SCIENCE GOALS AND OBJECTIVES THE PRIMARY GOAL OF THE PROPOSED RESEARCH IS TO ACHIEVE A BETTER UNDERSTANDING OF THE DUST AGGREGATION STAGE OF PLANET FORMATION IN PROTOPLANETARY NEBULAE. A CRUCIAL STEP IN THE EARLIEST STAGES OF PLANET FORMATION IS THE GROWTH OF SOLID BODIES IN THE MILLIMETER TO METER SIZE RANGE BY THE AGGREGATION OF MILLIMETER- TO SUB-MILLIMETER-SCALE DUST GRAINS. THE PROCESS BY WHICH DUST AGGREGATED INTO PLANETESIMALS IS NOT WELL UNDERSTOOD; EXPERIMENTS WITHOUT THE EFFECTS OF GRAVITY ARE NEEDED TO INVESTIGATE IT. THE PRIMARY SCIENCE OBJECTIVES OF THE PROPOSED WORK ARE AS FOLLOWS: TO DETERMINING THE EFFECTS OF: (1) PARTICLE SIZE; (2) NUMBER DENSITY; AND (3) COMPOSITION ON THE AGGREGATION (ACCRETION) OF DUST-SCALE GRAINS IN MICROGRAVITY CONDITIONS. METHODOLOGY THE INVESTIGATION WOULD BUILD ON OUR PREVIOUS RECORD OF SUCCESSFUL MICROGRAVITY EXPERIMENTS WITH GRANULAR MATERIALS (LOVE ET AL. 2014) TO EXTEND THESE RESULTS TO ADDITIONAL MATERIALS AND PARTICLE CONTAINERS USING MORE ADVANCED METHODS AND ANALYSES. THE PROPOSED WORK FOCUSES THE BULK OF ITS EXPERIMENTAL INVESTIGATION ON GRANULAR MEDIA RELEVANT TO PROTOPLANETARY ENVIRONMENTS SUCH AS VARIOUS SILICATE MINERALS AND POWDERED ORDINARY AND CARBONACEOUS CHONDRITE MATERIALS. THE RESULTS OF THE PROPOSED WORK WOULD GREATLY CONSTRAIN PARTICLE AGGREGATION AND CLUSTER GROWTH IN THE EARLY PROTOPLANETARY DISK. RELEVANCE TO CALL THE SCOPE OF PROGRAM FOR EMERGING WORLDS INCLUDES "INVESTIGATIONS RELATED TO UNDERSTANDING THE FORMATION AND EARLY EVOLUTION OF OUR SOLAR SYSTEM". THIS PROPOSAL IS FOCUSED ON RESEARCH DIRECTED AT "PROTOPLANETARY DISK FORMATION AND EVOLUTION PHYSICAL PROCESSING OF DUST AND THE FORMATION AND ACCRETION OF SOLAR SYSTEM BODIES" BY CONDUCTING MICROGRAVITY EXPERIMENTS ON THE AGGREGATION OF MILLIMETER- TO SUB-MILLIMETER-SCALE GRAINS UNDER CONDITIONS RELEVANT TO THOSE IN THE EARLY PROTOPLANETARY NEBULA. THE PROPOSAL ALSO EXPLICITLY INVOLVES THE SUBSEQUENT ANALYSES AND PUBLICATION OF THESE EXPERIMENTAL DATA.