Forbidden planetesimals: Conclusions from a parabolic flight experiment on wind-induced erosion of planetesimal surfaces

Laurent Schonau, Tunahan Demirci, Jens Teiser, Tetyana Bila, Kolja Joeris, Florence Chioma Onyeagusi, Niclas Schneider, Miriam Fritscher, Felix Jungmann, Maximilian Kruss, Lars Schmidt, Gerhard Wurm

During the formation of a planetary system, micrometer-sized dust particles grow into planets that are thousands of kilometers in size. Planetesimals in the kilometer size range represent an intermediate stage in this evolution. Due to their composition of loosely bound dust aggregates in combination with their weak self-gravity they are endangered by the omnipresent gas drag within the protoplanetary disk. Since planetesimals orbit the star slower than the gas, they experience a constant headwind that is in the order of 50 m/s at minimum. This head wind can increase strongly if the orbit becomes eccentric. As a result, there might be forbidden zones where planetesimals are disassembled by wind erosion.
To quantify these zones, we carried out microgravity experiments on wind erosion of a simulated planetesimal surface in parabolic flights. For this, we used a wind-tunnel with a shear flow over a sample bed at low pressure down to 1 Pa. As sample we used SiO2-dust aggregates that were produced by collisions of micrometer-sized particles, i.e. in an analogous way as dust aggregates at the bouncing barrier in protoplanetary disks might form.
Here we report the results of a parabolic flight campaign which support and expand earlier findings that wind erosion might indeed generate forbidden zones for planetesimals close to the star and filter out eccentric orbits. By using more realistic particles and observing erosion at lower pressure than in previous experiments we updated our calculations of forbidden zones according to the newly obtained parameters.</div>