A new analysis of samples collected by China’s Chang’e-5 mission has revealed that the Moon had a weak, but still active, magnetic field about 2 billion years ago. Researchers from the Institute of Geology and Geophysics (Igg) of the Chinese Academy of Sciences analyzed nine basalt samples reported by Chang’e-5 from Oceanus Procellarumlocated in the middle latitudes of the Moon. These rocks offer a unique opportunity to explore the lunar magnetic history from 3 to 1 billion years ago, a period still largely unexplored.
The results, published in the journal Science Advancesshow that the Moon had a weak magnetic field during this period, with a strength of between 2 and 4 microtesla, or less than 10% of the strength of Earth’s field today. This discovery fills an important gap in our understanding of lunar magnetic evolution and suggests that the lunar dynamo lasted at least until its “middle age”, as Cai Shuhui, one of the corresponding authors of the article, states.
The researchers also speculated the presence of ongoing thermal convection deep in the lunar mantle, which may have provided extra heat for volcanic activity before the complete disappearance of the lunar magnetic field. The force that drove the magnetic field could arise from processes such as the crystallization of the moon’s core, the wobbling and descent of dense primordial materials, according to the study.
The weak magnetic field detected in Chang’e-5 samples indicates the presence of a protective shield during this period, offering a focus for research into spatial weathering and volatile materials such as water on the lunar surface in the “mid age” of the Moon, Cai said.
Furthermore, the research team published a study in the journal Nature last monthindicating an unexpected resurgence in the strength of the lunar magnetic field 2.8 billion years ago. The discovery is based on rock samples collected from the far side of the Moon by the Chang’e-6 lunar probe. These two studies together suggest that the lunar magnetic field not only did it persist into its “middle age,” but it may also have undergone fluctuations during that period, Cai concluded.
In November 2024, An IGG team reported two volcanic events that occurred on the far side of the Moon 2.8 billion years ago and 4.2 billion years ago. Another study confirmed that low samples Titanium contents collected by Chang’e-6 are approximately 2.83 billion years old, providing evidence of volcanic activity on the far side of the Moon.
For the sake of completeness, it should also be remembered that on 25 June last year, the Chang’e-6 lunar probe returned to Earth with 1,935.3 grams of lunar samples collected from the far side of the Moonpreviously unexplored, while the Chang’e-5 probe, which returned to Earth on December 17, 2020, recovered 1,731 grams of lunar samples, consisting mainly of rocks and soil from the lunar surface.
Image credits Cnsa/Handout via Xinhua
