Microphysics of Saltation and Triboelectric Charging

Particle collisions of all sorts and scales happen regularly in many varieties in nature. If it is ash in a volcanic plume, sand rolling over the beach on a windy day, or two asteroids colliding in the Kuiper belt. Even though the environments and outcomes of those collisions may vary drastically, many underlying processes are similar. Here, studies on collisions in sand grain impacts during saltation on Mars, with the focus on microphysical aspects of the ejecta, such as size distribution, morphology and aggregation and studies on the triboelectrical charging and discharging and processes of colliding grains in protoplanetary disks are presented. The first part of this work will highlight the results achieved within the Roadmap project, where individual sand grain impacts have been simulated under laboratory conditions and different characteristics of their ejecta have been analyzed. These experiments showed, that not only is fine and porous dust directly emitted, but it can also carry rather strong charges. In the second part the focus lies on charging and discharging. Here, experiments on charging under conditions similar to those in a protoplanetary disk and long-time experiments on discharging and the mechanisms behind it have been conducted. It could be shown, that tribocharging may play a significant role during planet formation in some areas of protoplanetary disks.