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OBJECTIVES: MILLIMETER AND SUB-MILLIMETER OBSERVATIONS FROM GROUND-BASED TELESCOPES HAVE REVEALED THE PRESENCE OF AN UNEXPECTEDLY LARGE AMOUNT OF CARBON MONOXIDE IN NEPTUNE'S STRATOSPHERE THAT MAY HAVE BEEN DELIVERED DURING A LARGE COMETARY IMPACT THAT OCCURRED A COUPLE HUNDRED YEARS AGO (E.G. LELLOUCH ET AL. 2005; A&A 430 L3-L40). THE COMET-IMPACT HYPOTHESIS COULD ALSO EXPLAIN THE CURRENT PRESENCE OF HCN AND CS IN NEPTUNE'S STRATOSPHERE. THE GOAL OF THE PROPOSED WORK IS TO TRACK THE FATE OF GAS-PHASE SPECIES INTRODUCED INTO NEPTUNE'S UPPER ATMOSPHERE FROM THIS PUTATIVE COMETARY IMPACT. IN PARTICULAR WE SEEK TO FURTHER OUR UNDERSTANDING OF (1)THE COUPLED CARBON OXYGEN NITROGEN AND SULFUR CHEMISTRY RESULTING FROM SUCH AN IMPACT; (2) THE ORIGIN OF THE DIFFERENT VERTICAL PROFILES OF CO CS AND HCN CURRENTLY OBSERVED IN NEPTUNE'S STRATOSPHERE; (3) THE EFFECT OF THE COMET-DERIVED SPECIES ON THE CURRENT STRATOSPHERIC C2H6/C2H6 RATIO AND OTHER CONSEQUENCES FOR THE BACKGROUND HYDROCARBON PHOTOCHEMISTRY ON NEPTUNE; AND (4) THE IMPLICATIONS OF THE COMET-DERIVED CO ON OUR ABILITY TO DETERMINE THE DEEP OXYGEN ABUNDANCE ON NEPTUNE BY INDIRECT METHODS. METHODOLOGY: 1-D PHOTOCHEMICAL MODELS WILL BE USED TO TRACK THE NEUTRAL CARBON OXYGEN NITROGEN AND SULFUR PHOTOCHEMISTRY AND HAZE PRODUCTION THAT RESULTS AFTER A PUTATIVE LARGE COMETARY IMPACT ON NEPTUNE. MODEL PREDICTIONS REGARDING THE VERTICAL PROFILES OF TROPOSPHERIC AND STRATOSPHERIC SPECIES WILL BE COMPARED WITH PUBLISHED GROUND-BASED AND SPACECRAFT OBSERVATIONS. SIGNIFICANCE/RELEVANCE: THE PROPOSED INVESTIGATION SEEKS TO ADVANCE OUR UNDERSTANDING OF THE ATMOSPHERIC CHEMISTRY AND COMPOSITION OF NEPTUNE AND WILL HELP CONSTRAIN THE DEEP OXYGEN ABUNDANCE ON THE PLANET WHICH HAS IMPORTANT IMPLICATIONS FOR THE ORIGIN AND EVOLUTION OF ICE GIANTS. THE WORK IS LARGELY THEORETICAL IN NATURE AND CONTAINS NO DATA-ANALYSIS COMPONENT. AS SUCH THE PROPOSAL IS MOST RELEVANT TO THE NASA SOLAR SYSTEM WORKINGS PROGRAM WHOSE "CALL SEEKS TO ADDRESS THE PHYSICAL AND CHEMICAL PROCESSES THAT AFFECT THE... ATMOSPHERES... OF PLANETARY BODIES."

$275,302FY2020National Aeronautics and Space AdministrationNASA

Space Science Institute, Boulder CO

Investigators

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OBJECTIVES: MILLIMETER AND SUB-MILLIMETER OBSERVATIONS FROM GROUND-BASED TELESCOPES HAVE REVEALED THE PRESENCE OF AN UNEXPECTEDLY LARGE AMOUNT OF CARBON MONOXIDE IN NEPTUNE'S STRATOSPHERE THAT MAY HAVE BEEN DELIVERED DURING A LARGE COMETARY IMPACT THAT OCCURRED A COUPLE HUNDRED YEARS AGO (E.G. LELLOUCH ET AL. 2005; A&A 430 L3-L40). THE COMET-IMPACT HYPOTHESIS COULD ALSO EXPLAIN THE CURRENT PRESENCE OF HCN AND CS IN NEPTUNE'S STRATOSPHERE. THE GOAL OF THE PROPOSED WORK IS TO TRACK THE FATE OF GAS-PHASE SPECIES INTRODUCED INTO NEPTUNE'S UPPER ATMOSPHERE FROM THIS PUTATIVE COMETARY IMPACT. IN PARTICULAR WE SEEK TO FURTHER OUR UNDERSTANDING OF (1)THE COUPLED CARBON OXYGEN NITROGEN AND SULFUR CHEMISTRY RESULTING FROM SUCH AN IMPACT; (2) THE ORIGIN OF THE DIFFERENT VERTICAL PROFILES OF CO CS AND HCN CURRENTLY OBSERVED IN NEPTUNE'S STRATOSPHERE; (3) THE EFFECT OF THE COMET-DERIVED SPECIES ON THE CURRENT STRATOSPHERIC C2H6/C2H6 RATIO AND OTHER CONSEQUENCES FOR THE BACKGROUND HYDROCARBON PHOTOCHEMISTRY ON NEPTUNE; AND (4) THE IMPLICATIONS OF THE COMET-DERIVED CO ON OUR ABILITY TO DETERMINE THE DEEP OXYGEN ABUNDANCE ON NEPTUNE BY INDIRECT METHODS. METHODOLOGY: 1-D PHOTOCHEMICAL MODELS WILL BE USED TO TRACK THE NEUTRAL CARBON OXYGEN NITROGEN AND SULFUR PHOTOCHEMISTRY AND HAZE PRODUCTION THAT RESULTS AFTER A PUTATIVE LARGE COMETARY IMPACT ON NEPTUNE. MODEL PREDICTIONS REGARDING THE VERTICAL PROFILES OF TROPOSPHERIC AND STRATOSPHERIC SPECIES WILL BE COMPARED WITH PUBLISHED GROUND-BASED AND SPACECRAFT OBSERVATIONS. SIGNIFICANCE/RELEVANCE: THE PROPOSED INVESTIGATION SEEKS TO ADVANCE OUR UNDERSTANDING OF THE ATMOSPHERIC CHEMISTRY AND COMPOSITION OF NEPTUNE AND WILL HELP CONSTRAIN THE DEEP OXYGEN ABUNDANCE ON THE PLANET WHICH HAS IMPORTANT IMPLICATIONS FOR THE ORIGIN AND EVOLUTION OF ICE GIANTS. THE WORK IS LARGELY THEORETICAL IN NATURE AND CONTAINS NO DATA-ANALYSIS COMPONENT. AS SUCH THE PROPOSAL IS MOST RELEVANT TO THE NASA SOLAR SYSTEM WORKINGS PROGRAM WHOSE "CALL SEEKS TO ADDRESS THE PHYSICAL AND CHEMICAL PROCESSES THAT AFFECT THE... ATMOSPHERES... OF PLANETARY BODIES." · GrantIndex