Forget The Man in the Moon: Scientists may have solved the mystery of lunar swirls.

A joint Rutgers University and University of California Berkeley study hints at ancient volcanic activity and an internally generated magnetic field.

Lunar swirls resemble bright, snaky clouds painted onto the Moon’s dark surface.

The most famous example, Reiner Gamma, stretches about 40 miles across Earth’s satellite, and looks like “a swirl of cream in a mug of hot chocolate,” according to NASA.

Most of these optical anomalies share their location with powerful, localized magnetic fields, which scientists believe deflect particles from solar wind and cause some areas of the lunar surface to weather more slowly.

“But the cause of those magnetic fields, and thus the swirls themselves, had long been a mystery,” study co-author Sonia Tikoo, an assistant professor at Rutgers–New Brunswick, said in a statement. “To solve it, we had to find out what kind of geological feature could produce these magnetic fields—and why their magnetism is so powerful.”

This is an image of the Reiner Gamma lunar swirl from NASA’s Lunar Reconnaissance Orbiter (via NASA LRO WAC)

Using computer modeling, the team discovered that each swirl must be close to or above a narrow magnetic object near the Moon’s surface.

Their findings, published in the Journal of Geophysical Research — Planets, are consistent with lava tubes and dikes, formed on the planetoid by flowing magma during volcanic eruptions some 3 billion to 4 billion years ago.

It seems that Moon rock, when heated to more than 600℃ (1,112℉) in an oxygen-free environment, becomes highly magnetic; the extreme temperature causes minerals to break down and release metallic iron.

In the presence of a strong magnetic field, like the miniature lunar ones, iron becomes magnetized in the same direction of the field.

This doesn’t typically happen on Earth, where free-floating oxygen binds with iron, averting the reaction. And, as Rutgers pointed out, it wouldn’t happen today on the Moon, where there is no global magnetic field.

Tikoo previously determined that the orb’s ancient magnetic field lasted 1 billion to 2.5 billion years longer than we thought—perhaps existing in sync with the creation of lava tubes that magnetized as they cooled.

“No one had thought about this reaction in terms of explaining these unusually strong magnetic features on the Moon,” she said. “This was the final piece in the puzzle of understanding the magnetism that underlies these lunar swirls.”

Scientists last month confirmed the presence of water ice on the Moon, which was highlighted in a recent concert featuring mission images set to cosmic music. It’s also been uncovered that moon dust could be the key to lunar architecture. Stay up to date on all things lunar here.





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