SCIENTIFIC GOALS AND OBJECTIVES: THE PROPOSED RESEARCH CONSISTS OF TWO TASKS THAT ADDRESS FUNDAMENTAL UNCERTAINTIES IN THE ABSOLUTE DURATION OF MAGMATIC ACTIVITY AND UNCERTAINTIES IN THE NATURE AND TIMING OF METAMORPHIC PROCESSES OPERATIVE IN THE HOWARDITE EUCRITE DIOGENITE (HED) PARENT BODY (ASTEROID 4 VESTA). TASK 1 WILL INVESTIGATE THE DURATION OF MAGMATISM AND THE DEEP-CRUSTAL THERMAL HISTORY OF ASTEROID 4 VESTA WITH HIGH-PRECISION UPB DATING OF PETROLOGICALLY AND GEOCHEMICALLY CHARACTERIZED ZIRCON IN BASALTIC EUCRITES AND A ZIRCON-BEARING DIOGENITE USING CHEMICAL ABRASION ISOTOPE-DILUTION THERMAL IONIZATION MASS SPECTROMETRY (CA ID-TIMS). TASK 2 WILL INVESTIGATE THE THERMAL EVOLUTION AND TIMING OF VOLATILE-RICH MATERIAL MOBILITY IN HEDS BY IN SITU U-TH-PB (THERMO)CHRONOLOGY OF CA-PHOSPHATE MINERALS USING LASER ABLATION INDUCTIVELY-COUPLED PLASMA MASS SPECTROMETRY (LA-ICPMS). THEY WILL ADDRESS THESE QUESTIONS: DID THE PERIOD OF LATE HEAVY BOMBARDMENT (~4.1-3.3 GA) AS OBSERVED ON THE MOON ALSO OCCUR ON THE EUCRITE PARENT BODY (4 VESTA AND ITS REMNANTS)? WHAT IS THE SIGNIFICANCE OF GLOBAL VERSUS DISCREET THERMAL EVENTS AFFECTING THE HED PARENT BODY? AND IS THE AGE OF VOLATILE-RICH VEINING IN EUCRITES EARLY (COEVAL WITH MAGMATISM) OR LATE (RELATED TO SUBSEQUENT THERMAL EVENTS)? BOTH TASKS WILL RELY HEAVILY ON EXISTING AND NEW PETROLOGICAL CHARACTERIZATIONS OF THE SAMPLES SELECTED FOR STUDY. THE PROPOSAL TEAM HAS THE EQUIPMENT AND EXPERTISE TO FACILITATE ALL ASPECTS OF THE PROPOSED RESEARCH INCLUDING ASSISTING IN THE MENTORING OF THE GRADUATE STUDENT. METHODS: TASK 1: ZIRCONIUM-RICH MINERALS WILL BE DOCUMENTED IN THE SAMPLES BY X-RAY CHEMICAL MAPPING OF POLISHED THIN/ THICK SECTIONS. PETROLOGIC IMAGING AND HIGH SPATIAL RESOLUTION (50 NM) EBSD ANALYSES WILL BE CONDUCTED TO SEARCH FOR EVIDENCE OF MICROSTRUCTURAL DAMAGE ASSOCIATED WITH SHOCK DEFORMATION RELATED TO IMPACT. IN SITU TRACE ELEMENT CONCENTRATION AND PRELIMINARY UTH- PB DATING OF 2-3 REPRESENTATIVE ZIRCON GRAINS FROM EACH SAMPLE WILL BE DONE BY LA-ICPMS HIGH-PRECISION U-PB DATES OF ZIRCON WILL BE OBTAINED THROUGH STATE-OF-THE-ART CHEMICAL-ABRASION ID-TIMS ANALYSES APPLIED TO SUCH INITIATIVES AS CALIBRATING THE GEOLOGICAL TIME SCALE GRADSTEIN ET AL. 2012). THE U ISOTOPIC COMPOSITION OF NWA 10666 WILL BE MEASURED BY MC-ICP-MS AT THE UNIVERSITY OF HOUSTON USING ESTABLISHED SAMPLE DIGESTION CHEMICAL SEPARATION AND U ISOTOPIC ANALYSES BY DOUBLE SPIKE (IRMM-3636). THE SAMPLE SOLUTIONS REMAINING AFTER U-PB CHEMISTRY OF DIGESTED ZIRCON CONTAIN THE LU AND HF FROM THE DIGESTED MINERALS WHICH CAN BE FURTHER PROCESSED FOR ISOTOPIC ANALYSES. TASK 2: PETROLOGIC CHARACTERIZATIONS OF SAMPLES WILL USE LIGHT AND E-BEAM IMAGING AND EPMA FOR CHEMICAL ANALYSES OF CONSTITUENT PHASES. U-TH-PB ISOTOPE ANALYSIS WITH PRECISIONS SIMILAR TO OR BETTER THAN THAT OF AN ION PROBE WILL BE USED TO DATE CA-PHOSPHATE MINERALS WITH VERY HIGH SPATIAL RESOLUTION (7-10 M). RELEVANCE: THE EMERGING WORLDS PROGRAM SEEKS PROPOSALS THAT ANSWER THE FUNDAMENTAL SCIENCE QUESTION OF HOW THE SOLAR SYSTEM FORMED AND EVOLVED AND EXPLORE AND OBSERVE THE OBJECTS IN THE SOLAR SYSTEM TO UNDERSTAND HOW THEY FORMED AND EVOLVE. THE PROPOSED STUDY IS RELEVANT TO THE EMERGING WORLDS PROGRAM IN THAT THEY ARE TRYING TO UNDERSTAND THE TIMING OF DIFFERENTIATION IN EARLY SOLAR SYSTEM BODIES AND THE TIMING OF FORMATION OF PLANETARY CRUSTS. IN THIS CASE THEY WILL INVESTIGATE THE TIMING OF IGNEOUS PROCESSES IN THE HED PARENT BODY. THEY ARE ALSO INVESTIGATING THE TIMING OF VOLATILE ADDITION TO THE INNER SOLAR SYSTEM AND THERMAL PROCESSES ASSOCIATED WITH IMPACT HEATING THAT OCCUR EARLY (PERHAPS COEVAL WITH IGNEOUS ACTIVITY).