ROBUST LABORATORY ANALYSES OF METEORITIC AND RETURNED EXTRATERRESTRIAL MATERIALS ARE ESSENTIAL TO UNDERSTANDING SOLAR SYSTEM PROCESSES AND ARE PREREQUISITES TO HUMAN OR ROBOTIC EXPLORATION OF TARGET BODIES TO ENSURE MISSION SUCCESS. SUCH SAMPLES ARE LIMITED IN SIZE AND MASS. IT IS THUS CRITICALLY IMPORTANT TO MAXIMIZE SCIENCE RETURN FROM THESE MATERIALS USING NON-DESTRUCTIVE ANALYTICAL TECHNIQUES. ONE OF THE MOST IMPORTANT QUESTIONS RELATING TO PLANETARY MATERIALS IS THE ROLE PLAYED BY OXYGEN FUGACITY (FO2) WHICH CONSTRAINS THE EVOLUTION OF PLANETARY INTERIORS AS WELL AS POST-CRYSTALLIZATION PROCESSES. COMMON METHODS FOR CONSTRAINING FO2 MEASURE FE REDOX STATES USING MSSBAUER OR X-RAY ABSORPTION SPECTROSCOPIES (XAS). HOWEVER FE REDOX STATES ARE NOT PARTICULARLY SENSITIVE TO EXTREMELY REDUCED ENVIRONMENTS FOUND IN NUMEROUS PLACES IN OUR SOLAR SYSTEM INCLUDING THE MOON AND MANY TYPES OF METEORITES (E.G. CUMULATE EUCRITES LODRANITES DIOGENITES AND AUBRITES). FORTUNATELY OTHER MULTIVALENT ELEMENTS SUCH AS TI V CR AND MN CHANGE VALENCE STATES AT LOW FO2 VALUES AND MAY BE MORE DISCERNING AND USEFUL FOR SOLAR SYSTEM MATERIALS IF WELL CALIBRATED. CRYSTALLINE PHASES ARE COMMON IN MANY EXTRATERRESTRIAL MATERIALS AND MAY EXPERIENCE SLOW DIFFUSION RATES THAT MAKE THEM RESISTANT TO RESETTING FROM SUBSEQUENT PROCESSES. THEREFORE THEY MAY BE IDEAL RECORDERS OF MAGMATIC HISTORY. PYROXENE IN PARTICULAR SHOWS GREAT PROMISE AS A RECORDER OF FO2 VALUES BECAUSE IT TYPICALLY CONTAINS ALL THESE ELEMENTS AND IS UBIQUITOUS ON THE SURFACES OF TERRESTRIAL BODIES.