Radiance Contrasts at Possible Lunar Water Ice Exposures Seen by ShadowCam

Surface water ice within lunar permanently shadowed regions (PSRs) could have an enhanced visible wavelength reflectance relative to lunar regolith. Moon Mineralogy Mapper (M3) infrared spectroscopic detections compose one data set previously interpreted as surface ice occurrences within the PSRs. Here we investigate the M3 water ice identifications at higher resolution with broadband visible-wavelength mosaicked images (60 m pixel scale) obtained by the ShadowCam instrument aboard the Korea Aerospace Research Institute Korea Lunar Pathfinder Orbiter. Individual M3 positive water ice detections show no radiance contrast with their surroundings. However, north polar PSRs with at least one M3 water ice detection have a ∼4.4× higher modal radiance than those lacking M3 water ice detections, although this cannot be definitively attributed to water ice. Our findings are consistent with previous estimates of ice abundance as being less than ∼30 wt%, resulting in contrast too small to be detected by the ShadowCam instrument.