The strength of the Moon's magnetic field has been a topic of debate among scientists, prompting the question: Was it strong in the near past, or has it remained weak throughout its history? A recent study published in Nature Geoscience indicates that while there were periods of significant strength in the ancient history of the Moon, these periods were short-lived, and overall, the magnetic field has been quite weak for most of its 4.5 billion year existence. This finding challenges previous understandings and invites further scrutiny into lunar geological history.

The controversy surrounding the strength of the Moon's magnetic field stems from earlier analyses of lunar rocks collected during the Apollo missions between 1969 and 1972. These samples, predominantly sourced from specific regions on the Moon containing titanium-rich basaltic rocks, appeared to indicate the presence of stronger magnetic fields in the past. However, the new analysis reveals that these samples do not represent the entire history of the Moon, as they were collected from relatively few sites on the lunar surface, leading to biased results in the earlier interpretations.

The recent research found that samples with over 6% titanium content recorded extremely strong magnetic fields; yet, such strong fields were not the norm across the Moon’s surface. This discrepancy suggests that while localized areas may have experienced briefly strong magnetic fields, the broader context indicates a much weaker magnetic environment overall. The study's conclusions may have implications for our understanding of lunar evolution and the processes that have molded its current state, emphasizing the need for ongoing studies to fully grasp the Moon's magnetic history.