Unlocking Lunar Secrets: Chang’e-6 Samples Illuminate the Moon’s Magnetic Mysteries

Image: Institute of Geology and Geophysics (IGG), Chinese Academy of Sciences

Lunar rock specimens obtained from the moon’s far side by China’s Chang’e-6 lunar probe reveal an unforeseen revival in the moon’s magnetic field intensity 2.8 billion years ago, contradicting earlier results from the US Apollo mission, which indicated a decline in the moon’s magnetic field approximately 3.1 billion years ago, maintaining a low-energy state thereafter.

The evaluation of these specimens, released on Thursday in the journal Nature, represents the inaugural paleomagnetic data acquired from the moon’s far side, offering vital insights into the transitional evolutionary phases of the lunar dynamo, a geophysical process that produced the moon’s magnetic field historically, as reported by Guangming Daily. 

On June 25, 2024, the Chang’e-6 lunar probe made its return to Earth carrying 1,935.3 grams of lunar samples gathered from the previously uncharted far side of the moon.

Cai Shuhui from the Institute of Geology and Geophysics (IGG) affiliated with the Chinese Academy of Sciences, also the lead author of the published paper, explained that the Earth possesses a “magnetic field generator”—the motion of the conductive fluid in the Earth’s liquid outer core functions like a “generator,” producing a magnetic field that encases the Earth as a protective barrier. 

This magnetic field safeguards the planet from cosmic radiation and preserves crucial elements for sustaining life, including the atmosphere and water, thereby establishing an environment conducive to the growth of life.

Historically, the Moon had a comparable “magnetic field generator,” which ceased to operate ages ago. Investigations into the ancient magnetic field intensity based on samples returned by the US Apollo mission suggest that the Moon had a relatively operational “generator” generating a magnetic field from 4.2 billion to 3.5 billion years ago. This magnetic field experienced a significant reduction around 3.1 billion years ago and subsequently diminished again between 1.5 billion and 1 billion years ago, ultimately stopping entirely after 1 billion years ago.

The Chang’e 6 mission has successfully conducted the first-ever sample collection from the far side of the Moon, with the primary eruption age of the basalt dated at 2.8 billion years. This provides an unmatched opportunity to comprehend the temporal and spatial development of the Moon’s “magnetic field generator.”

Researchers from the IGG examined the sample and found the ancient magnetic field intensity to be greater than previously assumed. Cai mentioned that this indicates following a substantial decline in the lunar magnetic field 3.1 billion years ago, there might have been a rebound or activation around 2.8 billion years ago. 

IGG’s analysis suggests that this revival could stem from a variation in the principal energy source of the “generator” or a fortification of the initial driving mechanism.

The study conducted by IGG is not just the first set of data on the ancient magnetic field of the Moon acquired by humans; it also delivers essential information for understanding the evolution of the Moon’s magnetic field, according to Guangming Daily.