Estimation of nitrogen-to-carbon ratios of organics and carbon materials at the submicrometer scale

Alleon, Julien; Bernard, Sylvain; Rémusat, Laurent; Robert, François

doi:10.1016/j.carbon.2014.11.044

Cited by 24 publications

(35 citation statements)

References 44 publications

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“…3 and 12 of Zinner, 2014); SEM-EDS analysis only revealed C for this grain raising the possibility that it is indeed a presolar graphite that got sheared into two fragments during polishing of the DOM 08006 thin section. However, the NanoSIMS measurement of this grain revealed it to be rich in N, with a measured CN -/Csecondary ion ratio of ~0.8, roughly corresponding to ~10% N (Alleon et al, 2015), suggesting that it is in fact N-rich organic matter and not graphite. This does not rule out it being a presolar circumstellar organic grain, as organic molecules are indeed observed around evolved stars (Matsuura et al, 2014), but it does have a relatively unusual isotopic composition for AGB stardust.…”

Section: Organic Mattermentioning

confidence: 92%

High abundances of presolar grains and 15N-rich organic matter in CO3.0 chondrite Dominion Range 08006

Nittler

Alexander

Davidson

et al. 2018

Geochimica et Cosmochimica Acta

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NanoSIMS C-, N-, and O-isotopic mapping of matrix in CO3.0 chondrite Dominion Range (DOM) 08006 revealed it to have in its matrix the highest abundance of presolar O-rich grains (257 +76/-96 ppm, 2σ) of any meteorite. It also has a matrix abundance of presolar SiC of 35 (+25/-17, 2σ) ppm, similar to that seen across primitive chondrite classes. This provides additional support to bulk isotopic and petrologic evidence that DOM 08006 is the most primitive known CO meteorite. Transmission electron microscopy of five presolar silicate grains revealed one to have a composite mineralogy similar to larger amoeboid olivine aggregates and consistent with equilibrium condensation, two non-stoichiometric amorphous grains and two olivine grains, though one is identified as such solely based on its composition. We also found insoluble organic matter (IOM) to be present primarily as sub-micron inclusions with ranges of C- and N-isotopic anomalies similar to those seen in primitive CR chondrites and interplanetary dust particles. In contrast to other primitive extraterrestrial materials, H isotopic imaging showed normal and homogeneous D/H. Most likely, DOM 08006 and other CO chondrites accreted a similar complement of primitive and isotopically anomalous organic matter to that found in other chondrite classes and IDPs, but the very limited amount of thermal metamorphism experienced by DOM 08006 has caused loss of D-rich organic moieties, while not substantially affecting either the molecular carriers of C and N anomalies or most inorganic phases in the meteorite. One C-rich grain that was highly depleted in C andN was identified; we propose it originated in the Sun's parental molecular cloud.

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Section: Organic Mattermentioning

confidence: 92%

High abundances of presolar grains and 15N-rich organic matter in CO3.0 chondrite Dominion Range 08006

Nittler

Alexander

Davidson

et al. 2018

Geochimica et Cosmochimica Acta

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“…For the present study, samples were deposited on Si 3 N 4 windows (50 nm thick membrane). Image stacks were collected with energy increments of 1 eV over the 250-450 eV energy range to measure N/C values, following the procedure described in Alleon et al, (2015) . Additional image stacks were collected with energy increments of 0.1 eV over the carbon (270-350 eV) and the nitrogen (390-420 eV) absorption ranges to gain insights on carbon and nitrogen speciation.…”

Section: Xanes Spectroscopy 251 Xanes Data Acquisition Proceduresmentioning

confidence: 99%

Evolution of interstellar organic compounds under asteroidal hydrothermal conditions

Vinogradoff

Bernard

Guillou

et al. 2018

Icarus

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International audienceCarbonaceous chondrites (CC) contain a diversity of organic compounds. No definitive evidence for a genetic relationship between these complex organic molecules and the simple organic molecules detected in the interstellar medium (ISM) has yet been reported. One of the many difficulties arises from the transformations of organic compounds during accretion and hydrothermal alteration on asteroids. Here, we report results of hydrothermal alteration experiments conducted on a common constituent of interstellar ice analogs, Hexamethylenetetramine (HMT – C 6 H 12 N 4). We submitted HMT to asteroidal hydrothermal conditions at 150 °C, for various durations (up to 31 days) and under alkaline pH. Organic products were characterized by gas chromatography mass spectrometry, infrared spectroscopy and synchrotron-based X-ray absorption near edge structure spectroscopy. Results show that, within a few days, HMT has evolved into (1) a very diverse suite of soluble compounds dominated by N-bearing aromatic compounds (> 150 species after 31 days), including for instance formamide, pyridine, pyrrole and their polymers (2) an aromatic and N-rich insoluble material that forms after only 7 days of experiment and then remains stable through time. The reaction pathways leading to the soluble compounds likely include HMT dissociation, formose and Maillard-type reactions, e.g. reactions of sugar derivatives with amines. The present study demonstrates that, if interstellar organic compounds such as HMT had been accreted by chondrite parent bodies, they would have undergone chemical transformations during hydrothermal alteration, potentially leading to the formation of high molecular weight insoluble organic molecules. Some of the diversity of soluble and insoluble organic compounds found in CC may thus result from asteroidal hydrothermal alteration

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“…The morphological and chemical changes of experimental organic residues have been characterized using scanning electron microscopy (SEM) and X-ray absorption near edge structure (XANES) spectroscopy, a synchrotron-based technique offering a precise estimation of the nitrogen-to-carbon (N/C) atomic ratio of organics 36, 37 as well as key information about chemical structures, i.e. carbon and nitrogen speciation, with a submicrometric spatial resolution 24, 38 .…”

Section: Introductionmentioning

confidence: 99%

Organic molecular heterogeneities can withstand diagenesis

Alleon

Bernard

Guillou

et al. 2017

Sci Rep

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Reconstructing the original biogeochemistry of organic fossils requires quantifying the extent of the chemical transformations that they underwent during burial-induced maturation processes. Here, we performed laboratory experiments on chemically different organic materials in order to simulate the thermal maturation processes that occur during diagenesis. Starting organic materials were microorganisms and organic aerosols. Scanning transmission X-ray microscopy (STXM) was used to collect X-ray absorption near edge spectroscopy (XANES) data of the organic residues. Results indicate that even after having been submitted to 250 °C and 250 bars for 100 days, the molecular signatures of microorganisms and aerosols remain different in terms of nitrogen-to-carbon atomic ratio and carbon and nitrogen speciation. These observations suggest that burial-induced thermal degradation processes may not completely obliterate the chemical and molecular signatures of organic molecules. In other words, the present study suggests that organic molecular heterogeneities can withstand diagenesis and be recognized in the fossil record.The fossil record contains crucial information about the evolution of Life on Earth 1, 2 . Molecular investigations regarding ancient Life are yet limited by the poor quality of the 'biogeochemical' signals preserved in the fossil record: in addition to biodegradation, burial-induced alteration processes (i.e. thermal maturation) inevitably modify the original biochemical signatures of fossilized organic molecules 1, 3 . With increasing temperature, weaker organic bonds are thermally broken and significant deoxygenation and dehydrogenation reactions occur 1, 4 . Thermal degradation eventually promotes increasing structural reorganization and may ultimately lead to the formation of pure graphite 5,6 .It has long been recognized that biomacromolecules exhibit conspicuous differences in decay in natural environments 7,8 . For instance, cell-wall biopolymers that protect some algae, cysts, spores and pollen grains are intrinsically more resistant than polysaccharides, proteins and nucleic acids 9-11 . In some contexts, taxon-specific chemosystematic data can even be preserved in the fossil record 12,13 . Still, the general perception in paleobiology remains that thermal maturation processes lead to a converging composition of organic materials from different origins, thereby limiting the use of chemical composition for discriminating between possibly different fossilized taxa 14 .Taking advantage of advanced spectroscopic tools (including synchrotron-based techniques), a number of studies have demonstrated that organic molecules may undergo only partial degradation during diagenesis in natural settings [15][16][17][18][19][20][21][22][23][24] . In parallel, laboratory experiments have helped evaluating the influence of key factors such as the pressure-temperature conditions, the redox conditions, the presence or absence of a fluid or of certain mineral phases on the degradation of organics 22,[25][26][27][28...

show abstract

Estimation of nitrogen-to-carbon ratios of organics and carbon materials at the submicrometer scale

Cited by 24 publications

References 44 publications

High abundances of presolar grains and 15N-rich organic matter in CO3.0 chondrite Dominion Range 08006

High abundances of presolar grains and 15N-rich organic matter in CO3.0 chondrite Dominion Range 08006

Evolution of interstellar organic compounds under asteroidal hydrothermal conditions

Organic molecular heterogeneities can withstand diagenesis

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