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IN THIS PROPOSAL WE WILL EXPLORE THE INTERTWINED DYNAMICS OF THE PLANETS THEIR SATELLITES AND SMALL BODIES IN THE INNER SOLAR SYSTEM. OUR GOAL IS TO PRODUCE A SELF-CONSISTENT PICTURE OF THE INNER SOLAR SYSTEM'S EVOLUTION IN THE FIRST FEW TENS AND HUNDREDS OF MYR BEFORE IT REACHED ITS PRESENT DYNAMICAL CONFIGURATION. HUNGARIA ASTEROID GROUP IS A SLOWLY ERODING REMNANT OF A MUCH-LARGER INITIAL POPULATION WHICH WAS LIKELY RESPONSIBLE FOR THE LATE HEAVY BOMBARDMENT OF THE MOON (CUK 2012 BOTTKE ET AL. 2012). HOWEVER THERE IS STILL A FACTOR OF A FEW SHORTFALL BETWEEN THE PROJECTED NUMBERS OF PROTO-HUNGARIAS COMPARED TO LUNAR IMPACTORS 3.9 GYR AGO. HERE WE PROPOSE TO USE RECENT RESULTS OF CUK&NESVORNY (2018) ON THE SENSITIVE DEPENDENCE OF HUNGARIAS' STABILITY ON MARTIAN ECCENTRICITY AND TEST IF AN EXCESS OF LATE LUNAR IMPACTS COULD BE DUE TO LOW INITIAL ECCENTRICITY OF MARS WHICH RELAXED TO THE PRESENT STATE OVER THE FIRST FEW HUNDREDS OF MYR AFTER MARS' FORMATION. IN TASK 1 WE WILL USE NUMERICAL SIMULATIONS TO STUDY THE EVOLUTION OF A PRIMORDIAL MARS-CROSSER POPULATION THAT EVOLVES INTO HUNGARIAS IN THE PRESENCE OF CHAOTICALLY CHANGING ORBIT OF MARS. IN TASK 2 WE WILL COMPARE DIFFERENT REALIZATIONS OF THE EARLY SOLAR SYSTEM WITH VARYING TIME-HISTORIES OF MARS IN TERMS HOW THEY WOULD BE REFLECTED IN THE EARLY LUNAR RECORD. WE WILL BUILD ON RECENT WORK OF CO-I MINTON AND HIS COLLABORATORS AT PURDUE WHO HAVE DEVELOPED NEW MODELS THAT START WITH AN IMPACTOR POPULATION AND SHOW A VARIETY OF IMPACTS RECORDS THAT CAN RESULT FROM STOCHASTIC BOMBARDMENT BY THIS POPULATION. OUR GOAL IS TO IDENTIFY MODELS OF EARLY DYNAMICS OF TERRESTRIAL PLANETS AND PROTO-HUNGARIAS THAT ARE CONSISTENT WITH THE AVAILABLE CONSTRAINTS FROM THE MOON INCLUDING BASIN AND CRATER NUMBERS THEIR RELATIVE CHRONOLOGY AS WELL AS FORMATION TIME FOR THE IMBRIUM BASIN 3.9 GYA. IN TASK 3 WE WILL MODEL THE 2-DEGREE ORBITAL INCLINATION THAT THE MARTIAN MOON DEIMOS SHOULD HAVE OBTAINED FROM ENCOUNTERS WITH PASSING PLANETESIMALS A MECHANISM PREVIOUSLY PROPOSED FOR IAPETUS (NESVORNY ET AL. 2014) AND THE MOON (PAHLEVAN&MORBIDELLI 2015). USING DIRECT NUMERICAL METHODS AND A REALISTIC MODEL OF THE LATE PLANETESIMAL POPULATION WE WILL QUANTIFY THE AMOUNT OF ORBITAL EXCITATION THAT CAN BE EXPECTED FOR DEIMOS FROM PASSING PLANETESIMALS THAT WOULD NOT AT THE SAME TIME DISRUPT DEIMOS AND ERASE THE ORBITAL INCLINATION. WE WILL USE THE LUNAR CRATERING RECORD TO CONSTRAIN THE SIZE-DISTRIBUTION OF PLANETESIMALS AND THEIR FRAGMENTS. PAHLEVAN AND MORBIDELLI (2015) HAVE SHOWN THAT PLANETESIMAL ENCOUNTERS CAN IN SOME CASES PRODUCE THE OBSERVED LUNAR INCLINATION. HOWEVER THEIR LUNAR ORBITAL EVOLUTION MODEL WAS NOT SELF-CONSISTENT AND MAY VIOLATE CONSTRAINTS FROM LUNAR ECCENTRICITY. IN TASK 4 WE WILL REVISIT THIS ISSUE AND WE WILL ALSO INTRODUCE FLY-BYS INTO THE TIDAL EVOLUTION SCENARIOS OF CUK&STEWART(2012) TIAN&WISDOM(2016) AND CUK ET AL.(2016) WHICH ALL ACHIEVE ANGULAR MOMENTUM (AM) LOSS BY THE MOON SPENDING SOME TIME IN RESONANT NEAR-RESONANT OR EQUILIBRIUM-STATE ORBITS WHICH MAY BE UNSTABLE AGAINST "KICKS" FROM PLANETESIMAL FLYBYS. VENUS IS IN A VERY SLOW RETROGRADE ROTATION AND MODELS REQUIRE AN INITIAL ROTATION PERIOD>40 HR IF VENUS WAS SPUN DOWN BY SOLAR TIDES. IN TASK 5 WE WILL EXPLORE A POSSIBILITY THAT VENUS HAD A SATELLITE AND A HIGH OBLIQUITY (80-100 DEGREES) WHICH WOULD LEAD TO A RAPID EARLY AM TRANSFER TO HELIOCENTRIC ORBIT DUE TO LAPLACE PLANE INSTABILITY (TREMAINE ET AL. 2009 CUK ET AL. 2016). WE WILL ALSO EXPLORE LARGE SWINGS IN OBLIQUITY THAT ARE EXPECTED FROM PLANETARY PERTURBATIONS ONCE VENUS HAS BEEN PARTIALLY DESPUN AND A RELATIVELY SMALL MOON HAS EVOLVED OUTWARD. RESULTING LARGE AND CHAOTICALLY CHANGING MUTUAL INCLINATION BETWEEN THE MOON AND THE PLANET'S SPIN WOULD LEAD TO FURTHER AM DRAIN. WE WILL EXPLORE A RANGE OF INITIAL CONDITIONS TO DETERMINE IF THE DRASTIC AM LOSS AS OBSERVED FOR VENUS IS A COMMON DYNAMICAL OUTCOME.

$336,104FY2020National Aeronautics and Space AdministrationNASA

Seti Institute, Mountain View CA

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