OVERVIEW: THE MARS ODYSSEY GAMMA RAY SPECTROMETER (GRS) SUITE PROVIDES REGIONAL SCALE CHEMICAL INSIGHT AT DECIMETER DEPTHS. WE USED GRS DATA ACROSS TWO PILOT PROJECTS DEMONSTRATING THAT FE-SULFATES MAY CONTRIBUTE SIGNIFICANTLY TO HYDRATING THE REGOLITH. HOWEVER KEY ASPECTS OF THE RELATIVE ROLES OF DIFFERENT REGOLITH COMPONENTS IN HYDRATING THE MID-TO-LOW LATITUDES ARE POORLY KNOWN. FURTHERMORE WHILE MANY HYDRATED MINERALS HAVE BEEN OBSERVED IN THE MARTIAN REGOLITH THE RELATIVE SIGNIFICANCE OF DIFFERENT PROCESSES FOR THE DISTRIBUTION OF H2O REMAINS REGIONALLY UNCONSTRAINED. OUR GOAL IS TO RESOLVE SUCH UNCERTAINTIES WITH A DETAILED GLOBAL-SCALE CHARACTERIZATION OF THE REGOLITH AS AN H2O RESERVOIR OF MODERN MARS. OUTCOMES MAY ADDITIONALLY INFORM THE EXCHANGE OF H2O BETWEEN THE MARTIAN SHALLOW SUBSURFACE AND ATMOSPHERE OVER GEOLOGIC TIME AS WELL AS THE ROLE OF VOLCANIC PROCESSES SUCH AS ACID-FOG OR LEACHING IN THE PRODUCTION OF HYDRATED MINERALS. ACCORDINGLY WE PROPOSE A DETAILED REGION-BY-REGION CHARACTERIZATION OF MARTIAN REGOLITH HYDRATION ENABLED BY MULTIVARIATE DATA ANALYSES. THIS RESULTS IN TWO OBJECTIVES (AIMS) AIMS&METHODS: QUANTIFYING UNIQUE CORRELATIONS IS FUNDAMENTAL TO THE SUCCESS OF OUR APPROACH. OUR MULTIVARIATE SPACE CONSISTS OF THE 9 PUBLISHED CHEMICAL CONCENTRATION MAPS OF MARS (AL CA CL FE H2O K S SI AND TH) THE DUST COVER INDEX (DCI) AND TOPOGRAPHIC ROUGHNESS. THE CHEMICAL MAPS ENCOMPASS KEY MAJOR MINOR AND TRACE ELEMENTS ALLOWING DETAILED CHARACTERIZATION OF THE REGOLITH TO IDENTIFY CHEMICAL DRIVERS OF REGOLITH HYDRATION (A REPRESENTED BY H2O). AIM 1. WE WILL DEVELOP AN ANALYTICAL TOOLKIT FOR HYPOTHESIS TESTING. THE 11-DIMENSIONAL DATA SPACE CREATES POSSIBLY REDUNDANT AND SECONDARY CORRELATIONS WHICH WE WILL RESOLVE STATISTICALLY BY AN ORTHOGONAL TRANSFORMATION TO LINEARLY UNCORRELATED VARIABLES WITH EACH IDENTIFYING A DIRECTION OF HIGH VARIANCE. ONE TASK SUPPORTS OUR FIRST AIM: SYNTHESIZE METHODS TO REDUCE DIMENSIONALITY PROPAGATE UNCERTAINTY AND QUANTIFY UNIQUE CORRELATIONS. THIS SOFTWARE DEVELOPMENT WILL BE IMPLEMENTED IN PYTHON AS AN OPEN-ACCESS PLATFORM. AIM 2. WE WILL EXAMINE REGOLITH HYDRATION WITHIN AND ACROSS INDIVIDUAL REGIONS TO TEST THE HYPOTHESES. TWO TASKS SUPPORT OUR SECOND AIM. FIRST TO DELINEATE THE REGIONS AND COMPUTE CORRELATIONS. SECOND TO SYNTHESIZE RESULTS ACROSS THE REGIONS. TO REFLECT THE DIVERSITY OF POSSIBLE HYDRATION MECHANISMS THESE REGIONS WILL BE DETERMINED FROM THE TOPOGRAPHIC DICHOTOMY MAPPED GEOLOGY ENRICHMENTDEPLETION OF INDIVIDUAL VARIABLES OF OUR DATASET COMPARED TO GLOBAL AVERAGES MODELED EJECTA RANGES FROM VOLCANIC AND IMPACT SOURCES AND STATISTICAL CLASSIFICATION OF TOPOGRAPHIC ROUGHNESS. MDAP SUITABILITY: OUR OBJECTIVES APPLY TO MDAP BY SEEKING TO ENHANCE THE SCIENTIFIC RETURN OF GRS SPECTRA. OUR WORK WILL ALSO IMPROVE OUR UNDERSTANDING OF AN OPEN SCIENCE QUESTIONS AT MARS: THE PROCESSES DRIVING THE VARIABILITY OF REGOLITH HYDRATION AT REGIONAL SCALES. WITH THE DECIMETER DEEP COMPOSITIONAL SENSITIVITY OF GRS-DERIVED DATA THIS WILL ADVANCE THE BULK CHARACTERIZATION NECESSARY FOR IN SITU RESOURCE USE (ISRU) IN THE FUTURE AND BE BROADLY RELEVANT FOR HABITABILITY OF THE CURRENT MARTIAN REGOLITH. WE WILL ONLY USE DATA FROM THE PUBLISHED LITERATURE>30 DAYS PRIOR TO THE MDAP SUBMISSION DEADLINE.