EXPERIMENTAL EJECTA EMPLACEMENT IN REDUCED GRAVITY: PRELIMINARY RESULTS

Deposition of crater ejecta is ubiquitous on rocky or icy worlds, even on rubble pile asteroids. Like with impact cratering studies, the dynamics of ejecta are most readily studied in a laboratory due to cratering’s infrequent occurrence in nature on the timescale of human lifetimes. Crater ejecta plays a dominant role in affecting the surface topography of planetary bodies through deposition, erosion, exhumation, and burial. However, Earth has the highest surface gravity of any solid body in the solar system and so cratering and ejecta experiments are difficult to conduct at gravity levels relevant for places like Mercury, Mars, the large moons, asteroids, and other worlds. Here, we report on preliminary experimental ejecta emplacement results for 1G (1 Earth Gravity = 9.8 m/s²), 1/6^th G, and 2/5^th G. We achieved experimental results in reduced gravity by flying on parabolic aircraft flights with the company Zero-G. Notably, we show that crater ejecta emplacement in 1G follows the same scaling power-law from hypervelocity cratering experiments. Early analysis of reduced gravity experiments shows expected reduction in the gravity-scaled velocity (inverse Froude number) along with significant subsurface regolith simulant shearing. Mobilization of regolith by outward-flowing ejecta highlights the dynamic relationship between ballistic deposition and erosion. We hope our experimental results help to inform interpretation of crater ejecta facies and provenance interpretation of collected planetary samples.