A non-terrestrial 16O-rich isotopic composition for the protosolar nebula
A non-terrestrial 16O-rich isotopic composition for the protosolar nebula
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DOI：
10.1038/nature03432
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发表时间：
2005-03-31
期刊：
影响因子：
64.8
通讯作者：
Chaussidon, M
中科院分区：
文献类型：
--
作者：
Hashizume, K;Chaussidon, M
在陨石(1，2)的原始成分中发现了不能归因于与质量有关的分馏效应的大的氧同位素变化，这提出了一个基本的问题：形成宿主颗粒的原溶质气体的组成是什么？这种成分可能保存在太阳的外层，但天文光谱测量的分辨率仍然太低，无法与行星物质进行比较(3，4)。在这里，我们报道了从植入月球表层数百纳米金属颗粒中的粒子精确测定太阳风的氧同位素组成。相对于地球、火星和大型陨石，这些层的颗粒富含O-16，这意味着太阳吸积盘中存在未知的反应，能够以一种不严格依赖于同位素质量的方式改变O-17/O-16和O-18/O-16的比率。受紫外光(5-7)照射的CO气体的光化学自屏蔽可能是这些关键过程之一，因为它取决于同位素的丰度，而不是它们的质量。
The discovery in primitive components of meteorites(1,2) of large oxygen isotopic variations that could not be attributed to mass-dependent fractionation effects has raised a fundamental question: what is the composition of the protosolar gas from which the host grains formed? This composition is probably preserved in the outer layers of the Sun, but the resolution of astronomical spectroscopic measurements is still too poor to be useful for comparison with planetary material(3,4). Here we report a precise determination of the oxygen isotopic composition of the solar wind from particles implanted in the outer hundreds of nanometres of metallic grains in the lunar regolith. These layers of the grains are enriched in O-16 by >20 +/- 4 parts per thousand relative to the Earth, Mars and bulk meteorites, which implies the existence in the solar accretion disk of reactions-as yet unknown-that were able to change the O-17/O-16 and O-18/O-16 ratios in a way that was not dependent strictly on the mass of the isotope. Photochemical self-shielding of the CO gas irradiated by ultraviolet light(5-7) may be one of these key processes, because it depends on the abundance of the isotopes, rather than their masses.