3.1 billion years ago, the strength of the lunar magnetic field sharply decreased and has remained weak ever since? Chinese scientists have provided a different answer to this question. Based on the samples of Chang'e-6 lunar back, researchers from the Chinese Academy of Sciences found that the lunar magnetic field strength rebounded 2.8 billion years ago. This is not only the first ancient lunar magnetic field information obtained by humans, but also provides new insights into the evolution of the lunar magnetic field. The relevant paper was recently published online in Nature. The movement of the Earth's liquid outer core conductive fluid is like a "generator", generating a magnetic field that wraps around the Earth like a protective umbrella, shielding cosmic rays, protecting habitable elements such as the Earth's atmosphere and water, and helping to create an environment suitable for the reproduction of life. The moon once had a magnetic field 'generator' similar to that of Earth. Understanding the evolution process of the lunar magnetic field "generator" is of great significance for revealing the internal structure, thermal history, and surface environment of the moon. Both satellite observations and lunar surface measurements show that the moon no longer has a global dipole magnetic field. The study of Apollo lunar samples in the United States shows that there was a relatively active magnetic field generated by a "generator" on the moon between 4.2 billion and 3.5 billion years ago, with a strength similar to the current Earth's magnetic field. The magnetic field decreased by an order of magnitude about 3.1 billion years ago and has remained at a very low intensity ever since. Afterwards, the strength of the lunar magnetic field decreased again between 1.5 billion and 1 billion years ago, and eventually disappeared completely at some point after 1 billion years ago. Due to sample limitations, previously published data on lunar paleomagnetic field strength mainly focused on 3 billion years ago. There is relatively little research in the scientific community on the mid to late evolution of the lunar magnetic field over the past 3 billion years. Meanwhile, the existing data all come from samples returned from the near side of the moon, and people's understanding of the ancient magnetic field on the far side of the moon is basically blank Cai Shuhui, the corresponding author of the paper and associate researcher of the Institute of Geology and Geophysics, Chinese Academy of Sciences, said. In this study, researchers conducted magnetic research on four millimeter sized basalt debris samples. The results show that the lunar magnetic field may have rebounded 2.8 billion years ago. This indicates that the "power generation capacity" of the lunar "generator" may reactivate after a sharp decline in the early stages, possibly due to changes in the main energy source of the lunar "generator" or a re enhancement of the initial driving mechanism. The reviewers of Nature believe that this is a highly original study that fills a billion year gap in lunar paleomagnetic field records and provides for the first time paleomagnetic field measurements from the far side of the moon. (New Society)