The surface of the moon is constantly bombarded by solar wind hydrogen. When implanted, some of the hydrogen can react with lunar oxygen to form hydroxyl (OH) and possibly molecular water (H2O). In…

This is a $235,547.78 grant award from NASA's Shared Services Center to the University of Hawaii (UH) at Manoa for research on detecting molecular water on the lunar surface. The project aims to use the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST) on the Stratospheric Observatory for Infrared Astronomy (SOFIA) to observe the Moon and characterize the diurnal variability and spatial distribution of any water. This research is relevant to understanding the interactions between the lunar surface and the space environment, as well as the potential for in-situ resource utilization. The grant does not have a set-aside designation, reflecting UH's status as a large educational institution. The University of Hawaii System has extensive expertise in astronomy, earth and environmental sciences, and has received numerous federal contracts and grants from agencies like NASA, NOAA, and NSF for a wide range of specialized research and services.

The surface of the moon is constantly bombarded by solar wind hydrogen. When implanted, some of the hydrogen can react with lunar oxygen to form hydroxyl (OH) and possibly molecular water (H2O). In 2009, three spacecraft detected a 3 m absorption band on the lunar surface [pieters ET AL., 2009 sunshine ET AL., 2009 clark 2009] indicating the presence of hydration in the form of OH or possibly H2O. Molecular water has been hypothesized to account for part of the 3 m absorption due to diurnal variation in the band by migration of H2O [sunshine ET AL., 2009]. Other models propose the variation in the 3 m band is due to temperature dependent variation in abundance of OH through formation of transient bonds as hydrogen diffuses through surface grains [tucker ET AL., 2019 farrell ET AL., 2017 starukhina, 2006]. However, until recently the definitive presence of molecular water on the lunar surface could not be established as the 3 m band is unable to differentiate between OH and H2O [mcintosh ET AL., 2017]. Use of the 3 m band alone cannot directly test either of the proposed hypotheses regarding the species responsible for the observed diurnal variation. The presence or absence of H2O is important for understanding interactions of an airless surface with the space environment. Migration of H2O to the poles has been a central hypothesis in supplying water ICE to the polar cold traps for over fifty years [watson ET AL., 1961 arnold, 1979 schorghofer, 2014]. Recently the iron oxide mineral hematite has been detected at high lunar latitudes and has been hypothesized to originate from interaction of H2O with nanophase iron in the lunar surface [LI ET AL., 2019]. To detect H2O on the moon we developed a new method to unambiguously detect H2O on the surface of the moon using a new wavelength range. The water molecule exhibits a diagnostic feature at 6 m due to the h-o-h bend that cannot be produced by OH [mctintosh ET AL., 2017 starukhina, 2001]. A 6 m band has been observed on mars [ruff, 2004], in meteorite and lunar samples [takir ET AL., 2019] (though the latter is likely due to terrestrial contamination), and in spitzer data of some asteroids [marchis ET AL., 2012]. Currently the only instrument capable of observing the moon for detection of molecular water at 6 m is the faint object infrared camera for the sofia telescope (forcast) on the NASA/DLR stratospheric observatory for infrared astronomy (sofia). Using forcast on sofia we made the first detection of molecular water on the sunlit lunar surface at 6 m [honniball ET AL., submitted]. We have been granted 2 hours observing time on sofia in cycle 8 to begin addressing diurnal variability of H2O. In addition, in support of NASA's volatiles investigating polar exploration rover (viper) polar rover, an additional 20 hours of lunar observations with sofia forcast aimed at characterizing H2O have been granted as a sofia director s discretionary time legacy project. We propose to use sofia to address key questions surrounding our initial detection of water: where is the water located within the surface and across the moon? How does IT behave over the period of a lunar day? Do small geologic targets contain internal H2O? To address these questions, we will collect spectra of multiple locations at different lunar times of day. We will observe locations that span a wide range of latitudes, capturing variations with latitude, different compositions, and locations that are of high priority for potential landing sites, to estimate the abundance of water providing essential information regarding the potential of in-situ resource utilization. The project is relevant to solar system observations because IT uses earth-based astronomical observations of solar system objects 6 m data of the moon does not exist and is not planned by current spacecraft missions, either in development or in operation.