Formation of GEMS from interstellar silicate dust

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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.