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Updated: Sep 13, 2025

Simulation of the Planetary Interior Differentiation Processes in the Laboratory
Published on: November 15, 2013
A more reduced mantle beneath the lunar South Pole-Aitken basin
Huijuan Zhang1,2, Wei Yang3, Di Zhang1
1Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
Abstract:
The oxygen fugacity (fO2) of the lunar mantle is of pivotal significance in comprehending the formation and evolution of the Moon. However, the fO2 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 fO2 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 fO2 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 S2 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.
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