Zhang Huijuan, Yang Wei, Zhang Di, Hao Jialong, Liu Xiaoying, Zhu Honggang, Mitchell Ross N, Jia Lihui, Fan Yunhong, Wu Shitou, Gu Lixin, Tang Xu, Tian Heng-Ci, Pei Junling, Lin Yangting, Li Xian-Hua, Wu Fu-Yuan
Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
East China University of Technology, Nanchang, Jiangxi Province, China.
Nat Commun. 2025 Jul 30;16(1):6985. doi: 10.1038/s41467-025-62341-5.
The oxygen fugacity (fO) of the lunar mantle is of pivotal significance in comprehending the formation and evolution of the Moon. However, the fO of the lunar farside mantle remains unknown due to the lack of samples returned from the farside. Here, we determine the oxygen fugacity of 23 basaltic fragments from the Chang'e-6 (CE6) soil, the first farside sample collected from the South Pole-Aitken (SPA) basin. The spinel V oxybarometer and pyroxene Eu oxybarometer yield an average fO of ΔIW -1.93 ± 0.58 (2σ), indicating a more reduced state compared to the nearside Apollo and Chang'e-5 (CE5) basalts, which have an average fO of ΔIW -0.80 ± 0.64 (2σ). Such asymmetry in oxygen fugacity of the lunar mantle can be attributed to two processes: nearside mantle oxidation by a larger amount of Fe sinking into the core triggered by asymmetric crystallisation of the lunar magma ocean, and/or farside mantle reduction caused by S and CO degassing during the SPA massive impact. Nevertheless, the reduced nature of the underlying mantle beneath the SPA basin reveals another aspect of lunar asymmetry.
月球地幔的氧逸度（fO）对于理解月球的形成和演化至关重要。然而，由于缺乏来自月球背面的样本，月球背面地幔的fO仍然未知。在此，我们测定了嫦娥六号（CE6）土壤中23个玄武岩碎块的氧逸度，这些土壤是从南极艾特肯（SPA）盆地采集的首个月球背面样本。尖晶石V氧分压计和辉石Eu氧分压计得出的平均fO为ΔIW -1.93±0.58（2σ），这表明与月球正面的阿波罗和嫦娥五号（CE5）玄武岩相比，其状态更为还原，后者的平均fO为ΔIW -0.80±0.64（2σ）。月球地幔氧逸度的这种不对称性可归因于两个过程：月球岩浆海洋的不对称结晶引发大量铁沉入地核，导致正面地幔氧化，和/或在SPA大规模撞击期间，硫和一氧化碳脱气导致背面地幔还原。尽管如此，SPA盆地下方下地幔的还原性质揭示了月球不对称性的另一个方面。
