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还有一篇天文的 没看懂...好像是讲什么东西是从asteroid上分离出来的 很多生单词 出现了很多次S-typed 和 spectra这两个词
是原文吗?
https://www.newscientist.com/article/mg14920164-000-meteorites-the-children-of-the-asteroids/
In the early 1970s, Tom McCord, now of the University of Hawaii, Torrence Johnson of NASA’s Jet Propulsion Laboratory, Michael Gaffey of Rensselaer polytechnic Institute in New York state and I began a systematic spectral search for the meteorites’ parents. Most of the brighter asteroids had reflection spectra showing the fingerprints of the same silicates, olivine and orthopyroxene, that dominate chondrites. Because of this, they became known as silicaceous, or S-type, asteroids. Promisingly, they were the most abundant type of asteroid in the inner third of the asteroid belt, which is where the chief escape hatches to Earth are found.
But then things began to go wrong. We soon realised that there was something strange about the spectra of S-types. Instead of the strong infrared absorption bands that chondrites show in the lab, the S-type bands were always weak. Unlike the ordinary chondrites, S-type asteroids seem to reflect red and infrared light much better than green, blue and violet (see Figure, bottom right). McCord and Gaffey suggested that the S-types contain only a small amount of silicate, and mostly consist of a nickel-iron alloy. This alloy is slightly reddish and exhibits no absorption bands. |
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