The polymer-like organic material in the Orgueil meteorite

Abstract

The insoluble organic material in the Orgueil (Cl) chondrite was analyzed by combined high vacuum pyrolysis-gas chromatography-mass spectrometry. Stepwise pyrolyses at 150, 300, 450 and 600°C of Orgueil meteorite powder which had been exhaustively extracted with solvents yielded a series of alkenes and alkanes to C 8, an extensive series of alkylbenzene isomers, thiophene, alkylthiophenes, and benzothiophene, together with the nitrogen- and oxygen-containing breakdown products, acetonitrile, acrylonitrile, benzonitrile, acetone and phenol. The Orgueil polymer fragmentation products are very similar both qualitatively and quantitatively to pyrolysis products of solvent-extracted Pueblito de Allende (C3) chondrite described in the literature. Changes in the relative abundances of polymer degradation products between 150 and 600°C imply the preferential loss of aliphatic and certain heteroatomic portions of the polymer at lower temperatures to leave highly condensed aromatic and heteroaromatic portions of the polymer which begin to fragment only at 450–600°C. The Orgueil polymer-like matter thus appears to be a complex mixture of polymerized materials having different thermal stabilities. Similarities between vacuum pyrolyzates of the Orgueil polymer and terrestrial kerogen suggest the possibility that meteorite organic matter may have been subjected on the meteorite parent bodies to diagenetic processes similar to those by which terrestrial kerogen is formed.