Solar storms can vaporise soil in regions on the moon never reached by sunlight: Nasa study

Intense solar activity, such as solar storms, solar flares or coronal mass ejections send out streams of ions and electrons into space. The atmosphere of the Earth shields the planet from the radiation. However, the Moon does not have an atmosphere and the particles slam into the surface and accumulate there.

The positively charged ions do not penetrate much into the surface, and get collected in a layer close to the surface. The smaller, negatively charged electrons penetrate through the layer, and form a layer deeper into the surface. The two layers have opposite charges, so they tend to attract and balance out each other. There are regions on the moon where the sun light never reaches. These regions are called Permanently Shadowed Regions (PSRs) and are located near the poles of the Moon.

The PSRs are band conductors of electricity because of how frigid they are. The accumulated charges do not dissipate quickly in these regions, especially after periods of intense solar activity. The accumulated charges results sudden electric discharges, similar to lightning flashes, and are called dielectric breakdown. The phenomenon is not new to science, and is one of the major reasons for anomalies in spacecraft.

The dielectric breakdowns can pulverise the regolith, vaporising or melting the rock and sand, and even causing the material to blow up. The process is believed to change the landscape as much as meteoroid impacts, which is about ten percent of the surface. PSRs are important to understand the history of the Moon, because of their mostly pristine conditions. Scientists however, need to understand what kind of processes can affect PSRs, including meteoroid impact events and solar flares.

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The possibility of dielectric breakdowns affecting the PSRs was discovered using simulations. There might be “sparked” material in the samples obtained by the Apollo mission, but it is difficult to ascertain if the material has been affected by dielectric breakdowns or meteoroid impacts. Studies are being conducted to understand how dielectric breakdowns affect the material, and if there are any tell-tale signatures of such activity. The paper has been published in Icarus, and is titled Dielectric breakdown weathering of Lunar regolith.

Andrew Jordan of the University of New Hampshire, and lead author of the paper says “Lab experiments show that dielectric breakdown is an explosive process on a tiny scale. During breakdown, channels could be melted and vaporized through the grains of soil. Some of the grains may even be blown apart by the tiny explosion. The PSRs are important locations on the moon, because they contain clues to the moon’s history, such as the role that easily vaporized material like water has played. But to decipher that history, we need to know in what ways PSRs are not pristine; that is, how they have been weathered by the space environment, including solar storms and meteoroid impacts.”

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The next step is to gather the evidence. Data gathered from Nasa’s Lunar Reconnaissance Orbiter (LRO) indicates that the soil in the PSRs are more fluffy than the soil elsewhere on the Moon. The findings are in line with what the simulations suggest. However, further experiments are needed to verify if in fact dielectric breakdowns are responsible for the fluffiness in the material. The experiments are under way. According to the team, the two week long Lunar night means that areas on the Moon, that are not PSRs may also get cold enough for dielectric breakdowns.

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