Simulation of Space Weathering on airless bodies, moons and planets: Combining hypervelocity dust impacts with energetic irradiation

陨石及其母体小行星的化学和矿物学特征为我们提供了关于内太阳系形成时期的过程和条件的重要信息。然而，将陨石与其母体联系起来，例如通过红外反射光谱，仍然是有问题的。无大气层的天体表面不断受到太阳风、流星体、宇宙尘埃和宇宙射线的轰击。这些过程被概括为太空风化，导致这些天体的表面发生强烈的变化。天文观测旨在通过红外光谱重建小行星、卫星和行星表面的表面性质，但空间风化严重改变了薄表层的光学、成分和物理性质，从而阻碍了对其化学和矿物学的适当识别。对空间风化的影响进行了实验研究，主要是离子轰击和溅射，重点研究了玻璃涂层和纳米铁相的形成。其他研究旨在通过使用纳秒脉冲激光来模拟微流星体撞击的影响，然而，这不能与真实的微流星体撞击进行直接比较。这项研究提供了一种新的方法来模拟宇宙尘埃轰击，方法是使用由斯图加特大学空间系统研究所(IRS)运营的Max-Planck核物理研究所改装的2 MV van de Graaff尘埃加速器，并将其与美国佐治亚理工学院电子和光子诱导表面化学(EPICS)实验室的高能辐照和解吸实验相结合。通过模拟高度逼真的照射和轰击条件，这使得能够研究宇宙尘埃和太阳风对固体行星表面的照射过程，并使用各种硅酸盐材料研究纳米相铁的形成、含水矿物的作用以及对挥发收支的影响。我期望这项工作有助于更好地理解空间环境中的蚀变机制、纳米铁的形成以及干燥表面上挥发物的发展。

The chemical and mineralogical characterization of meteorites and their parent asteroids provides us with important information about the processes and conditions during the formation era of the inner Solar System. However, linking meteorites to their parent bodies, e.g., by infrared reflectance spectra, is still problematic. The surfaces of atmosphereless celestial bodies are continuously bombarded by solar wind, meteoroids, cosmic dust and cosmic rays. These processes, summarized under the term Space Weathering cause strong alterations of the surfaces of these bodies. Astronomical observations aim to reconstruct the surface properties of the surfaces of asteroids, moons and planets by infrared spectra, but space weathering severely modifies the optical, compositional and physical properties of thin surface layers and thus precludes proper identification of its chemistry and mineralogy. The effects of space weathering have been experimentally studied, mainly with respect to ion bombardment and sputtering and here, with emphasis on the formation of glassy coatings and nano phase iron. Other studies aimed to simulate the influence of micrometeoroid bombardment by using nanosecond-pulsed laser shots, which - however - cannot be directly compared to real micrometeoroid impacts. This study offers a new approach to simulate cosmic dust bombardment by using a modified 2 MV van de Graaff dust accelerator at the Max-Planck-Institute for Nuclear Physics, operated by the Institute for Space Systems (IRS) at the University of Stuttgart, and combine these with energetic irradiation and desorption experiments at the Electron and Photon Induced Chemistry on Surfaces (EPICS) laboratory at the Georgia Institute of Technology, USA. By simulating highly realistic irradiation and bombardment conditions, this allows to investigate the processes of both, cosmic dust bombardment and solar wind irradiation on solid planetary surfaces and to study the formation of nano phase iron, the role of hydrous minerals and the effect on volatile budgets, using a variety of silicate materials. I expect this work to contribute to a better understanding of alteration mechanisms in space environments, nanophase iron formation and the development of volatiles on desiccated surfaces.