A swirl of cream in a mug of hot chocolate. Tadpole-shaped. Striking. The diffuse appearance of abstract airbrush paintings. These are all phrases NASA has used to describe a famous lunar swirl named Reiner Gamma, one of a series of mysterious and exotic formations seen on the surface of the moon.
But there's no alien with an airbrush over there. Scientists already knew the lunar swirls coincide with locally elevated magnetic fields. A new study led by a team from Rutgers University and the University of California, Berkeley points to a deeper, volcanic-related understanding of the haunting surface features.
Researchers suspect magnetic anomalies are deflecting solar winds that can darken lunar soil, giving us the ethereal, tattoo-like swirls. The question is what causes those powerful magnetic fields.
The scientists created mathematical models for the geologic features that pointed to there being narrow magnetic objects near the lunar surface where the swirls are located. This coincides with the shape of lava tubes and dikes.
As placid as the moon seems now, it had a raucous volcanic past.
Scientists discovered some of the lunar rocks brought back by the Apollo missions were magnetic. Experiments found those rocks became highly magnetic when heated to extreme temperatures in an oxygen-free environment.
Rutgers says that magnetism is due to minerals breaking down and releasing metallic iron. "If there happens to be a strong enough magnetic field nearby, the newly formed iron will become magnetized along the direction of that field," the university notes.
The researchers combined that knowledge of moon rocks with a study published last year that found the moon's now-gone magnetic field lasted over 1 billion years longer that scientists previously thought.
This means the lava tubes and dikes formed by volcanic activity on the moon could have become very magnetic as they chilled out. We now have a good potential explanation for those scenic lunar swirls.
"No one had thought about this reaction in terms of explaining these unusually strong magnetic features on the moon," said study co-author Sonia Tikoo from Rutgers. "This was the final piece in the puzzle of understanding the magnetism that underlies these lunar swirls."
Taking the next step in exploring these ideas would involve a much closer look at the lunar swirls.
Last year, NASA considered a concept for an ambitious tethered CubeSat mission that would dangle a mini-satellite near the moon's surface. Meanwhile, Tikoo is on a committee that's proposing to send a lunar rover to study the swirls.
The researchers published their findings in the Journal of Geophysical Research.
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