High-energy particles from solar storms may have electrically charged the soil in the moon's frigid polar regions, altering its properties, a study suggests.
This could change our understanding of the evolution of planetary surfaces in the solar system.
The charging may create sparking, or electrostatic breakdown, and this "breakdown weathering" process has possibly changed the very nature of the moon's polar soil.
The study by University of New Hampshire (UNH) and NASA scientists suggests that permanently shadowed regions, which hold clues to our solar system's past, may be more active than previously thought.
"Decoding the history recorded within these cold, dark craters requires understanding what processes affect their soil," said Andrew Jordan from UNH.
They built a computer model to estimate how high-energy particles detected by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on board NASA's Lunar Reconnaissance Orbiter (LRO) can create significant electric fields in the top layer of lunar soil.
The scientists also used data from the Electron, Proton, and Alpha Monitor (EPAM) on the Advanced Composition Explorer.
CraTER and EPAM both detect high-energy particles, including solar energetic particles (SEPs).
SEPs, after being created by solar storms, stream through space and bombard the moon.
These particles can build up electric charges faster than the soil can dissipate them and may cause sparking, particularly in the polar cold of permanently shadowed regions.
"Sparking is a process in which electrons, released from the soil grains by strong electric fields, race through the material so quickly that they vaporise little channels," said Jordan.
Repeated sparking with each large solar storm could gradually grow these channels large enough to fragment the grains, disintegrating the soil into smaller particles of distinct minerals, the scientists hypothesised.
The study appeared in the Journal of Geophysical Research-Planets.
