What can a magnetic anomaly on the Moon tell us about its ancient interior?
This episode explores a 2026 study of the Dewar magnetic anomaly on the Moon’s far side by Xi Yang, Anna Mittelholz, Adrien Broquet, and Max Moorkamp at ETH Zurich, the German Aerospace Center (DLR), and TU Berlin. The episode is based on the original research and on the review of the study by Victor Kuklin, published by ALLATRA Media.
Using a joint analysis of NASA GRAIL gravity data and lunar magnetic-field measurements from Lunar Prospector and Kaguya/SELENE, the researchers reconstruct a shallow, dense, strongly magnetized body beneath the Dewar region. Their model is consistent with buried mare basalt and indicates a paleofield intensity greater than 11 μT around 4.2 billion years ago.
The interpretation is significant because it supports the possibility that the Moon’s core dynamo was already active at that time. The study also examines the role of horizontal magnetization in the formation of the nearby Dewar swirl and compares a core-generated magnetic field with a transient impact-generated field.
But the result comes with important limits. The 11 μT figure is a lower-bound estimate derived from modeled rock magnetization, not a direct measurement of the ancient lunar field. The dynamo interpretation is inferential, and the mechanism capable of sustaining such a strong field in the Moon’s small core remains unresolved. No Dewar rock sample was measured directly; the conclusions come from orbital observations and geophysical modeling.
The original research was published in Science Advances on September 23, 2026.
Xi Yang, Anna Mittelholz, Adrien Broquet & Max Moorkamp — Science Advances
https://www.science.org/doi/10.1126/sciadv.aec0341
ALLATRA Media Review
Victor Kuklin — A Buried Volcano on the Moon's Far Side Points to an Ancient Magnetic Field
https://allatra.media/news/space-moon-far-side-dewar-dynamo