考例句:
  • It is the primordial force that propels us forward.它是推动我们前进的原始动力。
  • The Neanderthal Man is one of our primordial ancestors.的尼安德特人是我们的原始祖先之一.
3 methane t1Eyx     
n.甲烷,沼气
参考例句:
  • The blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
  • Methane may have extraterrestrial significance.甲烷具有星际意义。
4 algae tK6yW     
n.水藻,海藻
参考例句:
  • Most algae live in water.多数藻类生长在水中。
  • Algae grow and spread quickly in the lake.湖中水藻滋蔓。
5 photosynthesis A2Czp     
n.光合作用
参考例句:
  • In apple trees photosynthesis occurs almost exclusively in the leaves.苹果树的光合作用几乎只发生在叶内。
  • Chloroplasts are the structures in which photosynthesis happens.叶绿体就是光合作用发生的地方。
6 solidifying c6b354d6b8d073b347fa117486619454     
(使)成为固体,(使)变硬,(使)变得坚固( solidify的现在分词 ); 使团结一致; 充实,巩固; 具体化
参考例句:
  • The substances are formed from a mixture of liquids solidifying under pressure. 这些材料是由几种液体混合在一起并加压使之凝固而成的。
  • Painting is an art solidifies time and space for solidifying. 绘画是凝固了的时间和空间的艺术。
7 mantle Y7tzs     
n.斗篷,覆罩之物,罩子;v.罩住,覆盖,脸红
参考例句:
  • The earth had donned her mantle of brightest green.大地披上了苍翠欲滴的绿色斗篷。
  • The mountain was covered with a mantle of snow.山上覆盖着一层雪。
8 disappearance ouEx5     
n.消失,消散,失踪
参考例句:
  • He was hard put to it to explain her disappearance.他难以说明她为什么不见了。
  • Her disappearance gave rise to the wildest rumours.她失踪一事引起了各种流言蜚语。
9 suffocating suffocating     
a.使人窒息的
参考例句:
  • After a few weeks with her parents, she felt she was suffocating.和父母呆了几个星期后,她感到自己毫无自由。
  • That's better. I was suffocating in that cell of a room.这样好些了,我刚才在那个小房间里快闷死了。
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