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Particle growth in outer disks – the role of CO₂

Presentation #510.03 in the session Origins of Planetary Systems.

Published onOct 20, 2022
Particle growth in outer disks – the role of CO₂

The coagulation of micrometer-sized solid particles is the first step in planetesimal formation. While silicate dust is the predominant material in the inner regions of a protoplanetary disk, volatile compounds such as H2O or CO2 condense further out beyond their respective snowlines and influence the growth processes. To understand the coagulation behavior and thus the first steps in planetesimal formation, it is essential to investigate the collisional and mechanical properties of the materials involved.

The experiments presented here contribute to a broader understanding of these properties of CO2.

Collisions of CO2 agglomerates with sizes of 10 μm to 150 μm are studied at a temperature of 100 K and a pressure of 1 mbar to investigate the collision behavior. The impact velocities reach up to 3.4 m/s. The collisional outcome is analyzed regarding the events of sticking, bouncing and fragmentation.

To examine the mechanical properties of CO2, the Brazilian test is used. The splitting tensile strength is determined for varying volume filling factors. The effective surface energy of CO2 ice is derived from the measured splitting tensile strength.

The experimental results suggest that the collision properties of CO2 and silicate dust are similar for a comparable grain size distribution. The known growth processes in protoplanetary disks, including the growth barriers, also apply for CO2 ice.

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