Deep dielectric charging and breakdown of lunar polar regolith

Galactic cosmic rays (GCRs) and solar energetic particles (SEPs) penetrate the regolith (layer of soil and dust) covering the Moon's surface and cause deep dielectric charging. To gain insight into this process, we have developed a data-driven, deep dielectric charging model using data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which is onboard the Lunar Reconnaissance Orbiter (LRO), and the Electron, Proton, and Alpha Monitor (EPAM) on the Advanced Composition Explorer (ACE). The model results indicate that GCRs produce a persistent electric field (∼700 V m^-1) within the top tens of centimeters of regolith, while large SEP events could potentially generate episodic subsurface electric fields (≥ 10⁶ V m^-1) capable of causing dielectric breakdown within the top millimeter of regolith. We also propose that this "breakdown weathering" may have significantly affected the regolith in the Moon's permanently shadowed regions (PSRs).