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Wm. R. Ward (Southwest Research Institute)
The formation of ~ km-sized planetesimals in the early solar nebula continues to be one of the more perplexing questions in cosmogony. Claims that gravitational instability is not a contributory mechanism has led to a default assumption of sticking in some accretion models, although this does not by itself constitute a solution. Unfortunately, further research on the possible role of collective gravitational behavior has been largely lacking in recent years. We are reexamining some features of the problem that have only received limited attention. Among these is the frictional destabilization of neutral modes in the particle sheet. These modes have wavelengths greater than the boundary layer thickness at the gas-particle interface, and may not be inhibited by turbulence. Some possible ramifications of this behavior to the process of planetesimal formation will be discussed.