Contact forces between sub-micrometer ice particles in protoplanetary environments
Final Report Abstract
In the colder regions of protoplanetary disks, ices are the dominant solids and dominate the surfaces of grains. Aim of the project was to quantify the sticking properties of such ice grains. In a number of different experiments and some numerical modeling the following results were obtained. The project provided data on sticking properties of CO2 ice for the first time. CO2 ice seems to equal silicates in strength. The project also provided new models for the velocity dependence for coefficients of restitution and fragmentation strengths and ways to measure tensile strength of weakly bound aggregates. Main result though is, that water ice grains are only as highly sticking as previously thought above 200 K temperature. At high temperatures, sintering is an important process to enhance the strength of ice contacts. Pull-off forces of rapidly sintered contacts studied followed a power law on grain size with power larger than 3 in contrast to an expected linear behavior for adhesive contacts. At temperatures of protoplanetary disks below 160 K, were water ice is stable, sticking is comparably weak and water ice is also not stickier than silicates are. Therefore, water ice is not promoting sticking in protoplanetary disks as previously thought at least in comparison to silicates of similar size. This strongly constrains models of planetesimal formation.
Publications
- Collisions of CO2 Ice Grains in Planet Formation, Astrophysical Journal, 818:16 1-10, 2016
G. Musiolik, J. Teiser, T. Jankowski, and G. Wurm
(See online at https://doi.org/10.3847/0004-637X/818/1/16) - Ice Grain Collisions in Comparison: CO2, H2O and their Mixtures, Astrophysical Journal, 827:63 1-5, 2016
G. Musiolik, J. Teiser, T. Jankowski, and G. Wurm
(See online at https://doi.org/10.3847/0004-637X/827/1/63) - Self-Sustained Recycling in the Inner Dust Ring of Pre-Transitional Disks, Astrophysical Journal, 829:111 1-13, 2016
T. Husmann, C. Loesche, and G. Wurm
(See online at https://doi.org/10.3847/0004-637X/829/2/111) - Analog Experiments on Tensile Strength of Dusty and Cometary Matter, Icarus, 296:110-116, 2017
G. Musiolik, C. de Beule, and G. Wurm
(See online at https://doi.org/10.1016/j.icarus.2017.05.009) - Sticking Properties of Ice Grains, in: EPJ Web of Conferences (Powders and Grains 2017), 140, 05007:1-4
M. Jongmanns, M. Kumm, G. Wurm, D. E. Wolf, and J. Teiser
(See online at https://doi.org/10.1051/epjconf/201714005007)
