Project P6: Collision properties of solids in debris disks at low to moderate impact velocities

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Debris disks form due to collisions among planetesimals in which the colliding bodies are partly fragmented. As the strength of the planetesimals and their fragments determines the size distribution, it is essential to study the collisional outcome of solids grown at the protoplanetary phase under the conditions of debris disks. Melting or sintering effects are rather unimportant for not too large planetesimals so that the colliding bodies should be aggregates of (sub-)micrometer-sized dust and ice particles, which are held together by van der Waals and dipole forces. We will investigate in the laboratory the collision physics of dust and ice aggregates formed at the protoplanetary phase under the conditions of debris disks. In particular, we will derive the onset velocity for fragmentation, the velocity at which the largest fragment equals half the mass of the colliding bodies, the size distribution of fragments as a function of impact velocity, and the mass-velocity correlation as well as the velocity-vector distribution of the fragments for dust and ice aggregates in the mm to dm size range. To achieve these goals, we will utilize existing experimental setups in the Braunschweig laboratory with which collision speeds between ~ 1 m/s and ~ 1000 m/s can be achieved. As a result, we will derive an empirical collision model for debris-disk dust and ice aggregates that will be directly usable in P1, P2, and P3. On top of that, we will also provide samples in a wide porosity range for P5 for further investigation of their optical properties.