Structural and Functional Micro-Infrared Survey of Pristine Carbonaceous Chondrites Insoluble Organic Matter

Introduction: Carbonaceous chondrites contain small amount of an insoluble organic matter (IOM). The macromolecular structure consists in aromatic domains linked one another by aliphatic chains and include several heteroatomic functions. This kind of structure has been proposed to be present in the interstellar medium dust and infrared fingerprints of chondrites and interstellar sources are often compared [1-3]. It is commonly admitted that aqueous altered chondrites hold the most pristine components and are the richest in IOM. They are remarkable samples for understanding a possible organochemistry on parent bodies. They exhibit a progressive trend of hydrothermalism intensity that seems to correlate with structural modification and oxidation of heteroatomic functions [4]. Infrared properties of the IOM bear key informations about structure and functions. This technique is commonly used in both teledetection and laboratory measurements. Aliphatic, aromatic and oxygen-rich functions vibrational modes fall in the mid infrared range. Crosslinkage degree can be deduced from relative abundance of CHX groups as was done in the case of terrestrial coals[5]. Double and simple oxygencarbon bonds abundance can be estimated toward aromatics. We present an infrared spectral study of CR, CM and CI chondrites IOM. Skeletal parameter of each chondrites group is related to its pristine character and oxygenated function to alteration degree.