Published in the journal Nature, the analysis of these samples reveals an unexpected resurgence in the moon's magnetic field strength 2.8 billion years ago, following a significant decline around 3.1 billion years ago. This discovery challenges the prevailing view that the lunar dynamo - responsible for generating the moon's magnetic field - remained in a low-energy state after its initial decrease.

This research marks the first paleomagnetic data obtained from the moon's far side, shedding light on the intermediate phases of the lunar dynamo's development. The lunar samples, weighing 1,935.3 grams, were returned to Earth on June 25 by the Chang'e-6 probe, which collected them from previously unexplored terrain.

Researchers from the Institute of Geology and Geophysics (IGG) under the Chinese Academy of Sciences examined four basalt fragments from the Chang'e-6 mission. They discovered a resurgence of paleomagnetic field strength, potentially indicating a reactivation of the lunar dynamo. The study suggests that this reactivation could be linked to changes in the energy sources driving the dynamo or a renewal of its original mechanisms.

While satellite data and lunar surface studies confirm the absence of a global magnetic field on the moon today, prior research has established that the moon's magnetic field resembled Earth's between 4.2 and 3.5 billion years ago. The field subsequently experienced two major declines before disappearing entirely around 1 billion years ago. However, data on the moon's magnetic field evolution after 3 billion years ago - particularly on the far side - has been sparse.

"The evolution of the lunar dynamo holds significant implications for understanding the moon's internal structure, thermal history, and surface environment," said Cai Shuhui, corresponding author of the study and a researcher at IGG.

A peer reviewer of the research described the findings as "highly original," noting that they fill a billion-year gap in the lunar paleomagnetic record and represent "a major advance in our understanding of lunar magnetism."

The Chang'e-6 mission continues to produce groundbreaking results. In November, IGG researchers reported evidence of two volcanic events on the moon's far side, dating to 2.8 billion and 4.2 billion years ago, respectively. Another study published in Science confirmed that low-titanium samples from the mission are about 2.83 billion years old, providing further evidence of volcanic activity on the far side.

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