THIS PROPOSAL SEEKS TO REFINE UNDERSTANDING OF THE FUNDAMENTAL PROCESSES INVOLVED IN ACCRETION AND DIFFERENTIATION OF THE MOON AND ASTEROIDS. THREE QUESTIONS WILL BE ADDRESSED ALL TARGETED AT THE EARLIEST STAGES OF PLANETESIMAL AND PLANET FORMATION:. 1. HOW AND WHEN WERE INDIGENOUS HIGHLY SIDEROPHILE ELEMENTS (HSE: OS IR RU RH PT PD RE AU) SET IN THE MOON AND ASTEROIDAL BODIES AND WHAT ARE THE DISTRIBUTIONS OF THESE ELEMENTS WITHIN THE SILICATE MANTLES OF THESE BODIES? .2. WHAT ARE THE RELATIVE TIMINGS OF METAL-SILICATE EQUILIBRIUM TO DEFINE CORE FORMATION AND THE ONSET OF POST-CORE FORMATION LATE ACCRETION AND CAN DIFFERENTIATED METEORITES BE LINKED TO SOME IRON METEORITE GROUPS? .3. WERE VOLATILE ELEMENTS LOST DURING PLANETESIMAL DIFFERENTIATION AND WHAT ARE THE POTENTIAL COLLATERAL EFFECTS OF 'DRYING OUT' OF SMALL PLANETESIMALS ON THE GROWTH AND VOLATILE INVENTORIES OF LARGER PLANETS? ..THESE QUESTIONS WILL BE INVESTIGATED THROUGH FOUR INTER-RELATED TASKS USING RE-OS RB-SR AND ZN ISOTOPES HSE AND TRACE ELEMENT ABUNDANCES AND PETROGRAPHY AND MINERAL CHEMISTRY OF METEORITES AND APOLLO SAMPLES. THE TASKS ADDRESS THE 'EARLY EVOLUTION OF THE SOLAR SYSTEM' AND ARE DIRECTLY RELEVANT TO THE EMERGING WORLDS PROGRAM. .. TASK 1 IS DESIGNED TO MORE FULLY CHARACTERIZE THE ZN AND OS ISOTOPE AND HSE ABUNDANCE COMPOSITION OF THE MOON. THIS TASK WILL INCLUDE STUDY OF FERROAN ANORTHOSITES AND MAGNESIAN SUITE ROCKS TO ASSESS PRISTINITY USING OS ISOTOPES AND HSE ABUNDANCES AND THEN TO USE THIS FILTER TO REFINE DETERMINATION OF THE INDIGENOUS HSE COMPOSITION OF THE LUNAR CRUST AND WHETHER IT IS HETEROGENEOUS WITH RESPECT TO THESE ELEMENTS. THESE RESULTS WILL BE IMPORTANT FOR DETERMINING VOLATILE AND SIDEROPHILE ELEMENT BEHAVIOR DURING LUNAR DIFFERENTIATION AND AS A BASELINE FOR INDIGENOUS HSE ABUNDANCES IN THE LUNAR CRUST.. TASK 2 WILL INVOLVE STUDY OF LUNAR "MANTLE" DERIVED MATERIALS INCLUDING MARE BASALTS AND VOLCANIC GLASSES. THE NEW DATA WILL BE USED TO ASSESS WHETHER THE HSE ARE HETEROGENEOUSLY DISTRIBUTED IN THE LUNAR MANTLE THROUGH COMPARISON OF APOLLO SITES. COMBINED ZN-HSE DATA WILL BE USED TO EVALUATE EFFECTS OF POST-CORE FORMATION LATE ACCRETION ON MANTLE SOURCE SIDEROPHILE-VOLATILE INVENTORIES. WE WILL ALSO SEEK TO ADDRESS WHETHER SOME MAGMATIC MATERIALS MIGHT REFLECT DERIVATION FROM A PRIMORDIAL VOLATILE-RICH LUNAR MANTLE SOURCE.. TASK 3 WILL EXAMINE HOW INDIGENOUS HSE AND VOLATILE ELEMENT ABUNDANCES WERE SET IN DIFFERENTIATED ASTEROIDAL BODIES. WE WILL EXTEND THE NEW 'PRISTINITY' INDEX THAT WE HAVE DEVELOPED FOR EUCRITES BY ANALYSIS OF MORE EUCRITE AND DIOGENITE SAMPLES TO EVALUATE THE FORMATION AND DEVELOPMENT OF THE HOWARDITE-EUCRITE-DIOGENITE PARENT BODY AND EXPAND THESE PRINCIPLES TO ANGRITE METEORITES. A PRISTINITY INDEX IS FUNDAMENTAL TO DETERMINING WHICH SAMPLES PRESERVE EVIDENCE FOR THE EARLIEST PHASES OF FORMATION OF A PARENT BODY AND FOR PROVIDING A CHRONOLOGICAL FRAMEWORK FOR UNDERSTANDING PLANETARY ACCRETION AND DIFFERENTIATION PROCESSES. THE WORK WILL ENABLE QUANTITATIVE ASSESSMENT OF SILICATE-METAL EQUILIBRIUM AND POST-CORE FORMATION ACCRETION ADDITIONS TO DIFFERENTIATED ASTEROIDS. THE DATA WILL ALSO BE USED TO ESTABLISH THE EXTENT AND CAUSE(S) OF VOLATILE-DEPLETION AS EVIDENT FROM ISOTOPICALLY 'HEAVY' ZN AND UNRADIOGENIC SR ISOTOPIC RATIOS IN SOME EUCRITES AND ANGRITES.. TASK 4 CONCERNS MEASUREMENT OF PRIMITIVE ACHONDRITE METEORITES INCLUDING FEO-RICH ACHONDRITE (E.G. BRACHINITE-LIKE) AND ACAPULCOITE-LODRANITE METEORITES USING HIGH-PRECISION OS AND HSE ABUNDANCES AS WELL AS NEW PETROLOGY AND GEOCHEMICAL TECHNIQUES. WE WILL EXAMINE THE PROCESSES OF METAL-SILICATE EQUILIBRIUM AND HOW THIS AFFECTS ELEMENT DISTRIBUTIONS INCLUDING VOLATILE ELEMENT BEHAVIOR. THE DATA WILL BE USED TO EVALUATE TEMPORAL AND GENETIC LINKS WITH PRIMITIVE ACHONDRITES AND SOME IRON METEORITE GROUPS. .