Rutgers professor sheds light on moon's mysterious bright patches
A joint study between Rutgers University and the Carnegie Institution for Science has recently added to the origins of lunar swirls by suggesting new hypotheses as to how these otherworldly phenomena are created.
"Lunar swirls are unusually bright markings on the moon’s surface, resembling bright white patches against the darker background," said Sonia Tikoo-Schantz, an assistant professor in the Department of Earth and Planetary Sciences. "They are challenging to study though, as the only place they can be observed is on the moon."
Tikoo-Schantz first became interested in lunar swirls because she was captivated by their beauty. They coincidentally appeared in strongly magnetized areas on the moon’s surface, which paralleled her own research program’s focus on lunar magnetism.
“I absolutely had to find a way to work on this problem,” she said.
Her study, which was conducted in collaboration with Douglas Hemingway, a Carnegie postdoctoral fellow in planetary geodynamics at the Carnegie Institution for Science, was able to build on prior work and hypotheses about lunar swirls.
Previous hypotheses assumed that magnetic fields controlled the shape of the swirls, and sought to discover what geological features could be the source of them. One prior hypothesis suggested that magnetic rocks on the moon caused lunar swirls because they shielded the surface from solar wind particles, which cause darkening.
“Our approach was multi-faceted. We needed to figure out what shape, depth and kind of magnetized rock would produce magnetic field lines that had similar geometries as observed lunar swirl patterns,” Tikoo-Schantz said. “Dr. Hemingway set up models where he studied what the magnetic field intensity and geometry of rectangular prisms with different widths, lengths, depths and magnetization intensities would look like and compared those to real swirl shapes and magnetic field strengths.”
The study concluded that in order for magnetic rocks to contribute to the formation of lunar swirls, they must be narrow and shallow on the surface of the moon. These constraints helped narrow what types of magnetic rocks were responsible for lunar swirls.
“We believe we have identified a couple strong contenders (dikes and lava tubes) that could do this,” she said.
Lava dikes are vertical sheets of magma within the crust of the moon and lava tubes are structures formed from flowing lava during volcanic eruptions, according to Rutgers Today.
"These two contenders do have some contradictions because lava rocks brought back from the moon during the Apollo missions were not magnetic enough to produce lunar swirls," Tikoo-Schantz said. "The paper proposes ways to combat these contradictions by suggesting possible reasons why rocks in certain parts of the lunar surface are more magnetic than other rocks on the moon."
She said it is unclear whether rocks that are associated with either of the two features could really be magnetic enough to produce the crustal magnetic field strengths observed at the swirls, so more work needs to be done to find out.
The study differed from previous others because it presented more options to explain the mysterious occurrence and circumstances of lunar swirls.
“Our hypothesis that swirls may be related to dikes or lava tubes presents a viable alternative to the impact-based hypotheses,” Tikoo-Schantz said.