Cai Shuhui, Qi Kaixian, Yang Saihong, Fang Jie, Shi Pingyuan, Shen Zhongshan, Zhang Min, Qin Huafeng, Zhang Chi, Li Xiaoguang, Chen Fangfang, Chen Yi, Li Jinhua, He Huaiyu, Deng Chenglong, Li Chunlai, Pan Yongxin, Zhu Rixiang
State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China.
Nature. 2024 Dec 19. doi: 10.1038/s41586-024-08526-2.
The evolution of the lunar dynamo is essential for deciphering the deep interior structure, thermal history and surface environment of the Moon. Previous palaeomagnetic investigations on samples returned from the nearside of the Moon have established the general variation of the lunar magnetic field. However, limited spatial and temporal palaeomagnetic constraints leave the evolution of the lunar dynamo ambiguous. The Chang'e-6 mission returned the first farside basalts dated at about 2.8 billion years ago (Ga) (refs. ), offering an opportunity to investigate a critical spatiotemporal gap in the evolution of the global lunar dynamo. Here we report palaeointensities (around 5-21 μT) recovered from the Chang'e-6 basalts, providing the first constraint on the magnetic field from the lunar farside and a critical anchor within the large gap between 3 Ga and 2 Ga. These results record a rebound of the field strength after its previous sharp decline of around 3.1 Ga, which attests to an active lunar dynamo at about 2.8 Ga in the mid-early stage and argues against the suggestion that the lunar dynamo may have remained in a low-energy state after 3 Ga until its demise. The results indicate that the lunar dynamo was probably driven by either a basal magma ocean or a precession, supplemented by other mechanisms such as core crystallization.
月球发电机的演化对于解读月球的深部内部结构、热历史和表面环境至关重要。此前对从月球近侧返回的样本进行的古地磁研究已经确定了月球磁场的总体变化。然而，有限的时空古地磁约束使得月球发电机的演化仍不明确。嫦娥六号任务带回了首批约28亿年前（Ga）的远侧玄武岩（参考文献），为研究全球月球发电机演化中的一个关键时空空白提供了契机。在此，我们报告了从嫦娥六号玄武岩中恢复的古强度（约5-21μT），这是对月球远侧磁场的首次约束，也是3Ga和2Ga之间巨大空白中的关键锚点。这些结果记录了磁场强度在约3.1Ga之前急剧下降后的反弹，这证明在中早期约2.8Ga时存在活跃的月球发电机，也反驳了月球发电机在3Ga之后可能一直处于低能量状态直至消亡的观点。结果表明，月球发电机可能由底部岩浆海洋或岁差驱动，并辅以其他机制，如核心结晶。
