COMETARY NUCLEI ARE PERHAPS THE MOST PRIMITIVE AND PRISTINE OBJECTS IN THE SOLAR SYSTEM; THEIR COMPOSITION IS REMARKABLY SIMILAR TO THAT OF INTERSTELLAR DUST-GRAIN ICES AND A NUMBER OF THE MOST COMPLEX ORGANIC MOLECULES DETECTED IN THE GAS PHASE OF STAR-FORMING CORES ARE ALSO DETECTED IN COMETARY COMAE. BUT THE COMPOSITION OF COMETARY ICES MAY BE YET MORE CHEMICALLY COMPLEX; THE STARDUST MISSION AND RECENTLY THE ROSETTA MISSION BOTH DETECTED COMETARY GLYCINE (WHICH HAS NOT YET BEEN FOUND IN THE ISM) AND MANY COMPLEX ORGANIC MOLECULES HAVE NOW BEEN DETECTED DIRECTLY ON THE SURFACE OF COMET 67P/CG BY THE PHILAE LANDER. COMET IMPACTS MAY ACCOUNT FOR PART OF OUR PLANET'S WATER AND THUS MAY HAVE DELIVERED IMPORTANT BIOTIC OR PRE-BIOTIC COMPOUNDS TO THE EARLY EARTH.HOWEVER WHILE MODELS OF COMPLEX CHEMICAL PROCESSES WITHIN ORGANIC ICES IN THE INTERSTELLAR MEDIUM ARE MOVING FORWARD RAPIDLY FOLLOWED BY SIMILAR MODELS OF PROTOPLANETARY DISK CHEMISTRY THERE ARE NO MODELS THAT CONSIDER THE CHEMISTRY WITHIN THE COMETARY ICES THEMSELVES - EITHER DURING THE "COLD-STORAGE" PHASE OR DURING THE "ACTIVE" PHASE WHEN COMETS ENTER THE INNER SOLAR SYSTEM. IT IS POSTULATED THAT THE OUTER ICE LAYERS OF OORT CLOUD OBJECTS UNDERGO HEAVY PHYSICAL AND CHEMICAL PROCESSING; SUCH MAY INCLUDE IRRADIATION BY PASSING LUMINOUS STARS OR BY NEARBY SUPERNOVA EVENTS. MEANWHILE NUMEROUS EXPERIMENTS HAVE DEMONSTRATED THE FORMATION OF AMINO ACIDS IN ORGANIC ICES BY PHOTOLYSIS OR ENERGETIC PARTICLES. BUT WHILE THERE ARE WELL-ESTABLISHED MODELS OF THE CHEMISTRY IN THE GAS-PHASE COMA WHICH IS FED BY SUBLIMATION OF THE NUCLEAR ICES DURING THE ACTIVE PHASE THE EFFECTS ON THE ICE CHEMISTRY OF THE INTENSE IRRADIATION AND HEATING CAUSED BY THE SOLAR APPROACH HAVE NOT BEEN SIMULATED IN ANY WAY.HERE IT IS PROPOSED TO USE THE PI'S ADVANCED CHEMICAL KINETICS MODELS OF INTERSTELLAR ICE CHEMISTRY TO INVESTIGATE THE SIMILAR PROCESSES OCCURRING WITHIN COMETARY ICES. BY SIMULATING BOTH THE COLD-STORAGE AND ACTIVE PHASES OF COMETARY-ICE EVOLUTION WITH WELL-ESTABLISHED INTERSTELLAR MODELS WE MAY INVESTIGATE TO WHAT DEGREE THE PRISTINE ICES - FORMED BY INTERSTELLAR OR PROTOPLANETARY CHEMICAL ACTIVITY - ARE FURTHER PROCESSED ONCE COMET FORMATION HAS ACTUALLY OCCURRED. THIS PROCESSING WOULD INCLUDE THE FORMATION OF THE LOW-ALBEDO HYDROCARBON-RICH OUTER SURFACE AS WELL AS THE POSSIBLE FORMATION OF GLYCINE AND OTHER COMPLEX ORGANICS RELEVANT TO LIFE. HOWEVER THE MODELS MAY ALSO HIGHLIGHT THE DESTRUCTION OF THOSE SAME SPECIES IF THEY ORIGINATED IN THE INTERSTELLAR OR PROTOPLANETARY ENVIRONMENT. THE DEPTH INTO THE ICE AT WHICH CHEMISTRY IS OCCURRING MAY ALSO BE IMPORTANT TO THE DEVELOPMENT AND/OR SURVIVAL OF COMPLEX ORGANICS.BY ADOPTING DIFFERENT PHYSICAL MODELS DIFFERENTIATION BETWEEN KUIPER BELT/SCATTERED-DISK OBJECTS AND OORT CLOUD OBJECTS WILL BE POSSIBLE SO THAT DIFFERING CHEMICAL EVOLUTIONARY HISTORIES MAY BE EXPLORED. A QUANTITATIVE UNDERSTANDING OF CHEMICAL TIMESCALES WILL ALSO YIELD INFORMATION AS TO THE DEGREE OF CHEMICAL ALTERATION UNDERGONE BY COMETS THAT BOMBARDED THE EARLY EARTH IN COMPARISON TO RECENTLY-OBSERVED OBJECTS AND TO WHAT DEGREE CURRENT COMETS REALLY ARE 'PRISTINE'. FINALLY THE CONSTRUCTION OF A MODEL FOR THE ACTIVE PHASE WILL ALLOW THE SIMULATION OF THE CHEMISTRY AS PHYSICAL CONDITIONS CHANGE DURING SEVERAL ELLIPTICAL ORBITS OF A COMET AS THE OUTER ICE LAYERS ARE EJECTED INTO THE COMA. THESE MODELS WILL BE THE FIRST ATTEMPT TO SIMULATE SUCH COMETARY ICE CHEMISTRY.THIS MODELING INVESTIGATION IS BOTH TIMELY AND CRUCIAL FOR A COMPLETE UNDERSTANDING OF IMPORTANT NEW DATA FROM THE ROSETTA MISSION AND FROM ALMA AND OTHER OBSERVATORIES. IT WILL ADDRESS STATED OBJECTIVES OF THE EMERGING WORLDS PROGRAM SPECIFICALLY: 'FORMATION OF ORGANIC MOLECULES IN SPACE'; 'THE CHEMICAL AND PHYSICAL PROPERTIES OF ANCIENT MATERIALS (INCLUDING ASTEROIDS AND COMETS)'; AND 'THE DELIVERY OF ORGANIC MOLECULES AND VOLATILES TO PLANETARY SURFACES'.