Scientists have found clues to strange 'magnetic' rocks on the moon

The Moon has no magnetic field. But scientists have recorded high levels of magnetisation in its rocks - especially on its back side - for decades. This contradiction has stumped science: how could such "magnetic" rocks form if there is no magnetic field?

A team of researchers from the Massachusetts Institute of Technology (MIT) has come up with an original explanation - and it could turn our understanding of the Moon's ancient history upside down.

Read more: Impact plasma amplification of the ancient lunar dynamo, Science Advances (2025). DOI: 10.1126/sciadv.adr7401

📌 Weak field, strong impact

Scientists have suggested that millions of years ago, the Moon did indeed have a weak magnetic field - a remnant of the internal "dynamo" from the molten core. It was very weak - 50 times weaker than Earth's. That's not enough to magnetise the rocks to the levels we can detect. But a giant asteroid intervened.

When the meteorite, which left behind the crater Imbrium, crashed into the Moon, it caused the surface to vaporise and formed a huge cloud of ionised plasma. This plasma is calculated to have flowed around the Moon and collected on the opposite side - just where the anomalously magnetised rocks are recorded.

At this point, the plasma not only strengthened the magnetic field locally, but also caused its short-term "burst" amplification. It lasted only about 40 minutes, but it was enough for the rocks in the impact zone to "remember" this anomaly - due to shaking from the shock wave.

🧲 Stones with magnetic memory

The mechanism, according to scientists, resembled shaking a pack of cards in a magnetic field: when electrons in minerals have time to reorient and "freeze" in a new position. This is the recording of magnetic information. So everything came together: local field enhancement, seismic shaking and a suitable rock chemistry.

The results of the modelling, published in Science Advances, showed that such a combination of factors - a weak ancient dynamo and a powerful shock with a plasma cloud - could well have caused the magnetic anomaly being recorded. Especially on the back side of the Moon, which "took on" both shock waves and plasma flow.

🚀 Can we check?

Yes. Stones with such features are found near the Moon's south pole, where NASA is planning landings as part of the Artemis programme. If the mission delivers samples, it will be possible to directly check for shock deformations and remnants of magnetic recording.

This will open a new page in understanding not only the Moon's history, but also how magnetic anomalies form on other lifeless bodies in the solar system.