Organic compounds in stony meteorites

Abstract

Eight carbonaceous chondrites (Orgueil, Cold Bokkeveld, Mighei, Murray, Felix, Lancé and Warrenton), five non-carbonaceous chondrites (Richardton, Bjurböle, Karoonda, Abee and Hvittis) and one achondrite (Norton County) were examined for organic constituents. Hydrocarbon-type organic matter was extracted from the samples with organic solvents (benzene-acetone and acetone-methanol) and studied by ultra-violet, visible and infra-red absorption spectroscopy and by nuclear magnetic resonance spectroscopy. Both aliphatic and aromatic compounds were detected; in addition carbonyl groups appeared to be present as well as unsaturated groups of the vinyl or allylic type. The extractions also separated elemental sulfur in Orgueil, Cold Bokkeveld, Mighei and Richardton. Amino acids and sugars were encountered in all the meteorites studied. The sugars were present in small quantities (5–26 μ g/g) with mannose and glucose the most abundant. Amino acids were present in greater concentrations—30–500 μ g/g in the carbonaceous chondrites and 8–50 μ g/g in the others. Seventeen amino acids were detected: serine, glycine, alanine, the leucines. glutamic acid, asparatic acid and threonine were found to be the most abundant. C'hondrules were isolated from Mokoia, Bjurböle and Richardton, and analysed for sugars and amino acids. Those from Mokoia and Bjurböle were carefully washed before analysed. No sugars were present and glycine was the only water-soluble amino acid found. Besides glycine a great variety of ninhydrin-positive compounds appeared on the chromatograms. In the acid hydrolyzate, alanine, serine, threonine, the leucines, glutamic acid and aspartic acid were also present. Acid hydrolyzates of carbonaceous chondrites contained 16 diazonium-sensitive compounds, four of which had the Chromatographic properties (in terms of R f value and color) of hydroxy-berizoic, p-hydroxybenzoic, p-hydroxyphenylacetic, and vanillic acids. In addition, fifteen unidentified, ultraviolet-absorbing and fluorescing compounds appeared on the chromatogram. All extracts were tested for optical rotation on a polarimeter capable of measuring 0.0005°. No rotation could be detected. The absence of rotation, the type and distribution pattern of amino compounds in chondrules and matrix, the lack of pigments, fatty acids and presumably nucleic acids in addition to other biochemical criteria, suggest that the organic material has been synthesized by chemical rather than known biochemical processes.