Samples collected from the surface/subsurface of C-type asteroid 162173 Ryugu by the Hayabusa2 mission were nondestructively analyzed in three dimensions (3D). Seventy-three small particles (approximately 10–180 µm in size) were observed using X-ray nanotomography, with an effective spatial resolution of approximately 200 nm. Detailed descriptions of these samples in terms of mineralogy, petrology, and variations among particles were reported. The 57 most common particles consisted of a phyllosilicate matrix containing mineral grains, mainly magnetite, pyrrhotite, dolomite and apatite. The remaining particles were mostly monomineralic particles (pyrrhotite, dolomite, breunnerite, apatite, and Mg-Na phosphate) with two unique particles (calcite in a AlSiO(OH) matrix, and CaCO, phyllosilicate, and tochilinite-chronstedtite inclusions in a carbonaceous material matrix). The results confirmed that the samples correspond to Ivuna-type carbonaceous chondrites (CI chondrites) or related materials. Many small inclusions of voids and carbonaceous materials were detected in pyrrhotite, dolomite, breunnerite, and apatite. However, no fluid inclusions were observed, except for those in pyrrhotite that have already been reported. Magnetite exhibited a wide variety of morphologies, from irregular shapes (spherulites, framboids, plaquettes, and whiskers) to euhedral shapes (equants, rods, and cubes), along with transitional shapes. In contrast, the other minerals exhibit predominantly euhedral shapes (pyrrhotite: pseudo-hexagonal plates, dolomite: flattened rhombohedrons, breunnerite: largely flattened rhombohedrons, and apatite: hexagonal prisms) or aggregates of faceted crystals, except for Mg-Na phosphate. The matrices were heterogeneous with variable phyllosilicate particle sizes, Mg/Fe ratios, density (1.7 ± 0.2 g/cm), nanoporosities (36 ± 9 %), and abundances of nanograins of Fe(-Ni) sulfides. The macroporosity of the particles was estimated as 12 ± 4 %.

中文翻译：

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龙宫样本的三维纹理及其对龙宫母体水蚀变演化的影响

Hayabusa2 任务从 C 型小行星 162173 Ryugu 的表面/地下收集的样本进行了三维 (3D) 无损分析。使用 X 射线纳米断层扫描技术观察到 73 个小颗粒（尺寸约为 10-180 µm），有效空间分辨率约为 200 nm。报告了这些样品在矿物学、岩石学和颗粒变化方面的详细描述。 57 种最常见的颗粒由含有矿物颗粒的页硅酸盐基质组成，主要是磁铁矿、磁黄铁矿、白云石和磷灰石。其余颗粒主要是单矿物颗粒（磁黄铁矿、白云石、镁黄铁矿、磷灰石和磷酸镁钠），具有两种独特的颗粒（AlSiO(OH) 基体中的方解石，以及碳质材料中的 CaCO3、层状硅酸盐和托硅石-铬锰矿夹杂物矩阵）。结果证实，这些样品对应于伊武纳型碳质球粒陨石（CI 球粒陨石）或相关材料。在磁黄铁矿、白云石、角磷灰石和磷灰石中检测到许多孔隙和碳质材料的小包裹体。然而，除了已经报道过的磁黄铁矿中的流体包裹体之外，没有观察到流体包裹体。磁铁矿表现出各种各样的形态，从不规则形状（球晶、草莓状、片状和晶须）到自形形状（等分体、棒状和立方体）以及过渡形状。相比之下，除磷酸镁钠外，其他矿物主要表现出自形形状（磁黄铁矿：假六方板、白云石：扁平菱面体、布氏石：大部分扁平菱面体和磷灰石：六方棱柱）或多面体晶体的聚集体。基质是异质的，具有不同的页硅酸盐颗粒尺寸、Mg/Fe 比率、密度 (1.7 ± 0.2 g/cm)、纳米孔隙率 (36 ± 9 %) 和 Fe(-Ni) 硫化物纳米颗粒的丰度。颗粒的大孔隙率估计为 12 ± 4%。