Scientists Uncover Source of Moon’s Mysterious Magnetism, Links It to a Violent Collision

The Moon is often known as an inactive planet. But for all its calm, it still holds secrets that have confused scientists. One of the most confusing among them? Magnetic rocks. Unlike Earth, the Moon generates no magnetic field. So the important question is how the moon rocks brought back by Apollo astronauts and magnetic anomalies observed from orbit reveal traces of a pinch of magnetism? For decades, theories have bounced between an ancient lunar dynamo and external solar influence. But a new study proposes something way more dramatic. A team of experts at MIT, led by a graduate student, Isaac Narrett, suggests that the magnetism seen in certain lunar rocks may have originated from huge asteroid impacts that created wide plasma clouds, a phenomenon powerful enough to temporarily supercharge the Moon’s magnetic field, as per Science Advances.

In a statement, Narrett remarked, “There are large parts of lunar magnetism that are still unexplained… But the majority of the strong magnetic fields that are measured by orbiting spacecraft can be explained by this process, especially on the far side of the moon,” according to Eureka Alert. As per their model, the moon, back then, had a weak magnetic field, likely generated by a molten core in a dynamo process, similar to Earth’s but almost 50 times weaker. The story does not end here, when asteroids slammed into the Moon’s surface, forming basins like Imbrium and Orientale. These deadly events vaporized lunar material, unleashing globe-encircling clouds of plasma.

Moreover, as these plasma clouds expanded and circled around to the opposite side of the Moon (the antipode), they compressed and amplified the magnetic field. Using MIT’s SuperCloud computing system, the experts simulated these effects in detail. Their results showed that even an initial field of just 2 microteslas could be amplified at the antipodal point to a whopping 43 microteslas, which is almost as strong as Earth’s current magnetic field, as per Astronomy.

Intriguingly, the phenomenon does not stop at plasma alone. Co-author Rona Oran explained, “For several decades, there’s been sort of a conundrum over the moon’s magnetism — is it from impacts or is it from a dynamo?... And here we’re saying it’s a little bit of both. And it’s a testable hypothesis, which is nice,” as per IFL Science. The impact also sends seismic shockwaves through the Moon’s interior. An important point to note is that these waves converge beneath the antipodal point, where the plasma arrives, which later creates a picture-perfect storm.

The seismic energy nudged the rocks at another level, making them more susceptible to being magnetized by the temporary magnetic field spike, as per Astronomy. One must note that this whole process could explain why some of the strongest magnetic anomalies are found exactly opposite major impact basins. And surprisingly, many of these sites are near the lunar south pole, the very region future Artemis missions aim to explore. If the hypothesis is correct, fingers crossed, new samples could soon provide physical evidence.