Collisional evolution is a key process in planetesimal formation and decimeter bodies play a key role in the different models .
However , the outcome of collisions between two dusty decimeter bodies has never been studied experimentally .
Therefore , we carried out microgravity collision experiments in the Bremen drop tower .
The agglomerates consist of quartz with irregularly shaped micrometer-sized grains and the mean volume filling factor is 0.437 \pm 0.004 .
The aggregates are cylindrical with 12 cm in height and 12 cm in diameter and typical masses are 1.5 kg .
These are the largest and most massive dust aggregates studied in collisions to date .
We observed rebound and fragmentation but no sticking in the velocity range between 0.8 and 25.7 cm s ^ { -1 } .
The critical fragmentation velocity for split up of an aggregate is 16.2 \pm 0.4 cm s ^ { -1 } .
At lower velocities the aggregates bounce off each other .
In this velocity range , the coefficient of restitution decreases with increasing collision velocity from 0.8 to 0.3 .
While the aggregates are very weak , the critical specific kinetic energy for fragmentation Q _ { \mu = 1 } is a factor six larger than expected .
Collisions of large bodies in protoplanetary disks are supposed to be much faster and the generation of smaller fragments is likely .
In planetary rings collision velocities are of the order of a few cm s ^ { -1 } and are thereby in the same range investigated in these experiments .
The coefficient of restitution of dust agglomerates and regolith covered ice particles , which are common in planetary rings , are similar .