Impact into a Graphite-Bearing Regolith: A Dynamic Shock Recovery Study

Abstract

Mercury’s surface is exposed to a multitude of surface altering effects that have a significant influence on its optical properties. Impact events – small or large – are one of the major surface-altering agents. Inferred from hypothetical modal abundances [1] graphite can comprise up to 4 wt% on Mercury’s surface. Graphite as a possible stable phase on Mercury can explain the relatively low albedo of the planet [2]. Our experimental setup probes the hypothetical impact into a graphite- and olivine-bearing, pyroxene-rich (Px (En87) = 68 wt%; Ol (Fo91) = 29 wt%, C = 3 wt%) surface. The effect of post-shock heating and pressure on a powder comprised of silicates with grain sizes ≤125 μm and hexagonal graphite was simulated in a classic shock recovery experiment [3]. The experiments were performed in the framework of the BepiColombo mission to Mercury. The onboard Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) will send thermal emissivity data once it reaches the Hermean orbit in 2025. A spectral database for mid infrared data is currently set up at the Institut für Planetologie in Münster. Published mid infrared data will soon be available and sample related spectral information of interest can be traced via assigned IDs (e.g., IDxxx).