As reviewed recently by Lucey et al. (2022), potential contributors of volatiles to the lunar surface include the solar wind ion bombardment, volatile-rich impactors, and interior outgassing. In particular, solar wind hydrogen can react with lunar oxygen to form hydroxyl (Zeller et al., 1966). The surface abundance of hydroxyl is observed to be reduced in areas with strong surface magnetic fields (swirls), implying that these anomalies significantly deflect the ion bombardment (Kramer, Besse, et al., 2011; see also Glotch et al., 2015). On the other hand, solar wind ion sputtering is one of several non-negligible loss mechanisms for water ice in permanently shadowed regions (PSRs) near the lunar poles (e.g., Zimmerman et al., 2011).Analyses of reflectance spectra obtained from the Moon Mineralogy Mapper (M 3 ) instrument, constrained by several other independent datasets, yield inferred water ice exposures that are much more numerous near the south pole than near the north pole (Li et al., 2018, and references therein). Because water ice is an important potential resource for manned outposts, a number of missions are currently being planned internationally for landings near the south pole (e.g., the NASA VIPER mission, https://www.nasa.gov/viper/overview). However, the origin and loss mechanisms of the observed water ice, and reasons for its greater prevalence near the south pole, remain poorly understood.Previous work has shown that, in the absence of crustal magnetic fields, significant fluxes of solar wind protons will reach the interiors of most PSRs near the lunar south pole (Rhodes & Farrell, 2020). Their calculations accurately model the diffusion of the solar wind plasma flow into a PSR, accounting for the effects of topography. Including the effect of ambipolar acceleration, typical ion energies incident on PSR interiors were calculated to be comparable to or larger than that of undisturbed solar wind ions (∼1 keV). Assuming a sputtering yield of 0.75
