CHARACTERIZING THE DISTRIBUTION AND VARIABILITY OF MARTIAN SUBSURFACE ICES USING SIXTEEN YEARS OF MARS ODYSSEY NEUTRON SPECTROMETER DATA MARTIAN ICE DEPOSITS BOTH POLAR (H2O AND CO2 ICE) AND NON-POLAR (H2O) PROVIDE VALUABLE CONSTRAINTS FOR EFFORTS TO UNDERSTAND CLIMATE CHANGE [EHLMANN B. L. ET AL. 2011] AND MOTIVATE LANDING SITE SELECTION [ARVIDSON R. ET AL. 2008]. THE EXTENT AND STRUCTURE OF THESE DEPOSITS INCLUDING THE SEASONAL AND RESIDUAL CO2 AND WATER-ICE POLAR DEPOSITS AND THE PERMANENT NON-POLAR DEPOSITS ARE HIGHLY SENSITIVE TO SMALL CHANGES IN MARS CLIMATE. FOR EXAMPLE ALBEDO CHANGES RESULTING FROM INCREASED DUST LOADING OR WATER ICE COVER CAN CAUSE THE SOUTH-POLAR RESIDUAL CAP (SPRC) TO SHIFT BETWEEN REGIMES OF LOOSING AND GAINING MASS [COLAPRETE ET AL. 2005]. THE EXPANSION OF THE SWISS CHEESE POLAR ICE FEATURES REPORTED BY MALIN ET AL. [2001] AND BYRNE AND INGERSOLL [2003] IS CONSISTENT WITH THIS HYPOTHESIS AND SUGGEST THAT SPRC MAY CURRENTLY BE UNDERGOING A REDUCTION IN SIZE. THE MARS ODYSSEY NEUTRON SPECTROMETER (MONS) DATASET PROVIDES MEASUREMENTS OF THERMAL EPITHERMAL AND FAST NEUTRON FLUXES THAT PROVIDE UNIQUE AND VALUABLE MEASUREMENTS OF THE EXTENT OF THESE DEPOSITS [E.G. PRETTYMAN ET AL. 2002]. TO DATE MONS DATA HAVE NOT BEEN USED TO INVESTIGATE EVOLUTION OF THESE DEPOSITS OVER SEVERAL (MARS) YEARS ADDITIONALLY THESE EFFORTS HAVE NOT UTILIZED ESTABLISHED NOISE-SUPPRESSING SPATIAL DECONVOLUTION TECHNIQUES [WILSON ET AL. 2018] THAT CAN GREATLY IMPROVE THE RESOLUTION OF MONS MEASUREMENTS. WE PROPOSE TO USE THE ENTIRE 16 EARTH-YEAR-LONG (2002-PRESENT) MONS DATASET TO MAP ICE DEPOSITS INCLUDE THEIR TIME-DEPENDENT SPATIAL EXTENTS FOR COMPARISONS WITH GLOBAL CLIMATE MODELS (GCMS) TO INVESTIGATE CLIMATE CHANGE ON MARS. THE PROJECT IS DIVIDED INTO FOUR TASKS: TASK 1: USING PDS-AVAILABLE MONS EDR DATA WE WILL APPLY THE ENHANCED DATA CALIBRATION AND CORRECTION ALGORITHMS OF MAURICE ET AL. [2011] TO PRODUCE NEW CORRECTED THERMAL EPITHERMAL AND FAST NEUTRON COUNT RATE MEASUREMENTS THAT COVER THE PERIOD FROM 8 FEBRUARY 2002 TO 31 DECEMBER 2015. TASK 2: USING THE GEANT4 [AGNOSTINELLI ET AL. 2003] MONTE CARLO PARTICLE TRANSPORT CODE WE WILL MODEL THE PRODUCTION AND MODERATION OF NEUTRONS IN THE MARTIAN POLAR SOIL WATER-ICE AND CO2-ICE CAPS TO DETERMINE QUANTITATIVELY HOW MONS NEUTRON OBSERVATIONS ARE RELATED TO WATER ABUNDANCE AND CO2-FROST COVER. TASK 3: WE WILL PRODUCE NEUTRON COUNT RATE MAPS OF MARS SURFACE ON AVERAGE AND DIVIDED BY TIME OR SEASON. MAPPED PRODUCTS WILL BE CREATED AT THE INTRINSIC RESOLUTION OF THE MONS DATA ~520 KM AS WELL AS AT IMPROVED RESOLUTION (BETTER THAN ~270 KM) AS DERIVED USING THE PIXON SPATIAL DECONVOLUTION TECHNIQUES OF WILSON ET AL. [2018]. TASK 4: WE WILL USE NEUTRON DATA TO LOOK AT THE SHORT-TERM EVOLUTION AND VARIABILITY IN THE CLIMATE WITH THE GOAL OF CONSTRAINING LONGTERM VARIABILITY VIA COMPARISON TO GCMS. IN TASK 4 WE WILL IDENTIFY SITES WITH HIGH POTENTIAL FOR SIGNIFICANT WATER RESOURCES AND CHARACTERIZE THE SIZE OF THE SEASONAL CO2 ICE CAPS AND THE RESIDUAL WATER-ICE CAPS. NEUTRON DATA WILL BE COMPARED TO MEASURES OF DUST COVER TO INVESTIGATE PRECISELY HOW DUST STORMS INFLUENCE THE TIMING OF DEPOSITION AND SUBLIMATION OF THE SEASONAL CAPS [BONEV ET AL. 2008]. THE IMPROVED SPATIAL RESOLUTION AND SUPPRESSION OF NOISE ACHIEVED VIA IMAGE RECONSTRUCTION WILL FOR THE FIRST TIME REVEAL THE FORMATION OF ANY HETEROGENEITIES WITHIN THE CAPS. AGOSTINELLI S. ET AL. (2003). NUC. INST. METH. 506 250. ARVIDSON R. ET AL. (2008) J. GEOPHYS. RES. 113. BONEV B. P. ET AL. (2008). PLA. SP. SCI. 56(2) 181. BYRNE S. &INGERSOLL A. P. (2003). GRL. 30(13). COLAPRETE A. ET AL. (2005). NATURE 435(7039) 184-188. EHLMANN B. L. ET AL. (2011). NATURE 479(7371) 53-60. MALIN M. C. ET AL. (2001). SCIENCE 294 2146. MAURICE S. ET AL. (2011) J. GEOPHYS. RES. 116. WILSON J. T. ET AL. (2018) ICARUS 288 148-160.