Spatial and Shape Distributions of Ejecta from Hypervelocity Impact Between Rocky Projectile and Metal Target

Abstract Introduction Hypervelocity impact on planetary bodies ejects materials from the surface, providing dust particles in the interplanetary space [e.g., 1, 2]. The size or spatial distribution of fine fragments ejected from silicate surfaces have been experimentally investigated using porous materials, such as foamed polystyrene and aerogel blocks, as secondary targets [3, 4]. On the other hand, in the hypervelocity impact of rock projectiles onto metal targets, molten rocky materials in ejecta were captured by aluminum plates used as the secondary targets and detected using a Scanning Electron Microscope (SEM) equipped with energy dispersive x-ray spectrometer, and it was suggested that such molten ejecta might be the origin of a type of chondrules [5]. Thin foil and film were also used as secondary targets for high-velocity impact experiments. Ejecta size and the minimum velocity were estimated based on the size distribution of holes on the secondary target [6], and the ejecta phase, i.e., solid or liquid, was suggested based on the shape of the holes [7]. We conducted hypervelocity impact experiments between a rock projectile and a metal target and captured the ejecta using aerogel blocks and aluminum foils as secondary targets. This study aims to constrain the spatial and shape distributions of ejecta, examine the effect of impact velocity on the distributions, and investigate the size of the molten ejecta.