Hydrodynamic instability at impact interfaces and planetary implications

Impact-induced mixing between bolide and target is fundamental to the geochemical evolution of a growing planet, yet aside from local mixing due to jetting - associated with large angles of incidence between impacting surfaces - mixing during planetary impacts is poorly understood. Here we describe a dynamic instability of the surface between impacting materials, showing that a region of mixing grows between two media having even minimal initial topography. This additional cause of impact-induced mixing is related to Richtmyer-Meshkov instability (RMI), and results from pressure perturbations amplified by shock-wave refraction through the corrugated interface between impactor and target. However, unlike RMI, this new impact-induced instability appears even if the bodies are made of the same material. Hydrocode simulations illustrate the growth of this mixing zone for planetary impacts, and predict results suitable for experimental validation in the laboratory. This form of impact mixing may be relevant to the formation of stony-iron and other meteorites. The authors describe a dynamic surface instability between impacting materials, showing that a region of mixing grows between two media. The study implies that this can explain mixed compositions and textures in certain meteorites.

Automated summary

Impact-induced mixing between bolide and target is crucial for the geochemical evolution of a growing planet. A dynamic instability between impacting materials has been discovered, suggesting that this can explain mixed compositions and textures in certain meteorites.