THE OVERARCHING GOAL OF THE PROPOSED WORK IS TO PROVIDE HIGH-RESOLUTION CONSTRAINTS ON THE PROVENANCE OF MATERIAL COMPRISING THE SOLAR NEBULA. SPECIFICALLY WE WILL OBTAIN SIDEROPHILE ELEMENT CHEMICAL/ISOTOPE DATA FROM METEORITES CHEMICAL DATA FROM HIGH PRESSURE/TEMPERATURE EXPERIMENT PRODUCTS AND GENERATE ASTROPHYSICAL MODELS UPDATING PATHWAYS OF TC ISOTOPE NUCLEOSYNTHESIS AND INTRODUCTION TO THE SOLAR NEBULA TO ADDRESS THE LONG-STANDING QUESTION OF WHETHER THERE IS DIRECT EVIDENCE OF TC IN THE EARLY SOLAR SYSTEM? WE TAKE A THREE-PRONGED APPROACH IN THIS PROJECT: (1) ISOTOPIC AND CHEMICAL ANALYSIS OF METEORITES (SUB-TASKS 1 AND 2): OBTAINING BOTH MO AND RU ISOTOPE COMPOSITION DATA AND MO AND HSE (HIGHLY SIDEROPHILE ELEMENT) CONCENTRATION DATA WILL ALLOW FOR POTENTIAL DETECTION OF RADIOGENIC DAUGHTER PRODUCTS OF TC ISOTOPE DECAY (E.G. 97MO* 98RU* AND 99RU*) CHARACTERIZATION OF THE SAMPLES AND CONSTRAINTS TO BE PLACED ON THE DEGREE OF CHEMICAL FRACTIONATION IN THE ELEMENTS OF INTEREST. WE WILL OBTAIN THESE DATA FROM A RANGE OF COSMOCHEMICAL MATERIALS (E.G. CAIS ACHONDRITES AND IRON METEORITES) TO BETTER DETERMINE THE TC ISOTOPE INITIAL ABUNDANCES (9XTC0) IN THE SOLAR SYSTEM. (2) TC PARTITION EXPERIMENTS BETWEEN LIQUID METAL-LIQUID SILICATE AT HIGH PRESSURE AND TEMPERATURES (SUB-TASK 3): BECAUSE AN ESTIMATE OF CHEMICAL FRACTIONATION BETWEEN TC/MO AND TC/RU IS DESIRABLE TO INTERPRETING THE ISOTOPE DATA A PILOT STUDY IN COLLABORATION WITH DR. ELIZABETH COTTRELL (SMITHSONIAN INSTITUTION NATIONAL MUSEUM OF NATURAL HISTORY NMNH) WILL SEE THE COLLECTION OF PARTITIONING DATA ON TC/MO AND TC/RU FRACTIONATION DURING METAL-SILICATE FRACTIONATION. THE GOAL OF THIS TASK IS TO IDENTIFY AN ELEMENTAL PROXY FOR 2 TC IN SOLID EARTH (METAL/SILICATE) SYSTEMS AT HIGH PRESSURES AND TEMPERATURES AND TO UNDERSTAND HOW THE PROCESS OF CORE FORMATION (METAL SEGREGATION) IN PLANETS MAY FRACTIONATE TC FROM MO RU AND RE. IN SERVICE OF THIS GOAL WE WILL SET-UP A WORKSPACE AND WORKFLOW FOR EXPERIMENTS ON RADIOACTIVE 99TC AT NMNH. WE WILL CONDUCT EXPERIMENTS TO (A) CREATE METAL AND GLASS STANDARDS FOR TC (B) TO DETERMINE TC S SOLUBILITY IN SIMPLE SILICATE MELT AS A FUNCTION OF TEMPERATURE (C) TO DETERMINE PARTITIONING OF TC RELATIVE TO MO RE AND POSSIBLY RU BETWEEN LIQUID-METAL AND LIQUID-SILICATE. (3) ASTROPHYSICAL MODELLING OF TC SYNTHESIS AND INTRODUCTION MECHANISMS TO THE SOLAR SYSTEM (SUBTASK 4): THE REFINED 9XTC0 DATA WILL BE INCORPORATED INTO MODELS OF TC NUCLEOSYNTHESIS TO ADDRESS QUESTIONS OF TC ISOTOPE SYNTHESIS AND INTRODUCTION INTO THE SOLAR SYSTEM IN COLLABORATION WITH PROF. BRADLEY MEYER (CLEMSON UNIVERSITY). THE PROPOSED WORK WILL PROVIDE THE HIGHEST RESOLUTION CONSTRAINTS ON 9XTC0 BY VIRTUE OF THE IMPROVED LEVELS OF ANALYTICAL PRECISION OBTAINABLE USING N-TIMS AND THE NEW CHEMICAL CONSTRAINTS FROM THE PROPOSED PARTITIONING EXPERIMENTS.