A Raman spectroscopic study of organic matter in interplanetary dust particles and meteorites using multiple wavelength laser excitation

Raman spectroscopy was used to investigate insoluble organic matter ( IOM ) from a range of chondritic meteorites, and a suite of interplanetary dust particles ( IDP s). Three monochromatic excitation wavelengths (473 nm, 514 nm, 632 nm) were applied sequentially to assess variations in meteorite and IDP Raman peak parameters (carbon D and G bands) as a function of excitation wavelength (i.e., dispersion). Greatest dispersion occurs in CV s >  OC s >  CM s >  CR s with type 3 chondrites compared at different excitation wavelengths displaying conformable relationships, in contrast to type 2 chondrites. These findings indicate homogeneity in the structural nature of type 3 chondrite IOM , while organic matter ( OM ) in type 2 chondrites appears to be inherently more heterogeneous. If type 2 and type 3 chondrite IOM shares a common source, then thermal metamorphism may have a homogenizing effect on the originally more heterogeneous OM . IDP Raman G bands fall on an extension of the trend displayed by chondrite IOM , with all IDP s having Raman parameters indicative of very disordered carbon, with almost no overlap with IOM . The dispersion effect displayed by IDP s is most similar to CM s for the G band, but intermediate between CM s and CR s for the D band. The existence of some overlapping Raman features in the IDP s and IOM indicates that their OM may share a common origin, but the IDP s preserve more pristine OM that may have been further disordered by ion irradiation. H, C, and N isotopic data for the IDP s reveal that the disordered carbon in IDP s corresponds with higher δ 15 N and lower δ 13 C.