Experimental Ejecta Emplacement in Variable Gravity and Its Effects on Landscape Evolution

Ballistic sedimentation, the process by which impact-generated ejecta is deposited and interacts with planetary surfaces, remains understudied despite its significant role in landscape evolution on cratered terrain across the solar system. We investigated the dynamical and geomorphological effects of ejecta emplacement under three different gravitational accelerations, focusing on how gravity influences the runout, erosion, and subsurface regolith shear characteristics of ballistic erosion and sedimentation. Building on previous ground-based experiments utilizing a meter-scale lever-arm catapult to simulate ejecta emplacement, we extend these studies by deploying a subscaled catapult on reduced-gravity parabolic flights aboard a modified Boeing 727–200. These experiments recreated lunar and Mercurian/Martian gravity conditions, allowing direct observation of ejecta–regolith interactions in reduced gravity. Our ejecta deposition results are consistent with nondimensional scaling relationships established for cratering experiments; they demonstrate gravity-independent ejecta runout lengths; and the results show gravity-dependent runout efficiency. Related experimental results show a logarithmic shear profile in the regolith bed beneath ejecta, similar to that predicted from fluid mechanics. We also explore a potential relation between ejecta emplacement and landslide runouts, highlighting areas of commonality and differences, and apply our results to case studies involving ejecta from Linné Crater on the Moon and the Ries Crater in Germany. This work provides an interpretive framework for future experimental, theoretical, observational, and field studies in cratering and landslide geology while highlighting areas for future research.