Low-velocity collision behaviour of clusters composed of sub-millimetre sized dust aggregates

Abstract

Context. The experiment results presented apply to the very first stages of planet formation, when small dust aggregates collide in the protoplanetary disc and grow into bigger clusters. In 2011, before flying on the REXUS 12 suborbital rocket in 2012, the Suborbital Particle and Aggregation Experiment (SPACE) performed drop tower flights. We present the results of this first microgravity campaign. Aims. The experiments presented aim to measure the outcome of collisions between sub-mm sized protoplanetary dust aggregate analogues. We also observed the clusters formed from these aggregates and their collision behaviour. Methods. The experiments were performed at the drop tower in Bremen. The protoplanetary dust analogue materials were micrometresized monodisperse and polydisperse SiO 2 particles prepared into aggregates with sizes between 120 µm and 250 µm. One of the dust samples contained aggregates that were previously compacted through repeated bouncing. During three flights of 9 s of microgravity each, individual collisions between aggregates and the formation of clusters of up to a few millimetres in size were observed. In addition, the collisions of clusters with the experiment cell walls leading to compaction or fragmentation were recorded. Results. We observed collisions amongst dust aggregates and collisions between dust clusters and the cell aluminium walls at speeds ranging from about 0

Unveiling Dust Aggregate Structure in Protoplanetary Disks by Millimeter-wave Scattering Polarization

“…Windmark et al (2012a) show that dust coagulation stalls at about 100 µm, which is also similar to the dust size expected from scattering polarization, although the dust size where coagulation stalls depends on disk properties, such as gas density, temperature, and turbulent strength. The dust evolution from a bouncing scenario seems to be consistent with that inferred from scattering polarization observa-tions; however, the onset of bouncing collisions is still a matter of debate (Wada et al 2011;Seizinger & Kley 2013;Kothe et al 2013;Brisset et al 2017), and hence, further studies are necessary to draw more robust conclusions.…”

Dust Evolution in Protoplanetary Discs and the Formation of Planetesimals

“…When the amount of energy dissipation during the collision is insufficient to allow sticking, but still not large enough to disrupt the colliding bodies (see below), the collisions result in bouncing. Bouncing was found in a variety of experimental investigations (Blum and Münch 1993;Heißelmann et al 2007;Weidling et al 2012;Kothe et al 2013;Landeck 2016;Brisset et al 2016Brisset et al , 2017. Although bouncing might seem to be important only for halting growth or stretching growth time scales, it turned out that bouncing collisions lead to the gradual compaction of dust aggregates.…”

“…identified three processes that lead to the complete transfer of both colliding bodies into a more massive dust aggregate, i.e., hit-and-stick behaviour for very small impact velocities, sticking with deformation/compaction of the aggregates, and deep penetration of a somewhat smaller projectile into a larger target aggregate. The supporting laboratory and microgravity experiments were performed by ; ; ; ; Krause and Blum (2004); Langkowski et al (2008); Weidling et al (2012); Kothe et al (2013); Weidling and Blum (2015); Brisset et al (2016Brisset et al ( , 2017; Whizin et al (2017). When colliding dust particles or aggregates are in the hit-and-stick regime (for which the impact energy is insufficient to cause rolling of the dust grains upon impact, see Dominik and Tielens (1997)), the corresponding aggregates develop a fractal morphology (Dominik and Tielens 1997;Kempf et al 1999;Krause and Blum 2004;Blum 2006), with a fractal dimension in the range D f ≈ 1.1 .…”

Fragmentación de planetesimales y formación planetaria

“…Güttler et al (2010) identificaron tres procesos, para velocidades bajas el impacto y adhesión, adhesión con deformación y/o compactación, y la penetración del proyectil en el blanco (e.g. Blum et al, 1998;Weidling et al, 2012;Kothe et al, 2013;Brisset et al, 2016Brisset et al, , 2017Whizin et al, 2017). Rebote: Cuando la energía de disipación durante la colisión no es suficiente para que se produzca la adhesión, pero no es tan grande como para generar la disrupción de los objetos que colisionan, el resultado es el rebote (e.g.…”

“…Rebote: Cuando la energía de disipación durante la colisión no es suficiente para que se produzca la adhesión, pero no es tan grande como para generar la disrupción de los objetos que colisionan, el resultado es el rebote (e.g. Blum & Münch, 1993;Kothe et al, 2013;Brisset et al, 2016Brisset et al, , 2017. A su vez, estos rebotes van compactando los agregados de polvo colisionantes.…”