Insoluble Organic Matter Research Articles

Organic geochemical characteristics and hydrocarbon generation simulation of shallow sediments in Shaobo Lake, Eastern China

We selected the two Holocene shallow surface sediments (depths of 1.42–1.48 and 1.56–1.62 m) of Shaobo Lake in Yangzhou City, Jiangsu Province, China, to analyze the geochemical characteristics and hydrocarbon generation ability of organic matter (OM) from its raw state to the formation of kerogen. We have used the Rock-Eval (RE) VI, low-temperature hydrous pyrolysis, and macerals identified under microscopy to test the whole-rock samples, as well as gas chromatography-mass spectrometry and gas chromatography analysis of the pyrolysis oil and pyrolysis gas. The results indicate that the surface sediments had poor to fair gas-prone hydrocarbon generation potential and that the type of insoluble OM was III-IV. The macerals were dominantly vitrinite, followed by sapropelic amorphogen. Bulk geochemistry data and biomarker compositions indicated that the studied samples deposited in a lacustrine environment with suboxic to anoxic conditions and OM of mixed plankton, bacterial, and land plant origin. RE data and the biomarker index suggested that unheated and thermally simulated samples were from immaturity to just entering the maturity stage. Under the thermal simulation conditions of 250°C–450°C, a peak of pyrolysis oil appeared at 300°C, and the yield increased slowly after 350°C. At 300°C, the hydrocarbon gas (C1–C5) began to produce. As the simulated temperature increased, the yield (in volume) of the hydrocarbon gas increased exponentially and the methane content was also gradually enriched. In general, thermal simulation experiments indicated that the OM could generate slight hydrocarbon from the death of living organisms to early diagenesis.

Selective chemical degradation of silica sinters of the Taupo Volcanic Zone (New Zealand). Implications for early Earth and Astrobiology.

Most organic matter (OM) on Earth occurs as kerogen-like materials, that is naturally formed macromolecules insoluble with standard organic solvents. The formation of this insoluble organic matter (IOM) is a topic of much interest, especially when it limits the detection of compounds of geomicrobiological interest. For example, studies that search for biomarker evidence of life on early Earth or other planets usually use solvent-based extractions. This leaves behind a pool of OM as unexplored post-extraction residues, potentially containing diagnostic biomarkers. Since the IOM has an enhanced potential for preservation compared to soluble OM, analysing IOM-released biomarkers can also provide even deeper insights into the ecology of ancient settings, with implications for early Earth and Astrobiology investigations. Here, we analyse the prokaryotic lipid biosignature within soluble and IOM of the Taupo Volcanic Zone (TVZ) silica sinters, which are key analogues in the search for life. We apply sequential solvent extractions and a selective chemical degradation upon the post-solvent extraction residue. Moreover, we compare the IOM from TVZ sinters to analogous studies on peat and marine sediments to assess patterns in OM insolubilisation across the geosphere. Consistent with previous work, we find significant but variable proportions-1%-45% of the total prokaryotic lipids recovered-associated with IOM fractions. This occurs even in recently formed silica sinters, likely indicating inherent cell insolubility. Moreover, archaeal lipids seem more prone to insolubilisation as compared to the bacterial analogues, which might enhance their preservation and also bias overall biomarkers interpretation. These observations are similar to those observed in other settings, confirming that even in a setting where the OM derives predominantly from prokaryotic sources, patterns of IOM formation/occurrence are conserved. Differences with other settings, however, such as the occurrence of archaeol in IOM fractions, could be indicative of different mechanisms for IOM formation that merit further exploration.

Early diagenetic sequestration of microbial mat lipid biomarkers through covalent binding into insoluble macromolecular organic matter (IMOM) as revealed by sequential chemolysis and catalytic hydropyrolysis

Analyses of lipids in modern microbial mat ecosystems provide valuable insights into the taxonomic affinities of the dominant biological producers and consumers as well as carbon flow within the mat community. Such microbial mat biomarker assemblages also provide a window into the ancient biomarker record, facilitating paleobiological and paleoenvironmental reconstructions of analogous ecosystems on early Earth. Our focus was to investigate the covalent binding of lipid biomarkers into insoluble macromolecular organic matter (IMOM) during diagenesis in the well-studied hypersaline microbial mat ecosystems and underlying sediments at Guerrero Negro, Baja California Sur, Mexico. Following exhaustive solvent extraction, three different chemical degradation reagents of varying reactivity (acid methanolysis, trichloroacetic acid extraction, and periodate oxidation) were applied to two shallow sedimentary layers prior to fragmentation of the recalcitrant insoluble residues using catalytic hydropyrolysis (HyPy). The hydrocarbons released by HyPy included a complex variety of linear, branched and polycyclic alkane structures, including hopanes, methylhopanes and steranes. Our findings indicate that a significant fraction of the bound biomarker pool was strongly linked by covalent binding through functional groups into IMOM but that a portion of this bound pool was not recoverable by chemolysis treatment. These results provide new insights about the mode and timing of chemical binding of steroids and hopanoids, and their early diagenetic transformation products, into IMOM. The formation of sedimentary IMOM from the earliest stages of organic matter diagenesis, commencing on a timescale of only years, aids the long-term preservation of biomarker lipids in the geological record.

Pore structure evolution of lacustrine shales containing Type I organic matter from the Upper Cretaceous Qingshankou Formation, Songliao Basin, China: A study of artificial samples from hydrous pyrolysis experiments

To characterize the pore evolution of lacustrine shales containing Type I organic matter, we performed hydrous pyrolysis experiments on a lacustrine shale sample to make it reach various maturities. The samples with various maturities were then extracted using dichloromethane. Total organic carbon content, Rock-Eval pyrolysis, and low-pressure gas (CO2 and N2) adsorption analyses were performed on the samples before and after extraction. The results showed that the volumes and surface areas of micropores (<2 nm) of the extracted samples were much higher than those of the artificial samples, but the parameters of mesopores (2–50 nm) of the extracted samples were close to the samples before extraction, indicating that liquid hydrocarbons are mainly stored in micropores. There were no any obvious correlations between pore volumes and mineral contents for the extracted samples, suggesting maturity is the dominant control of pore structure. The pore evolution of the extracted samples is similar to that of the artificial samples. During maturation, micropore volumes initially decreased over the interval 0.71%–0.97% EASY%Ro before increasing at EASY%Ro values exceeding 1.08%. The changes in micropore volume of the extracted samples may be related to the formation and cracking of insoluble organic matter. During this process, mesopore volumes kept increasing, which is mainly aroused by kerogen decomposition or carbon loss. Our results could improve the understanding of pore evolution of lacustrine shales and provide some implications for shale oil storage.

One-step construction of Pickering emulsion via commercial TiO2 nanoparticles for photocatalytic dye degradation

Pickering emulsion (PE) stabilized by semiconductors for photocatalysis applications has received growing endorsement over the last decade due to its high interfacial activity. However, since most semiconductors inherently possess a strongly hydrophilic or hydrophobic surface and are unable to stabilize PE microcapsules by themselves, pretreating the surface of semiconductor powder with foreign modifier was usually unavoidable and inconvenient before the PE construction. Even worse, the added modifier inevitably limited the contact between the semiconductor and the reactant during the photocatalysis process. Herein, an oil-in-water PE was successfully obtained in one step without pretratment of the semiconductor, where the dye-contained wastewater and insoluble organic matter acted as the water and oil phases, respectively, and the dye molecules in water could directly assist TiO2 particles to become the stabilizer. The TiO2 powder in the formed PE system exhibited markedly enhanced photoactivity for dye degradation over that in traditional non-emulsified systems, and the PE microcapsules could be easily recovered for reuse and withstand long-term irradiation without severe demulsification. This work not only highlights a convenient and promising approach to build Pickering emulsion as a novel photocatalytic system with extremely high efficiency and recyclability, but also provides a new way of thinking on how to simplify the PE construction to meet more requirement in future practical applications.

Bulk chemical characteristics of soluble polar organic molecules formed through condensation of formaldehyde: Comparison with soluble organic molecules in Murchison meteorite

Carbonaceous chondrites contain up to 2 wt% organic carbon, which is present as acid and solvent insoluble solid organic matter (IOM) and solvent soluble organic matter (SOM). The extraterrestrial organic matter should record chemical processes occurred in different environments in the early history of the Solar System, and the role of parent body aqueous alteration in the synthesis or subsequent modification of IOM and SOM still requires accurate constraints. We conducted hydrothermal experiments to simulate the synthesis of organic molecules during aqueous alteration on small bodies. Bulk chemical characteristics of soluble organic matter synthesized from formaldehyde in aqueous solutions were studied to compare them with that of chondritic SOM. We found that the redox state of synthesized organic molecules depends on temperature; the molecules become richer in hydrogen at higher temperatures. This can be explained by a cross-disproportionation reaction between organic molecules and formic acid, which occurs as a side reaction of the aldol condensation and works more effectively at higher temperatures. Comparison of the bulk chemical characteristics between the synthesized molecules and SOM extracted from the Murchison meteorite with methanol shows that the soluble organic molecules in Murchison are more reduced than the synthesized molecules. Considering the temperature condition for aqueous alteration on the CM parent body that is lower than or equivalent to the experimental temperatures, the reduced nature of Murchison organic molecules requires a reducing environment for them to be formed during hydrothermal alteration or imply that processes other than hydrothermal alteration were responsible for their synthesis. In case of hydrothermal synthesis, reducing conditions might be established by the interaction between water and iron-bearing silicates or metals on the parent body.

Reaction of Q to thermal metamorphism in parent bodies: Experimental simulation

AbstractPlanetary noble gases in chondrites are concentrated in an unidentified carrier phase, called “Q.” Phase Q oxidized at relatively low temperature in pure oxygen is a very minor part of insoluble organic matter (IOM), but has not been separated in a pure form. High‐pressure (HP) experiments have been used to test the effects of thermal metamorphism on IOM from the Orgueil (CI1) meteorite, at conditions up to 10 GPa and 700 °C. The effect of the treatment on carbon structural order was characterized by Raman spectroscopy of the carbon D and G bands. The Raman results show that the IOM becomes progressively more graphite‐like with increasing intensity and duration of the HP treatment. The carbon structural transformations are accompanied by an increase in the release temperatures for IOM carbon and 36Ar during stepped combustion (the former to a greater extent than the latter for the most HP treated sample) when compared with the original untreated Orgueil (CI1) sample. The 36Ar/C ratio also appears to vary in response to HP treatment. Since 36Ar is a part of Q, its release temperature corresponds to that for Q oxidation. Thus, the structural transformations of Q and IOM upon HP treatment are not equal. These results correspond to observations of thermal metamorphism in the meteorite parent bodies, in particular those of type 4 enstatite chondrites, e.g., Indarch (EH4), where graphitized IOM oxidized at significantly higher temperatures than Q (Verchovsky et al. ). Our findings imply that Q is less graphitized than most of the macromolecular carbonaceous material present during parent body metamorphism and is thus a carbonaceous phase distinct from other meteoritic IOM.

Electrolyte‐Regulated Solid‐Electrolyte Interphase Enables Long Cycle Life Performance in Organic Cathodes for Potassium‐Ion Batteries

AbstractOrganic cathode materials as economical and environment‐friendly alternatives to inorganic cathode materials have attracted comprehensive attention in potassium‐ion batteries (KIBs). Nonetheless, active material dissolution and mismatched electrolytes result in insufficient cycle life that definitely hinders their practical applications. Here, a significantly improved cycle life of 1000 cycles (80% capacity retention) on a practically insoluble organic cathode material, anthraquinone‐1,5‐disulfonic acid sodium salt, is realized, in KIBs through a solid‐electrolyte interphase (SEI) regulation strategy by ether‐based electrolytes. Such an excellent performance is attributed to the robust SEI film and fast reaction kinetics. More importantly, the ether‐electrolyte‐derived SEI film has a protective inorganic‐rich inner layer arising from the prior decomposition of potassium salts to solvents, as revealed by X‐ray photoelectron spectroscopy analysis and computational studies on molecular orbital energy levels. The findings shed light on the critical roles of electrolytes and the corresponding SEI films in enhancing performance of organic cathodes in KIBs.

Primordial heavy noble gases in the pristine Paris carbonaceous chondrite.

The Paris carbonaceous chondrite represents the most pristine carbonaceous chondrite, providing a unique opportunity to investigate the composition of early solar system materials prior to the onset of significant aqueous alteration. A dual origin (namely from the inner and outer solar system) has been demonstrated for water in the Paris meteorite parent body (Piani et al. 2018). Here, we aim to evaluate the contribution of outer solar system (cometary‐like) water ice to the inner solar system water ice using Xe isotopes. We report Ar, Kr, and high‐precision Xe isotopic measurements within bulk CM 2.9 and CM 2.7 fragments, as well as Ne, Ar, Kr, and Xe isotope compositions of the insoluble organic matter (IOM). Noble gas signatures are similar to chondritic phase Q with no evidence for a cometary‐like Xe component. Small excesses in the heavy Xe isotopes relative to phase Q within bulk samples are attributed to contributions from presolar materials. CM 2.7 fragments have lower Ar/Xe relative to more pristine CM 2.9 fragments, with no systematic difference in Xe contents. We conclude that Kr and Xe were little affected by aqueous alteration, in agreement with (1) minor degrees of alteration and (2) no significant differences in the chemical signature of organic matter in CM 2.7 and CM 2.9 areas (Vinogradoff et al. 2017). Xenon contents in the IOM are larger than previously published data of Xe in chondritic IOM, in line with the Xe component in Paris being pristine and preserved from Xe loss during aqueous alteration/thermal metamorphism.

Molecular Distribution, 13C-Isotope, and Enantiomeric Compositions of Carbonaceous Chondrite Monocarboxylic Acids.

The water-soluble organic compounds in carbonaceous chondrite meteorites constitute a record of the synthetic reactions occurring at the birth of the solar system and those taking place during parent body alteration and may have been important for the later origins and development of life on Earth. In this present work, we have developed a novel methodology for the simultaneous analysis of the molecular distribution, compound-specific δ13C and enantiomeric compositions of aliphatic monocarboxylic acids (MCA) extracted from the hot-water extracts of sixteen carbonaceous chondrites from CM, CR, CO, CV and CK groups. We observed high concentrations of meteoritic MCAs, with total carbon weight percentages which in some cases approached those of carbonates and insoluble organic matter. Moreover, we found that the concentration of MCAs in CR chondrites is higher than in the other meteorite groups, with acetic acid exhibiting the highest concentration in all samples. The abundance of MCAs decreased with increasing molecular weight and with increasing aqueous and/or thermal alteration experienced by the meteorite sample. The δ13C isotopic values of MCAs ranged from -52 to +27‰, and aside from an inverse relationship between δ13C value and carbon straight-chain length for C3-C6 MCAs in Murchison, the 13C-isotopic values did not correlate with the number of carbon atoms per molecule. We also observed racemic compositions of 2-methylbutanoic acid in CM and CR chondrites. We used this novel analytical protocol and collective data to shed new light on the prebiotic origins of chondritic MCAs.

Probing molecular and isotopic features of meteoritic insoluble organic matter by solid‐state nuclear magnetic resonance spectroscopy with sub‐milligram sample

AbstractWe recorded one‐ and two‐dimensional solid‐state nuclear magnetic resonance spectra of meteoric insoluble organic matter with unprecedented sensitivity and resolution permitting us to reveal unambiguous spectroscopic fingerprints relevant to its molecular and isotopic features. Two‐dimensional 1H‐1H and 1H‐13C correlation experiments have unveiled the spatial proximity between aliphatic and aromatic groups proving a highly branched character of a rigid macromolecular network composed of short aliphatic chains linking together small aromatic units. One‐dimensional 2H and two‐dimensional 1H‐2H correlation spectroscopy delivered evidence of significant reduction in the deuterium enrichment of aromatic species relevant to interstellar processes, proto‐planetary disk chemistry, and to determining the origin of the meteoritic insoluble organic matter. The experimental approach developed in this work opens new perspectives for systematic and nondestructive analysis at the molecular level of meteoritic insoluble organic matter even with a very small amount of sample from some particularly rare chondrites.

Prevalence and nature of heating processes in CM and C2-ungrouped chondrites as revealed by insoluble organic matter

Chondrites are exhumed from their parent bodies by impacts, which at the same time can result in heating and mechanical modification (compaction, deformation, fracturing, etc.). However, whether impacts are responsible for the occurrence of heated C2s remains controversial since radiogenic and solar heating have also been invoked to explain them. Here we report a Raman and infrared study of the composition and structure of Insoluble Organic Matter (IOM) in a series of 39 CM and C2-ungrouped chondrites. These parameters are tracers of the extent and nature of thermal metamorphism a meteorite has experienced and reflect the degree to which the thermally driven and irreversible carbonization of IOM has proceeded. We propose a carbon-based classification of heated C2 chondrites that reveals a high occurrence frequency of thermally processed C2 chondrites (>36%). This classification is in agreement with the mineralogical classification scheme of Nakamura (2005). Strongly heated C2 chondrites (PCA 02012, PCA 91008, Y 96720) display an IOM structural evolution that is dissimilar to that of type 3 chondrites that experienced long duration radiogenic thermal metamorphism. These differences almost certainly reflect kinetic constraints on IOM modification during short duration heating events. QUE 93005 is a weakly heated chondrite that experienced a retrograde aqueous alteration. Its very aliphatic-rich IOM points to a parent body hydrogenation through interactions with water. The closed-system conditions required by this mechanism could be satisfied by a kinetic confinement during a very short duration impact. MET 01072, a heavily compacted and uni-axially deformed chondrite, did not experience post-accretional heating. In this case, the deformation features probably reflect a low-velocity impact. In contrast, the weakly metamorphosed chondrite EET 96029 experienced one or several low pressure impacts that triggered mild heating and partial dehydration without deformation features. The study of a series of lithologies from the Tagish Lake C2-ungrouped chondrite confirms the coexistence of various degrees of post-accretional alteration, the most altered lithologies having experienced a moderate degree of heating. Overall, the high prevalence of heating in C2 chondrites, the evidence of short-duration heating in the most heated C2s and the ability of low velocity collisions to trigger heating favor impacts (against solar heating), as the dominant heating mechanism. Finally, our set of data does not support the action of a low temperature oxidation process that would control the aliphatic abundance in unheated primitive C2s.

Insights into the origin of carbonaceous chondrite organics from their triple oxygen isotope composition

Dust grains of organic matter were the main reservoir of C and N in the forming Solar System and are thus considered to be an essential ingredient for the emergence of life. However, the physical environment and the chemical mechanisms at the origin of these organic grains are still highly debated. In this study, we report high-precision triple oxygen isotope composition for insoluble organic matter isolated from three emblematic carbonaceous chondrites, Orgueil, Murchison, and Cold Bokkeveld. These results suggest that the O isotope composition of carbonaceous chondrite insoluble organic matter falls on a slope 1 correlation line in the triple oxygen isotope diagram. The lack of detectable mass-dependent O isotopic fractionation, indicated by the slope 1 line, suggests that the bulk of carbonaceous chondrite organics did not form on asteroidal parent bodies during low-temperature hydrothermal events. On the other hand, these O isotope data, together with the H and N isotope characteristics of insoluble organic matter, may indicate that parent bodies of different carbonaceous chondrite types largely accreted organics formed locally in the protosolar nebula, possibly by photochemical dissociation of C-rich precursors.

The effect of stylolites on the deterioration of limestone: possible mechanisms of damage evolution

This study presents five different lithotypes of limestone containing stylolites and commonly used as dimension stones in Egypt, Hungary and Israel. All the studied limestones are generally hard, dense, with high degree of cementation and have high strength and low porosity. Stylolites are small tooth-like irregular surfaces most often developed on the carbonate-rich stones. Insoluble particles, i.e., organic matter, oxides and clays are usually incorporated within the stylolitic planes. The presence of stylolites and their filling materials generally has a large effect on the physical and mechanical properties of the host stones. The main aim of this study is to evaluate the damage mechanism of different stylolitic limestones and to understand the role of the clay in the deterioration of these stones. Hundred cube samples (2 cm) of all the studied limestones were subjected to 500 thermal cycles (10–70 °C) and 20 cube samples (3 cm) of a grey Israeli limestone with high open porosity were subjected to multiple wet/dry cycles. The changes in mass, strength, and ultrasound Vp velocity, were measured to follow any damage that happened due to cycling. The thermal cycling was proved to be an effective deterioration mechanism of both Egyptian and Hungarian lithotypes. The response of Israel grey lithotype to the wet/dry cycling was clearly shown by the splitting of the tested samples through the stylolite planes and the sharp decrease of their strength.

Lithium–Organic Nanocomposite Suspension for High-Energy-Density Redox Flow Batteries

Organic redox-active materials are promising for redox flow batteries (RFBs) owing to their inherent low-cost, vast abundance, and high structure tunability. However, many organic RFBs suffer from low energy density owing to low solubility. We demonstrate a facile lithium–organic nanocomposite suspension (LIONS) by melting solid organic materials into the void of carbon networks in the semisolid posolyte to achieve high-energy-density Li-RFBs. We demonstrate the first organic-based semisolid Li-RFBs using 10-methylphenothiazine (MPT), delivering a high volumetric capacity (55 Ah L–1) and energy density (190 Wh L–1) with high Coulombic efficiency (>98%) and cycling stability (>100 cycles). The demonstrated volumetric capacity is 8 fold that of the liquid-MPT RFB, achieving the highest energy density among Li–organic-based RFBs. LIONS is a universal approach to enable the use of low-solubility organic materials in RFBs, providing a new direction for all insoluble organic active material to achieve low-cost ...

New Constraints on the Abundance and Composition of Organic Matter on Ceres

AbstractNear‐infrared reflectance spectra from the Dawn mission at Ceres were recently found to exhibit a 3.4 μm absorption indicative of the presence of aliphatic organic compounds. Constraints on abundance and composition of these organics are necessary to inform discussions of their origin. We model reflectance spectra of organic‐bearing regions on Ceres using laboratory spectra of insoluble organics of known composition extracted from terrestrial sedimentary rocks (i.e., kerogens) and carbonaceous chondrite meteorites (i.e., insoluble organic matter, IOM). The 3.4 μm aliphatic organic absorptions observed in Dawn near‐infrared data are stronger than those observed in lab spectra of carbonaceous chondrites, and modeling requires 45% to 65% spectral fraction of IOM to fit spectra from Ceres. The spectral fraction of kerogen necessary to fit the same Ceres spectra ranges from 5% to 15% depending on the hydrogen to carbon ratio of the kerogen. Any proposed mechanism of organic delivery or formation on Ceres should explain the presence of highly concentrated IOM or why the composition is distinct from meteorite‐derived IOM if lower organic abundances are considered more plausible.

High-temperature Ionization-induced Synthesis of Biologically Relevant Molecules in the Protosolar Nebula

Abstract Biologically relevant molecules (hereafter biomolecules) have been commonly observed in extraterrestrial samples, but the mechanisms accounting for their synthesis in space are not well understood. While electron-driven production of organic solids from gas mixtures reminiscent of the photosphere of the protosolar nebula (PSN; i.e., dominated by CO–N2–H2) successfully reproduced key specific features of the chondritic insoluble organic matter (e.g., elementary and isotopic signatures of chondritic noble gases), the molecular diversity of organic materials has never been investigated. Here, we report that a large range of biomolecules detected in meteorites and comets can be synthesized under conditions typical of the irradiated gas phase of the PSN at temperatures = 800 K. Our results suggest that organic materials—including biomolecules—produced within the photosphere would have been widely dispersed in the protoplanetary disk through turbulent diffusion, providing a mechanism for the distribution of organic meteoritic precursors prior to any thermal/photoprocessing and subsequent modification by secondary parent body processes. Using a numerical model of dust transport in a turbulent disk, we propose that organic materials produced in the photosphere of the disk would likely be associated with small dust particles, which are coupled to the motion of gas within the disk and therefore preferentially lofted into the upper layers of the disk where organosynthesis occurs.

Comparison of soluble and insoluble organic matter in analogues of Titan's aerosols

Titan, the biggest moon of Saturn, has a thick atmosphere which presents similarities with the one thought to be on Earth at its beginning. The study of Titan's photochemical haze is thus a precious tool in gaining knowledge of the primitive atmosphere of Earth. The chemistry occurring in Titan's atmosphere and the exact processes at act in the formation of the hazes remain largely unknown. The production of analogs samples on Earth has proved to be a useful tool to improve our knowledge of the aerosols formation on Titan. Such solid organic analogs samples, named tholins, were produced with the PAMPRE experiment (French acronym for Aerosols Microgravity Production by Reactive Plasma). PAMPRE tholins were found to be mostly insoluble, with only one-third of the bulk sample that can be dissolved in methanol. This partial solubility limited the previous studies in mass spectrometry, which were done only on the soluble fraction. The goal of the present study is to compare the two fractions of PAMPRE's tholins (insoluble and soluble) using a ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometer (FTICR) equipped with a laser desorption/ionization source. Using modified Van Krevelen diagrams, we compare the global distribution of the molecules within the samples according to their Hydrogen/Carbon ratio and Nitrogen/Carbon ratio. Major differences are observed in the molecular composition of the soluble and the insoluble fraction. The soluble fraction of tholins was previously identified as a set of polymers of average formula (C2H3N)n. In this work we observe that the insoluble fraction of tholins is comprised of a significantly different set of polymers with an average composition of (C4H3N2)n.

Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers

Abstract. Optical trapping combined with Mie spectroscopy is a new technique used to record the refractive index of insoluble organic material extracted from atmospheric aerosol samples over a wide wavelength range. The refractive index of the insoluble organic extracts was shown to follow a Cauchy equation between 460 and 700 nm for organic aerosol extracts collected from urban (London) and remote (Antarctica) locations. Cauchy coefficients for the remote sample were for the Austral summer and gave the Cauchy coefficients of A = 1.467 and B = 1000 nm2 with a real refractive index of 1.489 at a wavelength of 589 nm. Cauchy coefficients for the urban samples varied with season, with extracts collected during summer having Cauchy coefficients of A=1.465±0.005 and B=4625±1200 nm2 with a representative real refractive index of 1.478 at a wavelength of 589 nm, whilst samples extracted during autumn had larger Cauchy coefficients of A = 1.505 and B = 600 nm2 with a representative real refractive index of 1.522 at a wavelength of 589 nm. The refractive index of absorbing aerosol was also recorded. The absorption Ångström exponent was determined for woodsmoke and humic acid aerosol extract. Typical values of the Cauchy coefficient for the woodsmoke aerosol extract were A=1.541±0.03 and B=14800±2900 nm2, resulting in a real refractive index of 1.584 ± 0.007 at a wavelength of 589 nm and an absorption Ångström exponent of 8.0. The measured values of refractive index compare well with previous monochromatic or very small wavelength range measurements of refractive index. In general, the real component of the refractive index increases from remote to urban to woodsmoke. A one-dimensional radiative-transfer calculation of the top-of-the-atmosphere albedo was applied to model an atmosphere containing a 3 km thick layer of aerosol comprising pure water, pure insoluble organic aerosol, or an aerosol consisting of an aqueous core with an insoluble organic shell. The calculation demonstrated that the top-of-the-atmosphere albedo increases by 0.01 to 0.04 for pure organic particles relative to water particles of the same size and that the top-of-the-atmosphere albedo increases by 0.03 for aqueous core-shell particles as volume fraction of the shell material increases to 25 %.

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

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 13C and 15N was identified; we propose it originated in the Sun’s parental molecular cloud.