Understanding the Effects of Micrometeoroid Bombardment on Graphite-rich Mercury Analogs through Laboratory Experiments and Electron Microscopy Analysis

Abstract

Space weathering alters the spectral, microstructural, and chemical characteristics of the surface of Mercury, and an effective way to understand it is in the laboratory. To simulate energetic micrometeoroid impacts on the surface of Mercury, we irradiated pellets containing forsteritic olivine and graphite with a pulsed laser. Our analysis with scanning electron microscopy showed two morphological textures: one that is melt-rich and one consisting of fluffy, C-rich globules. Performing transmission electron microscopy on these textures, we identified the presence of new microstructural and chemical features resulting from simulated space weathering, including C-rich inclusions in the melt and vesiculated textures in the C-rich globules. Separate analysis of Si wafers, which were suspended near the target to collect the vapor and melt ejected during irradiation, show a variety of ejected material, including forsterite grains, melt splash, and C-rich particles. These observations suggest the possibility that space weathering products on the surface of Mercury may be different than on other airless bodies, which will be further explored by the BepiColombo mission.