Carbonaceous chondrites are a type of meteorite found on Earth that contain material formed in the early stages of the Solar System. Most carbonaceous chondrites consist of spheroidal inclusions called chondrules that are cemented within a clay-rich matrix. Some of these chondrules are surrounded by fine-grained rims (FGRs) made of similar materials as the matrix. The way these rims were formed is unclear. Three carbonaceous chondrites used in this study are thin sections of Cold Bokkeveld, Northwest Africa (NWA) 12748, and Tagish Lake. Cold Bokkeveld and NWA 12748 are classified as the same type of meteorite, a CM2. Tagish Lake does not fall into any defined carbonaceous chondrite group.

We analyzed the rims and matrix of the samples using a nano-Mid-Infrared Spectrometer due to its sub-micron resolution and the material’s small grain size. The spectra of the rims display similar features found in all three meteorites. However, when comparing the spectra of the rims to their respective matrix, the matrix shows more variability in features but also exclude a key feature found in the rim spectra. This could signify the rims originally formed separate from the matrix, but they may have gone through similar chemical processes throughout the meteorite’s history.