Fragmentation threshold of icy dust aggregates

Determine the exact fragmentation velocity threshold for icy dust aggregates across the temperature conditions found in protoplanetary discs, in order to assess whether grains can grow to the Stokes numbers required for dust collapse.

Background

The paper explains that collisional velocities determine whether dust grains stick, bounce, or fragment, and that the fragmentation threshold depends on grain composition and temperature. Although icy aggregates have traditionally been assigned a higher fragmentation threshold than silicate aggregates, laboratory measurements indicate that the enhanced stickiness of water ice may apply only over a restricted temperature range.

Because the appropriate fragmentation threshold directly affects whether dust can grow to Stokes numbers of approximately 0.1–1—the regime identified as most favourable for gravitational collapse—the unresolved value introduces uncertainty into predictions of early planet formation in gravito-turbulent discs.