Development of a micro-ice production apparatus and NIR spectral measurements of frosted minerals for future lunar ice exploration missions

Abstract

Knowledge of the occurrence of water in the solar system provides key information concerning the formation and evolution of the solar system and lifeforms. In recent years, multiple remote-sensing observations have suggested the existence of water ice in permanently shadowed regions on some inner solar system bodies; however, the exact amount of water ice is highly uncertain. To test the performance of ice detection equipment for future lunar polar exploration missions, we constructed an apparatus to produce minute amounts of water ice (0.1–2 wt%) on lunar regolith analog minerals and measured their near-infrared spectra. The relationship between the strength of water absorption and the water content was quantified using the absorption at 1.5 μm in the reflectance spectra. The results show that the detectability of water ice attached to mineral grains depends on the mineral species. Laboratory reflectance spectra were compared to Hapke model spectra, and the observed spectral feature similarities indicate that the Hapke model can be effectively used when the ice is mixed in the form of spherical grains.