Geometrical description of impact cratering under microgravity conditions

Abstract: Crater formation has been widely studied through different strategies. One of them simplifies the problem to the impact of a spherical projectile on a granular layer. Due to technical limitations, experimental studies have focused independently on either the corolla formation or the deformation inside the granular bed. Hence, so far, it has not been possible to link these two processes. Here, we present an original experiment that allows us to simultaneously observe the granular dynamics above and below the granular layer in microgravity conditions. The crater morphology is studied considering the dependency on the impact energy, grain size, and shape of the projectile. The results show that this type of experimental configuration makes it possible to quantify the effects of projectile geometry in the crater cavity, something that cannot be captured in traditional tridimensional (3D) deep layer experiments or without the help of advanced imaging techniques such as high-speed X-ray radiography. Finally, this setup opens a new way to study the possible effects of collisions between micrometer-sized dust grains under microgravity conditions, a fundamental process in the early formation of planets in protoplanetary disks. Graphic abstract: [Figure not available: see fulltext.]