For decades, scientists have debated whether the Moon once had a powerful magnetic field like Earth’s or only a weak one.
Now, a new study of rocks brought back by the Apollo missions suggests that both ideas are partly right. Researchers from the University of Oxford found that the Moon did experience extremely strong magnetic bursts in its early history—but only for very short periods.
The findings, published in Nature Geoscience, come from a fresh analysis of lunar samples collected by astronauts more than 50 years ago. Some of these rocks showed signs of a magnetic field even stronger than Earth’s today.
Others indicated a much weaker field. The new study reveals that the strong signals were rare events that lasted only a few thousand years, and possibly as little as a few decades.
Lead researcher Claire Nichols explains that the confusion lasted so long because the Apollo missions landed in similar locations on the Moon.
Those landing sites happened to contain rocks that recorded these unusual bursts of strong magnetism. Scientists had assumed the samples represented long stretches of lunar history, when in fact they captured brief episodes.
The Moon is much smaller than Earth, with a relatively small core. Because of this, many researchers believed it could not generate a strong magnetic field for long periods.
The new study suggests that temporary surges of magnetism were caused by melting deep inside the Moon. When titanium-rich material near the boundary between the Moon’s core and mantle melted, it likely created powerful but short-lived magnetic activity.
The team examined a type of volcanic rock called Mare basalt, which formed from ancient lava flows.
They discovered a clear pattern: rocks with high levels of titanium showed strong magnetization, while those with lower titanium levels showed weak magnetism. This link suggests that the same processes that formed these titanium-rich rocks also produced the temporary magnetic bursts.
The study also highlights how the choice of Apollo landing sites influenced scientific understanding.
Astronauts landed on relatively flat plains formed by these volcanic rocks because they were safer places to touch down. As a result, most of the samples collected came from regions rich in titanium, giving scientists a skewed picture of the Moon’s overall magnetic history.
Researchers say that if samples had been collected from different areas, scientists might have concluded long ago that the Moon’s magnetic field was usually weak. Future missions, including NASA’s Artemis program, could bring back rocks from new locations and help confirm the new findings.
Understanding the Moon’s magnetic past is important because magnetic fields protect planetary surfaces from harmful radiation and help reveal how planets evolve. The study shows that even a small world like the Moon can generate intense magnetic forces under the right conditions—though only briefly.
These ancient rocks are offering a new view of the Moon’s early history, showing that its invisible shield flickered on and off like a cosmic heartbeat billions of years ago.
Source: KSR.
