The crucial role of porosity in dust evolution in protoplanetary disks

In protoplanetary disks, pebble-sized solids form easily from micron-sized dust grains, but their subsequent growth to planetesimals is hindered by several barriers, such as radial drift or fragmentation. Grain porosity has been identified as a possible solution to help overcome these barriers. We present an improved model of the evolution of the porosity of dust aggregates as they grow, fragment, drift and settle, and apply it to numerical simulations of protoplanetary disks. We find that compaction during their fragmentation is crucial to obtain sizes and porosities comparable to those in observed disks. Finally, we show that the evolution of porous grains can produce large sections in the disks where the triggering conditions of the streaming instability, currently considered to be the best candidate mechanism to form planetesimals, are met.