Experimental study on the effect of target properties on high-velocity ejecta from rocks

Hypervelocity impacts play a key role in material transport among planetary bodies. To investigate how target material properties influence high-velocity ejecta, we conducted impact experiments using aluminum projectiles at velocities of about 7 km s −1 , with serpentinite, dolerite, and pyrophyllite as targets. Ejecta were impacted onto polycarbonate plates and analyzed using high-speed imaging and crater measurements. Ejecta velocities ranged from 5 to 13 km s −1 , with maximum fragment sizes decreasing from 100 to 7 μm as velocity increased. Ejecta with velocities exceeding twice the particle velocity existed, consistent with previous numerical simulations. No clear differences in size–velocity or ejection angle–velocity relationships were observed among the targets. The largest sizes of high-velocity ejecta in this study may suggest that near the impact point, the material may behave as if it were in a fully cracked state. The axial ratios of the craters, which are considered to reflect those of the ejecta, were approximately 0.6–0.7. Although direct extrapolation to planetary scales is not straightforward, these results provide new experimental constraints on the influence of target properties on high-velocity ejecta production, contributing to a better understanding of material transport between planetary bodies.