The insoluble carbonaceous material of CM chondrites: A possible source of discrete organic compounds under hydrothermal conditions

Abstract

Abstract-We report on the molecular analyses of the water-and solvent-soluble organic compounds released from the insoluble organic material (IOM) of the Murray meteorite upon treatment with weight-equivalent amounts of water and under conditions of elevated temperature and pressure. A varied suite of compounds was identified by gas chromatography-mass spectrometry (GC-MS). C 3 -C 17 alkyl dicarboxylic acids and N-and O-containing hydroaromatic and aromatic compounds were found in the water extracts. The solvent extracts contained N-, O-, and S-containing aromatic compounds, a large number of their isomers and homologs, and a series of polycyclic aromatic hydrocarbons (PAHs) of up to five rings, together with noncondensed aromatic species such as substituted benzenes, biphenyl, and terphenyls as well as their substituted homologs, and hydrated PAHs. Isotopic analyses showed that residue IOMs after hydrothermal treatment had lower deuterium and 15 N content than the untreated material (ΔD = −833‰ and Δ 15 N = −24.1) but did not differ from it in 13 C composition. The effect of the hydrothermolytic release was recorded in significant differences between the NMR spectra of untreated and residue IOM. A possible relation to common precursors for the dicarboxylic acids found in the IOM and bulk extracts is discussed.

Deuterium- and ¹⁵N-signatures of organic globules in Murchison and Northwest Africa 801 meteorites

“…Oba and Naraoka (2009) experimentally demonstrated a decrease of the dD value for IOM in Murchison (e.g., from 986‰ to 307‰ at 270∞C). Similar results were observed for the IOM of the Murray meteorite (CM2) (from 792‰ to -41‰ at 300∞C: Yabuta et al, 2007). Therefore, the lower amount of D-rich organic matter in Murchison than in NWA 801 suggests that modification of H isotopic composition occurred during aqueous alteration on the parent body of Murchison.…”

Organic and volatile elements in the solar system

“…This is consistent with higher content of phenols produced by pyrolysis of IOMs of CI compared to CM [54,89]. It must be noted that such process could lead to the formation of some soluble compounds [28,90]. Nevertheless these modifications appear to be limited, as the molecular structure of CI, CM and CR IOMs seems to be broadly similar.…”

Organic material in meteorites and the link to the origin of life

“…The soluble fraction is likely a mixing between moieties that could have been formed on the parent body, from the reaction of precursors that could have been accreted in ices or from the hydrolysis of the IOM, and compounds that could have been synthesized prior to accretion and preserved trapped in the matrix of the carbonaceous chondrites. The question of the genetic link between soluble and insoluble organic matter is still debated; the IOM could for instance release some soluble compounds during hydrothermal alteration [23,24]. To date, only aromatic hydrocarbons could be related to the macromolecular carbon [23].…”