Mysterious Lunar Swirls Finally Explained: Magnetic Rocks Deflecting Solar Wind
For decades, scientists have been baffled by the strange, swirling patterns on the Moon’s surface, known as lunar swirls. These bright, often meandering features, visible even through backyard telescopes, have puzzled researchers with their distinct light color andunusual shapes. Now, a new study has revealed the secret behind these celestial oddities: magnetic rocks.
The research, published in the Journal of Geophysical Research: Planets, suggests that the swirls are created by magnetized rocks that deflect the constant barrage of solar wind particles bombarding the Moon. This deflection protects the swirls from the darkening effects of solar wind interactions with the lunar surface, leaving them lighterthan their surroundings.
Lunar swirls are a unique feature of the Moon, explains Michael J. Krawczynski, Associate Professor of Earth, Environmental, and Planetary Sciences at Washington University in St. Louis. They look like brushstrokesin an abstract painting. Some of them extend for hundreds of miles, as seen in NASA images.
The study, led by Yuan Yuan Liang, a recent PhD graduate from the same department, used laboratory experiments to recreate the magnetic processes that could be responsible for the swirls. They focused on a mineral called ilmenite, abundant on the Moon, and studied its behavior under various conditions simulating the lunar environment.
Earth rocks are very easily magnetized because they usually contain tiny grains of magnetite, a magnetic mineral, says Krawczynski. A lot of the terrestrial studies that focus on magnetite don’t apply to the Moon becauseit doesn’t have this supermagnetic mineral.
However, the team discovered that ilmenite, under the right conditions, can react to form metallic iron particles, which can become magnetized. These particles, particularly when small, are more susceptible to magnetization due to their larger surface area to volume ratio.
The small particles we used seem to produce stronger magnetic fields because they have a larger surface area to volume ratio compared to larger particles, says Liang. With a larger surface area exposed, they are more susceptible to the reduction reaction.
The researchers believe that the magnetic fields generated by these magnetized rocks are strong enough todeflect the solar wind, shielding the swirls from the darkening effects experienced by the surrounding lunar surface.
Our simulations show that we can produce the necessary magnetizable material under lunar conditions, says Krawczynski. Therefore, it is plausible that these swirls are caused by magma beneath the surface.
Understanding the originof lunar swirls is crucial for gaining insights into the formation processes of the Moon’s surface, its magnetic history, and how planetary and satellite surfaces interact with their surrounding space environment. This research will be particularly valuable for interpreting data from future lunar missions, especially those exploring magnetic anomalies on the Moon’s surface.
NASAplans to send a rover to the Reiner Gamma lunar swirl region, a prominent swirl visible from Earth, as part of the Vertex mission in 2025. This mission will provide valuable data to further validate the new theory and deepen our understanding of these enigmatic features.
If you want to make a magnetic anomalyusing the method we describe, you need to have high titanium in the magma beneath the surface, says Krawczynski. We have seen hints of this reaction producing metallic iron in lunar meteorites and lunar samples from Apollo. But all of those samples are from surface lava flows, and our study suggests that underground cooling shouldsignificantly enhance these metal-forming reactions.
While further research is needed to fully understand the complex processes involved, this study provides a compelling explanation for the mysterious lunar swirls, opening a new window into the Moon’s magnetic history and its dynamic interaction with the solar wind.
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