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Volatile and rich in organic matter, C-type asteroids may be one of the main sources of water on Earth. At present, carbon-bearing chondrites give the best idea of ​​their chemical composition, but information about meteorites is distorted: only the most durable types survive entering the atmosphere and then interacting with the earth’s environment. Here we present the results of a detailed volumetric and microanalytical study of the primary Ryugu particle delivered to Earth by the Hayabusa-2 spacecraft. Ryugu particles show a close match in composition to chemically unfractionated but water-altered CI (Iwuna-type) chondrites, which are widely used as an indicator of the overall composition of the solar system. This specimen shows a complex spatial relationship between rich aliphatic organics and layered silicates and indicates a maximum temperature of around 30 °C during water erosion. We found an abundance of deuterium and diazonium consistent with an extrasolar origin. Ryugu particles are the most uncontaminated and inseparable alien material ever studied and best fit the overall composition of the solar system.
From June 2018 to November 2019, the Japan Aerospace Exploration Agency’s (JAXA) Hayabusa2 spacecraft conducted an extensive remote survey of asteroid Ryugu. Data from the Near Infrared Spectrometer (NIRS3) at Hayabusa-2 suggest that Ryugu may be composed of a material similar to thermally and/or shock-metamorphic carbonaceous chondrites. The closest match is CY chondrite (Yamato type) 2. Ryugu’s low albedo can be explained by the presence of a large number of carbon-rich components, as well as particle size, porosity, and spatial weathering effects. The Hayabusa-2 spacecraft made two landings and sample collection on Ryuga. During the first landing on February 21, 2019, surface material was obtained, which was stored in compartment A of the return capsule, and during the second landing on July 11, 2019, material was collected near an artificial crater formed by a small portable impactor. These samples are stored in Ward C. Initial non-destructive characterization of the particles in Stage 1 in special, uncontaminated and pure nitrogen-filled chambers at JAXA-managed facilities indicated that the Ryugu particles were most similar to CI4 chondrites and exhibited “various levels of variation”3 . The seemingly contradictory classification of Ryugu, similar to CY or CI chondrites, can only be resolved by detailed isotopic, elemental, and mineralogical characterization of Ryugu particles. The results presented here provide a solid basis for determining which of these two preliminary explanations for the overall composition of asteroid Ryugu is most likely.
Eight Ryugu pellets (approximately 60mg total), four from Chamber A and four from Chamber C, were assigned to Phase 2 to manage the Kochi team. The main goal of the study is to elucidate the nature, origin and evolutionary history of the asteroid Ryugu, and to document similarities and differences with other known extraterrestrial specimens such as chondrites, interplanetary dust particles (IDPs) and returning comets. Samples collected by NASA’s Stardust mission.
Detailed mineralogical analysis of five Ryugu grains (A0029, A0037, C0009, C0014 and C0068) showed that they are mainly composed of fine- and coarse-grained phyllosilicates (~64–88 vol.%; Fig. 1a, b, Supplementary Fig. 1). and additional table 1). Coarse-grained phyllosilicates occur as pinnate aggregates (up to tens of microns in size) in fine-grained, phyllosilicate-rich matrices (less than a few microns in size). Layered silicate particles are serpentine–saponite symbionts (Fig. 1c). The (Si + Al)-Mg-Fe map also shows that the bulk layered silicate matrix has an intermediate composition between serpentine and saponite (Fig. 2a, b). The phyllosilicate matrix contains carbonate minerals (~2–21 vol.%), sulfide minerals (~2.4–5.5 vol.%), and magnetite (~3.6–6.8 vol.%). One of the particles examined in this study (C0009) contained a small amount (~0.5 vol.%) of anhydrous silicates (olivine and pyroxene), which may help identify the source material that made up the raw Ryugu stone5. This anhydrous silicate is rare in Ryugu pellets and was only positively identified in C0009 pellet. Carbonates are present in the matrix as fragments (less than a few hundred microns), mostly dolomite, with small amounts of calcium carbonate and brinell. Magnetite occurs as isolated particles, framboids, plaques, or spherical aggregates. Sulfides are mainly represented by pyrrhotite in the form of irregular hexagonal prisms/plates or laths. The matrix contains a large amount of submicron pentlandite or in combination with pyrrhotite. Carbon-rich phases (<10 µm in size) occur ubiquitously in the phyllosilicate-rich matrix. Carbon-rich phases (<10 µm in size) occur ubiquitously in the phyllosilicate-rich matrix. Богатые углеродом фазы (размером <10 мкм) встречаются повсеместно в богатой филлосиликатами матрице. Carbon-rich phases (<10 µm in size) occur ubiquitously in the phyllosilicate-rich matrix.富含碳的相（尺寸<10 µm）普遍存在于富含层状硅酸盐的基质中。富含碳的相（尺寸<10 µm）普遍存在于富含层状硅酸盐的基质中。 Богатые углеродом фазы (размером <10 мкм) преобладают в богатой филлосиликатами матрице. Carbon-rich phases (<10 µm in size) predominate in the phyllosilicate-rich matrix. Other ancillary minerals are shown in Supplementary Table 1. The list of minerals determined from the X-ray diffraction pattern of the C0087 and A0029 and A0037 mixture is very consistent with that determined in the CI (Orgueil) chondrite, but differs greatly from the CY and CM (Mighei type) chondrites (Figure 1 with expanded data and Supplementary Figure 2). The total element content of Ryugu grains (A0098, C0068) is also consistent with chondrite 6 CI (expanded data, Fig. 2 and Supplementary Table 2). In contrast, CM chondrites are depleted in moderately and highly volatile elements, especially Mn and Zn, and higher in refractory elements7. The concentrations of some elements vary greatly, which may be a reflection of the inherent heterogeneity of the sample due to the small size of individual particles and the resulting sampling bias. All petrological, mineralogical and elemental characteristics indicate that Ryugu grains are very similar to chondrites CI8,9,10. A notable exception is the absence of ferrihydrite and sulfate in Ryugu grains, suggesting that these minerals in CI chondrites were formed by terrestrial weathering.
a, Composite X-ray image of Mg Kα (red), Ca Kα (green), Fe Kα (blue), and S Kα (yellow) dry polished section C0068. The fraction consists of layered silicates (red: ~88 vol%), carbonates (dolomite; light green: ~1.6 vol%), magnetite (blue: ~5.3 vol%) and sulfides (yellow: sulfide = ~2.5% vol. essay. b, image of the contour region in backscattered electrons on a. Bru – immature; Dole – dolomite; FeS is iron sulfide; Mag – magnetite; juice – soapstone; Srp – serpentine. c, high-resolution transmission electron microscopy (TEM) image of a typical saponite-serpentine intergrowth showing serpentine and saponite lattice bands of 0.7 nm and 1.1 nm, respectively.
The composition of the matrix and layered silicate (at %) of Ryugu A0037 (solid red circles) and C0068 (solid blue circles) particles is shown in the (Si+Al)-Mg-Fe ternary system. a, Electron Probe Microanalysis (EPMA) results plotted against CI chondrites (Ivuna, Orgueil, Alais)16 shown in gray for comparison. b, Scanning TEM (STEM) and energy dispersive X-ray spectroscopy (EDS) analysis shown for comparison with Orgueil9 and Murchison46 meteorites and hydrated IDP47. Fine-grained and coarse-grained phyllosilicates were analyzed, avoiding small particles of iron sulfide. The dotted lines in a and b show the dissolution lines of saponite and serpentine. The iron-rich composition in a may be due to submicron iron sulfide grains within the layered silicate grains, which cannot be excluded by the spatial resolution of the EPMA analysis. Data points with a higher Si content than the saponite in b may be caused by the presence of nanosized amorphous silicon-rich material in the interstices of the phyllosilicate layer. Number of analyzes: N=69 for A0037, N=68 for EPMA, N=68 for C0068, N=19 for A0037 and N=27 for C0068 for STEM-EDS. c, isotope map of trioxy particle Ryugu C0014-4 compared with chondrite values ​​CI (Orgueil), CY (Y-82162) and literature data (CM and C2-ung)41,48,49. We have obtained data for the Orgueil and Y-82162 meteorites. CCAM is a line of anhydrous carbonaceous chondrite minerals, TFL is a land dividing line. d, Δ17O and δ18O maps of Ryugu particle C0014-4, CI chondrite (Orgueil), and CY chondrite (Y-82162) (this study). Δ17O_Ryugu: The value of Δ17O C0014-1. Δ17O_Orgueil: Average Δ17O value for Orgueil. Δ17O_Y-82162: Average Δ17O value for Y-82162. CI and CY data from the literature 41, 48, 49 are also shown for comparison.
Mass isotope analysis of oxygen was performed on a 1.83 mg sample of material extracted from granular C0014 by laser fluorination (Methods). For comparison, we ran seven copies of Orgueil (CI) (total mass = 8.96 mg) and seven copies of Y-82162 (CY) (total mass = 5.11 mg) (Supplementary Table 3).
On fig. 2d shows a clear separation of Δ17O and δ18O between the weight average particles of Orgueil and Ryugu compared to Y-82162. The Δ17O of the Ryugu C0014-4 particle is higher than that of the Orgeil particle, despite the overlap at 2 sd. Ryugu particles have higher Δ17O values ​​compared to Orgeil, which may reflect the latter’s terrestrial pollution since its fall in 1864. Weathering in the terrestrial environment11 necessarily results in the incorporation of atmospheric oxygen, bringing the overall analysis closer to the terrestrial fractionation line (TFL). This conclusion is consistent with the mineralogical data (discussed earlier) that Ryugu grains do not contain hydrates or sulfates, while Orgeil does.
Based on the above mineralogical data, these results support an association between Ryugu grains and CI chondrites, but rule out an association of CY chondrites. The fact that Ryugu grains are not associated with CY chondrites, which show clear signs of dehydration mineralogy, is puzzling. Orbital observations of Ryugu appear to indicate that it has undergone dehydration and is therefore likely composed of CY material. The reasons for this apparent difference remain unclear. An oxygen isotope analysis of other Ryugu particles is presented in a companion paper 12. However, the results of this extended data set are also consistent with the association between Ryugu particles and CI chondrites.
Using coordinated microanalysis techniques (Supplementary Fig. 3), we examined the spatial distribution of organic carbon over the entire surface area of ​​the focused ion beam fraction (FIB) C0068.25 (Figs. 3a–f). Fine structure X-ray absorption spectra of carbon (NEXAFS) at the near edge in section C0068.25 showing several functional groups – aromatic or C=C (285.2 eV), C=O (286.5 eV), CH (287.5 eV) and C( =O)O (288.8 eV) – the graphene structure is absent at 291.7 eV (Fig. 3a), which means a low degree of thermal variation. The strong CH peak (287.5 eV) of the partial organics of C0068.25 differs from the insoluble organics of previously studied carbonaceous chondrites and is more similar to IDP14 and cometary particles obtained by the Stardust mission. A strong CH peak at 287.5 eV and a very weak aromatic or C=C peak at 285.2 eV indicate that organic compounds are rich in aliphatic compounds (Fig. 3a and Supplementary Fig. 3a). Areas rich in aliphatic organic compounds are localized in coarse-grained phyllosilicates, as well as in areas with a poor aromatic (or C=C) carbon structure (Fig. 3c,d). In contrast, A0037,22 (Supplementary Fig. 3) partially showed a lower content of aliphatic carbon-rich regions. The underlying mineralogy of these grains is rich in carbonates, similar to chondrite CI 16, suggesting extensive alteration of source water (Supplementary Table 1). Oxidizing conditions will favor higher concentrations of carbonyl and carboxyl functional groups in organic compounds associated with carbonates. The submicron distribution of organics with aliphatic carbon structures can be very different from the distribution of coarse-grained layered silicates. Hints of aliphatic organic compounds associated with phyllosilicate-OH were found in the Tagish Lake meteorite. Coordinated microanalytical data suggest that organic matter rich in aliphatic compounds may be widespread in C-type asteroids and closely associated with phyllosilicates. This conclusion is consistent with previous reports of aliphatic/aromatic CHs in Ryugu particles demonstrated by MicroOmega, a near-infrared hyperspectral microscope. An important and unresolved question is whether the unique properties of aliphatic carbon-rich organic compounds associated with coarse-grained phyllosilicates observed in this study are found only on the asteroid Ryugu.
a, NEXAFS carbon spectra normalized to 292 eV in the aromatic (C=C) rich region (red), in the aliphatic rich region (green), and in the matrix (blue). The gray line is the Murchison 13 insoluble organic spectrum for comparison. au, arbitration unit. b, Scanning transmission X-ray microscopy (STXM) spectral image of a carbon K-edge showing that the section is dominated by carbon. c, RGB composite plot with aromatic (C=C) rich regions (red), aliphatic rich regions (green), and matrix (blue). d, organics rich in aliphatic compounds are concentrated in coarse-grained phyllosilicate, the area is enlarged from the white dotted boxes in b and c. e, large nanospheres (ng-1) in the area enlarged from the white dotted box in b and c. For: pyrrhotite. Pn: nickel-chromite. f, Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS), Hydrogen (1H), Carbon (12C), and Nitrogen (12C14N) elemental images, 12C/1H element ratio images, and cross δD, δ13C, and δ15N isotope images – Section PG-1: presolar graphite with extreme 13C enrichment (Supplementary Table 4).
Kinetic studies of organic matter degradation in Murchison meteorites can provide important information about the heterogeneous distribution of aliphatic organic matter rich in Ryugu grains. This study shows that aliphatic CH bonds in organic matter persist up to a maximum temperature of about 30°C at the parent and/or change with time-temperature relationships (e.g. 200 years at 100°C and 0°C 100 million years) . . If the precursor is not heated at a given temperature for more than a certain time, the original distribution of aliphatic organics rich in phyllosilicate may be preserved. However, source rock water changes may complicate this interpretation, as carbonate-rich A0037 does not show any carbon-rich aliphatic regions associated with phyllosilicates. This low temperature change roughly corresponds to the presence of cubic feldspar in Ryugu grains (Supplementary Table 1) 20.
Fraction C0068.25 (ng-1; Figs. 3a–c,e) contains a large nanosphere showing highly aromatic (or C=C), moderately aliphatic, and weak spectra of C(=O)O and C=O. . The signature of aliphatic carbon does not match the signature of bulk insoluble organics and organic nanospheres associated with chondrites (Fig. 3a) 17,21. Raman and infrared spectroscopic analysis of nanospheres in Lake Tagish showed that they consist of aliphatic and oxidized organic compounds and disordered polycyclic aromatic organic compounds with a complex structure22,23. Because the surrounding matrix contains organics rich in aliphatic compounds, the signature of aliphatic carbon in ng-1 may be an analytical artifact. Interestingly, ng-1 contains embedded amorphous silicates (Fig. 3e), a texture that has not yet been reported for any extraterrestrial organics. Amorphous silicates may be natural components of ng-1 or result from amorphization of aqueous/anhydrous silicates by ion and/or electron beam during analysis.
NanoSIMS ion images of the C0068.25 section (Fig. 3f) show uniform changes in δ13C and δ15N, except for presolar grains with a large 13C enrichment of 30,811‰ (PG-1 in the δ13C image in Fig. 3f) (Supplementary Table 4). X-ray elementary grain images and high-resolution TEM images show only the carbon concentration and the distance between the basal planes of 0.3 nm, which corresponds to graphite. It is noteworthy that the values ​​of δD (841 ± 394‰) and δ15N (169 ± 95‰), enriched in aliphatic organic matter associated with coarse-grained phyllosilicates, turn out to be slightly higher than the average for the entire region C (δD = 528 ± 139‰). ‰, δ15N = 67 ± 15 ‰) in C0068.25 (Supplementary Table 4). This observation suggests that the aliphatic-rich organics in coarse-grained phyllosilicates may be more primitive than the surrounding organics, since the latter may have undergone isotopic exchange with the surrounding water in the original body. Alternatively, these isotopic changes may also be related to the initial formation process. It is interpreted that fine-grained layered silicates in CI chondrites were formed as a result of continuous alteration of the original coarse-grained anhydrous silicate clusters. Aliphatic-rich organic matter may have formed from precursor molecules in the protoplanetary disk or interstellar medium prior to the formation of the solar system, and then were slightly altered during the water changes of the Ryugu (large) parent body. The size (<1.0 km) of Ryugu is too small to sufficiently maintain internal heat for aqueous alteration to form hydrous minerals25. The size (<1.0 km) of Ryugu is too small to maintain sufficiently internal heat for aqueous alteration to form hydrous minerals25. Размер (<1,0 км) Рюгу слишком мал, чтобы поддерживать достаточное внутреннее тепло для водного изменения с образованием водных минералов25. Size (<1.0 km) Ryugu is too small to maintain sufficient internal heat for water change to form water minerals25. Ryugu 的尺寸（<1.0 公里）太小，不足以维持内部热量以进行水蚀变形成含水矿物25。 Ryugu 的尺寸（<1.0 公里）太小，不足以维持内部热量以进行水蚀变形成含水矿物25。 Размер Рюгу (<1,0 км) слишком мал, чтобы поддерживать внутреннее тепло для изменения воды с образованием водных минералов25. The size of Ryugu (<1.0 km) is too small to support internal heat to change water to form water minerals25. Therefore, Ryugu predecessors tens of kilometers in size may be required. Organic matter rich in aliphatic compounds may retain their original isotope ratios due to association with coarse-grained phyllosilicates. However, the exact nature of the isotopic heavy carriers remains uncertain due to the complex and delicate mixing of the various components in these FIB fractions. These can be organic substances rich in aliphatic compounds in Ryugu granules or coarse phyllosilicates surrounding them. Note that organic matter in almost all carbonaceous chondrites (including CI chondrites) tends to be richer in D than in phyllosilicates, with the exception of CM Paris 24, 26 meteorites.
Plots of volume δD and δ15N of FIB slices obtained for A0002.23 and A0002.26, A0037.22 and A0037.23 and C0068.23, C0068.25 and C0068.26 FIB slices (a total of seven FIB slices from three Ryugu particles) A comparison of NanoSIMS with other objects of the solar system is shown in fig. 4 (Supplementary Table 4)27,28. Volume changes in δD and δ15N in the A0002, A0037, and C0068 profiles are consistent with those in the IDP, but higher than in the CM and CI chondrites (Fig. 4). Note that the range of δD values ​​for Comet 29 sample (-240 to 1655‰) is larger than that of Ryugu. The volumes δD and δ15N of the Ryukyu profiles are, as a rule, smaller than the average for comets of the Jupiter family and the Oort cloud (Fig. 4). The lower δD values ​​of the CI chondrites may reflect the influence of terrestrial contamination in these samples. Given the similarities between Bells, Lake Tagish, and IDP, the large heterogeneity in δD and δN values ​​in Ryugu particles may reflect changes in the initial isotopic signatures of organic and aqueous compositions in the early solar system. The similar isotopic changes in δD and δN in Ryugu and IDP particles suggest that both could have formed from material from the same source. It is believed that IDPs originate from cometary sources 14 . Therefore, Ryugu may contain comet-like material and/or at least the outer solar system. However, this may be more difficult than we state here due to (1) the mixture of spherulitic and D-rich water on the parent body 31 and (2) the comet’s D/H ratio as a function of cometary activity 32 . However, the reasons for the observed heterogeneity of hydrogen and nitrogen isotopes in Ryugu particles are not fully understood, partly due to the limited number of analyzes available today. The results of hydrogen and nitrogen isotope systems still raise the possibility that Ryugu contains most of the material from outside the Solar System and thus may show some similarity to comets. The Ryugu profile showed no apparent correlation between δ13C and δ15N (Supplementary Table 4).
The overall H and N isotopic composition of Ryugu particles (red circles: A0002, A0037; blue circles: C0068) correlates with solar magnitude 27, the Jupiter mean family (JFC27), and Oort cloud comets (OCC27), IDP28, and carbonaceous chondrules. Comparison of meteorite 27 (CI, CM, CR, C2-ung). The isotopic composition is given in Supplementary Table 4. The dotted lines are the terrestrial isotope values ​​for H and N.
The transport of volatiles (eg organic matter and water) to Earth remains a concern26,27,33. Submicron organic matter associated with coarse phyllosilicates in Ryugu particles identified in this study may be an important source of volatiles. Organic matter in coarse-grained phyllosilicates is better protected from degradation16,34 and decay35 than organic matter in fine-grained matrices. The heavier isotopic composition of hydrogen in the particles means they are unlikely to be the only source of volatiles carried to the early Earth. They can be mixed with components with a lighter hydrogen isotopic composition, as was recently proposed in the hypothesis of the presence of solar wind-driven water in silicates.
In this study, we show that CI meteorites, despite their geochemical importance as representatives of the overall composition of the solar system,6,10 are terrestrial contaminated samples. We also provide direct evidence for interactions between rich aliphatic organic matter and neighboring hydrous minerals and suggest that Ryugu may contain extrasolar material37. The results of this study clearly demonstrate the importance of direct sampling of protoasteroids and the need to transport returned samples under completely inert and sterile conditions. The evidence presented here shows that Ryugu particles are undoubtedly one of the most uncontaminated solar system materials available for laboratory research, and further study of these precious samples will undoubtedly expand our understanding of early solar system processes. Ryugu particles are the best representation of the overall composition of the solar system.
To determine the complex microstructure and chemical properties of submicron scale samples, we used synchrotron radiation-based computed tomography (SR-XCT) and SR X-ray diffraction (XRD)-CT, FIB-STXM-NEXAFS-NanoSIMS-TEM analysis. No degradation, pollution due to the earth’s atmosphere, and no damage from fine particles or mechanical samples. In the meantime, we have carried out systematic volumetric analysis using scanning electron microscopy (SEM)-EDS, EPMA, XRD, instrumental neutron activation analysis (INAA), and laser oxygen isotope fluorination equipment. The assay procedures are shown in Supplementary Figure 3 and each assay is described in the following sections.
Particles from the asteroid Ryugu were recovered from the Hayabusa-2 reentry module and delivered to the JAXA Control Center in Sagamihara, Japan, without polluting the Earth’s atmosphere4. After initial and non-destructive characterization at a JAXA-managed facility, use sealable inter-site transfer containers and sample capsule bags (10 or 15 mm diameter sapphire crystal and stainless steel, depending on sample size) to avoid environmental interference. environment. y and/or ground contaminants (eg water vapour, hydrocarbons, atmospheric gases and fine particles) and cross-contamination between samples during sample preparation and transport between institutes and universities38. To avoid degradation and pollution due to interaction with the earth’s atmosphere (water vapor and oxygen), all types of sample preparation (including chipping with a tantalum chisel, using a balanced diamond wire saw (Meiwa Fosis Corporation DWS 3400) and cutting epoxy) preparation for installation) were carried out in glovebox under clean dry N2 (dew point: -80 to -60 °C, O2 ~50-100 ppm). All items used here are cleaned with a combination of ultrapure water and ethanol using ultrasonic waves of different frequencies.
Here we study the National Polar Research Institute (NIPR) meteorite collection of the Antarctic Meteorite Research Center (CI: Orgueil, CM2.4: Yamato (Y)-791198, CY: Y-82162 and CY: Y 980115).
For transfer between instruments for SR-XCT, NanoSIMS, STXM-NEXAFS and TEM analysis, we used the universal ultrathin sample holder described in previous studies38.
SR-XCT analysis of Ryugu samples was performed using the BL20XU/SPring-8 integrated CT system. The integrated CT system consists of various measurement modes: wide field of view and low resolution (WL) mode to capture the entire structure of the sample, narrow field of view and high resolution (NH) mode for accurate measurement of sample area. interest and radiographs to obtain a diffraction pattern of the volume of the sample, and perform XRD-CT to obtain a 2D diagram of the horizontal plane mineral phases in the sample. Note that all measurements can be performed without using the built-in system to remove the sample holder from the base, allowing for accurate CT and XRD-CT measurements. The WL mode X-ray detector (BM AA40P; Hamamatsu Photonics) was equipped with an additional 4608 × 4608 pixel metal-oxide-semiconductor (CMOS) camera (C14120-20P; Hamamatsu Photonics) with a scintillator consisting of 10 lutetium aluminum garnet single crystal thickness µm (Lu3Al5O12:Ce) and relay lens. The pixel size in WL mode is about 0.848 µm. Thus, the field of view (FOV) in WL mode is approximately 6 mm in offset CT mode. The NH mode X-ray detector (BM AA50; Hamamatsu Photonics) was equipped with a 20 µm thick gadolinium-aluminum-gallium garnet (Gd3Al2Ga3O12) scintillator, a CMOS camera (C11440-22CU) with a resolution of 2048 × 2048 pixels; Hamamatsu Photonics) and a ×20 lens. The pixel size in NH mode is ~0.25 µm and the field of view is ~0.5 mm. The detector for the XRD mode (BM AA60; Hamamatsu Photonics) was equipped with a scintillator consisting of a 50 µm thick P43 (Gd2O2S:Tb) powder screen, a 2304 × 2304 pixel resolution CMOS camera (C15440-20UP; Hamamatsu Photonics) and a relay lens. The detector has an effective pixel size of 19.05 µm and a field of view of 43.9 mm2. To increase the FOV, we applied an offset CT procedure in WL mode. The transmitted light image for CT reconstruction consists of an image in the range of 180° to 360° reflected horizontally around the axis of rotation, and an image in the range of 0° to 180°.
In XRD mode, the X-ray beam is focused by a Fresnel zone plate. In this mode, the detector is placed 110 mm behind the sample and the beam stop is 3 mm ahead of the detector. Diffraction images in the 2θ range from 1.43° to 18.00° (grating pitch d = 16.6–1.32 Å) were obtained with the X-ray spot focused at the bottom of the detector’s field of view. The sample moves vertically at regular intervals, with a half turn for each vertical scan step. If the mineral particles satisfy the Bragg condition when rotated by 180°, it is possible to obtain diffraction of the mineral particles in the horizontal plane. The diffraction images were then combined into one image for each vertical scan step. The SR-XRD-CT assay conditions are almost the same as those for the SR-XRD assay. In XRD-CT mode, the detector is positioned 69 mm behind the sample. Diffraction images in the 2θ range range from 1.2° to 17.68° (d = 19.73 to 1.35 Å), where both the X-ray beam and the beam limiter are in line with the center of the detector’s field of view. Scan the sample horizontally and rotate the sample 180°. The SR-XRD-CT images were reconstructed with peak mineral intensities as pixel values. With horizontal scanning, the sample is typically scanned in 500–1000 steps.
For all experiments, the X-ray energy was fixed at 30 keV, since this is the lower limit of X-ray penetration into meteorites with a diameter of about 6 mm. The number of images acquired for all CT measurements during 180° rotation was 1800 (3600 for the offset CT program), and the exposure time for the images was 100 ms for WL mode, 300 ms for NH mode, 500 ms for XRD, and 50 ms . ms for XRD-CT ms. Typical sample scan time is about 10 minutes in WL mode, 15 minutes in NH mode, 3 hours for XRD, and 8 hours for SR-XRD-CT.
CT images were reconstructed by convolutional back projection and normalized for a linear attenuation coefficient from 0 to 80 cm-1. The Slice software was used to analyze the 3D data and the muXRD software was used to analyze the XRD data.
Epoxy-fixed Ryugu particles (A0029, A0037, C0009, C0014 and C0068) were gradually polished on the surface to the level of a 0.5 µm (3M) diamond lapping film under dry conditions, avoiding the material coming into contact with the surface during the polishing process. The polished surface of each sample was first examined by light microscopy and then backscattered electrons to obtain mineralogy and texture images (BSE) of the samples and qualitative NIPR elements using a JEOL JSM-7100F SEM equipped with an energy dispersive spectrometer (AZtec). energy) picture. For each sample, the content of major and minor elements was analyzed using an electron probe microanalyzer (EPMA, JEOL JXA-8200). Analyze phyllosilicate and carbonate particles at 5 nA, natural and synthetic standards at 15 keV, sulfides, magnetite, olivine, and pyroxene at 30 nA. Modal grades were calculated from element maps and BSE images using ImageJ 1.53 software with appropriate thresholds arbitrarily set for each mineral.
Oxygen isotope analysis was performed at the Open University (Milton Keynes, UK) using an infrared laser fluorination system. Hayabusa2 samples were delivered to the Open University 38 in nitrogen-filled containers for transfer between facilities.
Sample loading was performed in a nitrogen glove box with a monitored oxygen level below 0.1%. For Hayabusa2 analytical work, a new Ni sample holder was fabricated, consisting of only two sample holes (diameter 2.5 mm, depth 5 mm), one for Hayabusa2 particles and the other for obsidian internal standard. During analysis, the sample well containing the Hayabusa2 material was covered with an internal BaF2 window approximately 1 mm thick and 3 mm in diameter to hold the sample during the laser reaction. The BrF5 flow to the sample was maintained by a gas mixing channel cut in the Ni sample holder. The sample chamber was also reconfigured so that it could be removed from the vacuum fluorination line and then opened in a nitrogen-filled glove box. The two-piece chamber was sealed with a copper gasketed compression seal and an EVAC Quick Release CeFIX 38 chain clamp. A 3 mm thick BaF2 window on the top of the chamber allows for simultaneous observation of the sample and laser heating. After loading the sample, clamp the chamber again and reconnect to the fluorinated line. Prior to analysis, the sample chamber was heated under vacuum to about 95°C overnight to remove any adsorbed moisture. After heating overnight, the chamber was allowed to cool to room temperature and then the portion exposed to the atmosphere during sample transfer was purged with three aliquots of BrF5 to remove moisture. These procedures ensure that the Hayabusa 2 sample is not exposed to the atmosphere and is not contaminated by moisture from the portion of the fluorinated line that is vented to atmosphere during sample loading.
Ryugu C0014-4 and Orgueil (CI) particle samples were analyzed in a modified “single” mode42, while Y-82162 (CY) analysis was performed on a single tray with multiple sample wells41. Due to their anhydrous composition, it is not necessary to use a single method for CY chondrites. The samples were heated using a Photon Machines Inc. infrared CO2 laser. power of 50 W (10.6 µm) mounted on the XYZ gantry in the presence of BrF5. The built-in video system monitors the course of the reaction. After fluorination, the liberated O2 was scrubbed using two cryogenic nitrogen traps and a heated bed of KBr to remove any excess fluorine. The isotopic composition of purified oxygen was analyzed on a Thermo Fisher MAT 253 dual-channel mass spectrometer with a mass resolution of about 200.
In some cases, the amount of gaseous O2 released during the reaction of the sample was less than 140 µg, which is the approximate limit of using the bellows device on the MAT 253 mass spectrometer. In these cases, use microvolumes for analysis. After analyzing the Hayabusa2 particles, the obsidian internal standard was fluorinated and its oxygen isotope composition was determined.
Ions of the NF+ NF3+ fragment interfere with the beam with mass 33 (16O17O). To eliminate this potential problem, most samples are processed using cryogenic separation procedures. This can be done in the forward direction before the MAT 253 analysis or as a second analysis by returning the analyzed gas back to the special molecular sieve and re-passing it after the cryogenic separation. Cryogenic separation involves supplying gas to a molecular sieve at liquid nitrogen temperature and then discharging it into a primary molecular sieve at a temperature of -130°C. Extensive testing has shown that NF+ remains on the first molecular sieve and no significant fractionation occurs using this method.
Based on repeated analyzes of our internal obsidian standards, the overall accuracy of the system in bellows mode is: ±0.053‰ for δ17O, ±0.095‰ for δ18O, ±0.018‰ for Δ17O (2 sd). Oxygen isotope analysis is given in the standard delta notation, where delta18O is calculated as:
Also use the 17O/16O ratio for δ17O. VSMOW is the international standard for the Vienna Mean Sea Water Standard. Δ17O represents the deviation from the earth fractionation line, and the calculation formula is: Δ17O = δ17O – 0.52 × δ18O. All data presented in Supplementary Table 3 have been gap-adjusted.
Sections approximately 150 to 200 nm thick were extracted from Ryugu particles using a Hitachi High Tech SMI4050 FIB instrument at JAMSTEC, Kochi Core Sampling Institute. Note that all FIB sections were recovered from unprocessed fragments of unprocessed particles after being removed from N2 gas-filled vessels for interobject transfer. These fragments were not measured by SR-CT, but were processed with minimal exposure to the earth’s atmosphere to avoid potential damage and contamination that could affect the carbon K-edge spectrum. After deposition of a tungsten protective layer, the region of interest (up to 25 × 25 μm2) was cut and thinned with a Ga+ ion beam at an accelerating voltage of 30 kV, then at 5 kV and a probe current of 40 pA to minimize surface damage. The ultrathin sections were then placed on an enlarged copper mesh (Kochi mesh) 39 using a micromanipulator equipped with FIB.
Ryugu A0098 (1.6303mg) and C0068 (0.6483mg) pellets were sealed twice in pure high purity polyethylene sheets in a pure nitrogen filled glove box on the SPring-8 without any interaction with the earth’s atmosphere. Sample preparation for JB-1 (a geological reference rock issued by the Geological Survey of Japan) was carried out at Tokyo Metropolitan University.
INAA is held at the Institute for Integrated Radiation and Nuclear Sciences, Kyoto University. The samples were irradiated twice with different irradiation cycles chosen according to the half-life of the nuclide used for element quantitation. First, the sample was irradiated in a pneumatic irradiation tube for 30 seconds. Fluxes of thermal and fast neutrons in fig. 3 are 4.6 × 1012 and 9.6 × 1011 cm-2 s-1, respectively, for determining the contents of Mg, Al, Ca, Ti, V and Mn. Chemicals such as MgO (99.99% purity, Soekawa Chemical), Al (99.9% purity, Soekawa Chemical), and Si metal (99.999% purity, FUJIFILM Wako Pure Chemical) were also irradiated to correct for interfering nuclear reactions such as (n, n). The sample was also irradiated with sodium chloride (99.99% purity; MANAC) to correct for changes in neutron flux.
After neutron irradiation, the outer polyethylene sheet was replaced with a new one, and the gamma radiation emitted by the sample and reference was immediately measured with a Ge detector. The same samples were re-irradiated for 4 hours in a pneumatic irradiation tube. 2 has thermal and fast neutron fluxes of 5.6 1012 and 1.2 1012 cm-2 s-1, respectively, for determining Na, K, Ca, Sc, Cr, Fe, Co, Ni, Zn, Ga, As, Content Se, Sb, Os, Ir and Au. Control samples of Ga, As, Se, Sb, Os, Ir, and Au were irradiated by applying appropriate amounts (from 10 to 50 μg) of standard solutions of known concentrations of these elements onto two pieces of filter paper, followed by irradiation of the samples. The gamma ray count was performed at the Institute of Integrated Radiation and Nuclear Sciences, Kyoto University and the RI Research Center, Tokyo Metropolitan University. Analytical procedures and reference materials for the quantitative determination of INAA elements are the same as those described in our previous work.
An X-ray diffractometer (Rigaku SmartLab) was used to collect the diffraction patterns of Ryugu samples A0029 (<1 mg), A0037 (≪1 mg) and C0087 (<1 mg) at NIPR. An X-ray diffractometer (Rigaku SmartLab) was used to collect the diffraction patterns of Ryugu samples A0029 (<1 mg), A0037 (≪1 mg) and C0087 (<1 mg) at NIPR. Рентгеновский дифрактометр (Rigaku SmartLab) использовали для сбора дифракционных картин образцов Ryugu A0029 (<1 мг), A0037 (≪1 мг) и C0087 (<1 мг) в NIPR. An X-ray diffractometer (Rigaku SmartLab) was used to collect diffraction patterns of Ryugu A0029 (<1 mg), A0037 (≪1 mg), and C0087 (<1 mg) samples in NIPR.使用X 射线衍射仪(Rigaku SmartLab) 在NIPR 收集Ryugu 样品A0029 (<1 mg)、A0037 (<1 mg) 和C0087 (<1 mg) 的衍射图案。使用X 射线衍射仪(Rigaku SmartLab) 在NIPR 收集Ryugu 样品A0029 (<1 mg)、A0037 (<1 mg) 和C0087 (<1 mg) 的衍射图案。 Дифрактограммы образцов Ryugu A0029 (<1 мг), A0037 (<1 мг) и C0087 (<1 мг) были получены в NIPR с использованием рентгеновского дифрактометра (Rigaku SmartLab). X-ray diffraction patterns of samples Ryugu A0029 (<1 mg), A0037 (<1 mg) and C0087 (<1 mg) were obtained at NIPR using an X-ray diffractometer (Rigaku SmartLab). All samples were ground into a fine powder on a silicon non-reflective wafer using a sapphire glass plate and then spread evenly on the silicon non-reflective wafer without any liquid (water or alcohol). The measurement conditions are as follows: Cu Kα X-ray radiation is generated at a tube voltage of 40 kV and a tube current of 40 mA, the limiting slit length is 10 mm, the divergence angle is (1/6)°, the in-plane rotation speed is 20 rpm, and the range is 2θ (double Bragg angle) is 3-100° and takes about 28 hours to analyze. Bragg Brentano optics were used. The detector is a one-dimensional silicon semiconductor detector (D/teX Ultra 250). X-rays of Cu Kβ were removed using a Ni filter. Using available samples, measurements of synthetic magnesian saponite (JCSS-3501, Kunimine Industries CO. Ltd), serpentine (leaf serpentine, Miyazu, Nikka) and pyrrhotite (monoclinic 4C, Chihua, Mexico Watts) were compared to identify peaks and use powder file data diffraction data from the International Center for Diffraction Data, dolomite (PDF 01-071-1662) and magnetite (PDF 00-019-0629). Diffraction data from Ryugu were also compared with data on hydroaltered carbonaceous chondrites, Orgueil CI, Y-791198 CM2.4, and Y 980115 CY (heating stage III, 500–750°C). The comparison showed similarities with Orgueil, but not with Y-791198 and Y 980115.
NEXAFS spectra with carbon edge K of ultrathin sections of samples made from FIB were measured using the STXM BL4U channel at the UVSOR synchrotron facility at the Institute of Molecular Sciences (Okazaki, Japan). The spot size of a beam optically focused with a Fresnel zone plate is approximately 50 nm. The energy step is 0.1 eV for the fine structure of the near edge region (283.6–292.0 eV) and 0.5 eV (280.0–283.5 eV and 292.5–300.0 eV) for the regions front and back fronts. the time for each image pixel was set to 2 ms. After evacuation, the STXM analytical chamber was filled with helium at a pressure of about 20 mbar. This helps to minimize thermal drift of the X-ray optics equipment in the chamber and sample holder, as well as to reduce sample damage and/or oxidation. NEXAFS K-edge carbon spectra were generated from stacked data using aXis2000 software and proprietary STXM data processing software. Note that the sample transfer case and glovebox are used to avoid sample oxidation and contamination.
Following STXM-NEXAFS analysis, the isotopic composition of hydrogen, carbon, and nitrogen of Ryugu FIB slices was analyzed using isotope imaging with a JAMSTEC NanoSIMS 50L. A focused Cs+ primary beam of about 2 pA for carbon and nitrogen isotope analysis and about 13 pA for hydrogen isotope analysis is rasterized over an area of ​​about 24 × 24 µm2 to 30 × 30 µm2 on the sample. After a 3-minute prespray at a relatively strong primary beam current, each analysis was started after stabilization of the secondary beam intensity. For the analysis of carbon and nitrogen isotopes, images of 12C–, 13C–, 16O–, 12C14N– and 12C15N– were simultaneously obtained using seven electron multiplier multiplex detection with a mass resolution of approximately 9000, which is sufficient to separate all relevant isotopic compounds. interference (i.e. 12C1H on 13C and 13C14N on 12C15N). For the analysis of hydrogen isotopes, 1H-, 2D- and 12C- images were obtained with a mass resolution of approximately 3000 with multiple detection using three electron multipliers. Each analysis consists of 30 scanned images of the same area, with one image consisting of 256 × 256 pixels for carbon and nitrogen isotope analysis and 128 × 128 pixels for hydrogen isotope analysis. The delay time is 3000 µs per pixel for carbon and nitrogen isotope analysis and 5000 µs per pixel for hydrogen isotope analysis. We have used 1-hydroxybenzotriazole hydrate as hydrogen, carbon and nitrogen isotope standards to calibrate instrumental mass fractionation45.
To determine the silicon isotopic composition of presolar graphite in the FIB C0068-25 profile, we used six electron multipliers with a mass resolution of about 9000. The images consist of 256 × 256 pixels with a delay time of 3000 µs per pixel. We calibrated a mass fractionation instrument using silicon wafers as hydrogen, carbon, and silicon isotope standards.
Isotope images were processed using NASA’s NanoSIMS45 imaging software. The data were corrected for electron multiplier dead time (44 ns) and quasi-simultaneous arrival effects. Different scan alignment for each image to correct for image drift during acquisition. The final isotope image is created by adding secondary ions from each image for each scan pixel.
After STXM-NEXAFS and NanoSIMS analysis, the same FIB sections were examined using a transmission electron microscope (JEOL JEM-ARM200F) at an accelerating voltage of 200 kV at Kochi, JAMSTEC. The microstructure was observed using a bright-field TEM and a high-angle scanning TEM in a dark field. Mineral phases were identified by spot electron diffraction and lattice band imaging, and chemical analysis was performed by EDS with a 100 mm2 silicon drift detector and JEOL Analysis Station 4.30 software. For quantitative analysis, the characteristic X-ray intensity for each element was measured in the TEM scanning mode with a fixed data acquisition time of 30 s, a beam scanning area of ​​~100 × 100 nm2, and a beam current of 50 pA. The ratio (Si + Al)-Mg-Fe in layered silicates was determined using the experimental coefficient k, corrected for thickness, obtained from a standard of natural pyropagarnet.
All images and analyzes used in this study are available on the JAXA Data Archiving and Communication System (DARTS) https://www.darts.isas.jaxa.jp/curation/hayabusa2. This article provides the original data.
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