Sticking and Bouncing of Pre-planetary Dust Grains

T. Poppe, J. Blum, L. O. Heim (University of Jena, Germany)

The first step of planet formation is thought to be the growth of micron-sized dust grains embedded in the dilute gas of the early solar nebula. Inelastic collisions driven by Brownian motion for the micron-sized pre-planetary dust particles and from differential sedimentation and gas drag-induced orbital decay for mm-sized dust aggregates result in the formation of planetesimals and cometesimals, which are large enough to continue the growth by gravitational attraction. While the state of the gas disk and the motion of the particles therein is comparatively well known, research on the collisional behavior of the dust grains and on the inter-particle forces is lacking. We investigated the sticking properties of small grains by simulation experiments with analogous materials. We will present results of individual grain-target collisions and of the measurement of inter-particle forces by atomic force microscopy and we will point out discrepancies between theoretical models and our measurements.