This study investigates the mid-infrared spectral correlation between four Carbonaceous Vigarano (CV) chondrites (Allende, Grosnaja, Efremovka and Leoville) and ten asteroids of Xk, L, & Ld types (Bus- Binzel taxonomy). It leverages the mid-infrared region of the electromagnetic spectrum, which is characterised by prominent peaks indicative of crystalline bond vibrations of silicates and ionic oxides. A novel statistical methodology, integrating four distinct similarity assessment techniques (normalised local change method, covariance, Euclidean distance, and cosine similarity), was employed to determine the spectral similarity coefficient (Z) between the CV chondrites and the chosen asteroids. The highest similarity is observed between the asteroids of L type, Victoria, (1284) Kassandra, and (1702) Latvia and the CV chondrites studied here, followed by the Xk type (114) Kassandra. The Z value between Ld asteroids (234) Barbara, (269) Justitia and CVs exhibit low similarities. This study establishes a framework for the statistical comparison of mid-infrared spectra of meteorites and asteroids by accounting for compositional variability within CV chondrites, thereby providing a basis for more detailed investigations into the parent-body association of these meteorites.

Isotopes of chromium (Cr) and other iron-group elements are predominantly made in the inner shells of supernovae and are later reprocessed via the slow neutron capture process ( s -process) in asymptotic giant branch (AGB) stars. Nucleosynthetic models of low-mass, solar metallicity AGB stars yield significant overproduction of ^54 Cr ( δ ^54 Cr values ∼ +160‰) with limited variations in other Cr isotopes, relative to solar system values. Here we report Cr, C, and N isotopic compositions of 16 individual presolar silicon carbide (SiC) grains of the KJG series (1.5–3 μ m) from the Murchison (CM2.0) meteorite. ^12 C/ ^13 C and ^14 N/ ^15 N ratios of the 14 mainstream SiC grains range from 29 to 108 and 259 to 7800, respectively. These C, N isotopic compositions are consistent with their formation in red giant and AGB stars. Two types of AB grains could have originated in a J-type C-star (AB2) and a type-II supernova (AB). The majority of mainstream grains display close-to-solar Cr isotopic compositions, indicating the Cr was not significantly processed within their parent AGB stars. A mainstream SiC grain with relatively high ^54 Cr enrichment of δ ^54 Cr ∼ 700‰ likely originated from a very low metallicity parent star based on the stellar nucleosynthesis model (FRUITY). We consider the plausible origin of this grain from Galactic halo stars, migration from the outer Galactic disk, and other scenarios. Elemental Cr concentrations of the grains vary from ∼1 to 9 ppm, with 75% of the grains displaying an average concentration of ∼2 ppm. Cr concentration does not vary significantly with grain size, suggesting that the Cr in the SiC grains condensed during grain formation and was not implanted at a later stage.

Calcium-aluminium-rich inclusions (CAIs) and chondrules are the oldest dated components of chondrites. They record the events and processes during the formation and early evolution of the solar system in their morphology, mineral phases and isotopic compositions. Al-26-Mg-26 isotopic systematics of two CAIs from Leoville (CV3.1-3.4), two chondrules from Queen Alexandra range 99177 (CR3.00), one mega chondrule from Semarkona (LL3.00), and a plagioclase rich chondrule from Chainpur (LL3.4) were carried out to understand the formation processes of these rare kinds of objects and to obtain constraints on early solar system events and processes. Petrographic and isotopic properties of Leoville CAI 1 (Type B2) suggest its formation c. 0.1 Ma after typical non-igneous CAIs characterized by the canonical ratio of Al-26/Al-27 = 5.25 x 10(- 5), from a partial melt heated to a maximum temperature of similar to 1420 degrees C and cooled slowly at <= 0.5 degrees C/h. Leoville CAI 3 (Type A) plausibly formed early within 1 Ma of the canonical CAI value and subsequently experienced parent body aqueous alteration. The analysed chondrules did not yield significant Mg-26 excess due to their small Al/Mg ratio or resetting by secondary processes.

We report the structural and chemical investigation of nine presolar silicate grains from the CH3/CBb3 chondrite Isheyevo and CR2 chondrite Northwest Africa (NWA) 801. Five of these grains belong to group 1, likely condensed in low- to intermediate-mass asymptotic giant branch (AGB) stars, super-AGB stars, or core-collapse supernovae, while the remaining four grains belong to group 4 and have a supernova origin. The advanced transmission electron microscopy and associated electron spectroscopy analyses show a diverse range of chemical and structural compositions for presolar silicates. Two GEMS (glass with embedded metal and sulfide)-like silicates, each from different groups, condensed under nonequilibrium conditions in stellar outflows. Two nonstoichiometric silicates from group 1 have dissimilar formation and alteration histories. An amorphous silicate from group 1 with olivine-like [(Mg,Fe)2SiO4] composition likely formed as a crystalline olivine that subsequently amorphized in the interstellar medium. An oldhamite (CaS) grain within a stoichiometric enstatite (MgSiO3) from group 1 probably formed by heterogeneous condensation in circumstellar outflows. Of the two crystalline grains from group 4, one is an antigorite [(Mg,Fe)3Si2O5(OH)4], while the other is a nontronite [Na,Fe2(Si,Al)4O10(OH)2.nH2O], both formed as a crystalline forsterite and later altered to have hydrated silicate composition. A group-4 silicate has a chemical composition similar to a low Ca-pyroxene [(Ca,Mg)(Si,Al)2O6]. Our data imply that presolar grains from different groups can have a similar range of grain-formation conditions.

We report on the discovery of 33 oxygen-anomalous grains from the CH3/CBb3 chondrite Isheyevo and the CR2 chondrite Northwest Africa (NWA) 801. Oxygen isotopic compositions indicate the origin of the majority grains in stellar outflows of low-mass (∼1.2 to ∼2.2 M ⊙), solar-metallicity red giant or asymptotic giant branch stars, while highly 17O-enriched grains probably have nova origins. Isotopic compositions of the eight 18O-rich grains, including an extremely 18O-rich grain (∼16 times solar 18O/16O ratio), are reproduced by zone mixing of SNe II ejecta. Close-to-normal silicon, magnesium, and calcium isotopic compositions of grains are consistent with the isotope exchange in the interstellar medium or the meteorite parent body, while two grains with Si isotopic anomalies and one grain with Mg isotopic anomalies reflect the Galactic chemical evolution. An Isheyevo clast showed several hot spots with moderate to high 15N enrichments, including a hot spot with an extreme 15N excess of (7225 ± 316)‰. However, no correlation between 15N enrichment and presolar oxygen-rich grain abundance is found. Grains with elliptical shapes probably indicate primary condensation feature. Two complex grains possibly display decoupling of the isotopic and elemental compositions in the grain formation environments. The low silicate-to-oxide abundance ratio for the fine-grained chondrule rims in NWA 801 likely reflects the preferential destruction of silicates due to terrestrial weathering. In NWA 801, the presolar O-rich grain abundance in fine-grained chondrule rims is higher than in the interchondrule matrix, similar to the trend observed for some aqueously altered chondrites of petrologic type 2.

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CANONICAL CAI IN VIGARANO. R. K. Mishra K. K. Marhas and M. Chaussidon, Independent researcher, Vill: Dhawalpura, Po: Kaitha, District Bhagalpur, Bihar 813211 India (riteshkumarmishra@gmail.com), Planetary Sciences Division, Physical Research Laboratory, Navrangpura, Ahmedabad, Gujarat, 380009 India, Université de Paris, Institut de Physique du Globe de Paris (IPGP) 1 rue Jussieu 75238 Paris Cedex 05 France.

Introduction Primitive extraterrestrial materials like carbonaceous chondrite matrices and interplanetary dust particles contain tiny dust grains that were formed in the winds of red giant branch, or asymptotic giant branch stars (AGB) and in the ejecta of novae and supernovae (SNe) explosions before the formation of our solar system. Presolar grains survived all the processes that created our solar system and carry the signatures of their parent stellar sources. Correlating isotopic data of individual presolar silicates with microstructural and chemical analyses obtained by STEM, provides a unique opportunity to provide better insights into physiochemical conditions of grain formation in stellar environments, grain alteration in the interstellar and parent body processes and also helps constraining various astrophysical grain condensation models. In this work, isotopic, structural and chemical analysis of nine presolar silicate grains from the CH3/CBb3 chondrite Isheyevo and CR2 chondrite NWA801 are reported.Experimental Presolar oxygen anomalous grain search using oxygen isotope imaging was done in-situ using NanoSIMS50 ion microprobe and five grains from AGB and four grains from SNe, were selected for (S)TEM investigations. The TEM lamellas were prepared using a TESCAN LYRA3 FIB-SEM at Curtin University. Structural and chemical analysis of presolar grains were performed by combining high-resolution scanning TEM imaging, spatially-resolved electron energy-loss spectroscopy (EELS) and spatially-resolved energy-dispersive X-ray spectroscopy (EDS) by using a FEI Titan Cubed Themis 60-300 microscope at Cádiz University which was operated at 200 kV. EDS quantification was corrected by using a standard reference sample of known composition and density and by taking into account the thickness of the probed area by using low-loss EELS. EELS spectrum images for fine structures (mostly, O-K, Si-L2,3 and Fe-L2,3 edges) analyses were acquired with the monochromator excited allowing an energy resolution of about 0.4 eV. After denoising using principal components analysis and removal of the multiple scattering, we were able to map the heterogeneities related to the Fe oxidation state and to the oxygen local chemical environment. This allowed us to compare the degree of aqueous alteration of the grain with the surrounding rim and matrix grains.Results TEM and STEM data have revealed a strong heterogeneity and a broad range of structural and chemical compositions of the grains that enabled us to compare the stellar grain condensation environments (e.g. AGB stars and SNe), and suggest widely varying formation conditions for the presolar silicates identified in this study. Only one of the grains originally condensed as an amorphous grain has shown preferential sputtering of Mg, indicating that Mg-rich amorphous grains are not preferentially destroyed. Several grains are found with signatures that represent interstellar, nebular and parent body alteration. An oldhamite-like grain within a presolar enstatite grain is probably the first observation of an oldhamite grain as a seed grain for the condensation of an enstatite grain in stellar atmospheres. All these results, which will be discussed in detail, point out the importance of coordinated isotopic, microstructural and chemical studies of presolar silicates to investigate the processes that may have played a role in shaping our solar system.

The fluence of dust particles < 10 micrometres in diameter was recorded by impacts on aluminium foil of the NASA Stardust spacecraft during a close fly-by of comet 81P/Wild 2 in 2004. Initial interpretation of craters for impactor particle dimensions and mass was based upon laboratory experimental simulations using >10 μm diameter projectiles and the resulting linear relationship of projectile to crater diameter was extrapolated to smaller sizes. We now describe a new experimental calibration programme firing very small monodisperse silica projectiles (470 nm to 10 μm) at ~ 6 km s -1 . The results show an unexpected departure from linear relationship between 1 and 10 μm. We collated crater measurement data and, where applicable, impactor residue data for 596 craters gathered during the post-mission preliminary examination (PE) phase. Using the new calibration, we recalculate the size of the particle responsible for each crater and hence reinterpret the cometary dust size distribution. We find a greater flux of small particles than previously reported. From crater morphology and residue composition of a sub-set of craters, the internal structure and dimensions of the fine dust particles is inferred and a ‘maximum-size’ distribution for the sub-grains composing aggregate particles is obtained. The size distribution of the small particles derived directly from the measured craters peaks at ~175 nm, but if this is corrected to allow for aggregate grains, the peak in sub-grain sizes is at <100 nm.

The sputtering rate of presolar silicon carbide grains due to galactic cosmic rays has been computed for their experimentally deduced lifetimes (similar to 1 Gyr) in the interstellar medium. An ion target simulator, SDTrimSP, was used to model the sputtering of interstellar grains with varying sizes and thicknesses of the ice mantle formed around the grain during their journey through the interstellar medium. Temperature, composition, and density for four different types of molecular cloud environments (quiescent, low-mass young stellar objects (YSOs), intermediate-mass YSOs, and high-mass YSO weak processing) considered indicate the sputtering rate on the mantle ice composition depends on water composition to a certain extent. The model simulations indicate galactic cosmic ray(s) with an energy range from 10 MeV to 1 GeV are just capable of sputtering/destructing similar to 13%-15% of the grain itself. This value, stretched over 1 Gyr is not as significant as the other destruction processes and therefore can be classified as a minor destruction process. The effect of galactic cosmic rays on the ice mantle and core is also noted with particular emphasis on amorphization/recoils generated inside the SiC core and their distribution within the grain.

A prime question in the formation and early evolution of the Solar system studies is to discern the source(s) of short-lived now extinct nuclides and to determine the ab-initio isotopic composition of our Solar System (ref. 1). The proposed genesis of a short-lived now extinct radionuclide,10Be, by spallation reactions of carbon and oxygen led to the hypothesis of enhanced irradiation in the early Solar system (ref. 2-8). An alternative scenario of production of 10Be (t1/2 =1.386 +- 0.016 million years (ref.9)) by neutrino process in a low mass star (11.8Msun) core collapse supernova has been recently suggested (ref. 10) that can explain the observed abundance of 10Be in the early Solar System. Here, we report well resolved excesses in 7Li/6Li of up to ~21.5 percent in a Type B1 Ca,-Al rich inclusion (CAI) from the Efremovka meteorite that correlate with 9Be/6Li, suggestive of in situ decay of 7Be. The in situ decay of 7Be, with characteristic half-life of 53.12+- 0.07 days (ref. 11) to 7Li, entails multiple episodes of enhanced irradiation in the ESS. The short half-life of 7Be limits its production by interaction of Solar energetic particles with the nebular gas and solids and provides constraints on genealogy and chronology of CAIs. Irradiation of precursor solids/gas of CAIs of Solar composition by a superflare (Lx=10 exp(32) erg/sec) during the terminal phase of class I or II of pre-main sequence stages of the Sun cogently explains the isotopic properties, distinctive petrographic features, and diffusivity constraints in the CAI.

Fossil meteoritic records of short-lived, now-extinct radionuclides provide crucial high-resolution temporal information about the events, processes and activity of the Sun during the early phases of Solar System formation 1 . The proposed genesis of one such radionuclide, 10 Be, by spallation reactions of carbon and oxygen 2 – 5 led to the hypothesis of enhanced irradiation in the early Solar System 6 – 8 . An alternative scenario of production of 10 Be (half-life t 1/2 = 1.386 ± 0.016 million years 9 ) by a neutrino process in a supernova arising from the core collapse of a low-mass star (11.8 solar masses, M ⊙ ) has recently been suggested 10 and can explain the observed abundance of 10 Be in the early Solar System. Here, we report well-resolved excesses in 7 Li/ 6 Li of up to ~21.5% in a calcium- and aluminium-rich inclusion (CAI) from the Efremovka meteorite that correlate with 9 Be/ 6 Li, suggestive of in situ decay of 7 Be. The in situ decay of 7 Be to 7 Li, with a characteristic half-life of 53.12 ± 0.07 days 11 , entails multiple episodes of enhanced irradiation in the early Solar System, which have been observed recently in other Sun-like stars 12 , 13 . The short half-life of 7 Be limits its production by interaction of solar energetic particles (SEPs) with the nebular gas and solids, and provides constraints on the genealogy and chronology of CAIs. Irradiation of the solid and gaseous precursors of CAIs of solar composition by a superflare (X-ray luminosity approximately 10 32 erg s −1 ) during the terminal phase of class I or II of the pre-main-sequence stages of the Sun explains the isotopic properties, distinctive petrographic features and diffusivity constraints in the CAI.

We compute the concentrations of five transition elements (Cr, Fe, Co, Ni, and Zn) via condensation and implantation in supernova presolar grains (Silicon Carbide Type X) from the time they condense until the end of the free expansion (or pre-Sedov) phase. We consider relative velocities of these elements with respect to grains as they condense and evolve at temperatures less than or similar to 2000 K; use zonal nucleosynthesis yields for three core collapse supernovae models -15 M-circle dot, 20 M-circle dot, and 25 M-circle dot; and use an ion target simulator SDTrimSP to model their implantation onto the grains. Simulations from SDTrimSP show that maximal implantation in the core of the grain is possible, contrary to previous studies. Among the available models, we find that the 15 M-circle dot model best explains the measured concentrations of SiC X grains obtained from the Murchison meteorite. For grains where measured concentrations of Fe and Ni are greater than or similar to 300 ppm, we find the implantation fraction to be less than or similar to 0.25 for most probable differential zonal velocities in this phase, which implies that condensation is more dominant than implantation. We show that radioactive corrections and mixing from the innermost Ni and Si zones are required to explain the excess Ni (condensed as well as implanted) in these grains. This mixing also explains the relative abundances of Co and Ni with respect to Fe simultaneously. The model developed can be used to predict concentrations of all other elements in various presolar grains condensed in supernova ejecta and compared with measured concentrations in grains found in meteorites.

We report correlated Si, and Ti isotopic compositions and elemental concentrations of 238 presolar SiC grains from the Murchison CM2 meteorite. Combined with measurements of the C and N isotopic compositions of these 238 grains, 220 were determined to be of type mainstream, 10 type AB, 4 type Y and 4 type Z. SiC grains of diameter ≳2.5µm, to ensure enough material to attempt Ti measurements, were randomly chosen without any other prejudice. The Ti isotopic compositions of the majority of the grains are characterized by enrichments in 46Ti, 47Ti, 49Ti, and 50Ti relative to 48Ti, and show linear isotopic correlations indicative of galactic chemical evolution and neutron capture of the grains parent stars. The variability in the observed Ti signal as a function of depth in most of the grains indicates the presence of distinct subgrains, likely TiC that have been previously observed in TEM studies. Vandium-51 concentrations correlate with those of Ti, indicating V substitutes for Ti in the TiC matrix in many of the grains. No isotopic anomalies in 52Cr/53Cr ratios were observed, and Cr concentrations did not correlate with those of either Ti or V.