Mysterious rotations on the Moon may be explained by underground magma

In the latest chapter of “The Mystery of the Moon’s Spins,” planetary scientists have a new theory to explain these strange markings on the Moon’s surface. It summons underground magma and strange magnetic anomalies.

Lunar swirls are scratchy features that appear much lighter than the surrounding landscape. They stretch for hundreds of kilometers and no one is quite sure why they exist. No astronaut has ever visited one of these strange regions, but that hasn’t stopped scientists from speculating based on images and measurements of the magnetic field. “Impacts can cause these types of magnetic anomalies,” said Michael J. Krawczynski, an associate professor of earth, environmental and planetary sciences in Arts and Sciences at Washington University in St. Louis. Krawczynski points out that meteorites supply iron-rich material to areas on the Moon’s surface. However, these rotations exist in regions that are not necessarily disturbed by meteorites. So what else could explain the rotations?

“Another theory is that you have lava underground, slowly cooling in a magnetic field and creating magnetic anomalies,” said Krawczynski, who, along with doctoral student Yuanyuan Liang, designed experiments to test this explanation. They measured the effects of different atmospheric chemicals and the rate of magmatic cooling on a mineral called ilmenite and found that under certain conditions, cooling subsurface lavas can cause lunar ghost rotations.

Using Earth-based geological principles to understand lunar rotations

Despite the fact that more than a dozen people have walked on the moon, no one visited a lunar orbit or collected samples of their dust. This let Earth-bound planetary scientists use Earth analogs for lunar rocks to understand lunar magnetism. “Earth rocks are very easily magnetized because they often have small pieces of magnetite in them, which is a magnetic mineral,” Krawczynski said. “A lot of the terrestrial studies that have focused on things with magnetite are not applicable to the Moon, where you don’t have this hypermagnetic mineral.”

So the research team turned to ilmenite as their test material. It is a titanium oxide mineral with a weak magnetic signal. Ilmenite exists throughout the Moon. It readily reacts to form magnetizable iron metal particles. “The smaller grains we were working with seemed to create stronger magnetic fields because the surface-to-volume ratio is greater for smaller grains compared to larger grains,” Liang said. “With more exposed surface area, it’s easier for smaller grains to undergo the reduction reaction.”

Interestingly, planetary scientists have seen a similar reaction creating iron metal in lunar meteorites in samples from the Apollo missions. The difference, however, is that those samples came from surface lava flows. Krawczynski and Liang’s study focused on the types of magma that cooled underground.

“Our analog experiments showed that under lunar conditions, we could create the magnetizable material we needed. So it is plausible that these rotations are caused by underground magma,” Krawczynski said. “If you’re going to make magnetic anomalies with the methods we’ve studied, then the underground magma has to be high in titanium.”

Why study rotations on the Moon?

Those mysterious dust patterns aren’t there by chance. They contain data on the processes that formed the lunar surface. In addition, if magnetism is involved in their formation, it says something about the magnetism on the Moon as a whole.

Until astronauts get to the moon to study these swirls themselves, the ilmenite experiment offers a good way to test the idea of ​​subsurface magma from afar, according to Krawczynski. Of course, it would be nice to get actual samples of subsurface rocks on the Moon, but that will have to wait. “If we could detect, we could see if this reaction was happening,” he said. “It would be nice, but it’s not possible yet. Right now, we’re stuck with the surface.”

Studies like Krawczynski’s and Liang’s will be very useful when NASA sends future lunar missions to the surface. There is an entire rover project, part of a mission called Lunar Vertex, planned to study Reiner Gamma. This is one of the most popular rotations of the Moon. Vertex is due to launch this year and is a precursor to the larger lunar return NASA plans for later this decade. This mission can confirm whether or not the spins are related to the magnetic field. If not, then there is something else going on in Reiner Gamma and other spin pages.

For more information

The Moon’s “spins” may be magnetized by invisible magmas
Possibility of lunar crustal magmatism producing strong crustal magnetism
Lunar Vertex Mission