IN RECENT YEARS THE SURFACE OF MERCURY HAS BEEN CHARACTERIZED IN UNPRECEDENTED DETAIL. ONE OF THE MOST INTRIGUING RESULTS HAS BEEN THE DETECTION OF DISTINCTIVE REFLECTANCE AND NEUTRON FLUX SIGNATURES IN MERCURY'S POLAR REGIONS BY INSTRUMENTS ON THE MESSENGER SPACECRAFT. THESE MEASUREMENTS COMBINED WITH EARTH-BASED RADAR DATA AND THERMAL MODELING PRESENT COMPELLING EVIDENCE FOR THE PRESENCE OF WATER ICE IN PERMANENTLY SHADOWED REGIONS NEAR MERCURY'S POLES WHERE TEMPERATURES ARE SO LOW THAT WATER (AND OTHER VOLATILES) CAN REMAIN THERMALLY STABLE OVER GEOLOGICAL TIMESCALES. MERCURY'S POLAR DEPOSITS PROVIDE A UNIQUE AND IMPORTANT GEOLOGICAL RECORD OF THE DELIVERY OF WATER TO THE INNER SOLAR SYSTEM. IN ORDER TO INTERPRET THIS RECORD IT IS CRUCIAL TO DEVELOP AN UNDERSTANDING OF THE ORIGIN AND NATURE OF POLAR ICE ON MERCURY. SEVERAL STUDIES HAVE INVESTIGATED MECHANISMS THAT MAY DELIVER WATER TO THE LUNAR POLES BUT FEW SUCH STUDIES EXIST FOR MERCURY DESPITE EVIDENCE THAT WATER ICE IS MORE ABUNDANT ON MERCURY THAN ON THE MOON. SEVERAL DISTINCT LINES OF EVIDENCE SUGGEST THAT THE WATER ICE DETECTED IN MERCURY'S POLAR COLD TRAPS MAY HAVE BEEN DELIVERED BY A RECENT COMET (OR VOLATILE-RICH ASTEROID) IMPACT. IN THIS WORK WE PROPOSE TO INVESTIGATE THROUGH NUMERICAL MODELING THE TRANSPORT AND DEPOSITION OF WATER ON MERCURY IN THE AFTERMATH OF A VOLATILE-RICH IMPACT. OUR OBJECTIVES ARE TO ADDRESS THE FOLLOWING QUESTIONS: HOW IS WATER TRANSPORTED AND REDISTRIBUTED IN THE AFTERMATH OF A VOLATILE-RICH IMPACT ON MERCURY? WHAT ARE THE CHARACTERISTICS OF THE TRANSIENT ATMO/EXOSPHERE GENERATED BY A VOLATILE-RICH IMPACT ON MERCURY? WHAT FRACTION OF IMPACT-DELIVERED VOLATILES MAY BE PRESERVED AS SURFACE DEPOSITS? COULD A RECENT IMPACT EXPLAIN ALL THE OBSERVED FEATURES OF MERCURY'S POLAR DEPOSITS? IN PARTICULAR THE HOKUSAI IMPACT HAS BEEN INVESTIGATED AS A POTENTIAL SOURCE CRATER FOR PRESENT-DAY POLAR DEPOSITS; DOES MODELING SUPPORT THIS SCENARIO AND/OR YIELD FURTHER INSIGHTS? TO CARRY OUT THE PROPOSED WORK WE PLAN TO USE A DIRECT SIMULATION MONTE CARLO (DSMC) CODE THAT MEMBERS OF OUR TEAM HAVE PREVIOUSLY APPLIED TO INVESTIGATE THE TRANSPORT AND DEPOSITION OF WATER IN THE AFTERMATH OF A LUNAR COMET IMPACT (PREM ET AL. 2015). THE DSMC CODE WILL BE ADAPTED TO ACCOUNT FOR DIFFERENCES BETWEEN THE MOON AND MERCURY IN TERMS OF GRAVITY SIZE SOLAR FLUX AND SURFACE THERMAL ENVIRONMENT (INCLUDING THE EFFECTS OF MERCURY'S 3:2 SPIN-ORBIT RESONANCE WITH THE SUN). TO FACILITATE COMPARISON OF MODEL RESULTS WITH REMOTE SENSING DATA A DETAILED REPRESENTATION OF THE COLD TRAPS MAPPED BY MESSENGER WILL BE INCORPORATED AND THE EFFECTS OF SUB-RESOLUTION COLD TRAPS AND SURFACE ROUGHNESS WILL BE MODELED STOCHASTICALLY. MEMBERS OF OUR TEAM HAVE PREVIOUSLY DERIVED CONSTRAINTS ON THE PARAMETERS OF THE HOKUSAI CRATER-FORMING IMPACT - A CANDIDATE SOURCE-CRATER FOR PRESENT-DAY POLAR DEPOSITS (ERNST ET AL. 2016). WE WILL PERFORM A SUITE OF SIMULATIONS TO EXPLORE THE PARAMETER SPACE ASSOCIATED WITH THE HOKUSAI IMPACT AND WILL ALSO EXAMINE THE INFLUENCE OF IMPACT TIME-OF-DAY ON VOLATILE FALLOUT. IN ORDER TO RUN THESE SIMULATIONS WE PLAN TO USE THE TEXAS ADVANCED COMPUTING CENTER'S STAMPEDE SUPERCOMPUTER. THIS PROPOSAL RESPONDS TO SSW OBJECTIVES OF SUPPORTING RESEARCH (INCLUDING NUMERICAL MODELING) INTO PROCESSES THAT AFFECT THE SURFACES AND ATMO/EXOSPHERES OF PLANETARY BODIES. THE FOCUS OF THIS STUDY IS MERCURY BUT THE PROPOSED WORK WOULD ALSO INCREASE OUR BROADER UNDERSTANDING OF THE BEHAVIOR OF VOLATILES ON NOMINALLY AIRLESS BODIES. THIS WORK WOULD ALSO ADDRESS SEVERAL IMPORTANT QUESTIONS HIGHLIGHTED IN THE DECADAL SURVEY: HOW ARE VOLATILE ELEMENTS AND COMPOUNDS DISTRIBUTED TRANSPORTED AND SEQUESTERED IN NEARSURFACE ENVIRONMENTS ON THE SURFACES OF THE MOON AND MERCURY? WHAT FRACTIONS OF VOLATILES REPRESENT LATE METEORITIC AND COMETARY INFALL? DO VOLATILES ON MERCURY AND THE MOON CONSTRAIN ANCIENT ATMOSPHERIC ORIGINS SOURCES AND LOSS PROCESSES?