Lunar far side rock discovery suggests ancient magnetic field

Researchers from ETH Zurich have identified a large, magnetized rock formation in the Dewar region on the Moon’s far side that provides evidence of an ancient internal magnetic field. The study, published in ‘Science Advances’, suggests that approximately 4.2 billion years ago, the Moon may have possessed a magnetic dynamo similar to Earth’s.

By analyzing orbital data, the team identified a high-density, magnetized body roughly 60 kilometers wide and 9 kilometers deep. They believe this structure is a buried volcanic complex consisting of solidified magma that rose from the Moon’s interior. The researchers estimate that the ancient magnetic field strength could have exceeded 11 microteslas, which is roughly one-fifth to one-third of Earth’s current magnetic field strength.

This discovery offers a new method for studying lunar history using orbital data rather than relying solely on physical rock samples from Apollo missions, which have previously yielded conflicting results. The findings help shift the scientific debate from whether a lunar dynamo existed to how it functioned.