PRINCIPAL INVESTIGATOR DOBRIC_A WILL PROVIDE OVERALL MANAGEMENT OF THIS WORK. DOBRIC_A WILL CARRY OUT ELECTRON-BEAM AND ION-BEAM MEASUREMENTS OF THE CARBONATE GRAINS IDENTI_ED IN ANTARCTIC MICROMETEORITES (AMMS). I WILL _NISH OBTAINING THE LAST DATA NECESSARY TO _NISH THE PROPOSED STUDY USING THE THE ION MICROPROBE (CAMECA IMS-1280) AT THE SCHOOL OF OCEAN EARTH SCIENCE AND TECHNOLOGY HAWAI`I INSTITUTE OF GEOPHYSICS AND PLANETOLOGY UNIVERSITY OF HAWAI`I AT M_ANOA. I WILL PERFORM 53MN{53CR MEASUREMENTS OF CARBONATES IDENTI_ED IN THE AMMS. COLLABORATOR KAZUHIDE NAGASHIMA WILL ASSIST IN ISOTOPIC MEASUREMENTS USING THE CAMECA IMS 1280. I WILL USE THE NEW ACQUIRED HYPERION II OXYGEN PLASMA ION SOURCE FOR THE IMS-1280. THIS SOURCE PROVIDES HIGHER BEAM DENSITY SMALLER MINIMUM SPOT SIZE BETTER BEAM STABILITY AND LONGER TIME BETWEEN MAINTENANCE THAT THE CURRENT DUO PLASMATRON SOURCE. THE PERFORMANCE OF THE HYPERION II SOURCE IS SIMILAR TO THAT FOR THE CS+ SOURCE THAT IS USED TO MEASURE OXYGEN AND OTHER ELEMENTS THAT MAKE NEGATIVE IONS. AFTER THE MANGANESE-CHROMIUM ISOTOPE MEASUREMENTS WE WILL PERFORM FIB/TEM STUDY TO UNDERSTAND THE CHEMISTRY AND TEXTURE OF THE CARBONATES IN DI_ERENT AMMS. WE WILL USE THE FEI TITAN3 G2 60-300 ?SU- PERSTEM? SCANNING TRANSMISSION ELECTRON MICROSCOPE. THIS IS A NASA-FUNDED INSTRUMENT FULLY OPERATIONAL INITS NEW LOCATION AT UH. THIS ABERRATION-CORRECTED (SCANNING) TRANSMISSION ELECTRON MICROSCOPE (S)TEM HAS A MONOCHROMATOR AND DUAL SPHERICAL ABERRATION CORRECTORS FOR THE PROBE AND IMAGE WHICH WILL ALLOW US TO OBSERVE OUR SAMPLES AT A SUB-NGSTRM SPATIAL RESOLUTION. WE WILL PREPARE MANUSCRIPTS FOR PUBLICATION.