Weak, localized magnetic fields cause variations in lunar surface brightness
Interaction with solar wind and isolated pockets of magnetic field on the Moon could be what are causing “sunburns” on the surface, like the Reiner Gamma lunar swirl in this image by NASA’s Lunar Reconnaissance Orbiter. Photo Credit: NASA
The Moon does not have a magnetic field to protect it from the solar wind, the particles and radiation that flow outward from the Sun, but it does have small, localized magnetic fields that deflect it, producing patterns of light and dark swirls on the lunar surface.NASA’s Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS), a spacecraft mission in lunar orbit to study interactions between the Sun and Moon, found that magnetized rocks close to the Moon’s surface create small magnetic “bubbles” in regions ranging from several hundred yards to several hundred miles.
Much weaker than Earth’s magnetic field, which deflects the solar wind away from the entire planet, these bubbles deflect solar radiation to adjacent areas on the Moon’s surface.
“The magnetic fields in some regions are locally acting as this magnetic sunscreen,” Andrew Poppe of the University of California at Berkeley, who studies lunar magnetic fields using both computer simulations and ARTEMIS data, said in a NASA news release. “The leading hypothesis is that the magnetic fields are blocking some portion of the solar wind from reaching the surface.”
Areas on the Moon protected by these magnetic bubbles appear as bright swirls while those that do not have such protection appear as dark swirls. The latter are produced by interaction between the Moon’s surface, known as regolith, and chemical reactions triggered by the solar wind.
The pattern of varying light and dark regions on the Moon can be seen from Earth with the naked eye. Closeup images of these varied terrains have been captured by NASA’s Lunar Reconnaissance Orbiter (LRO).
While these small magnetic regions on the lunar surface are not sufficient to protect future astronauts, once they are better understood, scientists may be able to artificially enhance them to sufficiently shield the astronauts from harmful solar radiation.
Solar wind interacts with all Solar System planets and moons, extending approximately three times the distance between the Sun and Pluto in a region known as the heliosphere.
Over the next decade, NASA plans a more in-depth study of the Moon’s contrasting light and dark regions and of its interaction with the solar wind. A paper on the current findings has been published in the Journal of Geophysical Research: Planets.
Video courtesy of NASA
Laurel Kornfeld
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.
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