Researchers at ETH Zurich have used gravity and magnetic field measurements from the far side of the Moon to provide new evidence that the Moon once possessed an internal magnetic field. By analyzing data from NASA's GRAIL probes and other missions, they focused on the Dewar region, where strong magnetic and gravity anomalies coincide. This allowed them to model the subsurface and conclude that 4.2 billion years ago, the Moon had a magnetic field stronger than ten microtesla.

This supports the dynamo theory, which suggests a core-generated field similar to Earth's, rather than magnetization from meteorite impacts. The findings help resolve contradictions in rock samples brought back by Apollo astronauts.