Here we present quantitative estimates of lunar surface hydration, including spatial and temporal variations, as derived from Moon mineralogy Mapper (M3) data. The M3 data have been thermally corrected with our new semi-empirical model that is developed from reflectance spectra of Apollo and Luna samples and validated with independently measured DIVINER temperature data. Our mapping results show that at low to equatorial latitudes (30°N - 30°S) there are no significant differences in hydration between highlands and maria, and all of these regions generally lack hydration absorption features. A significant exception to this general trend is that many pyroclastic deposits, such as those near Aristarchus, west of Mare Serenitatis, southwest of Mare Vaporum, south of Mare Moscoviense, and southwest of Mare Humorum, exhibit anomalously high hydration signatures. All localities in equatorial and mid-latitudes that exhibit increased hydration are associated with pyroclastic deposits, suggesting this water may be endogenous. Our mapping results also indicate that lunar surface hydration decreases from lunar local morning to noon and increases at local afternoon, a dynamic trend similar to observations of Sunshine et al.  and consistent with observations from the Lunar Exploration Neutron Detector. However, we observe that the hydrated pyroclastic deposits, such as those near Aristarchus, continue to exhibit a hydration feature even at local noon, in contrast to surrounding regions. If we assume a composition of basaltic glass, then our models and laboratory data suggest these deposits may contain up to 2000 ppm H2O during early morning and late afternoon. This value decreases to ~1000 ppm during local noon but does not reach 0, indicating that not all of the observed hydration signature may be attributable to exogenous hydration (e.g., solar wind implantation). Instead, these results may be consistent with endogenous lunar water emplaced during pyroclastic eruptions and thus provide information about volatile concentrations in lunar magma source regions. However, not all pyroclastic deposits exhibit hydration features, such as Aestuum and Carpatus, which might indicate volatile contents of magma source regions are highly variable. In order to understand the implications of these data for magma source regions, we are currently carrying out quantitative estimates of mineral abundances with M3 data for these pyroclastic deposits. In addition, we will continue to integrate these results with detailed geologic maps based on visible and near-infrared images. Additional laboratory experiments will help to determine if the increased hydration in these pyroclastic deposits may instead be attributed to preferential solar wind implantation in glass-rich materials. If endogenous, quantitative estimates of water content in lunar pyroclastic deposits has significant implications for understanding the water content of the lunar mantle, how it compares to Earth, and how such water may have affected the evolution of the Moon.
.Sunshine, J. M., T. L. Farnham, L. M. Feaga, O. Groussin, F. Merlin, R. E. Milliken, and M. F. A'Hearn (2009), Temporal and Spatial Variability of Lunar Hydration As Observed by the Deep Impact Spacecraft, Science, 326(5952), 565-568.