The Ni isotopic composition of Ryugu reveals a common accretion region for carbonaceous chondrites.

The isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct from other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI chondrites formed in a different region of the accretion disk, possibly around the orbits of Uranus and Neptune. We show that, like for Fe, Ryugu and CI chondrites also have indistinguishable Ni isotope anomalies, which differ from those of other carbonaceous chondrites. We propose that this unique Fe and Ni isotopic composition reflects different accretion efficiencies of small FeNi metal grains among the carbonaceous chondrite parent bodies.

Analysis of Cation Composition in Dolomites on the Intact Particles Sampled from Asteroid Ryugu.

Characterization of the elemental distribution of samples with rough surfaces has been strongly desired for the analysis of various natural and artificial materials. Particularly for pristine and rare analytes with micrometer sizes embedded on specimen surfaces, non-invasive and matrix effect-free analysis is required without surface polishing treatment. To satisfy these requirements, we proposed a new method employing the sequential combination of two imaging modalities, i.

Water circulation in Ryugu asteroid affected the distribution of nucleosynthetic isotope anomalies in returned sample.

Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform.

Abundant presolar grains and primordial organics preserved in carbon-rich exogenous clasts in asteroid Ryugu.

Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration.

Oxygen isotopes of anhydrous primary minerals show kinship between asteroid Ryugu and comet 81P/Wild2.

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: O-rich (associated with refractory inclusions) and O-poor (associated with chondrules). Both the O-rich and O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward.

Contribution of Ryugu-like material to Earth's volatile inventory by Cu and Zn isotopic analysis.

Initial analyses showed that asteroid Ryugu's composition is close to CI (Ivuna-like) carbonaceous chondrites -the chemically most primitive meteorites, characterized by near-solar abundances for most elements. However, some isotopic signatures (e.g.

Ryugu's nucleosynthetic heritage from the outskirts of the Solar System.

Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids.

Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites.

Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples.

Tungsten-182 evidence for an ancient kimberlite source.

Globally distributed kimberlites with broadly chondritic initial Nd-Hf isotopic systematics may be derived from a chemically homogenous, relatively primitive mantle source that remained isolated from the convecting mantle for much of the Earth's history. To assess whether this putative reservoir may have preserved remnants of an early Earth process, we report W/W and Nd/Nd data for "primitive" kimberlites from 10 localities worldwide, ranging in age from 1,153 to 89 Ma. Most are characterized by homogeneous μW and μNd values averaging -5.

Origin and Age of Metal Veins in Canyon Diablo Graphite Nodules.

Previous studies attributed the origin of metal veins penetrating graphite nodules in the Canyon Diablo IAB main group iron meteorite to condensation from vapor or melting of host metal. Abundances of 16 siderophile elements measured in kamacite within vein and host meteorite are most consistent with an origin by melting of the host metal followed by fractional crystallization of the liquid. The presence of the veins within graphite nodules may be explained by impact, as peak shock temperatures, and thus the most likely areas to undergo metal melting, are at metal-graphite interfaces.

Genetics, Age and Crystallization History of Group IIC Iron Meteorites.

The eight iron meteorites currently classified as belonging to the IIC group were characterized with respect to the compositions of 21 siderophile elements. Several of these meteorites were also characterized for mass independent isotopic compositions of Mo, Ru and W. Chemical and isotopic data for one, Wiley, indicate that it is not a IIC iron meteorite and should be reclassified as ungrouped.

New implications for the origin of the IAB main group iron meteorites and the isotopic evolution of the noncarbonaceous (NC) reservoir.

The origin of the IAB main group (MG) iron meteorites is explored through consideration of W isotopic compositions, thermal modeling of Al decay, and mass independent (nucleosynthetic) Mo isotopic compositions of planetesimals formed in the noncarbonaceous (NC) protosolar isotopic reservoir. A refined W model age for the meteorites Campo del Cielo, Canyon Diablo, and Nantan suggests that the IAB-MG parent body underwent some form of metal-silicate segregation as early as 5.3 ± 0.

A compositionally heterogeneous martian mantle due to late accretion.

The approximately chondritic estimated relative abundances of highly siderophile elements (HSE) in the bulk martian mantle suggest that these elements were added after Mars' core formed. The shergottite-nakhlite-chassigny (SNC) meteorites imply an average mantle Pt abundance of ≈3 to 5 parts per billion, which requires the addition of 1.6 × 10 kilograms of chondritic material, or 0.

Highly siderophile element and Re-Os isotopic systematics of ungrouped achondrite Northwest Africa 7325: Evidence for complex planetary processes.

The abundances of highly siderophile elements (HSE; including Re, Os, Ir, Ru, Pt, and Pd) and Re-Os isotopic systematics were determined for two fragments from ungrouped achondrite NWA 7325. Rhenium-Os systematics are consistent with closed-system behavior since formation or soon after. The abundances of the HSE were therefore largely unaffected by late-stage secondary processes such as shock or terrestrial weathering.

Rapid effects of terrestrial alteration on highly siderophile elements in the Sutter's Mill meteorite.

The Re-Os isotopic systematics of many bulk chondrites plot well beyond analytical uncertainties of a primordial isochron. Limited variations in Os/Os, coupled with large variations in Re/Os ratios among chondrites, suggest that this apparently open-system behavior is a result of the comparatively recent gain or loss of Re and/or Os. In order to assess whether or not rapid alteration in the terrestrial environment could be responsible for open-system behavior in chondrites, four pieces of the Sutter's Mill meteorite were examined for Os isotopic systematics and abundances of highly siderophile elements.

The origin of the unique achondrite Northwest Africa 6704: Constraints from petrology, chemistry and Re-Os, O and Ti isotope systematics.

Northwest Africa (NWA) 6704 is a unique achondrite characterized by a near-chondritic major element composition with a remarkably intact igneous texture. To investigate the origin of this unique achondrite, we have conducted a combined petrologic, chemical, and Re-Os, O, and Ti isotopic study. The meteorite consists of orthopyroxene megacrysts (EnWoFs; Fe/Mn = 1.

Genetics, crystallization sequence, and age of the South Byron Trio iron meteorites: New insights to carbonaceous chondrite (CC) type parent bodies.

The nucleosynthetic Mo, Ru, and W isotopic compositions of the South Byron Trio iron meteorite grouplet (SBT) are consistent with all three meteorites originating on a single parent body that formed in the carbonaceous chondrite (CC) isotopic domain within the Solar nebula. Consistent with a common origin, the highly siderophile element (HSE) concentrations of the SBT can be related to one another by moderate degrees of fractional crystallization of a parental melt with initially chondritic relative abundances of HSE, and with initial S and P contents of ~7 and ~1 wt. %, respectively.

Siderophile element constraints on the thermal history of the H chondrite parent body.

The abundances of highly siderophile elements (HSE: Re, Os, Ir, Ru, Pt, Pd), as well as Re-Os and Hf-W isotopic systematics were determined for separated metal, slightly magnetic, and nonmagnetic fractions from seven H4 to H6 ordinary chondrites. The HSE are too abundant in nonmagnetic fractions to reflect metal-silicate equilibration. The disequilibrium was likely a primary feature, as Re-Os data indicate only minor open-system behavior of the HSE in the slightly and non-magnetic fractions.

Excess W in IIAB iron meteorites: Identification of cosmogenic, radiogenic, and nucleosynthetic components.

The origin of W excesses in iron meteorites has been a recently debated topic. Here, a suite of IIAB iron meteorites was studied in order to accurately determine the contribution from galactic cosmic rays (GCR) and from potential decay of Os to measured excesses in the minor isotope W. In addition to W isotopes, trace element concentrations (Re, Os, Ir, Pt, W) were determined on the same samples, as well as their cosmic ray exposure ages, using Cl-Ar systematics.

Tungsten Isotopes in Planets.

The short-lived Hf-W isotope system has a wide range of important applications in cosmochemistry and geochemistry. The siderophile behavior of W, combined with the lithophile nature of Hf, makes the system uniquely useful as a chronometer of planetary accretion and differentiation. Tungsten isotopic data for meteorites show that the parent bodies of some differentiated meteorites accreted within 1 million years after Solar System formation.

Characterizing cosmochemical materials with genetic affinities to the Earth: Genetic and chronological diversity within the IAB iron meteorite complex.

The IAB iron meteorite complex consists of a main group (MG) and five chemical subgroups (sLL, sLM, sLH, sHL, and sHH). Here, mass-independent Mo and radiogenic 182W isotope compositions are reported for IAB complex meteorites to evaluate the genetics and chronology, respectively, of the MG and subgroups. Osmium isotopes are used to correct for cosmic ray exposure effects on isotopes of Mo andW.

Tungsten-182 heterogeneity in modern ocean island basalts.

New tungsten isotope data for modern ocean island basalts (OIB) from Hawaii, Samoa, and Iceland reveal variable W/W, ranging from that of the ambient upper mantle to ratios as much as 18 parts per million lower. The tungsten isotopic data negatively correlate with He/He. These data indicate that each OIB system accesses domains within Earth that formed within the first 60 million years of solar system history.

High-precision analysis of W/W and W/W by negative thermal ionization mass spectrometry: Per-integration oxide corrections using measured O/O.

Here we describe a new analytical technique for the high-precision measurement of W/W and W/W using negative thermal ionization mass spectrometry (N-TIMS). We improve on the recently reported method of Trinquier et al. (2016), which described using Faraday cup collectors coupled with amplifiers utilizing 10 Ω resistors to continuously monitor the O/O of WO and make per-integration oxide corrections.

High-precision molybdenum isotope analysis by negative thermal ionization mass spectrometry.

Procedures for the separation, purification, and high-precision analysis of mass-independent isotopic variations in molybdenum (Mo) using negative thermal ionization mass spectrometry are reported. Separation and purification of Mo from silicate and metal matrices are achieved using a two-stage anion exchange chromatographic procedure. Molybdenum is ionized as the MoO species using a double filament assembly.