SSS 2011-10-10
时间：2019-01-08 作者：英语课 分类：Scientific American(十)月
英语课
This is Scientific American's 60-Second Science. I'm John Matson. Got a minute?
Earth's surface is dominated by oceans. But where did all that water come from?
Asteroids 1 and comets smashing into the early Earth have long been thought to be a promising 2 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 3 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 4 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.
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.
Thanks for the minute. For Scientific American's 60-Second Science, I'm John Matson.
n.小行星( asteroid的名词复数 )；海盘车，海星
- Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
- Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。
adj.有希望的，有前途的
- The results of the experiments are very promising.实验的结果充满了希望。
- We're trying to bring along one or two promising young swimmers.我们正设法培养出一两名有前途的年轻游泳选手。
n.天文学者，天文学家( astronomer的名词复数 )
- Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
- Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》