This view shows the scene in the region of the earth less than a million years after the sun formed. Small grains of dust are aggregating into "planetesimals". The planets grew by collisional aggregation of these planetesimals. Scientists at PSI have developed the most advanced and detailed theoretical computer models to represent the processes by which dust and asteroid-like particles aggregated to form the planets of our solar system, and perhaps those of other solar systems as well. Painting © William K. Hartmann