The Magnetic History of the Moon Revealed by Mysterious Bright Lunar Vortexes

The moon, our only natural satellite, has long been the focus of major scientific studies and missions. It hosts a range of surface formations that provide insight into its birth and evolution over billions of years.

Many of these features are easy to study, but a particular element has attracted much attention from the scientific community: strange whirlpools observed at different locations on the lunar surface.

These light and dark patterns, one of which was named Reiner Gamma, look like swirls in a cup of cream and coincide with locally high but powerful magnetic fields. Scientists believe that these fields deflect particles from the solar wind, slowing lunar surface time and forming distinct marks.

Although all of this seems simple enough, scientists have long struggled to understand how these localized magnetic fields formed.

"The cause of these magnetic fields, and therefore whirls themselves, has long been a mystery," said Sonia Tikoo, an assistant professor at Rutgers University, 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 was so powerful."

Tikoo is therefore associated with researchers from the University of California to develop mathematical models that could explain how magnetic fields and associated eddies are produced. The results of their work revealed that the vortices are located above narrow magnetic objects buried near the lunar surface.

As explained by the team, these objects corresponded to the description of lava tubes and dikes formed during volcanic activity on the surface of the moon, about 3 billion years ago. But how could these volcanic characteristics be very magnetic?

This is an image of the lunar tourbillon Reiner Gamma of the Lunar Reconnaissance Orbiter of NASA. Photo: NASA LRO WAC science team

To explain the case, the researchers detailed the magnetism of the lunar rocks. Over the years, various experiments have shown that the rocks of the satellite can become very magnetic in environments without oxygen and at high temperatures.

As part of the process, the minerals break up and release metallic iron, which could be magnetized in the direction of a strong magnetic field. The moon we see today has no global magnetic field nor volcanic activity. But previous studies have shown that the old magnetic field of the satellite could have lasted more than 1 to 2.5 billion years longer than expected.

This, as they said, could have coincided with the moment of ancient volcanic activity, turning the lava tubes and dikes into magnetic magnet as they cooled down and helped in the formation of vortices.

"No one has thought of this reaction in terms of explaining these exceptionally strong magnetic features on the moon," Tikoo said in the statement. "This was the last piece of the understanding puzzle of magnetism that underlies these lunar whirlpools."

The team believes that further study of these features could provide insights into the dynamic history of our satellite.

The study entitled "Morphology of the lunar vortex constrains geometry, magnetization and the origins of lunar magnetic anomalies" is published in the Journal of Geophysical Research.