THE ISOTOPE COMPOSITIONS OF SIDEROPHILE (IRON-LOVING) ELEMENTS (E.G. MO RU PD W RE OS IR PT) CONTAIN A RECORD OF THE PROCESSES THAT BUILT THE PARENT BODIES OF THE NUMEROUS ASTEROIDS SAMPLED BY IRON METEORITES AND CHONDRITES. THE HF-W CHRONOMETER ALLOWS THE PRECISE DETERMINATION OF THE TIME OF CHEMICAL DIFFERENTIATION OF THE EARLIEST-FORMED BODIES IN THE SOLAR SYSTEM. THE RESOLUTION WITH WHICH W ISOTOPE AGES CAN BE DETERMINED IS LIMITED BY THE EXTENT OF THE CORRECTION OF COSMOGENIC NEUTRON CAPTURE EFFECTS. HOW CLOSE IN TIMING WAS THE DIFFERENTIATION OF THE VARIOUS BODIES THAT LEAD TO FORMING IRON METEORITES AND CHONDRITIC METAL? IS CHONDRITIC METAL YOUNGER THAN THAT OF IRON METEORITES? NUCLEOSYNTHETIC ISOTOPIC ANOMALIES OF ELEMENTS HEAVIER THAN THE FE-PEAK (E.G. MO RU PD) REVEAL THAT METEORITES EXHIBIT DEFICITS IN THE S-PROCESS ISOTOPES RELATIVE TO THE EARTH. WE HAVE RECENTLY SHOWN THAT PD ISOTOPE ANOMALIES CORRELATED WITH MO-RU ISOTOPES EXHIBIT EVIDENCE THAT THE PRESOLAR CARRIERS OF THESE ANOMALIES HAVE BEEN MODIFIED BY THERMAL PROCESSING IN THE SOLAR SYSTEM. NEW MEASUREMENTS OF THE RU-MO SYSTEM SHOW DISTINCT GROUPINGS OF IRONS INTO THOSE ASSOCIATED WITH CARBONACEOUS CHONDRITES AND THOSE ASSOCIATED WITH THE ENSTATITE AND ORDINARY CHONDRITE CLASSES. HOW DOES PD FIT INTO THIS PICTURE? HOW WIDE SPREAD IS THE PD-MO CORRELATION IN METEORITES AND DOES IT REMAIN CONSTANT WHEN EXTRACTING THE CARRIERS BY ACID LEACHING OF PRIMITIVE CHONDRITES? RECENT WORK HAS REVEALED THE PRESENCE OF S-PROCESS EXCESSES OF OS ISOTOPES IN SOME UREILITES WHICH LIKELY OCCURRED WHEN THE CARRIERS OF THESE ANOMALIES UNDERWENT PROCESSING ON THE PARENT BODY OF THE UREILITES. DID THIS ALSO CREATE PD ISOTOPE ANOMALIES? WE PROPOSE THE FOLLOWING TASKS: TASK 1: ORIGIN OF NUCLEOSYNTHETIC ISOTOPE ANOMALIES IN THE PD AND OS ISOTOPIC ABUNDANCES IN METEORITES. WE PROPOSE TO SEARCH FOR CORRELATED PD-(MO-RU)-OS ANOMALIES IN UREILITES IRON METEORITES AND CHONDRITES. TASK 2: EARLY CHRONOLOGY OF THE SOLAR SYSTEM FROM W-RE-OS ISOTOPE ABUNDANCES IN METEORITES. WE PROPOSE TO EXPLOIT THE FACT THAT NEUTRON CAPTURE ON W ISOTOPES PRODUCES RE ISOTOPES WHICH WE MEASURE PRECISELY TO CORRECT THE COSMOGENIC EFFECTS AND OBTAIN HIGHER FIDELITY W ISOTOPE CHRONOLOGY OF IRONS. METHODOLOGY: THE PROPOSED TASKS WILL BE ACCOMPLISHED BY THE ANALYSIS OF THE ISOTOPIC COMPOSITIONS OF PD W RE AND PT BY MULTICOLLECTOR INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (MC-ICP-MS) AT FLORIDA STATE UNIVERSITY AND OF OS BY THERMAL IONIZATION MASS SPECTROMETRY (TIMS) WITH COLLABORATOR ALAN BRANDON AT THE UNIVERSITY OF HOUSTON. WE HAVE PUBLISHED METHODS FOR PD W RE OS AND PT ISOTOPE MEASUREMENTS USING THESE FACILITIES. THE MC-ICP-MS AT FSU IS UNDER THE CONTROL OF THE PI. COLLABORATOR THORSTEN KLEINE WILL PROVIDE PD CUTS FROM THEIR MO-RU STUDIES. RELEVANCE: THE PROPOSED STUDIES OF NUCLEOSYNTHETIC ANOMALIES AND REFINED HF-W GEOCHRONOLOGY HELP TO ANSWER THE STRATEGIC SCIENCE GOAL EXPLORE AND OBSERVE THE OBJECTS IN THE SOLAR SYSTEM [METEORITES PLANETS] TO UNDERSTAND HOW THEY FORMED AND EVOLVE . THE PROPOSED RESEARCH INVOLVES STUDIES OF CHEMICAL AND ISOTOPIC PROPERTIES OF PLANETARY MATERIALS AND STUDIES OF RADIOMETRIC AGES INCLUDING HF-W AND RE-OS AGES. NUCLEOSYNTHETIC ISOTOPE ANOMALIES INFORM US ABOUT THE CHEMISTRY OF EVENTS . . . RELEVANT TO THE FORMATION OF PLANETS SATELLITES AND MINOR BODIES AND TO THE EARLY HISTORY OF THESE BODIES . AS SUCH THE PROPOSED RESEARCH FALLS SQUARELY WITHIN THE SCOPE OF THE EMERGING WORLDS (EW) PROGRAM AT NASA.