Formation of GEMS from interstellar silicate dust

在演化的M型恒星的拱壳或超新星中通过气相冷凝形成的硅酸盐可能是GEMS（嵌入金属和硫化物的玻璃）颗粒的前体。在第二个应用阶段，我们将继续研究通过离子诱导处理伴随适度退火过程从太阳前硅酸盐颗粒形成GEMS的可能途径。在我们的实验室里，将制备出具有不同组成和结构的硅酸盐。具有辉石和橄榄石化学计量的无定形或部分结晶硅酸盐粉尘类似物、纯硅酸镁、含有金属铁夹杂物的不均匀硅酸盐和含有有机碳的硅酸盐将暴露于用H+、He+以及丰富的和反应性离子（例如不同能量范围（10.100和400.1000 keV）的Fe+和C+阳离子）的离子辐照。此外，将研究适度退火和离子诱导处理的组合，以模拟GEMS的形态和结构特性。全球环境监测系统中硫化铁的来源仍有争议。将进行第一项专门研究硫化物在离子辐照下的稳定性。由于溅射、缺陷形成、多孔结构形成和可能的结晶过程，硅酸盐或硫化铁的结构、化学和形态变化将通过卢瑟福背散射光谱法（RBS）、电子显微镜、能量色散X射线分析（EDX）和红外光谱法进行监测。这些结果将有助于了解GEMS的起源，GEMS属于太阳系中开始行星形成过程的最原始物质。

Silicates formed via gas-phase condensation in circumstellar shells of evolved M-type stars or in supernovae are the possible precursors for the GEMS (glass with embedded metal and sulfide) particles. In the second application period, we will continue our studies on the possible formation pathways of GEMS from presolar silicate grains by ion-induced processing accompanied by moderate annealing processes. Differently composed and structured silicates will be prepared in our laboratory. Amorphous or partly crystalline silicate dust analogs with pyroxene and olivine stoichiometry, pure magnesium silicates, inhomogeneous silicates containing metallic iron inclusions, and silicates containing organic carbon will be exposed to ion irradiation with H+, He+, but also abundant and reactive ions such as Fe+ and C+ cations in different energy ranges (10.100 and 400.1000 keV). In addition, the combination of moderate annealing and ion-induced processing will be studied to simulate the morphological and structural properties of GEMS. The origin of iron sulfide in GEMS is still a matter of debate. First studies dedicated to the stability of sulfide under ion irradiation will be performed. Structural, chemical, and morphological changes in the silicates or in iron sulfide due to sputtering, defect formation, formation of porous structures, and possible crystallization processes will be monitored by Rutherford backscattering spectroscopy (RBS), electron microscopy, energy dispersive X-ray analyses (EDX) and IR spectroscopy. The results will help to understand the origin of GEMS which belong to the most primitive materials that began the planet forming processes in our solar system.