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Introduction: Macromolecular organic matter in primitive small body materials is one of the reliable indicators to determine the chemical evolution in the early Solar System. JAXA's Hayabusa2 mission explored the carbonaceous asteroid Ryugu and collected its surface materials [1]. On December 6, 2020, the asteroid sample was returned to the Earth. Through the curatorial work at JAXA, it was reported that the Ryugu samples contain high abundances of hydrous minerals and organic matter [2, 3]. Afterward, the initial sample analysis has started from June 2021 to classify and characterize the Ryugu samples in the context of the Solar System formation. In order to uncover the significance of organic matter on C-type asteroid, the Initial Analysis Organic Macromolecule team unveiled the chemical, isotopic, and morphological compositions of macromolecular organic matter from the Ryugu samples. Samples and Methods: Chamber A aggregates (A0108) and Chamber C aggregates (C0109) collected at the first and second touchdown sites, respectively, have been analyzed. The individual intact grains from A0108 and C0109 range from 200 to 900 µm in size. Additional aggregates from Chamber A (A0106) and Chamber C (C0107) were transferred from the Soluble Organic Molecules team after their water and solvent extractions, and were treated with 6M HCl and 1M HCl/9M HF to yield insoluble organic matter (IOM) at Hiroshima University [4]. The main stream of the analytical procedures included a combination of µ-FTIR, µ-Raman spectroscopy, synchrotron-based STXMXANES, STEM-EELS-EDS, AFM-IR, NanoSIMS [4]. Additional protocols by Xe-PFIB, TXM, XRF, Solid-state 1H and 13C NMR, ToF-SIMS, Visible spectroscopy, and AFM have been included for the latter half of the initial analysis. EA-IRMS and noble gas isotope analysis of Ryugu IOM were also performed in collaboration with Soluble organic molecule (SOM) team [5] and Volatile team [6], respectively. Results and discussion: Macromolecular organic matter were abundant and has complex structures consisting of aromatic carbons, aliphatic carbons, ketones and carboxyls [7, 8]. The functional group compositions are typically seen in IOM from CI and CM chondrites. The functional group variations correlated with the morphologies of nanosized organic matter; organic nanoglobules and nanoparticles are aromatic-rich, while organic matter mixed with Mgrich phyllosilicate matrix and carbonates are IOM-like or diffuse carbon [8, 9]. The observed functional group diversity is likely influenced by aqueous evolution on the asteroid parent body without significant heating event. The dD distributions of Ryugu IOM from the Ryugu samples were within the dD range of CM, CI, and Tagish Lake chondrites [10]. The d15N of bulk C and insoluble organics from the Ryugu samples showed similar values to those from CI chondrites [10]. Extreme D and/or 15N enrichments or depletions in some carbonaceous grains could possibly have been derived from the solar nebula or protosolar molecular cloud. A very small fraction of carbonaceous particles show anomalous carbon isotopes including presolar SiC grains [11]. Ryugu organic matter likely resulted from heterogeneous aqueous processing that occurred on carbonaceous asteroids from the common primordial materials formed at an earlier stage of the solar nebula. These results proved the direct link between macromolecular organic matter in the carbonaceous asteroid and that in primitive carbonaceous chondrites. [ABSTRACT FROM AUTHOR]

Introduction: Ultra Carbonaceous Antarctic MicroMeteorites (UCAMMs) are sub-millimeter extraterrestrial particles with high abundance of organic matter and low abundance of minerals (C/Si ? 10 - 103), identified independently in the French and Japanese micrometeorite collections [1-6]. The organic matter in UCAMMs present high N/C ratios ranging from 0.02 to 0.2 [2, 7] and can present extreme D/H ratio. The characteristics of UCAMMs suggest that they were formed by irradiation by Galactic Cosmic Rays (GCRs) of nitrogen-rich ice mantles at the surface of small icy bodies [4, 8]. We investigated the isotopic signature of light elements in the organic matter of UCAMMs to study their links with organic matter from carbonaceous chondrites and interplanetary dust particles (IDPs). We present here a summary of our recent results, including sample analyses and ice irradiation experiments that aim at synthesizing analogs of the organic matter in UCAMMs. NanoSIMS analyses of UCAMMs: the H, C and N isotopic compositions of the 4 UCAMMs DC06-05-94 (DC94), DC06-07-18 (DC18), DC06-14-309 (DC309) and DC06-04-43 (DC43) were analyzed by nanoscale secondary ion mass spectrometry (NanoSIMS) at the Carnegie Earth and Planets Laboratory, the Museum National d'Histoire Naturelle and the Institut Curie [9]. The 4 UCAMMs do not exhibit similar isotopic compositions, with δD bulk values ranging from 1000‰ to 9000‰, δ13C from -90‰ to 30‰ and δ15N from -120‰ to 270‰. Each UCAMM is characterized by isotopic heterogeneities, typically at scales of a few μm [9]. Ice irradiation experiments: We performed ice irradiation experiments during 3 sessions in 2019, 2020 and 2021 at GANIL (Caen, France) [10], using the IGLIAS experimental setup connected to the IRRSUD ion beam (0.5-1 MeV/u). We formed 10μm - thick ice films by gas condensation on IR-transparent windows cooled down to 10K [8, 11]. The ice films consisted in one layer of isotopically labeled ice (with D, 15N and/or 13C-rich ice) between 2 layers of isotopically unlabeled ice (14N2-12CH4 or 14NH3-12CH4), forming an ice sandwich. The labeled layer accounted for 1% to 4% of the total thickness. Ice sandwiches were subsequently irradiated by heavy ions and slowly warmed up to the room temperature to obtain refractory organic residues. The residues, exhibiting an IR signature comparable to that of the organic matter in UCAMMs [8], were subsequently analyzed by NanoSIMS at the Institut Curie, to map the H, C and N isotopic heterogeneities. This study shows that the ion-processing of ice sandwiches made of N2-CH4 form an organic refractory residue that keeps the large isotopic heterogeneities of the initial ice sandwich, while that of NH3-CH4 ice sandwiches appears less favorable to the formation of isotopic heterogeneities. Extreme isotopic heterogeneities at low scale were observed in organic residues, indicating that local preservation of the initial ice sandwich composition can occur, maybe related to sporadic events during the annealing of the ice films. Results and discussion: These irradiation experiments demonstrate the possibility to form large micron-scale isotopic heterogeneities in organic residues from multilayer, isotopically heterogeneous, ice precursors. The organic matter of UCAMMs can thus have formed by irradiation by GCRs of isotopically heterogeneous ice mantles. Numerical models of the evolution of the early solar system predict the existence of gaseous reservoirs isotopically fractionated in H, C and N at different locations in the protoplanetary disk [12, 13]. The parent body/bodies of UCAMMs may have inherited from these fractionated reservoirs, condensed on its/their surface under the form of ice mantles. The diversity of isotopic signatures from one UCAMM to another also suggest that UCAMMs do not have anomalies inherited from one single parent gaseous reservoir. Further investigations on the correlation of elemental and isotopic ratios in the organic matter of UCAMMs will bring new insights to better constrain the characteristics of the parent reservoirs of UCAMMs. Acknowledgments: This work was funded by contract ANR-18-CE31-0011, CNES (MIAMI2), DIM-ACAV+ (C3E), CNRS-INSU/IN2P3 (PNP). The work at CONCORDIA Station (Projet#1120) was supported by IPEV and PNRA. [ABSTRACT FROM AUTHOR]

Introduction: Regolith samples of the carbonaceous asteroid 162173 Ryugu were returned by the Hayabusa2 spacecraft in December 2020. Preliminary investigation of selected grains from each sampling site has revealed the occurrence of an abundant macromolecular insoluble material, similar to that of carbonaceous chondrites [1]. Understanding the origin of organic matter on carbonaceous asteroids and its subsequent evolution due to secondary processes as well as space weathering is one of the prime goals of the Hayabusa2 sample-return mission. Isotope composition of organic material found in extraterrestrial samples is a powerful proxy for tracking its origin and evolution during the solar system events [2]. To document the H- and N-isotope signatures of IOM contained in the Ryugu samples, we have used the NanoSIMS installed at the National Muséum of Natural History in Paris. We present here data acquired on the IOM isolated from grains of two touchdown sites. We have imaged between 2800 and 3200 ?m2 of the IOM of chamber A and C, respectively. The comparison with the IOM of carbonaceous chondrites allows for evaluating the influence of space weathering and aqueous alteration on the IOM in carbonaceous asteroids. Results: N-isotope distributions: the bulk δ15N is +17.4‰ and +30‰ for the IOM of chamber A and chamber C, respectively. These IOMs contain both 15N-enriched and depleted carbonaceous grains, with 180‰<δ15N< 800‰ for hotspots and -380‰ < δ15N < -180‰ for coldspots. Hotspots define a Poisson distribution with a mode value of +241‰ and +348‰ for chamber A and chamber C, respectively. Elemental ratios: Bulk N/C, O/C and S/C of Ryugu IOM are 0.035, 0.12, 0.032, respectively, for chamber A and 0.027, 0.04, 0.025 for chamber C. The N/C ratio of individual 15N-rich and depleted grains are comprised between 0.01 and 0.07, with those in the IOM of A0106 being slightly more N rich. Similarly, O/C and S/C ratios are also slightly higher in A0106. H-isotope distribution: Ryugu IOM exhibits bulk enrichments in D with δD = +306‰ and +440‰ for chamber A and chamber C, respectively. Numerous D-rich hotspots, are observed, with +600‰ < δD < +6000‰. They define a Poisson distribution, with a mode value of +1030‰ and +1374‰ for chamber A and chamber C, respectively. Of note, a few D-depleted organic grains are also observed (-200‰ < δD < 0‰). Discussion: Subtle differences are observed between the IOM of chamber A and chamber C: the IOM is less enriched in heavy isotopes in chamber A, and more enriched in N, O and S. This may reflect some heterogeneity at the scale of the asteroid, or the influence of sampling depth, hence the influence of space weathering. However, the elemental and isotope compositions of the IOM in Ryugu are comparable to those of hydrated carbonaceous chondrites. The bulk δ15N in Ryugu IOM is commensurable to levels reported in CI chondrites, despite the occurrence of hotspots being more 15N-rich in Ryugu [3]. The range of δ15N covered by these hotspots is, however, consistent with the IOM of CM chondrites and Tagish Lake, but remains in the lower end of the hotspots in CR chondrites. The most notable difference is the bulk δD which is lower than in the IOM of hydrated carbonaceous chondrites. The distribution of δD in Ryugu IOM is consistent with the IOMs in CI and CM chondrites. We did not observe enrichments as large as those reported in CR chondrites and in Tagish Lake [4,5]. The abundance of D- and 15N-rich hotspots appears similar in Ryugu and carbonaceous chondrites. Differences between Ryugu and carbonaceous chondrites may result from different intensity of aqueous alteration or the impact of space weathering, which could have induced a decrease of D/H in organic compounds by H implantation. Acknowledgments: The NanoSIMS facility at MNHN in Paris is supported by CNRS and MNHN. L. R. is grateful to the European Research Council (ERC consolidator grant HYDROMA). [ABSTRACT FROM AUTHOR]

Introduction: JAXA's Hayabusa2 mission returned the surface samples from the carbonaceous (C-type) asteroid Ryugu. The first touchdown samples and second touchdown samples were separately stored in the sample container chamber A and chamber C, respectively [1]. Fourier transform infrared (FTIR) spectroscopy is a nondestructive technique for functional group chemistry and structures which is suitable for both organic and inorganic compounds. As a part of the Hayabusa2-initial-analysis organic macromolecule team, infrared absorption spectra from the intact Ryugu particles and extracted insoluble organic matter (IOM) were obtained using FTIR microspectroscopy, to understand the nature of organic matter in Ryugu. Methods: Several samples were analyzed in parallel in the team, in Japan (Yokohama National Univ., YNU) and in France (IPAG, Grenoble and Orsay-lab teams) to increase the robustness of the analysis. The aggregates in chamber A (A0108 and A0106) and chamber C (C0109) were analyzed as intact Ryugu particles. IOM was obtained after solvent extraction followed by HF/HCl demineralization from the aggregates A0106 and C0107 (Hiroshima U) [2]. During drying, most IOM was precipitated, but there was a little left suspended (sticky phase). The samples were pressed between two diamond windows and then FTIR measurements were performed on the diamond windows in transmission mode. Results and Discussion: The organic features shown in the FTIR spectra of the Ryugu intact particles (Fig. 1) were aliphatic C-H stretching at 2960 cm-1 (CH3 asymmetric), 2930-2925 cm-1 (CH2 asymmetric), 2855-2850 cm-1 (CH3 and CH2 symmetric) and aromatic C=C stretching (~1600 cm-1). Carbonyl C=O stretching modes (~1700 cm-1) were not always visible. Extracted IOM displayed these organic peaks more clearly. In addition, C=O at 1660 cm-1 newly appeared, which may be assigned to unsaturated ketones/aldehydes or amides. There was no significant difference between the samples from surface and interior of a mm-sized grain (A0108-58) from the A0108 aggregate. Moreover, both in the case of intact particles and extracted IOM, the IR absorption spectra of chamber A and chamber C were almost identical, but some local heterogeneity exists. The Ryugu IOM had the highest CH2/CH3 with the highest aliphatic CH/aromatic C=C ratios compared to IOM from unheated carbonaceous chondrites [3], indicating that it is rich in long chain aliphatic moieties. We also observed possible N-H features at 3350 cm-1 and 3180 cm-1 in the Ryugu IOM. The N-H absorption was previously detected from reflectance IR measurements of intact Ryugu particles by JAXA curation [4,5], but the peak positions were ~80-90 cm-1 lower than the Ryugu IOM. Overall, the FTIR organic signatures of the Ryugu samples generally agree with CI chondrites but some differences do exist. The high CH2/CH3 ratios, aliphatic-rich, and N-rich nature of Ryugu organic matter might indicate primitiveness and freshness of the Ryugu particles. The differences between Ryugu and carbonaceous chondrites could be attributed to modification of organic matter in carbonaceous chondrites due to long preservation on the Earth, which Ryugu samples escaped. [ABSTRACT FROM AUTHOR]

Primordial carbon delivered to the early earth by asteroids and meteorites provided a diverse source of extraterrestrial organics from pre-existing simple organic compounds, complex solar-irradiated macromolecules, and macromolecules from extended hydrothermal processing. Surface regolith collected by the Hayabusa2 spacecraft from the carbon-rich asteroid 162173 Ryugu present a unique opportunity to untangle the sources and processing history of carbonaceous matter. Here we show carbonaceous grains in Ryugu can be classified into three main populations defined by spectral shape: Highly aromatic (HA), Alkyl-Aromatic (AA), and IOM-like (IL). These carbon populations may be related to primordial chemistry, since C and N isotopic compositions vary between the three groups. Diffuse carbon is occasionally dominated by molecular carbonate preferentially associated with coarse-grained phyllosilicate minerals. Compared to related carbonaceous meteorites, the greater diversity of organic functional chemistry in Ryugu indicate the pristine condition of these asteroid samples., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Micrometeorites are estimated to represent the main part of the present flux of extraterrestrial matter found on the Earth's surface and provide valuable samples to probe the interplanetary medium. Here, we describe large and representative collections of micrometeorites currently available to the scientific community. These include Antarctic collections from surface ice and snow, as well as glacial sediments from the eroded top of nunataks-summits outcropping from the icesheet-and moraines. Collections extracted from deep-sea sediments (DSS) produced a large number of micrometeorites, in particular, iron-rich cosmic spherules that are rarer in other collections. Collections from the old and stable surface of the Atacama Desert show that finding large numbers of micrometeorites is not restricted to polar regions or DSS. The advent of rooftop collections marks an important step into involving citizen science in the study of micrometeorites, as well as providing potential sampling locations over all latitudes to explore the modern flux. We explore their strengths of the collections to address specific scientific questions and their potential weaknesses. The future of micrometeorite research will involve the finding of large fossil micrometeorite collections and benefit from recent advances in sampling cosmic dust directly from the air. This article is part of the theme issue 'Dust in the Solar System and beyond'.

Most low-mass stars form in stellar clusters that also contain massive stars, which are sources of far-ultraviolet (FUV) radiation. Theoretical models predict that this FUV radiation produces photodissociation regions (PDRs) on the surfaces of protoplanetary disks around low-mass stars, which affects planet formation within the disks. We report James Webb Space Telescope and Atacama Large Millimeter Array observations of a FUV-irradiated protoplanetary disk in the Orion Nebula. Emission lines are detected from the PDR; modeling their kinematics and excitation allowed us to constrain the physical conditions within the gas. We quantified the mass-loss rate induced by the FUV irradiation and found that it is sufficient to remove gas from the disk in less than a million years. This is rapid enough to affect giant planet formation in the disk.

Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu's parent body.