NASA-funded research has found that it's possible for powerful solar storms to charge up soil found in permanently shadowed, frigid regions near the moon's poles, producing "sparks" capable of melting and vaporizing the soil in a manner similar to meteoroid impacts.
Unlike the Earth, the moon doesn't an atmosphere. This leaves its surface exposed to harsh conditions in space, openly hit by small meteoroids that "garden" or churn the top layer of rock and dust known as regolith. According to Andrew Jordan, lead author for a study published in Icarus, about 10 percent of the gardened layer of the lunar surface has been melted or vaporized, no thanks to meteoroid impacts, and a similar percentage could be melted or vaporized by sparks from solar storms in the moon's permanently shadowed regions.
Solar Storms And The Moon
Coronal mass ejections, flares, and other explosive solar activity blast electrically charged, highly energetic particles into space, which directly slam into the moon's surface. These particles - electrons and ions - accumulate beneath the lunar surface in two layers: smaller electrons in the deeper layer and bulkier ions at the top. As electrons are negatively charged and ions are positively charged, they balance out each other as they flow toward each other.
Back in 2014, however, the researchers released results from a simulation that predicted that powerful solar storms would result in regolith in the permanently shadowed regions of the moon accumulating charge within the two layers until an explosion is released. Think miniature lightning strikes.
Because the moon's permanently shadowed regions are so frigid, the regolith turns into a poor electricity conductor, which is expected to release built-up charge slowly during powerful solar storms to prevent destructive effects associated with sudden discharges of electricity. According to the researchers, this strain to the regolith can alter it.
"[E]lectrostatic discharges can occur in any poorly conducting (dielectric) material exposed to intense space radiation," explained Timothy Stubbs, saying the process is not completely new to space science and is actually the main reason behind anomalies in spacecrafts.
In fact, the researchers' analysis was based on their experience of a spacecraft anomaly. Using sample analysis and spacecraft studies from the Apollo lunar missions, the researchers figured out the frequency at which large solar storms occur. They were also able to estimate that the regolith's top millimeter will be buried after about 1 million years because of meteoroid impacts, making it too deep to be affected by solar storm electric charging.
Additionally, energy deposited by dielectric breakdown and meteoroid impacts driven by solar storms over a period of million years will be released in such a way that the regolith will be altered with similar severity.
Future Lunar Research
The next step for the researchers is to find proof of dielectric breakdown in permanently shadowed regions of the moon and to determine if it also occurs in other lunar areas. There's already evidence that soil in permanently shadowed regions are "fluffier" or more porous, which may be expected if an area experiences blasts, but the researchers have yet to confirm what's behind the soil breakdown.
To get the answers they need, the researchers are working with scientists from the Johns Hopkins University Applied Physics Laboratory.