Space Weathering of airless bodies in the Solar System – Combining hypervelocity dust impacts with energetic irradiation experiments

Abstract:

The chemical and mineralogical characterization of meteorites and their parent asteroids provides us with information about the processes and conditions during the formation of the inner Solar System. However, linking meteorites to their parent bodies is problematic. Astronomical observations aim to reconstruct the surface properties of these bodies primarily by visible and infrared spectra, but space weathering severely modifies the optical, compositional and physical properties of thin surface layers and thus precludes proper identification of chemistry and mineralogy. The effects of space weathering have been experimentally studied mainly with respect to ion bombardment and sputtering. Other studies aimed to simulate the influence of micrometeoroid bombardment by using laser ablation techniques. However, there is sufficient evidence that laser ablation does not realistically lead to the same effects as produced during real micrometeorite impacts. We performed micrometeorite bombardment using a 2MV dust accelerator at the Institute for Space Systems at University of Stuttgart, Germany, capable of generating impact speeds up to 100 km s^-1. These results are combined with energetic irradiation experiments at the Electron and Photon Induced Chemistry on Surfaces (EPICS) laboratory at Georgia Institute of Technology, USA. By simulating highly realistic irradiation conditions, we are able to investigate the processes of particle and solar wind irradiation on solid planetary surfaces and study the formation of e.g., nanophase iron in minerals, the effects on hydrous minerals regarding their volatile budgets, or possible OH-formation in nominally anhydrous minerals and relate these to their optical properties. Using a variety of minerals, this work aims to contribute to a better understanding of the general alteration mechanisms in space environments in dependence of weathering agent and available material. We here present the results of initial comparison analysis and the first irradiation experiments.