The water content of CM carbonaceous chondrite falls and finds, and their susceptibility to terrestrial contamination
The water content of CM carbonaceous chondrite falls and finds, and their susceptibility to terrestrial contamination
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CM碳质球粒陨石的含水量下降和发现及其对陆地污染的敏感性
DOI：
10.1111/maps.14099
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发表时间：
2023
影响因子：
2.2
通讯作者：
Lee M
中科院分区：
文献类型：
--
作者：
Lee M
Cm碳质球粒陨石可以用来约束C-复合体小行星中水和OH的丰度和氢同位素组成。以前对CMS的水/羟基含量的测量是在遥感确定的小行星成分范围的较高端。一种可能的解释是，由于陨石在地球上的时间受到污染，它们的本土水/羟基含量被高估了。在这里，我们试图通过逐步热解来量化CM瀑布中大地水和本地水的浓度和氢同位素组成，以更好地了解陆地污染的程度和速率。这些测量结果与已公布的CM Fall and Found的热解数据进行了整合。一旦暴露在地球大气层中，CM瀑布很快就会受到污染，其中一些会在几天内获得重量百分比的水浓度。添加的水量不会随着时间的推移而逐渐增加，因为CM瀑布的吸附水分含量范围与发现的相似。相反，CMS的岩石学类型强烈影响它们可以获得的陆地水的数量。这种关系可能由陨石的矿物学和/或岩石物理性质控制，这些性质影响了它们的吸湿性。无论样品吸收的水的数量或其陆地年龄，土著层状硅酸盐中与陆地环境的H交换很少。这里讨论的瀑布和发现含有1.9-10.5 wt%的原生水(平均7.0 wt%)，这与最近对包括本努在内的C-复合体小行星的测量一致。
CM carbonaceous chondrites can be used to constrain the abundance and H isotopic composition of water and OH in C‐complex asteroids. Previous measurements of the water/OH content of the CMs are at the higher end of the compositional range of asteroids as determined by remote sensing. One possible explanation is that the indigenous water/OH content of meteorites has been overestimated due to contamination during their time on Earth. Here we have sought to better understand the magnitude and rate of terrestrial contamination through quantifying the concentration and H isotopic composition of telluric and indigenous water in CM falls by stepwise pyrolysis. These measurements have been integrated with published pyrolysis data from CM falls and finds. Once exposed to Earth's atmosphere CM falls are contaminated rapidly, with some acquiring weight percent concentrations of water within days. The amount of water added does not progressively increase with time because CM falls have a similar range of adsorbed water contents to finds. Instead, the petrologic types of CMs strongly influence the amount of terrestrial water that they can acquire. This relationship is probably controlled by mineralogical and/or petrophysical properties of the meteorites that affect their hygroscopicity. Irrespective of the quantity of water that a sample adsorbs or its terrestrial age, there is minimal exchange of H in indigenous phyllosilicates with the terrestrial environment. The falls and finds discussed here contain 1.9–10.5 wt% indigenous water (average 7.0 wt%) that is consistent with recent measurements of C‐complex asteroids including Bennu.
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影响因子：
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作者：
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