China's Chang'e-6 lunar probe has brought back compelling data that alters our understanding of the moon's magnetic history.

Rock samples collected from the moon's far side suggest an unexpected resurgence in the lunar magnetic field strength approximately 2.8 billion years ago—a finding that starkly contrasts with the established data from the US Apollo missions, which proposed that the moon's magnetic field diminished around 3.1 billion years ago and remained largely inactive thereafter.

The findings, published in the prestigious journal Nature, mark the first instance of paleomagnetic data derived from the moon’s far side, offering new perspectives on the intermediate evolutionary phases of the lunar dynamo—a geophysical mechanism responsible for generating the moon's magnetic field in its early history.

This breakthrough was made possible when, on June 25, 2024, the Chang'e-6 mission triumphantly returned to Earth with 1,935.3 grams of lunar material from this hitherto unexplored region.

Cai Shuhui, a leading researcher from the Institute of Geology and Geophysics (IGG) under the Chinese Academy of Sciences and the principal author of the study, explains that much like Earth, which generates a magnetic field through the movement of conductive fluids in its outer core, the moon also possessed a similar magnetic field in the past.

Earth's magnetic field acts as a crucial protective shield, safeguarding the planet from cosmic radiation and preserving essential life-supporting elements such as the atmosphere and water.

Previously, analysis of lunar samples from the Apollo missions suggested the moon's dynamo was particularly active between 4.2 to 3.5 billion years ago.

Following a decline approximately 3.1 billion years ago, it was thought to have experienced another reduction in strength between 1.5 billion and 1 billion years ago, eventually ceasing its activity completely sometime after 1 billion years ago.

However, the Chang'e-6's groundbreaking mission, which captured samples from basalt with a primary eruption age of 2.8 billion years, provides a fresh opportunity to examine the moon's magnetic history.

The higher than expected magnetic field strength discovered in these samples opens the possibility of a transient reactivation or rebound around that period, indicating changes in the moon's dynamo.

According to the IGG's analysis, these findings could be attributed to either a shift in the primary energy source of the moon's magnetic generator or a fortification of its initial driving mechanism.

This pioneering study not only represents the first documentation of the moon's ancient magnetic field obtained by human scientists but also provides critical insights into the evolution of the moon’s dynamo, adding a new layer to our understanding of our celestial neighbor's history.