Research using data from NASA's Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission suggests that lunar swirls could be the result of solar wind interactions with the Moon's isolated pockets of magnetic field.
The Moons ‘sunburns’ — distinctive patterns of swirls — are a result of interactions between the Sun’s damaging radiation with pockets of lunar magnetic field, according to NASA data. Every object, planet or person travelling through space has to contend with the Sun’s damaging radiation. Research using data from NASA’s Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission suggests that lunar swirls could be the result of solar wind interactions with the Moon’s isolated pockets of magnetic field. The Sun releases a continuous outflow of particles and radiation called the solar wind.
The solar wind washes over the planets, moons and other bodies in our solar system, filling a bubble of space — called the heliosphere — that extends far past the orbit of Pluto. On Earth, we are largely protected from the damaging effects of the solar wind. Since the solar wind is magnetised, Earth’s natural magnetic field deflects the solar wind particles around our planet so that only a small fraction of them reach our planet’s atmosphere. Unlike Earth, the Moon has no global magnetic field. However, magnetised rocks near the lunar surface do create small, localised spots of magnetic field that extend anywhere from hundreds of yards to hundreds of miles. This is the kind of information that needs to be well understood to better protect astronauts on the Moon from the effects of radiation, researchers said.
The magnetic field bubbles by themselves are not robust enough to protect humans from that harsh radiation environment, but studying their structure could help develop techniques to protect our future explorers. “The magnetic fields in some regions are locally acting as this magnetic sunscreen,” said Andrew Poppe, a scientist at the University of California, Berkeley in the US. These small bubbles of magnetic “sunscreen” can also deflect solar wind particles — but on a much smaller scale than Earth’s magnetic field. While they are not enough to protect astronauts by themselves, they do have a fundamental effect on the Moon’s appearance.
Under these miniature magnetic umbrellas, the material that makes up the Moon’s surface, called regolith, is shielded from the Sun’s particles. As those particles flow toward the Moon, they are deflected to the areas just around the magnetic bubbles, where chemical reactions with the regolith darken the surface. This creates the distinctive swirls of darker and lighter material that are so prominent they can be seen from Earth — one more piece of the puzzle to help us understand the neighbour NASA plans to re-visit within the next decade.