Chang’E-4 landed in the South Pole-Aitken (SPA) basin, providing a unique chance to probe the composition of the lunar interior. Its landing site is located on ejecta strips in Von Kármán crater that possibly originate from the neighboring Finsen crater. A surface rock and the lunar regolith at 10 sites along the rover Yutu-2 track were measured by the onboard Visible and Near-Infrared Imaging Spectrometer in the first three lunar days of mission operations. In situ spectra of the regolith have peak band positions at 1 and 2 μm, similar to the spectral data of Finsen ejecta from the Moon Mineralogy Mapper, which confirms that the regolith's composition of the landing area is mostly similar to that of Finsen ejecta. The rock spectrum shows similar band peak positions, but stronger absorptions, suggesting relatively fresh exposure. The rock may consist of 38.1 ± 5.4% low-Ca pyroxene, 13.9 ± 5.1% olivine and 48.0 ± 3.1% plagioclase, referred to as olivine-norite. The plagioclase-abundant and olivine-poor modal composition of the rock is inconsistent with the origin of the mantle, but representative of the lunar lower crust. Alternatively, the rock crystallized from the impact-derived melt pool formed by the SPA-impact event via mixing the lunar crust and mantle materials. This scenario is consistent with fast-cooling thermal conditions of a shallow melt pool, indicated by the fine to medium-sized texture (<3 mm) of the rock and the SPA-impact melting model [Icarus 2012; 220: 730–43].

中文翻译：

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月球车玉兔2号探测到的橄榄石-紫砂岩很可能是从SPA撞击熔池中结晶出来的

嫦娥四号降落在南极-艾特肯 (SPA) 盆地，提供了一个独特的机会来探测月球内部的成分。它的着陆点位于 Von Kármán 陨石坑的喷射带上，可能来自邻近的芬森陨石坑。在月球任务运行的前三个月球日，机载可见光和近红外成像光谱仪测量了月球车玉兔 2 号轨道沿线 10 个地点的地表岩石和月球风化层。就地风化层的光谱在 1 和 2 μm 处有峰带位置，与 Moon Mineralogy Mapper 的芬森喷射物的光谱数据相似，这证实了着陆区的风化层成分与芬森喷射物的成分大体相似。岩石光谱显示出相似的波段峰值位置，但吸收更强，表明曝光相对较新。岩石可能由 38.1 ± 5.4% 低钙辉石、13.9 ± 5.1% 橄榄石和 48.0 ± 3.1% 斜长石组成，称为橄榄石-紫长石。岩石的斜长石丰富和橄榄石贫乏的模态组成与地幔的起源不一致，但代表了月球下地壳。或者，岩石是由 SPA 撞击事件通过混合月球地壳和地幔材料形成的撞击衍生熔池结晶的。伊卡洛斯2012; 220：730-43]。