WE PROPOSE TO CONDUCT A COMPREHENSIVE PETROLOGICAL AND GEOCHEMICAL STUDY OF THE UNDERSTUDIED MARTIAN POIKILITIC SHERGOTTITE METEORITES IN ORDER TO UNDERSTAND THEIR FORMATION THEIR LINKS WITH OTHER SHERGOTTITES AND MORE BROADLY THE EVOLUTION OF THE MARTIAN INTERIOR DURING THE AMAZONIAN. MARTIAN METEORITES ARE THE ONLY SOURCE MATERIAL FROM MARS AVAILABLE FOR STUDY WITH TERRESTRIAL LABORATORY PRECISION AND SPATIAL RESOLUTION. AS SUCH THEY REPRESENT A FUNDAMENTAL SUITE OF ROCKS FOR CONSTRAINING THE GEOLOGICAL HISTORY OF MARS. SHERGOTTITES THE MOST COMMON TYPE OF MARTIAN METEORITES ARE DIVIDED INTO THREE PETROLOGIC SUB-GROUPS: OLIVINEPHYRIC BASALTIC AND POIKILITIC. THE FOCUS OF THIS STUDY ARE THE POIKILITIC SHERGOTTITES. THEY ARE GABBROIC INTRUSIVE ROCKS THAT LIKELY REPRESENT A MAJOR LITHOLOGY OF THE MARTIAN CRUST. THE TERM POIKILITIC REFERS TO THEIR UNIQUE TEXTURE AMONGST THE MARTIAN METEORITES WHICH CONSISTS OF TWO DOMAINS (FIG. 1): (DOMAIN 1) LARGE PYROXENE GRAINS (OIKOCRYST GRAINS) WITH INCLUSIONS OF PREVIOUSLY CRYSTALLIZED MINERALS WHICH ARE FORMED EARLY IN THE MAGMA EVOLUTION AT THE BASE OF THE CRUST AND (DOMAIN 2) INTERSTITIAL MATERIAL ENCLOSING THESE LARGE GRAINS WHICH CRYSTALLIZED NEAR THE SURFACE AFTER ASCENT THROUGH THE CRUST. THESE TEXTURES ARE BELIEVED TO RESULT FROM SLOW MAGMA COOLING IN A DEEP RESERVOIR FOLLOWED BY RAPID COOLING LIKELY ASSOCIATED WITH EMPLACEMENT AS HYPABYSSAL OR VOLCANIC ROCKS. THE POIKILITIC SHERGOTTITES RECORD IN THEIR CHEMISTRY TWO GEOCHEMICAL RESERVOIRS ENRICHED AND INTERMEDIATE DEFINED BY THEIR INCOMPATIBLE ELEMENT COMPOSITIONS AND COMPOSITIONS OF RADIOGENIC SR ND AND HF ISOTOPES. THE TWO DOMAINS IN BOTH ENRICHED AND INTERMEDIATE POIKILITIC SHERGOTTITES ALLOW US TO INVESTIGATE THE EVOLUTION OF THEIR PARENTAL MAGMA FROM THE CRUST/MANTLE BOUNDARY TO SHALLOW LEVELS AS WELL AS POSSIBLE CRUSTAL CONTAMINATION. THE CURRENT MAJOR UNKNOWNS OF MARTIAN SHERGOTTITE MAGMATISM INCLUDE: THE RELATIONSHIP BETWEEN METEORITE TEXTURES AND THEIR CONDITIONS OF CRYSTALLIZATION MAGMA MANTLE/CRUSTAL INTERACTIONS PETROGENETIC CONNECTIONS (OR NOT) BETWEEN SHERGOTTITES AND ORIGIN OF SHERGOTTITE SOURCES. BECAUSE OF THE UNIQUE BIMODAL TEXTURE THEIR HIGH ABUNDANCES AND THEIR DIFFERENT SOURCE RESERVOIRS WE AIM TO USE THE POIKILITIC SHERGOTTITE METEORITES TO ADDRESS THESE KEY PROBLEMS THAT REMAIN CONTENTIOUS IN THE ORIGIN AND EVOLUTION OF SHERGOTTITE MAGMAS. WE WILL ADDRESS THESE ISSUES BY: (GOAL 1) INVESTIGATING FORMATION PROCESSES OF POIKILITIC SHERGOTTITES AND PETROGENETIC COMPARISON WITH OTHER SHERGOTTITES; (GOAL 2) CONSTRAIN PARENTAL MAGMA COMPOSITION OF POIKILITIC SHERGOTTITES ITS EVOLUTION AND POTENTIAL CRUSTAL CONTAMINATION; AND (GOAL 3) ASSESSING TIME OF FORMATION SPATIAL DISTRIBUTION AND SOURCES OF POIKILITIC SHERGOTTITES AND LINK WITH OTHER SHERGOTTITES. TO ACHIEVE THESE GOALS THE PROPOSED WORK WILL BE DIVIDED INTO THREE ANALYTICAL TASKS. THESE TASKS ARE EACH DESIGNED TO ADDRESS THE THREE MAJOR INVESTIGATIVE GOALS. TASK 1 A COMPREHENSIVE PETROLOGIC STUDY OF POIKILITIC SHERGOTTITES IS PLANNED WHICH INCLUDES DETAILED IN SITU MAJOR AND TRACE ANALYSIS OF MINERALS IN TEXTURAL DOMAINS 1 AND 2 IN ALL ENRICHED AND INTERMEDIATE POIKILITIC SHERGOTTITES (GOAL 1). TASK 2 CORRESPONDS TO MELT INCLUSIONS CHEMISTRY ANALYSES (GOAL 2). TASK 3 IS THE INVESTIGATION OF EJECTION AND CRYSTALLIZATION AGES AND SOURCE COMPOSITIONS USING HIGH PRECISION TECHNIQUES TO ANALYZE RADIOGENIC NOBLE GAS AND METAL ISOTOPES RESPECTIVELY (GOAL 3). THIS PROPOSAL IS RELEVANT TO THE SOLAR SYSTEM WORKINGS (SSW) PROGRAMS MAIN GOAL WHICH IS TO SUPPORT RESEARCH INTO ATMOSPHERIC CLIMATOLOGICAL DYNAMICAL GEOLOGIC GEOPHYSICAL AND GEOCHEMICAL PROCESSES OCCURRING ON PLANETARY BODIES SATELLITES AND OTHER MINOR BODIES (INCLUDING RINGS) IN THE SOLAR SYSTEM. BECAUSE THE PROPOSED RESEARCH WILL CONSTRAIN MARTIAN MAGMATIC PROCESSES AND EVOLUTION OF THE MARTIAN INTERIOR THROUGH METEORITE STUDIES.