22-EPN3-083: SHOCKchar: Charring of Wood Induced by a Shock Wave during a Hypervelocity Impact
Visit by Anna Losiak, Institute of Geological Sciences Polish Academy of Sciences (Poland) to TA2.7 Light Gas Gun Laboratory, University of Kent (UK)
Dates of visit: 23 November – 01 December 2023
Report summary: Proximal ejecta blankets of very small (<200 m in diameter) impact craters contain fragments of charcoal (Losiak et al. 2022). They were found in Campo del Cielo, Whitecourt, Kaali Main, Kaali 2/8, and Morasko, as well as in two suspected craters: Sobolev and Ilumetsa. Those charcoals can be used to: precisely and accurately date impact structures, determine environmental effects of impact of small asteroids and, potentially in the future, better understand the energy distribution during formation of very small impact craters or identify impact origin of yet unknown structures. The formation mechanism of impact charcoals is unknown. The first hypothesis, based on field observations, assumes impact charcoals were formed by burial of branches in locally warm ejecta, resembling charcoals buried within pyroclastic flows. An alternative explanation, based on numerical modelling (Svetsov and Shuvalov 2020), is that charcoals are formed by shock-wave propagation through trees. THE AIM of this project is to test if impact charcoals can be formed by a shock wave passage, and to characterize the properties of resulting charcoals. The Light Gas Gun laboratory at the University of Kent was selected to conduct the experiment because it is one of very few in the world that allows to reach >5km/s velocities as well as perform experiments at atmospheric pressure.
During the Europlanet TA visit we have performed 8 experiments. We have varied the following parameters: 1) velocity: 5 / 3 / 2 km/s, 2) wood dryness: fresh / dried, 3) atmospheric pressure: 1 bar / ~0 bar.
The initial evaluation of the results suggests that wood hit at 5 km/s results in production of a very small amount of thermally processed material. It is not clear if this material has similar properties to impact charcoals. The full analysis is ongoing
