The Moon has virtually no global magnetic field and is thought to have lost it early in its evolution. However, new research carried out by the Chinese probe Chang’e-6 shows that this is not entirely true.
Research by Chinese scientists
The evolution of the lunar dynamo is crucial for understanding the moon’s deep interior structure, thermal history, and surface environment. A study by Chinese scientists conducted paleomagnetic analyses on basalts returned by the Chang’e-6 mission and revealed a significant reinforcement of the lunar dynamo approximately 2.8 billion years ago (Ga). This work is published in Nature.
Previous paleomagnetic studies of nearside lunar samples have established a general timeline for the evolution of the Moon’s magnetic field. However, limited spatial and temporal constraints have left the evolutionary trajectory of the lunar dynamo unclear.
The Chang’e-6 mission, which returned the first farside basalt samples dated to approximately 2.8 billion years ago Ga, provides a unique opportunity to fill this critical gap in our understanding of the lunar dynamo’s spatiotemporal evolution.
Measuring the strength of the ancient magnetic field
Led by Prof. Zhu Rixiang at the Institute of Geology and Geophysics of the Chinese Academy of Sciences (CAS), Associate Professor Cai Shuhui and her colleagues measured the ancient magnetic field strength from the Chang’e-6 basalts, obtaining values ranging from approximately 5 to 21 microteslas (µT).
These findings revealed an unexpected resurgence in field strength at 2.8 Ga, following a sharp decline around 3.1 Ga. This challenges the prevailing hypothesis that the lunar dynamo entered a low-energy state after 3 Ga and remained in this condition until its cessation.
The researchers proposed that the lunar magnetic field during this period may have been driven by a basal magma ocean and/or powered by precessional forces. Additional mechanisms, such as core crystallization, may also have a role.
Evolution of the lunar dynamo
These findings suggest that the Moon’s deep interior remained hot and geologically active well into its mid-early history.
This study represents the first-ever paleomagnetic data obtained from the moon’s farside, providing critical insights into the intermediate stages of the lunar dynamo’s evolution. By synthesizing this data with existing findings, the researchers suggested significant fluctuations in the lunar magnetic field between 3.5 and 2.8 Ga billion years ago, indicating a highly unstable dynamo during this period.
These results offer valuable guidance for future lunar exploration missions, including the search for potential magnetic reversals.
Provided by phys.org
