Diversity of chondritic organic matter probed by ultra-high resolution mass spectrometry

Abstract

Primitive carbonaceous chondrites exhibit an unparalleled diversity in terms of their organic content, in addition to a variable degree of hydrothermal alteration. Whether this diversity results from the circulation of fluids or from a multiplicity of precursors remains an open question of prime interest to understand the formation of carbonaceous asteroids. We applied laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (LDI-FTICR-MS) on the macromolecular carbon of recent CM carbonaceous chondrite falls, as well as Orgueil (CI) and Tarda (C2). We probed the diversity of molecular fragments released under low power laser beam. The abundance of the chemical families is correlated to the extent of aqueous alteration, which promotes a structural aromatisation. The weakly altered Paris has retained the largest chemical heterogeneity, whilst it is lost in more altered chondrites. Orgueil and Tarda insoluble organic matter share similarities; this is consistent with Tarda and Orgueil originating from the outer belt region. Applied to returned asteroidal samples, FTICR-MS may help unravelling the origin and evolution of organic compounds during the early stages of the solar system.