THE GOAL OF THIS PROPOSAL IS TO RESOLVE THE FUNDAMENTAL PROBLEM OF THE ORIGIN OF MOLECULAR OXYGEN (O2) IN COMET 67P/CHURYUMOV- GERASIMENKO (67P) THROUGH THE METHODICAL ANALYSIS OF ROSINA/DFMS DATA. ROSINA/DFMS MADE THE FIRST EVER DETECTION OF O2 IN THE COMA OF A COMET. ITS LARGE RELATIVE ABUNDANCE DESPITE ITS HIGH REACTIVITY AND LOW INTERSTELLAR ABUNDANCE IS A MYSTERY FOR 67P AND POTENTIALLY OTHER COMETS. THIS DISCOVERY HAS SINCE PROMPTED A FEW STUDIES THAT TRY TO EXPLAIN THE PRODUCTION AND ORIGIN OF O2 IN 67P. SUGGESTED EXPLANATIONS RANGE FROM IN SITU PRODUCTION MECHANISMS TO VARIOUS PRIMORDIAL OR PROTOSOLAR NEBULA ORIGINS. HOWEVER THESE FEW EXISTING STUDIES RELY HEAVILY ON THE ONLY TWO AVAILABLE PUBLICATIONS OF THE ROSINA/DFMS O2 DATA. THE CORRELATIONS AND RATIOS REPORTED IN THESE PUBLICATIONS INCLUDED ALL THE DATA COMBINED WITHOUT ACCOUNTING FOR IMPORTANT LATITUDINAL AND POSSIBLY EVEN LONGITUDINAL FACTORS. IN PREVIOUS STUDIES WE HAVE SHOWN THAT OUTGASSING FROM THE TWO HEMISPHERES DEMONSTRATE DISTINCT PATTERNS THAT MUST BE TAKEN INTO ACCOUNT WHEN TRYING TO RELATE OBSERVATIONS IN THE COMA TO PROCESSES OCCURRING IN THE NUCLEUS. THEREFORE AN EXTENDED AND CAREFULLY RESOLVED ANALYSIS OF THE DFMS DATA IS NECESSARY TO CONFIDENTLY ADDRESS MANY OF THE EXISTING CONTROVERSIES SURROUNDING THE FORMATION AND ORIGIN OF O2. IN ORDER TO ACHIEVE THE GOAL OF THIS PROPOSED EFFORT WE WILL DETERMINE THE MOST LIKELY ORIGIN AND DOMINANT FORMATION MECHANISM(S) OF O2 IN 67P. WE DEFINE A SET OF TASKS THAT SYSTEMATICALLY ASSESSES THE EXISTING FORMATION SCENARIOS IN THE LITERATURE TO DETERMINE WHICH SCENARIO(S) IS DOMINANT. THESE PROPOSED TASKS INCLUDE A SYSTEMATIC CORRELATION STUDY OF O2 WITH THE MAJOR COMA SPECIES H2O CO2 AND CO WITH THE MINOR SPECIES N2 CH4 C2H6 AND H2O2 AND THE RELEVANT WATER-DERIVED ION SPECIES (E.G. H2O+ H3O+ OH+ O+) FOR EACH HEMISPHERE OVER APPROPRIATE ORBITAL SEGMENTS. WE WILL ALSO DETERMINE THE O2/H2O O2/H2O2 AND O2/CO RATIOS AS A FUNCTION OF HEMISPHERE AND HELIOCENTRIC DISTANCE. AFTER ACCOMPLISHING THESE DATA ANALYSIS TASKS AND APPLYING SIMPLE THERMODYNAMIC CONSIDERATIONS AND A STATISTICAL THERMODYNAMIC MODEL OUR TEAM HAS EXTENSIVE EXPERIENCE WITH WE WILL BE ABLE TO ANSWER THE FOLLOWING INTERCONNECTED SCIENCE QUESTIONS: 1. IS THE MAJORITY OF OBSERVED O2 PRODUCED IN SITU IN PRESENT TIMES OR WAS IT PRODUCED PRIOR TO NUCLEUS AGGLOMERATION? 2. DOES THE MAJORITY OF MEASURED O2 HAVE A PRIMORDIAL (MOLECULAR CLOUD) OR PROTOSOLAR NEBULA ORIGIN? 3. WHAT IS THE PHASE OF ICE O2 MAY CURRENTLY BE STORED IN THE NUCLEUS? AT THE END OF THIS PROJECT WE WILL HAVE A SIGNIFICANTLY DEEPER UNDERSTANDING OF THE DOMINANT MECHANISMS(S) PRODUCING COMETARY O2 AND WE WILL BE ABLE TO MORE CONFIDENTLY ADDRESS ITS ORIGIN COMPARED TO THE CURRENT STATE OF KNOWLEDGE. THE PROPOSED WORK IS DIRECTLY RELEVANT TO THE NASA RDAP PROGRAM BECAUSE IT RELIES ON THE ANALYSIS AND INTERPRETATION OF NEW ROSINA/DFMS NEUTRAL AND ION OBSERVATIONS. THIS PROPOSAL WILL ADVANCE SCIENTIFIC KNOWLEDGE BY ANSWERING SCIENCE QUESTIONS WITH IMPORTANT IMPLICATIONS FOR NOT ONLY COMETARY SCIENCE BUT ALSO FOR SOLAR SYSTEM FORMATION MODELS INTERSTELLAR AND DISK CHEMISTRY AND ASTROCHEMICAL MODELS. AS SUCH THE PROPOSED WORK WILL DIRECTLY ENHANCE THE SCIENTIFIC RETURN OF THE ROSETTA MISSION.