Infrared spectroscopy on various kinds of primitive fine-grained silicate material: Deciphering the nature of protoplanetary nebula dust components

This project investigates the mid-infrared (IR) spectral properties of primitive fine-grained silicate material in carbonaceous and unequilibrated ordinary chondrites. Such materials are considered remnants of dust from the early protoplanetary nebula and are therefore key to understanding the formation and evolution of small bodies in the Solar System. Using high-resolution IR spectroscopy, we demonstrate the high sensitivity of mid-IR spectral parameters to the degree of aqueous alteration. Importantly, correlations become significantly stronger when data are averaged by petrologic subtype, indicating that intrinsic variability within subtypes can obscure global trends. At the same time, we show that spectral parameters in the 600–1400 cm⁻¹ range exhibit significant variability within each petrologic subtype of the clast in the CM chondrites. This variability (excluding Mg–OH feature) increases with decreasing alteration degree. The results offer improved laboratory constraints for interpreting remote mid-infrared observations of carbonaceous asteroids (such as Bennu and Ryugu) and cometary materials. For the first time, mid-IR data were obtained for primitive fine-grained silicate material in different textural units of the Krymka (LL3.2) chondrite. The observed chemical and spectral variability in the fine-grained materials indicates that the dust in the protoplanetary nebula was heterogeneous at small spatial scales. The presence of a chondritic impact melt rock xenolith further demonstrates that early-formed materials were processed, fragmented, and later in-corporated into new parent bodies, supporting a model of dynamic recycling in the early Solar System. Our data demonstrate that spectral characteristics (CF and RB features) can serve as qualitative indicators of mineralogical variability within fine-grained primitive materials. The results expand the IRIS spectral database and provide new constraints for interpreting remote sensing data of small Solar System bodies.