用离子和飞秒- laser -辐照的橄榄石和辉石比较太阳风和微流星体撞击引起的空间风化光谱变化
Comparison of space weathering spectral changes induced by solar wind and micrometeoroid impacts using ion- and femtosecond-laser-irradiated olivine and pyroxene
摘要：
太空风化是一个改变无空气行星表面的过程。空间风化的主要因素是太阳风辐照和微流星体撞击。这些过程改变行星的反射光谱，并经常修改其组成诊断功能。在这项工作中，我们侧重于模拟和比较的光谱变化所造成的太阳风照射和微流星体轰击，以获得更好地了解这些个人的空间风化过程。我们用橄榄石和辉石小球作为行星物质的替代物。为了模拟太阳风辐射，我们使用了能量从5到40 keV的氢、氦和氩离子，能量密度高达$10^{18}$粒子/cm $^2$。为了模拟微流星体撞击，我们使用了单个飞秒激光脉冲。分析了应用修正高斯模型确定的不同光谱参数对应的演化规律，并进行了主成分分析。原始矿物的表面影响的光谱演化比风化剂，从不同的演化的光谱斜率的橄榄石和辉石辐照。在橄榄石中观察到的光谱斜率变化与A型小行星的观测结果一致，而在辉石中观察到的中度或无斜率变化与小行星（4）灶神星一致。我们还观察到两种风化剂引起的光谱效应的一些差异。模拟太阳风的离子比模拟微流星体撞击的激光辐照对光谱的较长波长的影响要小。这很可能是由于离子和激光脉冲的穿透深度不同。我们的研究结果表明，在某些情况下，它可能是可以区分的两个代理人的风化表面上的贡献。
英文摘要：
Space weathering is a process that changes the surface of airless planetary bodies. Prime space weathering agents are solar wind irradiation and micrometeoroid bombardment. These processes alter planetary reflectance spectra and often modify their compositional diagnostic features. In this work we focused on simulating and comparing the spectral changes caused by solar wind irradiation and by micrometeoroid bombardment to gain a better understanding of these individual space weathering processes. We used olivine and pyroxene pellets as proxies for planetary materials. To simulate solar wind irradiation we used hydrogen, helium, and argon ions with energies from 5 to 40 keV and fluences of up to $10^{18}$ particles/cm$^2$. To simulate micrometeoroid bombardment we used individual femtosecond laser pulses. We analysed the corresponding evolution of different spectral parameters, which we determined by applying the Modified Gaussian Model, and we also conducted principal component analysis. The original mineralogy of the surface influences the spectral evolution more than the weathering agent, as seen from the diverse evolution of the spectral slope of olivine and pyroxene upon irradiation. The spectral slope changes seen in olivine are consistent with observations of A-type asteroids, while the moderate to no slope changes observed in pyroxene are consistent with asteroid (4) Vesta. We also observed some differences in the spectral effects induced by the two weathering agents. Ions simulating solar wind have a smaller influence on longer wavelengths of the spectra than laser irradiation simulating micrometeoroid impacts. This is most likely due to the different penetration depths of ions and laser pulses. Our results suggest that in some instances it might be possible to distinguish between the contributions of the two agents on a weathered surface.
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