Synchrotron Fe‐K X‐ray absorption spectroscopy and transmission electron microscopy have been used to investigate the mineralogy and Fe‐redox variations in the space‐weathered (SW) rims of asteroidal samples. This study focuses on the FIB lift‐out sections from five Itokawa grains, returned by the Hayabusa spacecraft, including samples RB‐QD04‐0063, RB‐QD04‐0080, RB‐CV‐0011, RB‐CV‐0089, and RB‐CV‐0148. Each of the samples featured partially amorphized SW rims, caused by irradiation damage from implanted low mass solar wind ions, and the impacting of micrometeorites. Using bright‐field and HAADF‐STEM imaging, vesicular blistering and nanophase Fe metal (npFe⁰) particles were observed within grain rims, and solar flare tracks were observed in the substrate host grain, confirming the presence of SW zones. We use Fe‐K XANES mapping to investigate Fe‐redox changes between the host mineral and the SW zones. All SW zones measured show some increases in the ferric‐ferrous ratio (Fe³⁺/ΣFe) relative to their respective host grains, likely the result of the implanted solar wind H⁺ ions reacting with the segregated ferrous Fe in the surface material.

中文翻译：

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丝川空间风化轮辋中的铁氧化还原变化

同步加速器Fe‐KX射线吸收光谱法和透射电子显微镜已用于研究小行星样品的空间风化（SW）边缘的矿物学和Fe‐redox变化。这项研究的重点是the鸟号航天飞机返回的五种丝川纹谷的FIB抬升部分，包括样本RB-QD04-0063，RB-QD04-0080，RB-CV-0011，RB-CV-0089和RB- CV-0148。每个样品都具有部分非晶化的SW轮缘，这是由于注入的低质量太阳风离子造成的辐照损伤以及微陨石的撞击所致。使用明场和HAADF‐STEM成像，水疱和纳米相铁金属（npFe ⁰）在晶粒边缘内观察到颗粒，并且在基质基质晶粒中观察到太阳耀斑痕迹，从而确认了SW区的存在。我们使用Fe‐K XANES映射来研究主体矿床和西南地区之间的Fe‐redox变化。相对于其各自的主体晶粒，所有测得的西南区都显示出铁-铁比（Fe ³⁺ /ΣFe）有所增加，这很可能是由于注入的太阳风H ⁺离子与表面材料中的偏析出的亚铁反应的结果。