Isotopic characterisation of kerogen-like material in the Murchison carbonaceous chondrite

Abstract

Isotopic data for C, H and N in acid-resistant residues from carbonaceous chondrites show substantial variability during stepwise pyrolysis and/or combustion. After subtraction of contributions due apparently to inorganic C grains, of probably circumstellar origin, considerable isotopic variability remains, attributable to the kerogen-like organic fraction. That variability may be interpreted in terms of three or four distinct components, based on C, H and N isotopes. The relative proportions of those components vary significantly from sample to sample. The different isotopic components are tentatively identified in terms of specific chemical/structural moieties within the kerogen-like material. This combination of chemical, structural and isotopic information suggests a complex history for meteoritic organic matter. At least three components within the organic population as a whole still carry a signature of apparently interstellar Denrichment. Part, at least, of the interstellar carrier consisted of reactive entities, not solely polymers.