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IN THE PAST DECADE OBSERVATIONS OF THE MOON BY SPACECRAFT AND THE INCREASED SENSITIVITY OF ANALYTICAL METHODS APPLIED TO LUNAR SAMPLES HAVE CREATED A NEW PARADIGM FOR THE ABUNDANCE OF WATER BOTH ON AND IN THE MOON. WHILE THE MOON WAS PREVIOUSLY BELIEVED TO BE COMPLETELY DRY IT IS NOW KNOWN THAT WATER IS PRESENT ON THE SURFACE AND IN MANY LUNAR SAMPLES AT THE LEVEL OF 100 PARTS PER MILLION OR GREATER. SPACECRAFT OBSERVATIONS ESTABLISHED THAT A 3 UM ABSORPTION FEATURE ATTRIBUTABLE TO WATER OR HYDROXYL WAS PRESENT ON THE SURFACE ESPECIALLY AT HIGH LATITUDES AND AWAY FROM THE SUBSOLAR POINT AT LOW LATITUDES. THE SPACECRAFT DATA REVEAL THAT THE 3 UM FEATURE VARIES IN STRENGTH AND SPECTRAL PROPERTIES WITH THE LUNAR TIME OF DAY AND THE LOCAL GEOLOGY OF THE MOON. LIMITATIONS OF EXISTING SPACECRAFT DATA LEAVE MANY QUESTIONS UNANSWERED. WHILE THE 3UM FEATURE VARIES WITH LUNAR TIME OF DAY ESPECIALLY AT MID TO HIGH LATITUDES CONTROVERSIES REGARDING THE REMOVAL OF THERMAL EMISSION FROM THE SPECTRA LEAVE OPEN THE QUESTION AS TO WHETHER THE ABUNDANCE OF WATER INDEED VARIES WITH TIME. THE THERMAL CORRECTIONS OF 3UM DATA THAT SUGGEST ABUNDANCE VARIATIONS IMPLY A LARGE DIURNAL SUPPLY OF WATER TO THE LUNAR ATMOSPHERE AND TO THE LUNAR COLD TRAPS. THIS SUPPLY IF QUANTIFIED AND ASSOCIATED WITH WELL UNDERSTOOD UNCERTAINTIES WOULD PROVIDE AN IMPORTANT CONSTRAINT ON THE NATURE OF THE LUNAR ATMOSPHERE AND THE SUPPLY OF WATER TO THE LUNAR POLAR COLD TRAPS WHERE ICE HAS BEEN REPORTED. OBSERVATIONS OF THE MOON AT HIGH SPATIAL RESOLUTION (~KM SCALE) HAS REVEALED VARIATIONS IN THE NATURE OF THE 3 UM BAND INDEPENDENT OF TEMPERATURE STRONGLY SUGGESTING A COMPOSITIONALLY DEPENDENT VARIATION IN THE TYPE OF WATER AND ITS ACCOMMODATION IN LUNAR MATERIALS. THE MARE AND HIGHLANDS SHOW DIFFERENT BAND STRENGTHS WHERE LUNAR VOLCANIC PYROCLASTIC DEPOSITS OFTEN SHOW 3 UM BAND DEPTHS GREATER THAN THE BACKGROUND SUGGESTING HIGHER WATER ABUNDANCES. SMALL LOCAL 3UM ANOMALIES THAT MAY BE ASSOCIATED WITH WATER OR HYDROXYL IN LUNAR IGNEOUS MINERALS ARE ALSO FOUND IN MANY PLACES. YET THE SPECTRAL DATA FOR ALL THESE LOCATIONS ARE CONFINED TO WAVELENGTHS LESS THAN 3 UM GREATLY LIMITING INSIGHTS INTO THE TYPES OF WATER OR MATERIALS THAT MIGHT BE PRESENT. GROUND-BASED OBSERVATIONS OF THE MOON CAN OVERCOME MANY OF THESE LIMITATIONS. IN THIS PROJECT WE PROPOSE USING THE SPEX LONG CROSS-DISPERSED INFRARED SPECTROGRAPH AT THE NASA INFRARED TELESCOPE FACILITY TO OBTAIN SPECTRA IN THE 3UM REGION. SPEX COVERS THE REGION OF CHARACTERISTIC WATER ABSORPTIONS OF SOLIDS AND IS COMMONLY USED IN ASTEROID SPECTROSCOPY. GROUND-BASED DATA CAN BE OBTAINED AT PHOTOMETRIC AND PHASE ANGLES MORE CONDUCIVE TO THE THERMAL CORRECTION OF REFLECTANCE DATA THAN SPACECRAFT DATA. DATA CAN ALSO BE COLLECTED AT 2 KM RESOLUTION ENABLING DETAILED CHARACTERIZATION OF THE WATER ABSORPTION OF IDENTIFIED 3 UM ANOMALIES. THESE OBSERVATIONS WILL SUBSTANTIALLY IMPROVE OUR UNDERSTANDING OF THE SPATIAL AND TEMPORAL VARIATION IN WATER ON THE MOON. THIS PROJECT IS RELEVANT TO SOLAR SYSTEM OBSERVATIONS BECAUSE IT COLLECTS AND ANALYZES NEW DATA FROM GROUNDBASED TELESCOPES. THE PROJECT IS RELEVANT TO NASA BECAUSE IT DIRECTLY ADDRESSES PROBLEMS CALLED OUT IN THE NASA DECADAL SURVEY INCLUDING: HOW ARE VOLATILE ELEMENTS AND COMPOUNDS DISTRIBUTED TRANSPORTED AND SEQUESTERED IN NEAR-SURFACE ENVIRONMENTS ON THE SURFACES OF THE MOON AND MERCURY? WHAT FRACTIONS OF VOLATILES WERE OUTGASSED FROM THOSE PLANETS INTERIORS AND WHAT FRACTIONS REPRESENT LATE METEORITIC AND COMETARY INFALL? WHAT ARE THE INVENTORIES AND DISTRIBUTIONS OF VOLATILE ELEMENTS AND COMPOUNDS (SPECIES ABUNDANCES AND ISOTOPIC COMPOSITIONS) IN THE MANTLES AND CRUSTS OF THE INNER PLANETS?

$572,310FY2020National Aeronautics and Space AdministrationNASA

University Of Hawaii, Honolulu

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