Growth and form of planetary seedlings: Results from a microgravity aggregation experiment

The outcome of the first stage of planetary formation, which is characteriz ed by ballistic agglomeration of preplanetary dust grains due to Brownian m otion in the free molecular flow regime of the solar nebula, is still somew hat speculative. We performed a microgravity experiment flown onboard the s pace shuttle in which we simulated, for the first time, the onset of free p replanetary dust accumulation and revealed the structures and growth rates of the first dust agglomerates in the young solar system. We find that a th ermally aggregating swarm of dust particles evolves very rapidly and forms unexpected open-structured agglomerates.