Lunar swirls are light-colored, sinuous features on the Moon’s surface, bright enough to be visible from a backyard telescope. Some extend for hundreds of miles. Lunar swirls have defied easy explanation, but new lab experiments suggest they could be rocks magnetized by magma activity underground.

I’ve linked to the press release in the post above. In this comment, for those interested, here’s the link to the peer reviewed journal article:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JE008179

From the linked article:

Moon ‘swirls’ could be magnetized by unseen magmas

Mysterious, light-colored swirls on Moon’s surface could be rocks magnetized by magma activity underground, WashU laboratory experiments confirm

Lunar swirls are light-colored, sinuous features on the Moon’s surface, bright enough to be visible from a backyard telescope. Some people think they look like the brushstrokes in an abstract painting. But these are not mere artistic flourishes: NASA images show that the tendrils from some lunar swirls extend for hundreds of miles.

Lunar swirls have defied easy explanation, but recent modeling and spacecraft data shed light on the twisty mystery. The data shows that rocks in the swirls are magnetized, and these rocks deflect or redirect solar wind particles that constantly bombard the Moon. Nearby rocks take the hit instead. Over time, neighboring rocks become darkened by chemical reactions caused by the collisions, while the swirls remain light colored.

But how did the rocks in lunar swirls get magnetized? The Moon does not have a magnetic field today. No astronaut or rover has yet visited a lunar swirl to investigate.

“Impacts could cause these types of magnetic anomalies,” said Michael J. Krawczynski, an associate professor of earth, environmental and planetary sciences in Arts & Sciences at Washington University in St. Louis. He notes that meteorites regularly deliver iron-rich material to areas on the Moon’s surface. “But there are some swirls where we’re just not sure how an impact could create that shape and that size of thing.”

Krawczynski believes it’s more likely that something else has locally magnetized the swirls.

“Another theory is that you have lavas underground, cooling slowly in a magnetic field and creating the magnetic anomaly,” said Krawczynski, who designed experiments to test this explanation. His results are published in the Journal of Geophysical Research: Planets.