Glenar, David - Influence of Faint Light Sources on the Moon's Permanently Shadowed Regions

Light from numerous sources is incident on the surface within permanently shadowed regions (PSRs) near the lunar poles that are never directly exposed to sunlight. In this study we collate predictions for faint light sources that cover a broad range of wavelengths from the infrared to the far-UV, and consider their potential importance for the conditions within PSRs, which could have implications for the stability of volatiles and the suitability of the Moon as a platform for astronomical observatories. We consider the sources of incident light within a typical near-polar PSR from: (i) direct and scattered Earthshine, (ii) zodiacal light created by sunlight scattered from dust in the inner solar system; (ii) Lyman-alpha resonantly scattered by interplanetary hydrogen; (iii) the diffuse broadband galactic background; (iv) bright stellar sources; (v) emission lines from exospheric species that vary in intensity depending on the space environment at the Moon, which are typically dominated by sodium and potassium; and (vi) sunlight scattered by exospheric dust. For the latter, we consider dust in the lunar exosphere created by several processes, including possible naturally occurring transport phenomena, as well as dust agitated by exploration and in-situ resource utilization (ISRU) activities.