A tale of pebble formation

Hauyu Baobab Liu  (National Sun Yat-sen University)

A complete model of planet formation needs to explain the co-existence of water/carbon deficient planets such as Earth and Mars and the icy giants such as Neptune and Uranus. This implies that we need to understand the coagulations of the water-ice-coated and water-ice-free dust grains. I will base on observational case studies to suggest that the water-ice-free dust grains in the innermost part of the protoplanetary disks can grow to larger than 1 mm size without being limited by the classical fragmentation/bouncing barrier. The coagulation of water-ice-coated dust seems to be limited by the fragmentation/bouncing barriers in general, while icy-pebble formation in some localized regions appears possible. While I do not yet have a good idea about the physical mechanism that promotes the formation of the icy-pebble, it seems to me that icy-pebble tends to show azimuthally asymmetric distributions.