Space-Weathering on Vesta: Ion-Implantation Induced Spectroscopic Changes on HEDs

Abstract

Introduction: The NASA/Dawn mission explored Vesta between 2011 and 2012 [1], confirming the asteroid to be the parent body of the howardite, eucrite, diogenite (HED) clan of meteorites [2]. Dawn allowed the first extensive high spatial resolution mapping of Vesta’s surface, shedding light on its mineralogy and spectral properties [3]. Space-weathering (SpWe) on Vesta still constitutes a significant conundrum as Vesta’s spectroscopic features in the near-IR appear to be less affected compared to lunar-type space-weathered features [4]. This suggests the absence of lunar-like nanophase iron on Vesta as a product of SpWe (observed on the Moon and Itokawa samples [5]). Regolith resurfacing processes at the surface of Vesta may also contribute to diluting the spectral effects on classical SpWe tracers - such as slope reddening and darkening - of older, more weathered materials. Hence, to better identify the weathering state of surfaces on V-type asteroids, there is a need to investigate SpWe effects on such materials while expanding and redefining this set of parameters. In this work, we look for the optimal parameters for distinguishing between fresh and weathered materials on Vesta and other V-type objects. To perform these investigations, we emulate the effects of SpWe on Vesta in a laboratory environment. This study can be done by using HEDs as analog material for Vesta’s surface. In particular, we focus on emulating the effects of the solar wind component of SpWe via ion implantation.