Growing beyond the meter barrier: Aggregation and fragmentation in single and multiple high-velocity collisions

An unsolved problem in collisional growth of planetesimals is the often-called meter-barrier. Models of protoplanetary disks suggest that meter sized bodies collide with smaller bodies at velocities of several tens of m/s. Forming planetesimals by collisions is only possible if collisions at high speed with mass gain win over destructive or eroding collisions. The laboratory experiments in the preceeding project showed that a typical decimeter body as progenitor to meter size bodies is a compact dust aggreate with a unique porosity. Collisions with such a compact dust aggregate suggest that sub-mm aggregates might add mass to a larger body at high speed even beyond 50m/s. However, projectiles larger than mm lead to erosion of a target. In detail, a fragmentation / coagulation model is a viable path to form larger bodies. For such a model the mass balance and fragment sizes for projectiles of varying parameters and for given collisions velocities are essential. The project aims at measuring the outcome of individual but especially multiple high speed collisions to model the growth of planetesimals to bridge the meter-barrier.

Principle Investigator

Dr. Gerhard Wurm