Early Planet Formation: A Facility to Study the Time Evolution and Equilibrium States of Multitudes of Interacting sub-millimeter to centimeter Dust and Ice Aggregate Ensembles
Final Report Abstract
Collisional evolution is a primary mechanism working in protoplanetary disks to form larger bodies. From dust size to mm-size, this growth mechanism works well. From this size on, aggregates tend to bounce off each other rather than stick. The project studied the evolution of an ensemble of dust aggregates at this mm size bouncing barrier. It could be shown in laboratory experiments that a dust reservoir naturally evolves into a bouncing aggregate ensemble. It could further be seen that despite of variations in size or shape, bouncing is dominant at typical collision velocities. Therefore, bouncing barriers are very robust. However, it could also be shown that a small grain particle supply allows the individual aggregates within the bouncing ensemble to grow by feeding on the small dust. This offers a way to grow out of the critical size scale. Levitation at low pressure by thermal creep was applied technically for these experiments. The effect of thermal creep gas flow has fundamental applications to gas flow through porous bodies in protoplanetary disks due to the disk's low pressure. This can lead to direction transport of gaseous or solid matter and even disruptions of porous pre-planetary bodies. Based on a number of experiments which were carried out, a model was formulated to quantitatively describe the gas flow due to thermal creep for granular media. This allows a detailed study of gas flow through (pre-)planetary soil and the effects in future work.
Publications
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(2017) Is There a Temperature Limit in Planet Formation at 1000 K?. ApJ (The Astrophysical Journal) 846 (1) 48
Demirci, Tunahan; Teiser, Jens; Steinpilz, Tobias; Landers, Joachim; Salamon, Soma; Wende, Heiko; Wurm, Gerhard
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(2017) Lifting particles in martian dust devils by pressure excursions. Planetary and Space Science 145 9–13
Koester, Marc; Wurm, Gerhard
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Experimental Study on Bouncing Barriers in Protoplanetary Discs, Astrophysical Journal, 783:111 1-7, 2014
T. Kelling, G. Wurm, and M. Köster
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An Insolation Activated Dust Layer on Mars, Icarus, 260:23-28, 2015
C. de Beule, G. Wurm, T. Kelling, M. Köster, and M. Kocifaj
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Failed Growth at the Bouncing Barrier in Planetesimal Formation, Astrophysical Journal, 827:110 1-5, 2016
M. Kruss, T. Demirci, M. Koester, T. Kelling, and G. Wurm
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Growing Into and Out of the Bouncing Barrier in Planetesimal Formation, Astronomy and Astrophysics, 600:A103 1-4, 2017
M. Kruss, J. Teiser, and G. Wurm
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Tracing Thermal Creep in Granular Media, Microgravity Science and Technology
T. Steinpilz, J. Teiser, M. Koester, M. Schywek, and G. Wurm
