REGOLITH FORMATION AND EVOLUTION IS FUNDAMENTAL TO EVERY SOLID OBJECT IN THE SOLAR SYSTEM. UNDERSTANDING HOW REGOLITH DEVELOPS IS CENTRALLY IMPORTANT TO UNRAVELING THE GEOLOGIC HISTORY OF PLANETARY BODIES AND THE EVOLUTION OF OUR SOLAR SYSTEM. THE THERMAL PROPERTIES OF THE REGOLITH ARE A CENTRAL COMPONENT IN SOLAR SYSTEM EXPLORATION. REMOTELY SENSED TEMPERATURES ARE ROUTINELY USED TO DERIVE THERMAL INERTIA AND ITS CONSTITUENT VALUE THERMAL CONDUCTIVITY FOR A VARIETY OF TARGETS: MARS MOONS ASTEROIDS AND COMETS. THESE VALUES ARE THEN USED TO INTERPRET THE REGOLITH S PHYSICAL STRUCTURE (GRAIN SIZE INDURATION BEDROCK EXPOSURE) WEATHERING PROCESSES VOLATILE STABILITY AND INSTABILITY AND EVEN THE ORBITAL DYNAMICS OF SMALLER BODIES. THEREFORE IT IS ESSENTIAL TO HAVE A STRONG UNDERSTANDING OF THE RELATIONSHIP BETWEEN THESE REGOLITH CHARACTERISTICS AND THE THERMAL SIGNATURES THAT REVEAL THEM. PREVIOUS QUANTITATIVE EFFORTS TO UNDERSTAND THESE SIGNATURES HAVE FOCUSED ON MEASUREMENTS OF MONO-DISPERSED (SINGLE-SIZED) PARTICLES. WHILE PROVIDING VALUABLE INSIGHT NATURAL REGOLITH TYPICALLY EXHIBITS A RANGE OF GRAIN SIZES OFTEN WITH SUPERPOSED PEAK OR MODAL SIZES REFLECTIVE OF COMPETING WEATHERING PROCESSES. WHAT FEW STUDIES THAT HAVE EXPLORED THE THERMAL CONDUCTIVITY OF SIZE DISTRIBUTIONS WERE UNKNOWINGLY IMPAIRED BY THE USE OF THE TRANSIENT HEATED-WIRE METHOD WHICH DISTURBS MIXEDGRAIN PACKING AND CAN BIASES LARGER GRAINS WITHIN THE SAMPLE. TO EXPLORE THIS ISSUE WE CONDUCTED A PRELIMINARY STUDY USING A STANDARD GUARDED-HEAT-FLOW METHOD WHICH DOES NOT SUFFER THESE PROBLEMS. WE SHOWED THAT BIMODAL GRAIN SIZES HAVE A MARKEDLY DIFFERENT SIGNATURE THAN PREVIOUSLY THOUGHT. IN ADDITION MOST ASPECTS OF THE THERMAL CONDUCTIVITY OF GRAIN POPULATIONS VS. ENVIRONMENTAL CONDITIONS HAVE NEVER BEEN MEASURED IN THE LAB. WHILE OUR PILOT STUDY CLEARLY ILLUSTRATES THE IMPORTANCE OF MIXED GRAINS ON THERMAL CONDUCTIVITY IT FALLS WELL SHORT OF PROVIDING THE QUANTITATIVE DATA NEEDED TO FULLY TACKLE KEY SCIENCE PROBLEMS. THEREFORE I PROPOSE A RESEARCH PROGRAM FOCUSED ON CHARACTERIZING THE THERMAL CONDUCTIVITY OF UNIMODAL AND BIMODAL GRAIN-SIZE POPULATIONS. THESE MEASUREMENTS WILL HAVE BROAD REACHING APPLICATIONS TO GEOLOGIC STUDIES OF MARS AND AIRLESS BODIES IN THE SOLAR SYSTEM COMET EVOLUTION AND ASTEROID DYNAMICS. THE PROPOSE WORK WILL SPECIFICALLY FOCUS ON MEASUREMENT CAMPAIGNS INTENDED TO HELP TEST HYPOTHESES IN MARS AND ASTEROID GEOLOGY COMET ACTIVITY AND EVOLUTION AND ASTEROID DYNAMICS. FROM THESE MEASUREMENTS I WILL ADJUST EXISTING PREDICTIVE MODELS OF THE THERMAL CONDUCTIVITY OF GRANULAR MATERIALS TO FACILITATE THEIR EXTENSION TO A BROADER SET OF APPLICATIONS.