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New Raman and NMR spectroscopy data on hydrous Ca aluminosilicate melts and glasses, with eutectic quartz–anorthite–wollastonite composition, are presented here. The glasses were obtained by rapid quench of melts equilibrated at high P and high T in a piston–cylinder apparatus. In situ Raman observations of the structure of the melts were also performed during hydrothermal diamond cell experiments. Using the intensities of the ${\sim }860~\text{cm}^{-1}$ and ${\sim }1630~\text{cm}^{-1}$ Raman signals, respectively assigned to vibrations of T–OH and $\text{H}_2\text{O}_{\mathrm{mol}}$ species, we determined the speciation of water in the glasses. T–OH and $\text{H}_2\text{O}_{\mathrm{mol}}$ values compare well with those determined from infrared (IR) spectra, except above ${\sim }5$ wt% total water where IR determinations actually underestimate the proportion of hydroxyl groups. The analysis of the polarized Raman spectra and of the ${}^{29}\text{Si}$ MAS NMR spectra of the hydrous glasses suggests limited changes in glass polymerization with variations in dissolved water content. However, at high temperatures, in situ Raman spectroscopy observations indicate that the hydrous melt structure differs very strongly from that of a glass containing a comparable concentration of dissolved water. Because of this, this study reinforces the fact that using glass data to try understanding high temperature processes in hydrous melts, like viscous flow or water diffusion toward bubbles during volcanic degassing, may not be very appropriate.

Bisulfite (HSO3−) and sulfite (SO32−) compounds play key roles in numerous geochemical and biochemical processes extending from the atmosphere to the subseafloor biosphere. Despite decades of spectroscopic investigations, the molecular composition of HSO3− in solution remains uncertain and, thus, the role of bisulfite in (bio)chemical and isotope fractionation processes is unclear. We report new experimental estimates for the bisulfite isomer quotient (Qi = [(HO)SO2−]/[(HS)O3−]; [] = concentration) as a function of temperature from the interpretation of Raman spectra collected from aqueous NaHSO3 solutions contained in fused silica capsules. In pure NaHSO3 solutions (1Na+:1HSO3−, stoichiometric) over [NaHSO3] = 0.2–0.4 m (moles/kg H2O), the following relationship is obtained: ln(Qi)=[formula ommited]-1.9642(±0.1081),where T = 278–358 K (5–85 °C) (based on 50 determinations; additional significant figures are provided to avoid rounding errors). This relationship suggests that the minor isomer, (HS)O3−, may comprise 23–38% (±3%) of the mole fraction of HSO3− over 5–85 °C, respectively, which is higher in relative abundance than has generally been understood previously. We additionally provide estimates for Qi in NaHSO3 solutions containing a total ionic strength of µ = 1.0 m (0.2 m NaHSO3 + 0.8 m NaCl) and different pH (3.3–4.5), but do not appear to resolve any significant differences in Qi as a function of these additional variables. These new values of Qi are employed to re-assess the bulk sulfur isotope fractionations among bisulfite and other S(IV) compounds as a function of temperature, which appear to be highly dependent on the amount of (HS)O3− present. Our new constraints on the bisulfite isomer quotient may allow for a detailed assessment of the molecular composition and isotope mass balance of S(IV) solutions containing HSO3−, and may be useful in the further investigation of the mechanisms and isotope fractionations associated with a number of processes that involve bisulfite compounds. These may include the intracellular enzymatic transformations of sulfite and bisulfite compounds that occur as part of dissimilatory sulfate reduction, which is a major and geologically important form of anaerobic respiration.

Primitive xenolithic clasts, often referred to as “dark clasts”, are well known in many regolith breccias. The Sharps H3.4 ordinary chondrite contains unusually large dark clasts up to ∼1 cm across. Poorly-graphitized carbon (PGC), with Fe, Ni metal and described as “carbon-rich aggregates”, has been reported in these clasts (Brearley, 1990). We report detailed analyses of carbonaceous matter in several identical Sharps clasts using FTIR, Raman, C-XANES, and TEM that provide insight on the extent of thermal processing and possible origin of such clasts. We also prepared acid residues of the clasts using the HCl/HF method and conducted mass spectrometric analysis of the entrained noble gases. Carbonaceous matter is often used to infer thermal history due to its sensitivity to thermal processes. The FTIR spectra of the acid residue from the Sharps clast suggest that carbonaceous matter in the clast contains less hydrogen and oxygen compared to acid residues from typical type 3.4 ordinary chondrites. The metamorphic temperatures obtained by Raman spectroscopy ranges between ∼380 °C and ∼490 °C. TEM observations indicate that the clasts experienced a peak temperature of 300 °C to 400 °C, based on the carbon d002 layer lattice spacing of C-rich aggregates. These estimates are consistent with an earlier estimate of 330 ± 50 °C, that is also estimated by the d002 layer lattice spacing (Brearley, 1990). It should be noted that the lattice spacing thermometer is based on terrestrial metamorphose rocks, and thus temperature was probably underestimated. Meanwhile, the C-XANES spectra of the C-rich aggregates show high exciton intensities, indicative of graphene structures that developed at around 700–800 °C following an extensive period of time (millions of years), however, the surrounding matrix areas experienced lower temperatures of less than 300–500 °C. Noble gas analysis of the acid residue from the Sharps clasts shows that the residue is almost identical with some material reported in carbonaceous chondrites, i.e., heavily enriched in the Q-gas component as well as HL-gas from presolar diamonds and Ne-E(H) from presolar SiC. These results indicate that the C-rich aggregates in the Sharps clasts formed under relatively high temperature conditions, up to 800 °C, and were subsequently mixed with lower temperature matrix, probably in a different parent body, before they were incorporated into the final Sharps lithology by collision.

We present here an investigation of Ryugu particles recovered by the Hayabusa2 space mission and their extracted carbonaceous acid residues using Raman spectroscopy. Raman parameters of Ryugu intact grains and their acid residues are characterized by broad D (defect induced) and G (graphite) band widths, indicating the presence of polyaromatic carbonaceous matter with low thermal maturity. Raman spectra of Ryugu particles and CI (type 1) chondrites exhibit stronger laser‐induced fluorescence backgrounds compared to Type 2 and Type 3 carbonaceous chondrites. The high fluorescence signatures and wide bandwidths of the D and G bands of Ryugu intact grains are similar to the Raman spectra observed in CI chondrites, reflecting the low structural order of their aromatic carbonaceous matter, and strengthening the link between Ryugu particles and CI chondrites. The high fluorescence background intensity of the Ryugu particles is due to multiple causes, but it is likely that the relative abundance of geometry‐bearing macromolecular organic matter in total organic carbon contents makes a large contribution to the fluorescence intensities. Locally observed high fluorescence in the acid‐extracted residues of Ryugu is due to nitrogen‐bearing outlier phase. The high fluorescence signature is one consequence of the low degree of thermal maturity of the organic matter and supports evidence that the Ryugu particles have escaped significant parent body thermal metamorphism. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy analyses of Hayabusa2 samples show that Ryugu organic matter exhibits a range of morphologies, elemental compositions, and carbon functional chemistries consistent with those of carbonaceous chondrites that have experienced low‐temperature aqueous alteration. Both nanoglobules and diffuse organic matter are abundant. Non‐globular organic particles are also present, and including some that contain nanodiamond clusters. Diffuse organic matter is finely distributed in and around phyllosilicates, forms coatings on other minerals, and is also preserved in vesicles in secondary minerals such as carbonate and pyrrhotite. The average elemental compositions determined by energy‐dispersive spectroscopy of extracted, demineralized insoluble organic matter samples A0107 and C0106 are C100N3O9S1 and C100N3O7S1, respectively, with the difference in O/C slightly outside the difference in the standard error of the mean. The functional chemistry of the nanoglobules varies from mostly aromatic C=C to mixtures of aromatic C=C, ketone C=O, aliphatic (CHn), and carboxyl (COOH) groups. Diffuse organic matter associated with phyllosilicates has variable aromatic C, ketone and carboxyl groups, and some localized aliphatics, but is dominated by molecular carbonate (CO3) absorption, comparable to prior observations of clay‐bound organic matter in CI meteorites. [ABSTRACT FROM AUTHOR]

We report a Fourier transform infrared analysis of functional groups in insoluble organic matter (IOM) extracted from a series of 100–500 μm Ryugu grains collected during the two touchdowns of February 22 and July 11, 2019. IOM extracted from most of the samples is very similar to IOM in primitive CI, CM, and CR chondrites, and shows that the extent of thermal metamorphism in Ryugu regolith was, at best, very limited. One sample displays chemical signatures consistent with a very mild heating, likely due to asteroidal collision impacts. We also report a lower carbonyl abundance in Ryugu IOM samples compared to primitive chondrites, which could reflect the accretion of a less oxygenated precursor by Ryugu. The possible effects of hydrothermal alteration and terrestrial weathering are also discussed. Last, no firm conclusions could be drawn on the origin of the soluble outlier phases, observed along with IOM in this study and in the preliminary analysis of Ryugu samples. However, it is clear that the HF/HCl residues presented in this publication are a mix between IOM and the nitrogen‐rich outlier phase. [ABSTRACT FROM AUTHOR]

The infrared spectral characteristics of organic‐rich acid residues prepared from Ryugu samples returned by the JAXA Hayabusa2 mission generally match those from unheated carbonaceous chondrite meteorites, but the residues from Ryugu are richer in methyl and methylene functional groups and have higher CH2/CH3 ratios. Moreover, two distinct outlier carbonaceous phases are found; one with spectral characteristics of N‐H functional groups, likely amides, and a second phase containing less nitrogen. Such infrared characteristics of Ryugu organic matter might indicate the pristine nature of the freshly collected samples and reflect the near‐surface chemistry in the parent asteroid. [ABSTRACT FROM AUTHOR]

This study analyzed samples of the Murchison and Sutter's Mill carbonaceous chondrite meteorites in support of the future analysis of samples returned from the asteroid (10155) Bennu by the OSIRIS‐REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission. Focusing specifically on the insoluble organic matter (IOM), this study establishes that a total of 1.3 g of bulk sample from a single chondritic meteorite are sufficient to obtain a wide range of cosmochemical information, including light element analysis (H, C, and N), isotopic analysis (D/H, 13C/12C, and 15N/14N), and x‐ray fluorescence spectroscopy for major elemental abundances. IOM isolated from the bulk meteorite samples was analyzed by light element and isotopic analysis as described above, 1H and 13C solid‐state nuclear magnetic resonance spectroscopy, Raman spectroscopy, and complete noble gas analyses (abundances and isotopes). The samples studied included a pair from Murchison (CM2), one of which had been irradiated with high‐energy x‐rays in the course of computed tomographic imaging. No differences between the irradiated and non‐irradiated Murchison samples were observed in the many different chemical and spectroscopic analyses, indicating that any x‐ray–derived sample damage is below levels of detection. Elemental, isotopic, and molecular spectroscopic data derived from IOM isolated from the Sutter's Mill sample reveals evidence that this meteorite falls into the class of heated CM chondrites. [ABSTRACT FROM AUTHOR]