Allende Meteorite Research Articles

Abiotic formation of alkylsulfonic acids in interstellar analog ices and implications for their detection on Ryugu

For the last century, the source of sulfur in Earth’s very first organisms has remained a fundamental, unsolved enigma. While sulfates and their organic derivatives with sulfur in the S(+VI) oxidation state represent core nutrients in contemporary biochemistry, the limited bioavailability of sulfates during Earth’s early Archean period proposed that more soluble S(+IV) compounds served as the initial source of sulfur for the first terrestrial microorganisms. Here, we reveal via laboratory simulation experiments that the three simplest alkylsulfonic acids—water soluble organic S(+IV) compounds—can be efficiently produced in interstellar, sulfur-doped ices through interaction with galactic cosmic rays. This discovery opens a previously elusive path into the synthesis of vital astrobiological significance and untangles fundamental mechanisms of a facile preparation of sulfur-containing, biorelevant organics in extraterrestrial ices; these molecules can be eventually incorporated into comets and asteroids before their delivery and detection on Earth such as in the Murchison, Tagish Lake, and Allende meteorites along with the carbonaceous asteroid Ryugu.

Strontium isotope evidence for the repeated formation of refractory inclusions in the Allende meteorite

Calcium-aluminum-rich inclusions (CAIs) in chondrite meteorites are the oldest rocks in the Solar System and were formed by condensation from nebular gas. Recent mass spectrometric measurements have revealed that CAIs possess nucleosynthetic isotopic compositions different from those of terrestrial materials for various elements, indicating a heterogeneous distribution of nuclides from various stellar sources in the early Solar System. CAIs are classified into coarse-grained (CGs) and fine-grained (FGs) inclusions. The former have experienced secondary melting through thermal events after their formation, while the latter evidently avoided the remelting. Thus, FGs are considered to be direct condensates from a high-temperature gas, making them ideal for the investigation of the origin and formation process of CAIs. In this study, the elemental abundances and Sr isotopic compositions in eight FGs from a carbonaceous chondrite Allende were analyzed by utilizing a micromilling technique. These FG samples were found to have rare-earth element (REE) patterns reflecting various degrees of elemental fractionation and variable µ84Sr values ranging from 61 to 844 ppm. It cannot be ruled out that matrix contamination during micromilling or secondary alteration on the Allende parent body has affected the elemental abundances and µ84Sr values observed in FGs to some extent; however, the large variation in µ84Sr values could reflect the variability in the FG formation processes. Importantly, REE-fractionated FGs, which were depleted in heavy REEs relative to light REEs, had relatively high µ84Sr values. This suggests that the formation of REE-fractionated FGs was triggered by rapid heating events, such as FU Orionis that occurred periodically in the early Solar System, and that at least two different heating events probably formed FGs with two different µ84Sr values.

Possible Relevance of the Allende Meteorite Conditions in Prebiotic Chemistry: An Insight into the Chondrules and Organic Compounds

Possible Relevance of the Allende Meteorite Conditions in Prebiotic Chemistry: An Insight into the Chondrules and Organic Compounds

In Situ Argon Isotope Analyses of Chondrule-Forming Materials in the Allende Meteorite: A Preliminary Study for 40Ar/39Ar Dating Based on Cosmogenic 39Ar

The argon isotopic compositions of chondrule-forming minerals of the Allende (CV3) meteorite were examined to evaluate the possibility of in situ 40Ar/39Ar dating of planetary surface rocks based on cosmogenic 39Ar without neutron irradiation in a reactor. The investigated Allende meteorite sample (ME-247H: 50 mm × 45 mm × 5 mm; 28.85 g) contains at least three textural types of chondrules: barred olivine chondrule (BOC), porphyritic olivine chondrule (POC), and unclassified chondrule (UC). Most chondrules contain olivine, low-Ca pyroxene, clinopyroxene, and plagioclase as primary phases, with minor amounts of nepheline and sodalite formed during aqueous alteration of the CV3 parent body of the early solar system. In situ argon isotope analyses on selected chondrule-forming minerals in petrographic sections of two BOCs, two POCs, and one UC using a Nd:YAG pulse laser confirmed a significant amount of cosmogenic 39Ar that formed by a 39K (n, p) 39Ar reaction in an extraterrestrial environment. Laser step-heating analyses of five bulk chondrules irradiated in a reactor revealed a plateau age (3.32 ± 0.06 Ga) from one of the five chondrules. The age spectra of all chondrules show the younger age in the low-temperature fractions, resulting in the integrated ages from 2.7 to 3.2 Ga. These results suggest that the Allende meteorite experienced argon isotopic homogenization at 3.3 Ga and the argon loss in part after the 3.3 Ga. Apparent ages of chondrule-forming minerals that were calculated using the J values of nephelines in one BOC and two POCs do not show any consistent relationship among the three types of chondrules (BOC, POC, and UC). This might be attributed to the fact that the isotopic heterogeneity among minerals took place during the heterogeneous argon loss stage after the 3.3 Ga event.

Three-dimensional imaging of high-velocity-impact induced crack growth in carbonaceous meteorites

The material strength of meteorites provides useful information on the make-up and history of asteroids. However, the unique determination of the material strength of a meteorite is difficult because of the wide range of strengths many meteorites exhibit. Even within a single sample, complicated textures and mineral granular compositions make measurements difficult. Michikami et al. (2019) investigated the impact-induced crack growth in ordinary (L5) chondrites and indicated that crack growth is largely affected by the strength of individual mineral grains (and/or chondrules). In this study, we examine the strengths of mineral grains in carbonaceous meteorites qualitatively. To this end, we use X-ray microtomography to investigate how chondrules are affected by impact-induced crack growth in carbonaceous meteorites. Spherical alumina projectiles with a diameter of 1.0 mm were fired into the surfaces of seven Allende (CV) meteorite target samples with sizes of ∼1 to 2 cm at a nominal impact velocity of 2.0 km/s. In addition, spherical glass projectiles with a diameter 0.8 mm were fired into the target surfaces of two Murchison (CM) and two Aguas Zarcas (CM) meteorite target samples with sizes of ∼2 cm at a nominal impact velocity of 4.0 km/s. The results show that most cracks in CV chondrites tend to grow along the boundary surfaces of the chondrules, while most chondrule-related cracks in CM samples grow regardless of the boundary surfaces of the chondrules. This suggests that crack growth is largely affected by the chondrules' strength as indicated by Michikami et al. (2019). The weaker the strength of chondrules, the more likely crack growth tends to occur regardless of chondrule boundaries. We found that the mesostasis of chondrules in CM meteorite Murchison (and likely Aguas Zarcas) has experienced aqueous alteration and the chondrules have become structurally weak as a whole. This indicates that impact-induced crack propagation in CM chondrites differs from thermal-fatigue induced crack propagation inferred from previous studies. As the sample material to be returned from asteroid Bennu is considered to be related to CM chondrites, we propose that observation of the cracks in chondrules in Bennu samples might tell us whether those cracks are impact- or thermal-fatigue-induced.

Analysis of individual matrix particles in the Allende meteorite by high-resolution FIB-TOF-SIMS.

The matrix in the "Allende meteorite" was analyzed by high-spatial-resolution focused ion beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS), and consisted of fine grains with sizes of several micrometers. It is difficult to analyze the matrix particles individually. As FIB-TOF-SIMS has a high spatial resolution, it can analyze the matrix individually. In addition, if the sample can be smoothed, no other pretreatment is required. By this method, it was clarified that Al, Cr, etc., which were conventionally detected as trace components in mass spectra, existed as fine particles between the matrix particles, rather than as impurities within them. The Al-rich particles did not match the minerals already found in the Allende meteorite matrix. Although the identity of the aluminum-rich particles has not been clarified, the abundance and localization could be observed correctly. Al-rich particles are likely to be affected by metamorphism and have important information to clarify the metamorphism process.

The Fine‐Scale Magnetic History of the Allende Meteorite: Implications for the Structure of the Solar Nebula

AbstractMagnetic fields in the early solar system may have driven the inward accretion of the protoplanetary disk (PPD) and generated instabilities that led to the formation of planets and ring and gap structures. The Allende carbonaceous chondrite meteorite records a strong early solar system magnetic field that has been interpreted to have a PPD, dynamo, or impact‐generated origin. Using high‐resolution magnetic field imaging to isolate the magnetization of individual grain assemblages, we find that only Fe‐sulfides carry a coherent magnetization. Combined with rock magnetic analyses, we conclude that Allende carries a magnetization acquired during parent body chemical alteration at ~3.0–4.2 My after calcium aluminum‐rich inclusions in an >40 µT magnetic field. This early age strongly favors a magnetic field of nebular origin instead of dynamo or solar wind alternatives. When compared to other paleomagnetic data from meteorites, this strong intensity supports a central role for magnetic instabilities in disk accretion and the presence of temporal variations or spatial heterogeneities in the disk, such as ring and gap structures.

Atomic-scale structure and non-stoichiometry of meteoritic hibonite: A transmission electron microscope study

Abstract Hibonite (CaAl12O19) is a common refractory mineral in Ca-Al-rich inclusions (CAIs) in primitive meteorites. Transmission electron microscope (TEM) studies have identified enigmatic planar defects in different occurrences of hibonite in the Allende meteorite that give rise to strong streaking along c* in electron diffraction patterns. Atomic resolution high-angle annular dark-field (HAADF) imaging and energy-dispersive X-ray (EDX) analyses were used to determine the nature and origin of these planar features. HAADF images of hibonite grains reveal lamellar intergrowths of common 1.6 nm spacing, and less commonly 2.0 and 2.5 nm spacings, interspersed in stoichiometric hibonite showing 1.1 nm (002) spacing. Stoichiometric hibonite consists of alternating Ca-containing (“R”) and spinel-structured (“S”) blocks stacked in a sequence RS. In contrast, the 1.6 nm layers result from a doubled S block such that the stacking sequence is RSS, while in the widest defect observed, the stacking sequence is RSSSS. These intergrowths are epitaxial and have coherent, low-strain boundaries with the host hibonite Meteoritic hibonite shows common Ti and Mg substitution for Al in its structure. Atomic-resolution EDX maps of hibonite grains in the Allende CAI confirm the preferred site occupancy of Mg on tetragonal M3 sites in S blocks and of Ti on trigonal bipyramidal M2 and octahedral M4 sites in R blocks. Mg is highly concentrated, but Ti is absent in the planar defects where wider S blocks show Al-rich compositions compared to stoichiometric MgAl2O4 spinel. Therefore, Mg likely played the major role in the formation and metastability of planar defects in hibonite. Electron energy loss spectroscopy data from the Ti L2,3 edge show the presence of mixed Ti oxidation states with ~15–20% of Ti as Ti3+ in hibonite, suggesting a direct substitution of Ti3+ ↔ Al3+ in hibonite. The remaining ~80–85% of Ti is present as Ti4+ and corresponding EDX analyses are consistent with the well-known coupled substitution 2Al3+ ↔ Ti4+ + Mg2+ being the major mechanism for Ti and Mg substitution in hibonite. The formation of planar defects in hibonite occurred during high-temperature nebular condensation or melting/crystallization processes. The occurrence of non-stoichiometric hibonite in the Allende CAI deviates from the mineral formation sequence predicted from equilibrium condensation models. Overall, our atomic resolution TEM observations signify non-equilibrium, kinetic-controlled crystal growth during the high-temperature formation of refractory solids in the early solar nebula.

The chemical composition and homogeneity of the Allende matrix

The abundances of C, O, S, Na, K, Li, Mn, P, Cr, Si, Fe, Mg, Ni, Co, V, Ca, Ti, Al and Sc were determined in-situ in a sample of the Allende meteorite using a laser ablation/ionization mass spectrometer to quantify the bulk chemical composition of the matrix and its spatial chemical variability.The high lateral resolution of the instrument makes it possible to measure the elemental composition of Allende matrix, without any sample treatment prior to analysis. The measurements of solely Allende matrix allow investigating the variability of the element abundances in the matrix material on different scales from 50 ​μm to 0.5 ​mm.The comprehensive data set provides constraints on models for the formation of matrix material of carbonaceous chondrites in the solar nebula. A key observation of this study is a high degree of chemical homogeneity of the matrix, indicating that it formed independently from or in parallel with the chondrules and that the process that led to the formation of the parent body was a fast collapse of the dust-gas cloud following chondrule formation.

Raman spectral peak positions of olivine (Fo‐Fa) as fast methodology for classifying chondrites

AbstractChondrites are the most common meteorites in the world. However, the carbonaceous chondrites represent only a small fraction of those. Among them, Allende meteorite is one of the most studied carbonaceous chondrites. The main objective of this paper is to use the Raman spectral peak positions of olivine as a parameter to chondrite classification, here, specifically, Allende meteorite. Although these correlations are not new in the literature, this approach has not been used to classify carbonaceous chondrites yet. To develop the olivine calibration, only the peak positions of the doublet in the 700–1100 cm−1 region were analyzed in this study. The typical Raman spectrum of olivine displays two major peaks, here called Peak A, with Raman shifting in the 814–824 cm−1 range, and Peak B, in the 836–857 cm−1 range. The results of measurements found were perfectly matched to a linear correlation between Peak A and Peak B. The peak position versus composition plot shows a good correlation between the samples used as reference. The correlation curve obtained from the reference olivines is consistent with the data found in literature, as well as the peak versus peak plot. Finally, from the analysis of the olivine Raman spectral peak positions present in Allende meteorite, it is possible to conclude that there is little Fe in its matrix. Actually, the proportion of metallic Fe is less than 3% when the range of fayalite content is between Fa26–32.Thus, although the exact amount of iron present in the sample is not entirely clear, this kind of methodology quickly and effectively provides a response regarding the Fa ratio in the meteorite.

In situ Si isotope and chemical constraints on formation and processing of chondrules in the Allende meteorite

Chondrules in undifferentiated meteorites are former silicate melt droplets of variable texture and composition. Although widely studied, the chondrule formation mechanisms and conditions that explain all properties of chondrules are yet to be identified. To further constrain the processes that affected chondrules in the solar nebula and on the meteorite parent body, we determined in situ Si isotope ratios and major and trace element compositions of minerals in chondrules of variable types and sizes from the Allende CV3 chondrite.The δ30Si in chondrule minerals ranges from −1.28 ± 0.19 to 0.55 ± 0.20‰ (2SE). The δ30Si in chondrules shows no direct relationship with chondrule sizes or with distance between core and rim. Barred olivine-rich chondrules record the highest δ30Si, likely because of faster cooling and less interaction with isotopically light nebular gas. Type I non-porphyritic and some porphyritic chondrules show overall higher δ30Si compared to type II porphyritic chondrules. Furthermore, Mg-rich olivine and Mg-rich pyroxene have systematically higher δ30Si compared to Fe-rich olivine and Fe-rich pyroxene.The variable δ30Si of type I chondrule silicates (Mg-rich) compared to type II chondrule silicates (Fe-rich) may be explained by variable interaction of chondrule silicates with the nebular gas in the solar nebula. We envision a combination of equilibrium and kinetic isotope fractionation of Si between nebular gas and Fe-poor silicates (such as forsterite, anorthite, enstatite and mesostasis) and Fe-rich olivine and orthopyroxene. Petrographic evidence suggests that the enrichment of Fe in some highly altered porphyritic chondrules and at chondrule rims was likely caused by hydrothermal alteration on the parent body. Therefore, the correlation of Fe and δ30Si of the chondrule minerals might serve as an indicator for the extent of further secondary processing of some chondrule minerals. The sum of these observations suggests that the formation and alteration of type II chondrules occurred by oxidation of originally reduced, metal-rich type I chondrules, both in the solar nebula and later on the meteorite parent body. Remaining 30Si depleted gas contributed to the isotopic composition of matrix silicates. The evidence favours the formation of chondrules and matrix of the Allende meteorite in nebular settings rather than by asteroid impacts.

Optical Constants of a Solar System Organic Analog and the Allende Meteorite in the Near- and Mid-infrared (1.5–13 μm)

Abstract Measurements of visible and near-infrared reflection (0.38–5 μm) and mid-to-far-infrared emission (5–200 μm) from telescope and satellite remote-sensing instruments make it possible to investigate the composition of planetary surfaces via electronic transitions and vibrational modes of chemical bonds. Red spectral slopes at visible and near-infrared wavelengths and absorption features at 3.3 and 3.4 μm observed in circumstellar disks, in the interstellar medium (ISM), and on the surfaces of solar system bodies are interpreted to be due to the presence of organic material and other carbon compounds. Identifying the origin of these features requires measurements of the optical properties of a variety of relevant analog and planetary materials. Spectroscopic models of dust within circumstellar disks and the ISM, as well as planetary regoliths, often incorporate just one such laboratory measurement despite the wide variation in absorption and extinction properties of organic and other carbon-bearing materials. Here we present laboratory measurements of transmission spectra in the 1.5–13 μm region and use these to derive real and imaginary indices of refraction for two samples: (1) an analog to meteoritic insoluble organic matter and (2) a powdered Allende meteorite sample. We also test our refractive index retrieval method on a previously published transmission spectrum of an Mg-rich olivine. We compare optical measurements of the insoluble organic matter analog to those of other solar system and extrasolar organic analogs, such as amorphous carbon and tholins, and find that the indices of refraction of the newly characterized material differ significantly from other carbonaceous samples.

Speciation of organosulfur compounds in carbonaceous chondrites

Despite broad application of different analytical techniques for studies on organic matter of chondrite meteorites, information about composition and structure of individual compounds is still very limited due to extreme molecular diversity of extraterrestrial organic matter. Here we present the first application of isotopic exchange assisted Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for analysis of alkali extractable fraction of insoluble organic matter (IOM) of the Murchison and Allende meteorites. This allowed us to determine the individual S-containing ions with different types of sulfur atoms in IOM. Thiols, thiophenes, sulfoxides, sulfonyls and sulfonates were identified in both samples but with different proportions, which contribution corroborated with the hydrothermal and thermal history of the meteorites. The results were supported by XPS and thermogravimetric analysis coupled to FTICR MS. The latter was applied for the first time for analysis of chondritic IOM. To emphasize the peculiar extraterrestrial origin of IOM we have compared it with coal kerogen, which is characterized by the comparable complexity of molecular composition but its aromatic nature and low oxygen content can be ascribed almost exclusively to degradation of biomacromolecules.

STEM-EELS Investigation of Planar Defects in Olivine in the Allende Meteorite

The present study focuses on a detailed structural investigation at atomic scale of the planar defects that appear in the olivine grains in the Allende meteorite, and it aims to clarify their nature and the related formation mechanism. The investigation was performed using advanced spectro-microscopy techniques such as atomically resolved high-angle annular dark field (HAADF) images coupled with electron energy loss spectroscopy in the scanning transmission electron microscopy mode (STEM-EELS). Two prominent structural features appear in the investigated olivine grains: (i) Exsolution platelets with a thickness between 2 and 10 nm with the spinel structure and chemical composition expressed as a solid solution between magnetite, chromite, and MgAl2O4. (ii) Thinner planar defects appeared with thickness between 2 to 4 atomic planes, which were rich in Fe and had a strong Fe3+ contribution. The structure of these defects was described by the crystalline lattice of the olivine grains with small distortion of the measured cationic distances, which can be related to Fe3+-Si substitution in the tetrahedral sites. Those metastable defects should have preceded the formation of the thicker spinel exsolutions and could have formed during an oxidizing event in the Allende parent body.

Meteoritic Evidence for a Ceres-sized Water-rich Carbonaceous Chondrite Parent Asteroid.

Carbonaceous chondrite meteorites record the earliest stages of Solar System geo-logical activities and provide insight into their parent bodies' histories. Some carbonaceous chondrites are volumetrically dominated by hydrated minerals, providing evidence for low temperature and pressure aqueous alteration1. Others are dominated by anhydrous minerals and textures that indicate high temperature metamorphism in the absence of aqueous fluids1. Evidence of hydrous metamorphism at intermediate pressures and temperatures in carbonaceous chondrite parent bodies has been virtually absent. Here we show that an ungrouped, aqueously altered carbonaceous chondrite fragment (numbered 202) from the Almahata Sitta (AhS) meteorite contains an assemblage of minerals, including amphibole, that reflect fluid-assisted metamorphism at intermediate temperatures and pressures on the parent asteroid. Amphiboles are rare in carbonaceous chondrites, having only been identified previously as a trace component in Allende (CV3oxA) chondrules2. Formation of these minerals requires prolonged metamorphism in a large (~640-1800 km diameter), unknown asteroid. Because Allende and AhS 202 represent different asteroidal parent bodies, intermediate conditions may have been more widespread in the early Solar System than recognized from known carbonaceous chondrite meteorites, which are likely a biased sampling.

Robust Spin Control Design for the AOSAT+ Mission Concept

The surfaces of asteroids are a challenging environment to explore due to their low gravity. Active small-body missions rely on short-duration touch-and-go operations to mitigate this risk. An in-depth understanding of the surface geophysics of asteroids and comets can open the door to prolonged surface and subsurface exploration of these small bodies. We propose the AOSAT+ mission concept, which will provide rich physics data of a simulated asteroid surface. The mission consists of a 12U CubeSat that will operate as a centrifuge laboratory in low Earth orbit (LEO). The CubeSat will carry 2.5 kg of crushed Allende meteorite, along with a suite of science instruments. The spacecraft will rotate at 0.1-1.1 RPM to simulate the milli-gravity environment of a desired small body. A major challenge with operating a centrifuging spacecraft is that it contains shifting masses, which result in perturbation torques on the spacecraft. This requires a robust attitude controller to spin the spacecraft at its target rotation speed. This article presents the development of a sliding-mode attitude control law that enables the operation of the AOSAT+ centrifuge mode. The perturbations of the regolith are modeled using a discrete element model (DEM), where the regolith grains are treated as inelastically colliding hard spheres. We begin by presenting a detailed overview of the AOSAT+ mission concept and its different operations. The regolith motion model implementation and the detailed derivation of the required sliding-mode controller are then presented. The constraints presented by the actuators and tools to study their limitations are then developed. Finally, the controller is shown to successfully demonstrate the spin rate requirements of the AOSAT+ centrifuge mode. Key insights on the operation of the centrifuge mode and important mission design considerations on the spacecraft are then noted.

Meteoritic Nanodiamonds: Alternative Composition of Xenon Components

For the first time, abundances of the main xenon components (Xe-P3, Xe-P3(fr), Xe-P6 and Xe-pr instead Xe-HL) in the nanodiamonds of Orgueil (CI), Tieschitz (H3.6) and Indarch (EH3-4) meteorites have been calculated. The Xe-pr component is the excess fraction of xenon isotopes in the Xe-HL component relative to Xe-P3 (fr) and mainly consists of the 124, 126, 134, 136Хе isotopes formed in p- and r-processes of nucleosynthesis in a type II supernova explosion. Analysis of the data has shown the following. (1) The main nanodiamond component of Xe is Xe-P3 (fr), and its maximum during pyrolysis, like Xe-pr and Xe-P6, is high-temperature (>1000°C), irrespectively of the petrological type of meteorites. (2) The relative abundance of the Xe-pr component in the nanodiamonds of Indarch meteorite, which is most enriched in anomalous xenon components, is about 15% of the total xenon abundance in the diamond of this meteorite, which is significantly lower than the abundance of the Xe-HL component – about 87%. (3) The xenon components are contained in the individual populations of the diamond grains with different thermo-oxidative stability. The data we obtained and in (Huss, Lewis, 1994b) on the abundances and the yield kinetics of xenon components in meteoritic nanodiamonds, based on the Xe-pr and Xe-HL isotope compositions, respectively, most likely show their limiting values. Тhe real properties of xenon components are assumed to be similar to those obtained when using Xe-pr component for calculations, taking into account the data on the carbon isotope composition in the nanodiamond grains of the Allende meteorite (Lewis et al., 2019).

Constraints on the thermal history of the Allende (CV3) meteorite by gradual and stepwise pyrolyses of insoluble organic matter

Constraints on the thermal history of the Allende (CV3) meteorite by gradual and stepwise pyrolyses of insoluble organic matter

Determination of trace rare earth elements in rock samples including meteorites by ICP-MS coupled with isotope dilution and comparison methods

Combining isotope dilution mass spectrometry with a calibration method and choosing appropriate internal standard elements, 14 lanthanides (rare earth elements, REEs) were precisely and accurately determined for rock samples by using quadruple ICP-MS instruments. An enriched spike of 149Sm was used to determine Sm content by an isotope dilution method. Simultaneously, Sm content was determined by a calibration method and the ratio of the two Sm values was used for correcting the preparation loss of the other REEs, which were analyzed only by a calibration method. Indium and Tl were chosen for use as internal standard elements. Applying the procedure developed in this study to the homogenized Allende meteorite powder sample prepared by the Smithsonian Institution, Washington, D. C., US and several geological reference samples issued by the Geological Survey of Japan and the US geological Survey, precision and accuracy of the data obtained were evaluated and the accuracy was found to be equivalent to isotope dilution values obtained by thermal ionization mass spectrometry. Rare earth element concentrations in several meteorite samples were determined, and results indicate that our procedure is appropriate for a wide variety of whole rock compositions.

Multimodal x-ray and electron microscopy of the Allende meteorite.

Multimodal microscopy that combines complementary nanoscale imaging techniques is critical for extracting comprehensive chemical, structural, and functional information, particularly for heterogeneous samples. X-ray microscopy can achieve high-resolution imaging of bulk materials with chemical, magnetic, electronic, and bond orientation contrast, while electron microscopy provides atomic-scale spatial resolution with quantitative elemental composition. Here, we combine x-ray ptychography and scanning transmission x-ray spectromicroscopy with three-dimensional energy-dispersive spectroscopy and electron tomography to perform structural and chemical mapping of an Allende meteorite particle with 15-nm spatial resolution. We use textural and quantitative elemental information to infer the mineral composition and discuss potential processes that occurred before or after accretion. We anticipate that correlative x-ray and electron microscopy overcome the limitations of individual imaging modalities and open up a route to future multiscale nondestructive microscopies of complex functional materials and biological systems.