Effect of target properties and impact velocity on ejection dynamics and ejecta deposition

10 Impact craters are formed by the displacement and ejection of target material. Ejection 11 angles and speeds during the excavation process depend on specific target properties. In order 12 to quantify the influence of the constitutive properties of the target and impact velocity on 13 ejection trajectories we present the results of a systematic numerical parameter study. We 14 have carried out a suite of numerical simulations of impact scenarios with different 15 coefficients of friction (0.0 – 1.0), porosities (0% 42%) and cohesions (0 MPa – 150 MPa). 16 Furthermore, simulations with varying pairs of impact velocity (1-20 km/s) and projectile 17 mass yielding craters of approximately equal volume are examined. We record ejection speed, 18 ejection angle, and the mass of ejected material to determine parameters in scaling 19 relationships, and to calculate the thickness of deposited ejecta by assuming analytical 20 parabolic trajectories under Earth gravity. For the resulting deposits we parameterise the 21 thickness as a function of radial distance by a power law. We find that strength—that is, the 22 coefficient of friction and target cohesion—has the strongest effect on the distribution of 23 ejecta. In contrast, ejecta thickness as a function of distance is very similar for different target 24 porosities and for varying impact velocities larger than ~6 km/s. We compare the derived 25 ejecta deposits with observations from natural craters and experiments. 26 27

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