Molecular study of insoluble organic matter in Kainsaz CO3 carbonaceous chondrite: Comparison with CI and CM IOM Item Type Article; text Authors Remusat, L.; Le Guillou, C.; Rouzaud, J.-N.; Binet, L.; Derenne, S.; Robert, F. Citation Remusat, L., Le Guillou, C., Rouzaud, J.-N., Binet, L., Derenne, S., & Robert, F. (2008). Molecular study of insoluble organic matter in Kainsaz CO3 carbonaceous chondrite: Comparison with CI and CM IOM. Meteoritics & Planetary Science, 43(7), 1099-1111. DOI 10.1111/j.1945-5100.2008.tb01115.x Publisher The Meteoritical Society Journal Meteoritics & Planetary Science Rights Copyright © The Meteoritical Society Download date 01/10/2021 18:57:36 Item License http://rightsstatements.org/vocab/InC/1.0/ Version Final published version Link to Item http://hdl.handle.net/10150/656447 Meteoritics & Planetary Science 43, Nr 7, 1099–1111 (2008) Abstract available online at http://meteoritics.org Molecular study of insoluble organic matter in Kainsaz CO3 carbonaceous chondrite: Comparison with CI and CM IOM Laurent REMUSAT1‡, Corentin Le GUILLOU2, Jean-Noël ROUZAUD2, Laurent BINET3, Sylvie DERENNE1*, and François ROBERT4 1Laboratoire de Chimie Bioorganique et Organique Physique, UMR CNRS 7618 BioEMCo, Ecole Nationale Supérieure de Chimie de Paris, 11 rue Pierre et Marie Curie, 75005 Paris, France ‡Present address: Laboratoire de Géologie des Systèmes Volcaniques, UMR CNRS 7154, Institut de Physique du Globe de Paris/Université Pierre et Marie Curie, 4 place Jussieu, 75005 Paris, France 2Laboratoire de Géologie, UMR CNRS 8538, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 5, France 3Laboratoire de Chimie de la Matière Condensée de Paris, UMR CNRS 7574, Ecole Nationale Supérieure de Chimie de Paris, 11 rue Pierre et Marie Curie, 75005 Paris, France 4Laboratoire d’Etude de la Matière Extraterrestre, UMS CNRS 2679 NanoAnalyses, Museum National d’Histoire Naturelle, 61 rue Buffon, 75005 Paris, France *Corresponding author. E-mail: [email protected] (Received 25 May 2007; revision accepted 28 August 2007) Abstract–Kainsaz CO3 insoluble organic matter (IOM) was studied using Curie point pyrolysis, electronic paramagnetic resonance (EPR), and high-resolution transmission electron microscopy (HRTEM) to determine the effect of thermal metamorphism on molecular chondritic fingerprints. Pyrolysis released a very low amount of products that consist of one- and two-ring aromatic units with methyl, dimethyl, and ethyl substituents. Moreover, Kainsaz IOM contains two orders of magnitude fewer radicals than Orgueil, Murchison, and Tagish Lake IOM. In addition, no diradicaloids were found in Kainsaz, although they are thought to constitute a specific signature for weakly organized extraterrestrial organic compounds in contrast to terrestrial ones. HRTEM reveals a very heterogeneous structure, with microporous disordered carbon, mesoporous graphitic carbons and graphite. Graphitization likely occurs and explains the differences between Kainsaz and CI or CM IOM. Heating stress experienced by Kainsaz IOM, on the parent body and/or prior its accretion, is likely responsible for the differences in molecular and structural organizations compared with those of CI and CM IOM. INTRODUCTION molecular structure of IOM from CI and CM chondrites. It is now admitted that the IOM constitutes of rather small Carbonaceous chondrites are among the most studied aromatic units, highly cross-linked with short, branched objects from the solar system because of their primitive bulk aliphatic chains. Oxygen atoms are located in ether or ester compositions, noble gases concentration and composition, linkages between aromatic units. In contrast, nitrogen atoms and occurrence of primitive condensates and organic are involved into aromatic structures as pyrroles. These compounds. These organics can be recovered as soluble features are consistent with recent high-resolution compounds and, predominantly, as a macromolecular transmission electron microscopy (HRTEM) observations insoluble fraction, hereafter named insoluble organic matter performed on Orgueil and Murchison IOM (Derenne et al. (IOM). Organics have been so far almost exclusively studied 2005). Indeed, HRTEM is an efficient tool to study organic in CI and CM carbonaceous chondrites due to high abundance samples at the nanometer scale (Papoular et al. 1996; Galvez (for a review, see Pizzarello et al. 2006). The combination of et al. 2002; Le Guillou et al. 2007); it was extensively used to results from pyrolysis (Levy et al. 1973; Sephton et al. 2000, characterize coals, chars, and soots (Boulmier et al. 1982; 2004; Remusat et al. 2005a), chemical degradation (Hayatsu Rouzaud and Oberlin 1990; Beyssac et al. 2002), et al. 1980; Remusat et al. 2005b), and solid-state nuclear Precambrian organic matter (Jehlicka and Rouzaud 1993; magnetic resonance (Gardinier et al. 2000; Cody and Alexander Westall et al. 2006) and IOM of various carbonaceous 2005) allowed the determination of key features of the chondrites including Allende, Orgueil, and Murchison 1099 © The Meteoritical Society, 2008. Printed in USA. 1100 L. Remusat et al. (Daulton et al. 1996; Harris et al. 2000; Garvie and Buseck used. Organic matter is supposed to have kept the overprint of 2004). HRTEM clearly shows that Orgueil and Murchison thermal stress on the parent body, assuming a common IOMs are poorly organized and constitute of aromatic units organic precursor. Nevertheless, the modifications at the with an average size of 2–3 aromatic rings in diameter, and molecular level induced by this stress are not well assessed. that the aromatic units are smaller than PAHs observed in the We applied some methods used on CI and CM IOM to interstellar medium, which could be the result of a selective study the molecular structure of Kainsaz (CO3) IOM. Little is preservation of small PAHs in the IOM before their known about molecular structure of IOM from CO chondrites destruction by UV radiation (Derenne et al. 2005). compared to data available on CI and CM chondrites. Bonal Electronic paramagnetic resonance (EPR) is a powerful et al. (2007) have reported Raman spectra showing that method to determine the occurrence of radicals in natural organics in Kainsaz, and especially IOM, reveal a higher samples and their distribution. For instance, it allowed the degree of organization than CI and CM. Indeed, the spectra are determination of radical concentration in organic matter of characteristic of weakly graphitized carbons (important defect Precambrian chert, which is highly refractory (Gourier et al. band at about 1350 cm−1), which is consistent with noticeable 2004). EPR has also successfully determined a typical thermal stress since the D band is not so broad (FWHM = behavior for chondritic IOM through the study of Orgueil, 117 cm−1) compared to Orgueil and Murchison IOM. Murchison, and Tagish Lake IOM (Binet et al. 2002, 2004a, In the present study, we used pyrolysis, HRTEM, and 2004b). It clearly shows that these disordered IOM share two EPR to characterize the IOM of Kainsaz meteorite and we common signatures that discern these organic samples from compare the obtained data with those from CI and CM IOM. terrestrial ones: the occurrence of abundant diradicaloid Our goal was to asses the effect, at the molecular level, of a moieties—i.e., aromatic moieties with two unpaired electron thermal stress on carbonaceous chondrites parent bodies. radicals that can be stabilized by delocalization of electrons Furthermore, our purpose was to examine if Kainsaz IOM over the aromatic rings—and a heterogeneous distribution of would exhibit the same EPR signatures as Orgueil, organic radicals. These two features are interpreted as the Murchison, and Tagish Lake IOM. fingerprint of an interstellar-like process involved in the organosynthesis of extraterrestrial organic matter. EXPERIMENTAL Along with isotopic data, these features are used to describe the origin and evolution of the organic matter of the Sample Preparation most primitive object of the solar system. It is not simple to determine a scenario for the story of the IOM, as it could be Kainsaz fell in Russia (Tatarstan republic) in 1937. About the result of several processes taking place in the interstellar 9 g of Kainsaz were provided by the Museum National d’Histoire medium, the protosolar nebula, and the parent bodies of the Naturelle of Paris, France. The sample was crushed in an carbonaceous chondrites. To distinguish the contribution of agate mortar and IOM was subsequently isolated as described these processes, it is essential to study the variability between in Remusat et al. (2005b). In brief, the ground sample was several classes of carbonaceous chondrites. Indeed, subjected to several extractions in water (stirring under reflux carbonaceous chondrites are divided into different classes that for 48 h), acetone (stirring at room temperature for 2 h twice) represent different stages of thermal metamorphisms and and dichloromethane/methanol (2:1, v/v, stirring at room aqueous alterations (Scott and Krot 2003). As described temperature for 2 h twice). The solid residue was then before, most of the previous studies on organic contents in subjected to HF/HCl treatment: it was successively stirred in carbonaceous chondrites have focused on CI and CM, i.e., the HCl (6N) for 24 h at room temperature, in a mixture of HF/ most aqueously and the least thermally altered carbonaceous HCl (28N/6N, 2:1, v/v) for 24 h at room temperature under chondrites. nitrogen flux and finally in HCl (6N) for 4 h at 60 °C. The Kainsaz is a member of the Ornans type (i.e., CO) acid residue was then extracted with acetone and a mixture of carbonaceous chondrites, which constitute a metamorphic CH2Cl2/MeOH, 2:1, v/v and was dried under N2. Carbon and series analogous to that seen in ordinary chondrites hydrogen contents were determined by the SGS laboratory in (McSween 1977). Several studies have dealt with the Evry, France. determination of the petrographic type by using various The acid residue represents about 1.4 wt% of the ground proxies as mineralogical associations (Scott and Jones 1990; Kainsaz meteorite and contains 30.5 wt% and 0.4 wt% of Chizmadia et al.