The role of porosity in collisions between micrometer-sized aggregates: Fragmentation or agglomeration?

PLANES, MARÍA BELÉN; MILLAN, E. N.; URBASSEK, HERBERT M; BRINGA, EDUARDO

Antofagasta

Congreso; Latin American Regional Meeting of the IAU; 2019

IAU

Collisions between agglomerates of micrograins can lead to fragmentation or agglomeration, allowing the formation of larger bodies, for instance in protoplanetary disk evolution. Previous studies have proposed that the fundamental parameters involved are the mass ratio between the colliding agglomerates (μ) and their impact velocity (v) [Blum & Wurm, Annu. Rev. Astron. Astrophys. 46:21-56 (2008); Whizin et al., ApJ 836:94-102 (2017)]. However, in experimental studies the porosity (p) is difficult to specify.In this work, numerical simulations were carried out for collisions between μm-sized agglomerates composed of silica grains, varying v and p. Projectile and target have the same p, and μ remains constant. For collisions between the most porous agglomerates, the fragmentation velocity threshold decreases more than one order of magnitude with respect to previous work, demonstrating that p is a relevant factor which should be taken into account in models of planetesimal formation.