Moon's Ancient Magnetic Field Revealed by Buried Rock

A significant discovery of a dense, highly magnetized rock formation buried on the far side of the moon is providing critical new insights into the moon's ancient magnetic field. This subterranean feature, measuring approximately 60 kilometers wide and 9 kilometers deep, suggests that the moon maintained a magnetic field around 4.2 billion years ago. This field is estimated to have been between one-fifth and one-third the strength of Earth's current magnetic field.

The existence and strength of the moon's early magnetic field have been a subject of scientific debate since the 1970s. While many scientists believed the moon's dynamo was active from roughly 4.25 to 3.5 billion years ago, recent analyses of Apollo samples have introduced uncertainty. This new study, published in Science Advances, utilized data from lunar orbiters like Lunar Prospector, Kaguya, and GRAIL, combining magnetic and gravity data to pinpoint the buried structure, offering a new perspective independent of potentially disturbed Apollo samples.

Understanding the moon's past magnetic field is crucial for comprehending its geological evolution and history. The findings could also have broader implications for studying other celestial bodies, providing data on the minimum conditions required to sustain a dynamo. Researchers also noted preliminary observations linking lunar swirls to magnetic anomalies, which may offer protection from solar wind for future lunar missions.