The Moon Has Tan Lines, NASA Says

Magnetic hotspots on the Moon might contain clues about how to protect humans from radiation on other planets.
​Reiner Gamma lunar swirl. Image: NASA Goddard Space Flight Center
Reiner Gamma lunar swirl. Image: NASA Goddard Space Flight Center

The Moon has tan lines and sunburns just like the rest of us, according to NASA. Scientists know this because some parts of the lunar surface are brighter due to protection from what NASA calls “magnetic sunscreen.”

Lunar swirls are sinuous features on the Moon’s surface that outshine the grayish terrain surrounding them. They turn up on parts of the Moon that exhibit strong magnetic field strength, suggesting that the local magnetic hotspots are shielding the Moon’s surface from the Sun’s damaging rays.


Studying these bright patches could help scientists prepare for human habitation on the Moon and other planets, NASA said in a video posted on Wednesday.

The Sun is constantly releasing a stream of charged particles called the solar wind. Here on Earth’s surface, we only experience mild doses of the torrent because our planet’s magnetosphere wards off most of it. Your tan or burn after a day out in the Sun is caused by the limited amount of ultraviolet radiation that makes it through Earth’s magnetic field.

The Moon lacks a global magnetic field, but some of the rocks on its surface have strong magnetic properties. Scientists aren’t exactly sure why they are magnetized, but it could be the result of of asteroid impacts. Another theory is they date back to a time when the Moon had a core magnetic field similar to the one on Earth.

Read More: The Moon May Have Been Home to Simple Lifeforms, New Study Shows

Regardless, observations from NASA’s ARTEMIS mission confirm that the lunar swirls are formed by magnetic field bubbles. Sometimes, darker stripes are also visible, which were created by magnetic field lines channeling and dropping radiation particles onto the swirls.


Animation showing the creation of lunar swirls. Image: NASA Goddard Space Flight Center

The radiation protection inside the swirls is not strong enough to keep a human safe in the magnetic bubble. However, studying these hotspots could help scientists develop artificial magnetic shields on the Moon or other planets, which might eventually support human communities.

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