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托福听力练习-科学美国人60秒:海水来自彗星

2017-04-19 08:38:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：海水来自彗星

　　科学美国人60秒听力练习：海水来自彗星

　　科学美国人60秒英文文本

　　Earth's surface is dominated by oceans. But where did all that water come from?

　　Asteroids and comets smashing into the early Earth have long been thought to be a promising source. But measurements of Halley's Comet and five others threw cold water on the idea that comets provided a large share of the oceans. Because the chemical signatures of the comets did not match the oceans. Specifically, the ratio of heavy hydrogen, or deuterium, to regular hydrogen was too high in the comets.

　　But now astronomers have gotten a glimpse of a comet with a different origin, and it matches the oceans much better. They used the Herschel space telescope to examine Comet Hartley 2, which originated in the Kuiper Belt. Halley and its ilk came from a distant swarm of comets called the Oort Cloud.

　　At a planetary science meeting last week in France, and in a study in Nature, the researchers announced that Comet Hartley 2 has the same deuterium-to-hydrogen ratio as ocean water. [Paul Hartogh et al., "Oceanlike water in the Jupiter-family comet 103P/Hartley 2"]

　　So maybe comets did play a major role in delivering Earth's oceans. Something to ponder next time you have a day at the beach.

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人 科学60秒sss

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