Pierwsze(?) polskie miejskie mikrometeoryty : analiza chemiczna i fazowa

Micrometeorites are extraterrestrial particles smaller than 2 mm that fall on the surface of a planetary body, allowing them to be collected and investigated. In this study, we collected a 30 kg sample of sediment gathered on the rooftop of Wroclaw University, Poland. After separation and hand-picking, potentially extraterrestrial spherules were analysed using SEM-EDS and a Raman spectrometer. Nine spher¬ules were positively identified as micrometeorites. They are characterized by a chemical composition comparable to carbonaceous chondrites. Six of them represent the barred olivine type, and the remaining three are of the cryptocrystalline type. Five out of the nine spherules contain metallic beads that are characterized by variable contents of oxygen, iron, and nickel, while one of the grains, partly covered in iron oxide, exhibits morphological features suggesting that the metallic bead escaped from the silicate body. Raman spectroscopic analyses revealed that the cosmic spherules consist mainly of olivine and magnetite. Additional Raman analyses were performed on the cryptocrystalline spherule with two beads along its elongation, revealing a continuous shift of characteristic olivine Raman peaks. The ~820 cm-1and ~850 cm-1 Raman shift values near the heavier bead approach ~817 cm-1 and ~846 cm-1 towards the lighter one, which also corresponds with the change of the micrometeorite ’s black colour to a more greenish and translucent appearance near the lighter metallic bead. This suggests that at least surface crystallization of micrometeorites starts from a more forsteritic melt in the front, progressing towards more fayalitic compositions in the aerodynamic tail.

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Opracowanie rekordu ze środków MNiSW, umowa nr POPUL/SP/0154/2024/02 w ramach programu "Społeczna odpowiedzialność nauki II" - moduł: Popularyzacja nauki (2025).