THE OBJECTIVE OF THIS WORK IS TO UTILIZE THE HIGH RESOLUTION 26AL-26MG AND 53MN-53CR SHORT-LIVED CHRONOMETERS TO GAIN INSIGHT INTO THE TIMING OF DIFFERENTIATION AND CRYSTALLIZATION ON THE PARENT BODIES OF SELECTED ACHONDRITES. SPECIFICALLY THE PROPOSED INVESTIGATION FOCUSES ON TWO NEW ANGRITES AND TWO RECENTLY RECOVERED UNGROUPED ACHONDRITES. THE TWO ANGRITES PROPOSED TO BE STUDIED HERE REPRESENT NEW AND UNIQUE MEMBERS OF THIS SMALL BUT IMPORTANT GROUP OF ACHONDRITES SOME OF WHICH HAVE PREVIOUSLY SERVED AS KEY AGE ANCHORS FOR THE APPLICATION OF SEVERAL HIGH RESOLUTION CHRONOMETERS TO PROCESSES OCCURRING IN THE EARLY SOLAR SYSTEM. THE TWO UNGROUPED ACHONDRITES THAT WILL BE STUDIED ARE ADDITIONALLY IMPORTANT SINCE THEY REPRESENT PREVIOUSLY UNSAMPLED PARENT BODIES AND THUS PROVIDE THE OPPORTUNITY TO BROADEN OUR UNDERSTANDING OF PLANETESIMAL DIFFERENTIATION PROCESSES AND TIMESCALES IN THE EARLY SOLAR SYSTEM. FOR THE INVESTIGATIONS PROPOSED HERE WE WILL OBTAIN HIGH PRECISION INTERNAL 26AL-26MG AND 53MN-53CR ISOCHRONS FOR THESE SELECTED ACHONDRITES. TO ACHIEVE THIS WE HAVE RECENTLY DEVELOPED THE ANALYTICAL PROTOCOLS AND TECHNIQUES FOR HIGH PRECISION ISOTOPIC ANALYSES OF MG AND CR USING MULTICOLLECTOR INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY. THE PROPOSED RESEARCH BROADLY ADDRESSES OBJECTIVE 1.5 OF NASA S STRATEGIC PLAN: ASCERTAIN THE CONTENT ORIGIN AND EVOLUTION OF THE SOLAR SYSTEM AND THE POTENTIAL FOR LIFE ELSEWHERE. MORE SPECIFICALLY THE INVESTIGATIONS PROPOSED HERE ADDRESS ONE OF THE GOALS OF NASA S PLANETARY SCIENCE RESEARCH PROGRAM (DESCRIBED IN CHAPTER 4.3 OF NASA S 2014 SCIENCE PLAN) TO ADVANCE THE UNDERSTANDING OF HOW THE CHEMICAL AND PHYSICAL PROCESSES IN THE SOLAR SYSTEM OPERATE INTERACT AND EVOLVE .