[PPS07-P16] Heating effects on the structures and elemental ratios of IOM in Jbilet Winselwan and Y 793321 CM chondrites
Keywords:CM chondrite, C-type asteroid, Insoluble Organic Matter
The results of Raman analysis of both IOMs show negligible difference from IOMs in other unheated and heated CM chondrites. The solid-state 13C NMR spectra indicate that low molar ratios of aliphatic carbon to aromatic carbon (~0.14) for both IOM. These ratios are clearly lower than that ratio of lower heating stage-I samples (~0.5) (Yabuta et al. 2005). This indicates that the loss of aliphatic component or the increase of aromatic component of IOMs during heating of the meteorites in asteroids. Elemental analysis shows low H/C ratios (~0.40) in the two meteorites. These ratios are lower compared with stage-I samples (~0.70) (Yabuta et al. 2005). Therefore, the structural and elemental properties of IOMs in both two CM chondrites are similar and consistent with heating stage-II samples.
The results of Raman analysis of IOMs in the two meteorites show no difference from heating stage-I samples in contrast to the NMR and elemental analysis results. The difference suggest that the stageⅡheating transformed most organic carbon into aromatic but did not transform the carbon to graphitic. The results suggest that incipient structural changes by low-temperature heating of IOMs can be better characterized by NMR and elemental analysis, and further graphitization at high temperature can be well detected by Raman spectroscopy (e.g., Busemann et al. 2007).