Stanley G. Love¹, Donald R. Pettit¹ and Scott R. Messenger²

¹NASA Lyndon B. Johnson Space Center, Houston, Texas, USA
²Robert M. Walker Laboratory for Space Science, Astromaterials Research and Exploration Science Directorate, NASA Lyndon B. Johnson Space Center, Houston, Texas, USA

We conducted experiments in space to investigate the aggregation of millimeter- and submillimeter-sized particles in microgravity, an important early step in planet formation. Particulate materials included salt (NaCl), sugar (sucrose), coffee, mica, ice, Bjurböle chondrules, ordinary and carbonaceous chondrite meteorite fragments, and acrylic and glass beads, all triply confined in clear plastic containers. Angular submillimeter particles rapidly and spontaneously formed clusters strong enough to survive turbulence in a protoplanetary nebula. Smaller particles generally aggregated more strongly and quickly than larger ones. We observed only a weak dependence of aggregation time on particle number density. We observed no strong dependence on composition. Round, smooth particles aggregated weakly or not at all. In a mixture of particle types, some phases aggregated more readily than others, creating selection effects that controlled the composition of the growing clumps. The physical process of aggregation appears to be electrostatic in nature.

Reference
Love SG, Pettit DR and Messenger SR (in press) Particle aggregation in microgravity: Informal experiments on the International Space Station. Meteoritics & Planetary Science
[doi:10.1111/maps.12286]
Published by arrangement with John Wiley & Sons

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