标题： 太阳风离子照射下汞硫化物的表面响应 显示英文标题

标题： Surface Response of Mercury's Sulfides under Solar Wind Ion Irradiation

摘要： MESSENGER任务揭示了水星表面出人意料的高硫含量，这与月球风化层不同，而月球风化层直到最近还被认为是水星的良好类比。水星受到诸如陨石撞击和太阳风溅射等能量空间天气过程的影响，表明这种高硫浓度应在水星外逸层的超热硫群体中得到反映。紫外线光谱学尚未检测到外逸层中的硫，这一结果主要归因于其低发光因子。BepiColombo任务的质量谱分析仪未来能否检测到硫取决于外逸层中的硫丰度。在常见的硫化物铁硫矿（FeS）中已观察到辐射诱导的分异，这种矿物是返回的月球样品、陨石和小行星的组成矿物，其中形成的金属帽预计会减少硫向水星外逸层的喷射。在本研究中，我们调查了与水星相关的硫化物的辐射响应。尼宁格ite（MgS）和奥尔德姆ite（CaS）被以太阳风速度2 keV H$_2^+$或4 keV He$^+$进行辐照，并使用XPS显微探针对通量函数的原位成分和化学键分析进行了研究。MgS和CaS均未表现出可检测的损伤诱导分异，而是随着辐照达到了接近整体的金属与硫比率。基于这一发现、结构信息和文献分析，我们推断S-S阴离子间距超过$\sim$3.2\AA{}会抑制辐射诱导的硫消耗并促进计量溅射。因此，我们预测水星硫化物中不会出现阳离子（金属）表面分异，也不会因TiS、CrS和Ca-Mg硫化物中金属包覆层的形成而导致超热硫发射减少。这种对与水星相关的硫化物的辐射耐受性是新颖且出乎意料的，应该有助于BepiColombo任务在水星外逸层中进行检测。 显示英文摘要

摘要： The MESSENGER mission revealed unexpectedly high sulfur content within Mercury's surface, deviating from the Lunar regolith, which was, until recently, considered a good Mercury analogue. Mercury's exposure to energetic space weathering processes such as meteoritic impact and solar-wind sputtering suggests this high sulfur concentration should be reflected in the suprathermal sulfur population of the Hermean exosphere. UV spectroscopy has not yet detected exospheric sulfur, a result attributed primarily to its low glow-factor. Future detection by BepiColombo's Mass Spectrum Analyzer depends on sulfur abundance in the exosphere. Radiation-induced segregation has been observed in the common sulfide troilite (FeS), a constituent mineral in returned Lunar samples, meteorites, and asteroids, where the resulting metal cap is expected to reduce sulfur ejection to Mercury's exosphere. In this work, we investigate the irradiation response of Mercury-relevant sulfides. Niningerite (MgS) and oldhamite (CaS) were irradiated with solar-wind speed 2 keV H$_2^+$ or 4 keV He$^+$, and in-situ compositional and chemical bond analysis as a function of fluence was performed using an XPS microprobe. Neither MgS nor CaS expressed detectable damage-induced segregation and instead reached metal-to-sulfur ratios close to bulk with irradiation. Based on this finding, structural information, and literature analyses, we infer that an S-S anionic spacing exceeding $\sim$3.2 \AA{} inhibits radiation-induced sulfur depletion and promotes stoichiometric sputtering. We therefore predict no cation (metal) surface segregation in Hermean sulfides and no reduction in suprathermal sulfur emission caused by metal cladding formation in TiS, CrS, and Ca-Mg sulfides. This radiation-hardness for Mercury-relevant sulfides is novel and unexpected, and should facilitate detection in Mercury's exosphere by the BepiColombo mission.