Incipient Space Weathering Observed on the Surface of Itokawa Dust Particles
Incipient Space Weathering Observed on the Surface of Itokawa Dust Particles
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DOI：
10.1126/science.1207794
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发表时间：
2011-08
期刊：
影响因子：
56.9
通讯作者：
T. Noguchi;Tomoki Nakamura;M. Kimura;M. Zolensky;Masahiko Tanaka;T. Hashimoto;M. Konno;A. Nakato-A.
中科院分区：
文献类型：
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作者：
T. Noguchi;Tomoki Nakamura;M. Kimura;M. Zolensky;Masahiko Tanaka;T. Hashimoto;M. Konno;A. Nakato-A.
对从小行星带回的样本进行实验室分析，确立了小行星和陨石之间的直接联系，并为小行星及其表面的复杂历史提供了线索。最丰富的陨石（普通球粒陨石）的反射光谱与丰富的s型（硅质助记符）小行星的反射光谱不同。这种差异被认为是由于空间风化，即暴露在空间环境中的无空气物体表面的变化。在这里，我们报告了由隼鸟号宇宙飞船从s型小行星25143 Itokawa返回的粒子的空间风化证据。10个颗粒中有5个发现了表面修饰，这取决于矿物的种类。含硫富铁纳米颗粒存在于橄榄石、低钙辉石和斜长石表面的薄层（5 ~ 15纳米）中，提示气相沉积。无硫富铁纳米颗粒存在于镁铁硅酸盐内部深处（<60纳米）。它们的结构表明是由变质作用和Fe2+原位还原形成的。
Laboratory analysis of samples returned from an asteroid establishes a direct link between asteroids and meteorites and provides clues to the complex history of the asteroid and its surface. The reflectance spectra of the most abundant meteorites, ordinary chondrites, are different from those of the abundant S-type (mnemonic for siliceous) asteroids. This discrepancy has been thought to be due to space weathering, which is an alteration of the surfaces of airless bodies exposed to the space environment. Here we report evidence of space weathering on particles returned from the S-type asteroid 25143 Itokawa by the Hayabusa spacecraft. Surface modification was found in 5 out of 10 particles, which varies depending on mineral species. Sulfur-bearing Fe-rich nanoparticles exist in a thin (5 to 15 nanometers) surface layer on olivine, low-Ca pyroxene, and plagioclase, which is suggestive of vapor deposition. Sulfur-free Fe-rich nanoparticles exist deeper inside (<60 nanometers) ferromagnesian silicates. Their texture suggests formation by metamictization and in situ reduction of Fe2+.