E014042 SCIENTIFIC GOALS AND OBJECTIVES: JUPITER'S MOON EUROPA IS THOUGHT TO POSSESS A SUBSURFACE OCEAN BENEATH AN ICE SHELL THAT IS LIKELY BETWEEN 5 AND 30 KILOMETERS THICK YET NUMEROUS OBSERVATIONS SUGGEST THAT POCKETS OF MELT MAY BE PRESENT ONLY 1 TO 2 KM BENEATH THE SURFACE. CHAOS TERRAIN AND DOUBLE RIDGES MAY BOTH FORM IN RESPONSE TO NEAR-SURFACE WATER BODIES THAT DEFORM THE SURFACE. NEAR-SURFACE MELT COULD BE SOURCED DIRECTLY FROM THE SUBSURFACE OCEAN OR COULD BE GENERATED LOCALLY BY TIDAL HEATING OR SHEAR-HEATING BENEATH TIDALLY-DRIVEN STRIKE-SLIP FAULTS. IN ADDITION TO PLAYING A PROFOUND ROLE IN THE GEOLOGIC EVOLUTION OF EUROPA NEAR-SURFACE MELT BODIES COULD BE POTENTIALLY HABITABLE ENVIRONMENTS AND THE MIGRATION OF NEAR-SURFACE MELT COULD ALLOW FOR CHEMICAL EXCHANGE BETWEEN THE SURFACE AND SUBSURFACE OCEAN. WHILE MANY GEOLOGIC OBSERVATIONS STRONGLY SUGGEST THE PRESENCE OF NEAR-SURFACE MELT PHYSICAL MODELS FOR HOW NEAR-SURFACE MELTS ARE GENERATED FACE MANY CHALLENGES. MELTS WOULD BE THERMALLY AND GRAVITATIONALLY UNSTABLE AND COULD QUICKLY FREEZE OR MIGRATE DOWN TOWARD THE OCEAN. A MORE ROBUST PHYSICAL MODEL IS REQUIRED TO DEEPEN OUR UNDERSTANDING OF NEAR-SURFACE MELT BODIES ONE THAT SELF-CONSISTENTLY TREATS TIDAL DEFORMATION EUTECTIC MELTING MELT-MIGRATION AND ICE SHELL CONVECTION. UNDERSTANDING THE DYNAMICS OF NEAR-SURFACE MELT FEATURES INCLUDING THEIR SIZE DISTRIBUTION LONGEVITY AVERAGE MELT FRACTION AND SALINITY IS ESSENTIAL FOR BUILDING OUR UNDERSTANDING OF EUROPA S EVOLUTION AND TO INTERPRETING DATA COLLECTED AT EUROPA BY FUTURE SPACECRAFT. IN ORDER TO ADDRESS OUTSTANDING QUESTIONS ABOUT THE FORMATION AND EVOLUTION OF NEAR-SURFACE MELTS WE WILL: 1) INVESTIGATE FEEDBACKS BETWEEN TIDAL HEATING FAULT SLIDING AND MELT GENERATION ALONG STRIKE-SLIP FAULTS 2) ESTIMATE THE RATE OF DOWNWARD MIGRATION BY POROUS FLOW AND HYDROFRACTURE 3) INVESTIGATE THE EVOLUTION OF PERCHED BODIES OF WATER AND ASSOCIATED ICE BLISTERS ON ANTARCTIC ICE SHELVES CALLED DOLINES TO PLACE CONSTRAINTS ON THE DYNAMICS OF PERCHED MELTS ON EUROPA. METHODOLOGY: WE WILL DEVELOP A NUMERICAL MODEL TO EXPLORE THE COUPLED PROCESSES OF TIDAL/SHEAR HEATING MELT GENERATION MELT MIGRATION AND MELT-FRACTURE INTERACTION IN EUROPA S ICE SHELL. WE WILL BUILD ON OUR EXISTING TWO-DIMENSIONAL FINITE ELEMENT CODES IN MATLAB AND COMSOL. OUR TREATMENT OF MELT MIGRATION WILL BE INFORMED BY STUDIES OF THE EVOLUTION OF SEA-ICE MELT MIGRATION IN TERRESTRIAL MAGMA CHAMBERS AND THE DRAINAGE OF SUPRA-GLACIAL LAKES THROUGH CREVASSES. USING OUR NUMERICAL MODEL WE WILL MAKE QUANTIFIED PREDICTIONS ON THE LONGEVITY SPATIAL EXTENT MELT FRACTION AND SALINITY IN POSSIBLE NEAR-SURFACE MELT BODIES ON EUROPA. WE WILL PLACE CONSTRAINTS ON THE HEATING RATES SLIDING RATES AND PERMEABILITIES REQUIRED TO GENERATE AND MAINTAIN NEAR SURFACE MELTS. BY TRACKING THE MOVEMENT OF SALTS THROUGH THE ICE SHELL WE WILL ALSO BUILD AN UNDERSTANDING OF HOW THE CHEMICAL EVOLUTION OF THE ICE SHELL COUPLES WITH GEOLOGIC ACTIVITY. RELEVANCE OF THE PROPOSED RESEARCH: THE PROPOSED WORK WILL FURTHER OUR UNDERSTANDING OF THE MYRIAD OF GEOLOGICAL PROCESSES AFFECTING THE SOLAR SYSTEM BY PLACING CONSTRAINTS ON HOW NEAR-SURFACE MELT FEATURES ON EUROPA LIKELY FORM AND EVOLVE. OUR STUDY WILL SHED LIGHT ON HOW GEOLOGIC PROCESSES ON EUROPA MAY DIFFER FROM OTHER ICY BODIES SUCH AS ENCELADUS. OUR PREDICTIONS WILL ALSO BE EXTREMELY RELEVANT TO THE UPCOMING EUROPA CLIPPER MISSION AS CONSTRAINTS ON THE SIZE AND MELT FRACTION OF NEAR-SURFACE MELT BODIES IS PARTICULARLY IMPORTANT FOR THE RADAR INSTRUMENT.$36,797
· FY2022 · National Aeronautics and Space Administration