Mid-Infrared Spectroscopy of Components in Chondrites: Search for Processed Materials in Young Solar Systems and Comets

Abstract

We obtained mid-infrared spectra of chondrules, matrix, CAIs and bulk material from primitive type 1-4 chondrites in order to compare them with the dust material in young, forming solar systems and around comets. Our aim is to investigate whether there are similarities between the first processed materials in our early Solar System and protoplanetary disks currently forming around other stars. Chondrule spectra can be divided into two groups. 1) Chondrules dominated by olivine features at ~11.3 µm and ~10.0 µm. 2) mesostasis rich chondrules that show main features at ~10 µm. Bulk ordinary chondrites show similar features to both groups. Fine-grained matrix is divided into three groups. 1) phyllosilicate-rich with a main band at ~10µm, 2) olivine-rich with bands at 11.3 µm and ~10 µm, 3) pyroxene rich with several peaks between 9.3 µm and 11.2 µm. Impact shock processed matrix from Murchison (CM2) shows features from phyllosilicate-rich, amorphous and olivine rich material. CAIs show melilite/spinel rich features between 10.2 µm and 12.5 µm. Astronomical spectra are divided into four groups based on their spectral characteristics amorphous (group 1), pyroxene-rich (group 2), olivine rich (group 3) and 'complex' (group 4). Group 2 is similar to enstatite-rich fine grained material like e.g. Kakangari (K3) matrix. Group 3 and 4 can be explained by a combination of varying concentrations of olivine and mesostasis-rich chondrules and fine-grained matrix, but also show very good agreement with shock processed material. Comparison of band ratios confirms the similarity with chondritic material e.g. for HD100546, while the inner disk of HD142527 show no sign of chondrule material. Comparison between the laboratory infrared-red IR data and astronomical spectra indicate a general similarity between primitive solar system materials and circumstellar dust and comets, especially in the inner disks of young solar systems. However, other amorphous materials like IDP/GEMS have to be taken into account.