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Analytical techniques are essential in investigating the unique features of extra‐terrestrial geomaterials, and the use of in situ analytical tools is becoming increasingly common, as it facilitates a quick initial bulk chemical analysis, identification and classification. In this work, a handheld laser‐induced breakdown spectroscopy (hLIBS) instrument has been used to identify the qualitative and quantitative composition, and generate compositional micro‐maps, of a suite of iron meteorite samples representative of the different chemical and structural classes by analysing the spectra released from the plasma formed by the laser impact. Furthermore, the analytical performance of hLIBS was compared with that of portable X‐ray fluorescence spectrometry (pXRF). The analytical precision and accuracy of the calibration curves previously built in the laboratory for a set of certified reference metal alloys was assessed, so that the same protocol could be used to measure those of the investigated iron meteorites. A good agreement was achieved between hLIBS and reference data in the quantitative estimate of the elements Fe, Ni, Co and Cu. An attempt to quantify Ga by LIBS in two classified iron meteorites was also successful. [ABSTRACT FROM AUTHOR]

The first in‐depth geochemical and petrological analyses of new lunar meteorite Northwest Africa (NWA) 11788 were conducted with the aim of better understanding the diversity of lunar rock types. Petrography, microcomputed tomography, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry were employed to analyze mineralogic/elemental makeup, petrologic profile, melt history, and inferred composition of the lunar mantle from which the crystals in this sample originated from. Geochemical maps of the lunar surface were generated to constrain potential lunar launch locations for NWA 11788. Potential launch locations are concentrated in the outer rims of impact basins on the lunar Eastern nearside limb (e.g., Crisium, Fecunditatis, Marginis, Smythii) and around the South Pole–Aitken Basin. Similarities in the major, minor, and trace element chemistry of NWA 11788 along with its potential launch locations suggest a petrogenetic relationship with regolith samples returned from the Luna 20 mission and the Apollo 16 and 17 magnesian granulites. Additionally, the results of this study add to the growing body of evidence that KREEP (potassium, rare earth elements, phosphorous)‐poor, Mg‐suite‐“like” lithologies are common in non‐Apollo‐type locales, that KREEP may not be required to generate lithologies like the Mg‐suite, and that KREEP is not globally distributed at present. [ABSTRACT FROM AUTHOR]

The isotope abundance of cosmogenic K, especially the ratios of cosmogenic 40K/41K, can be used to determine reliable cosmic-ray exposure (CRE) ages for iron meteorites. Despite this potential, there are only very few studies and essentially no new data since the pioneering work by H. Voshage more than 40 years ago. This shortfall is likely due to the immense analytical difficulties encountered when extracting cosmogenic K from iron meteorites with typical concentrations in the range of a few ppb or below. Chemical extraction procedures are very challenging, resulting in large blank contributions that must be subtracted, and do have low yields preventing an efficient separation of K from the Fe matrix. The K extracted from iron meteorites is dominated by native K (non-cosmogenic K from the sample), includes K from terrestrial contamination, and only a tiny amount is of cosmogenic origin. In order to separate K from iron meteorites a physical extraction technique was developed that involves extraction of K from molten iron meteorites. In this set-up, terrestrial and native K can be partly separated from cosmogenic K by sophisticated pre-heating and extraction techniques. Sample K is ion-optically collected on a rhenium filament. The filaments are then used as evaporation filaments in a double filament set-up of a Triton Plus Thermal-Ionization Mass Spectrometer (TIMS). Though, cosmogenic K is detectable in all samples, the measured isotope ratios are always close to terrestrial, indicating that the majority of the measured 39K and 41K is from K with almost terrestrial isotope composition. The measured 40K signal is dominantly of cosmogenic origin. The K background is either native K from the sample or terrestrial contamination. The measurements are compromised by unstable signals, i.e., by large fluctuations of the ion currents and/or large variations in the isotope ratios during the course of a single run, sometimes even with fractionation reversals. Such difficulties are likely due to the fact that the K ions are implanted into the filament rather than deposited onto the surface. In addition, parts of the filaments are covered with condensed iron, also affecting the signal stability. Despite these analytical challenges, clear cosmogenic signals were detected in almost all studied iron meteorites and cosmogenic 40K/41K ratios could be determined. However, the data quality is not yet sufficient for precise K isotope studies and for calculating reliable 40K/41K CRE ages for iron meteorites. [ABSTRACT FROM AUTHOR]

We present the first rock magnetic and paleomagnetic analyses of the Martian meteorite Grove Mountains (GRV) 020090, a suitable candidate for paleomagnetic study due to its low degree of weathering and shock metamorphism. Petrological and rock magnetic investigation indicates that pyrrhotite is the dominant magnetic mineral in GRV 020090, where it occurs as a primary phase without significant shock metamorphism or alteration. The magnetic grains in GRV 020090 exhibit single‐domain behavior that facilitates high‐fidelity magnetic recording. We obtained a positive fusion‐crust baked contact test, which supports an extraterrestrial origin of the primary remanence in GRV 020090. The nature of the primary remanence was identified as thermoremanence acquired during crystallization of the rock on Mars. Anhysteretic remanent magnetization and isothermal remanent magnetization paleointensity methods indicated paleofield strengths of 1.6 and 2.6 μT, respectively, for the primary remanence. However, the shock pressure that GRV 020090 experienced may have partially demagnetized the primary remanence, leading to underestimated paleointensity values. Therefore, 1.6 μT is regarded as the lower limit on the paleointensity of GRV 020090. This lower limit is higher than the model‐predicted surface magnetic field strength in the source region for GRV 020090, suggesting that it may have recorded a small‐scale crustal magnetic field previously undetected by orbital magnetic data. This small‐scale crustal field is likely generated by the underlying ancient, magnetized layers, as the crustal magnetization of the surficial terrane with lithology similar to GRV 020090 is too weak to produce such a crustal field. [ABSTRACT FROM AUTHOR]

Photogrammetry is a low‐cost, nondestructive approach for producing 3‐D models of meteorites for the purpose of determining sample bulk density. Coupled with the use of a nondestructive magnetic susceptibility/electrical conductivity field probe, we present measurements for the interrogation of several physical properties, on a set of Antarctic meteorites. Photogrammetry is an effective technique over a range of sample sizes, with meteorite bulk density results that are closely comparable with literature values, determined using Archimedean glass bead or laser scanning techniques. The technique is completely noncontaminating and suitable for the analysis of rare or fragile samples, although there are limitations for analyzing reflective samples. It is also flexible, and, with variations in equipment setup, may be appropriate for samples of a wide range of sizes. X‐ray computed tomography analyses of the same meteorite samples yielded slightly different bulk density results, predominantly for samples below 10 g, although the reason for this is unclear. Such analyses are expensive and potentially damaging to certain features of the sample (e.g., organic compounds), but may be useful in expanding the measurements to accommodate an understanding of internal voids within the sample, lending itself to measurement of grain density. Measurements of bulk density are valuable for comparisons with estimates of the bulk densities of asteroids that are suggested as meteorite parent bodies. [ABSTRACT FROM AUTHOR]

The Sample Analysis at Mars (SAM) instrument aboard the Curiosity Rover at Gale crater can characterize organic molecules from scooped and drilled samples via pyrolysis of solid materials. In addition, SAM can conduct wet chemistry experiments which enhance the detection of organic molecules bound in macromolecules and convert polar organic compounds into volatile derivatives amenable to gas chromatography‐mass spectrometry analyses. Specifically, N‐tert‐butyldimethylsilyl‐N‐methyltrifluoroacetamide (MTBSTFA) is a silylation reagent whereas tetramethylammonium hydroxide (TMAH) is a thermochemolysis methylation reagent. Shortly after arriving at Mars, the SAM team discovered that at least one of the MTBSFTA cups was leaking, contributing to a continuous background inside SAM with the potential to interfere with future TMAH reactions. Therefore, here we characterized possible interactions between the two reagents to determine byproducts and implications for the detection of indigenous organics. SAM‐like pyrolysis experiments supplemented with flash pyrolysis were accordingly conducted with fragments of the Murchison meteorite as a reference for exogenous organic matter delivered to Mars. Flash TMAH experiments yielded various aromatic acids, dicarboxylic acids, and amino acids while SAM‐like pyrolysis presented mixtures of methylated and non‐methylated compounds due to decreased reaction efficiency at slower ramp rates. All experiments in the presence of simulated MTBSTFA vapor produced pervasive silylated byproducts which co‐elute and obscure the identification of Murchison‐derived compounds. Despite challenges, a significant diversity of pyrolyzates and TMAH derivatives could still be identified in flash pyrolysis in presence of MTBSTFA. However SAM‐like experiments with TMAH and MTBSTFA are hindered by both decreased methylation yields and additional co‐eluting compounds. Plain Language Summary: The Sample Analysis at Mars (SAM) instrument aboard the Curiosity Rover on Mars can detect and analyze organic molecules that might be used by life as we know it. SAM does this by heating scooped soil or drill samples in order to vaporize and uncover any organic content that might be present. In addition, SAM can detect different types of organics that have more direct similarities to those used by modern organisms by adding one of two different kinds of chemical reagents prior to heating. However, shortly after arriving at Mars, it was discovered that one type of reagent, called MTBSTFA, was leaking inside of SAM with the potential to eventually interfere with the other, called TMAH, whenever it might be utilized. This study therefore reports on the chemical interactions between the two reagents and how they might impact the detection of indigenous organics on Mars. We determined heating samples in the presence of both reagents produces a series of byproducts which obscure the identification of organic compounds of interest. Still, despite analytical challenges, it is possible SAM may detect different types of organics which have yet to be detected on Mars with TMAH despite interference from leaking MTBSTA. Key Points: TMAH experiments with Murchison meteorite produces various aromatic acids, dicarboxylic acids, and amino acidsSAM‐like TMAH pyrolysis presents mixtures of methylated and non‐methylated compounds due to decreased reaction yields at slower ramp ratesAll experiments with simulated MTBSTFA vapor produce byproducts that obscure the identification of Murchison‐derived compounds [ABSTRACT FROM AUTHOR]

Meteorites are an essential reference for human exploration of the universe and its cosmic evolution and an essential research object for searching for extraterrestrial life. Ways to quickly identify and screen suspected meteorite samples have become the foundation and prerequisite for research on high-value meteorite samples. Therefore, this paper proposes a Raman mapping-assisted micro-laser induced breakdown spectroscopy (micro-LIBS) technology for field detection of suspected meteorite material composition without sample pre-processing, with a high detection speed and cost-effectiveness, to realize the detection of element composition and molecular structure. Raman mapping carries out multispectral imaging with high spectral resolution of the region of interest. The fusion of Raman mapping and optical microscopy images can provide mineral categories and spatial distribution characteristics in regions of interest. A quantitative analysis model for Fe, Mg, and Na elements was constructed based on the multidimensional scaling–back propagation neural network (MDS-BPNN) algorithm. The determination coefficient of the model test set was better than 0.997, and the root mean square error was better than 0.65. The content of Fe, Mg, and Na elements in the meteorite was preliminarily evaluated, providing a reference for further analysis of element information in spectral image fusion data. The Raman–LIBS combined technology has significant application potential in rapidly evaluating suspected meteorite samples. Without high-end precision instruments or field research, this technology can provide scientists with significant reference value atomic and molecular spectral information. At the same time, this technology can be extended to other petrology research. We offer a fast, efficient, cost-effective, and reliable analysis scheme for reference. [ABSTRACT FROM AUTHOR]

Meteorites are the space messengers bringing us the unique information about the Solar System formation and evolution as well as about the effects of various extreme space conditions on meteorites and their parent bodies. The main iron-bearing compounds in meteorites are Fe-Ni-Co alloy, olivine (Fe, Mg)2SiO4, orthopyroxene (Fe, Mg)SiO3, clinopyroxene (Ca, Fe, Mg)SiO3, troilite FeS, chromite FeCr2O4, hercynite FeAl2O4, ilmenite FeTiO3, daubréelite FeCr2S4, schreibersite (Fe, Ni)3P and some other compounds. Therefore, 57Fe Mössbauer spectroscopy was successfully applied for the analyses of various meteorites for about 60 years of experience. The development of Mössbauer spectrometers with a high velocity resolution, i.e., with a high discretization of the velocity reference signal up to 212, provides much better adjustment to resonance and significantly increases the spectra quality and analytical possibilities of Mössbauer spectroscopy. In fact, this permits us to decompose the complex Mössbauer spectra of meteorites using the larger number of spectral components related to reliable compounds in comparison with the results obtained using conventional Mössbauer spectrometers with discretization of the velocity reference signal up to 29. In the present review we consider the results and advances of various meteorites analyses by means of Mössbauer spectroscopy with a high velocity resolution. [ABSTRACT FROM AUTHOR]

We report the result of a non‐destructive elemental analysis of lunar meteorites using a negative muon beam at J‐PARC. An experimental system of six Ge semiconductor detectors and a newly designed He analysis chamber (to enable quantitative analysis of Al) was used to provide a high signal‐to‐noise ratio for the detection of major elements from lunar rocks (Mg, Si, Fe, O, Ca, and Al). We performed a Monte Carlo simulation to determine the chemical compositions at two sides and the center of a sample (at depths of 0.33 and 0.96 mm below the sample surface, respectively) of the lunar meteorite DEW 12007. These results indicate that the three interior regions of DEW 12007 are likely to be 55.8:44.2, 51.4:48.6, and 54.4:45.6 wt% mixtures of anorthositic and basaltic clasts, respectively. This study is the first quantitative analysis of a heterogeneous meteorite interior using a negative muon beam. As elemental analysis using a muon beam is non‐destructive and highly sensitive to light elements, including C, N, and O, the protocols established in this study are applicable to initial characterization of returned samples from the South Pole of the Moon. [ABSTRACT FROM AUTHOR]

Cosmic geochemistry Tankersley et al.[1] misinterpret recent evidence for high-temperature components in comets leading to problematic geochemical analyses and interpretations of supposed pallasite samples. Neuhäuser and Neuhäuser[25] using different sources also challenged Tankersley et al.'s identification of a comet, and Tankersley et al.[26] acknowledge that the airburst may have been an asteroid. Data availability The data used in this contribution are the original data presented in Tankersley et al.'s paper and supplemental material, the original technical reports required to be submitted by Tankersley to the Indiana Division of Historic Preservation and Archaeology (DHPA), and other references cited herein. Had Tankersley et al.[1] correctly identified pallasites, it would in fact be evidence against a comet airburst. [Extracted from the article]

The nucleobases, namely the purines adenine and guanine and the pyrimidines cytosine, thymine, and uracil, are the key monomers of the information polymers DNA and RNA. All the nucleobases were recently detected in the analysis of certain meteorites known as carbonaceous chondrites. The concentration of the nucleobases found in meteorites is smaller than the concentration of amino acids. However, the nucleobases were successfully synthesized abiotically by ultraviolet irradiation of interstellar ice analogues at 10 K. Consequently, it is possible that the purines and pyrimidines may be present in the interstellar medium or in other space environments and may be detectable by the new orbiting telescopes that indeed are able to cover not only the mid-infrared spectral range but also the far-infrared. This work supplies the reference spectra of the five nucleobases used by the terrestrial biochemistry in the mid-infrared and in the far-infrared with the purpose to facilitate the search and identification of these astrobiological and astrochemical relevant molecules in space. The mid-infrared spectra of all nucleobases were recorded at three different temperatures from −180 °C to nearly ambient temperature and at +250 °C. Furthermore, the molar extinction coefficients (ε) of all mid- and far-infrared bands were determined, as well as the integrated molar absorptivities (ψ). With the reported infrared spectra together with the ε and ψ values, it will be possible to identify qualitatively the nucleobases and estimate their relative abundance in space. [ABSTRACT FROM AUTHOR]

The analysis of Martian meteorites is a key research to understand the mineralogical composition of Mars. However, they suffer different types of alteration due to the environment where they fall on Earth. These differences should be identified in order to characterize correctly the original Martian compounds. Most of the meteorites found on Earth are collected in Antarctica where the environmental conditions are such that, in general and based on many previous investigations, produce fewer alterations compared with other terrestrial environments such as hot deserts. In this study, the weathering alterations of minerals from the MIL 090030 Martian Nakhlite found in Antarctica were analyzed to determine which minerals are formed by Antarctic environmental conditions. It was confirmed that the south-polar region environment can contaminate Martian meteorites and, in this study, several minerals like halite, nitratine and niter, were detected as weathering alteration products that have not been referenced in the literature before. [ABSTRACT FROM AUTHOR]

Evidence of impact‐induced compaction in the carbonaceous chondrites, specifically CMs and CVs, has been widely investigated utilizing microscopy techniques and impact experiments. Here, we use high‐resolution photography and large area and high‐resolution electron backscattered diffraction (EBSD) mapping analyses in tandem, to explore the effects of impact‐induced compaction at both the meso‐ and micro‐scales in the Allende CV3.6 carbonaceous chondrite. Macro‐scale photography images of a ~25 cm slab of Allende captured meso‐scale features including calcium‐aluminum inclusions (CAIs) and chondrules. CAIs have a long‐axis shape‐preferred orientation (SPO). Examination of such meso‐scale features in thin section revealed the same trend. Matrix grains from this section display a large amount of heterogeneity in petrofabric orientation; microscale, high‐resolution, large area EBSD mapping of ~300,000 olivine matrix grains; high‐resolution large area EBSD map across an elongate CAI; and a series of high‐resolution EBSD maps around two chondrules and around the CAI revealed crystallographic preferred orientations (CPOs) in different directions. Finally, internal grains of the CAI were found to demonstrate a weak lineation CPO, the first crystallographic detection of possible CAI "flow." All results are consistent with multiple, gentle impacts on the Allende parent body causing hemispheric compaction. The larger, more resistant components are likely to have been compressed and oriented by earlier impacts, and the matrix region petrofabrics and CAI "flow" likely occurred during subsequent impacts. Meteoritic components respond differently to impact events, and consequently, it is likely that different components would retain evidence of different impact events and angles. [ABSTRACT FROM AUTHOR]

Martian meteorites are key for assessing the isotopic characteristics of nitrogen in different martian reservoirs (i.e., mantle, crust, and atmosphere), and, ultimately, for constraining the source(s) of nitrogen trapped during the earliest stages of planetary accretion in the terrestrial planet-forming region. In this study, we analysed, for the first time, the nitrogen content and isotopic composition of glassy melt inclusions of Chassigny and of the mesostasis of five nakhlites (MIL 03346, Nakhla, NWA 6148, NWA 998, and Y 000593) by in situ secondary ion mass spectrometry. The nitrogen content of Chassigny melt inclusions, corrected for olivine overgrowth on the inclusion walls, varies from 4 ± 1 to 860 ± 45 ppm N, and the majority of δ15N values range from –35 ± 41 to +73 ± 36‰. The estimated nitrogen isotopic signature of the primitive melt, prior to degassing of N 2 or NH 3 , is 0 ± 32‰. The mesostasis of nakhlites contains 2.7 ± 0.2 to 943 ± 156 ppm N, with δ15N values from –30 ± 37 to +348 ± 43‰. Whereas degassing of N 2 or NH 3 can explain the lowest nitrogen isotopic ratios measured in the nakhlite mesostasis, the 15N-enriched isotopic composition (δ15N > 150‰) of four nakhlites (MIL 03346, Nakhla, NWA 6148, and Y 000593) likely results from interaction of the mesostasis melt with the martian atmosphere during ejection. The δ15N values (+25 ± 42 and +77 ± 19‰) of two melt inclusions in Y 000593 are comparable to those of Chassigny, further confirming that these meteorites likely sample a common volatile reservoir in the martian interior. Overall, the new results indicate that the chassignite-nakhlite reservoir did not inherit nitrogen from the solar nebula but, instead, from chondritic-like materials. These findings further confirm that planetary bodies in the inner solar system accreted (isotopically) chondritic nitrogen during the first few million years of solar system history. [ABSTRACT FROM AUTHOR]

Analysis of bulk meteorite compositions has revealed small isotopic variations due to the presence of material (e.g., stardust) that preserved the signature of nuclear reactions occurring in specific stellar sites. The interpretation of such anomalies provides evidence for the environment of the birth of the Sun, its accretion process, the evolution of the solar proto-planetary disk, and the formation of the planets. A crucial element of such interpretation is the comparison of the observed anomalies to predictions from models of stellar nucleosynthesis. To date, however, this comparison has been limited to a handful of model predictions. This is mostly because the calculated stellar abundances need to be transformed into a specific representation, which nuclear astrophysicists and stellar nucleosynthesis researchers are not familiar with. Here, we show in detail that this representation is needed to account for mass fractionation effects in meteorite data that can be generated both in nature and during instrumental analysis. We explain the required internal normalisation to a selected isotopic ratio, describe the motivations behind such representation more widely, and provide the tools to perform the calculations. Then, we present some examples considering two elements produced by the slow neutron-capture (s) process: Sr and Mo. We show which specific representations for the Sr isotopic composition calculated by s-process models better disentangle the nucleosynthetic signatures from stars of different metallicity. For Mo, the comparison between data and models is improved due to a recent re-analysis of the 95 Mo neutron-capture cross section. [ABSTRACT FROM AUTHOR]

We present a detailed study of petrography, mineralogy, mineral chemistry and bulk chemistry of the Berduc L6 ordinary chondrite, which fell in 2008 in Colonia Berduc, Argentina. Modal abundance of the constituent phases is similar to the other L6 chondrites. The preserved phases of oxide and sulphide point towards a low-grade thermal metamorphism in Berduc parent body. Presence of melt veins and evidence of element redistribution in constituent phases indicate Berduc underwent localised melting processes, due to shock loading (S4). Further, highly volatile elements are depleted as compared to CI-chondrite. The heating process in Berduc parent mass took place in an open environment allowing volatiles to get lost from the system at low temperatures. These conditions enabled the preservation of pristine non-silicate assemblages. The fact that the bulk REE and refractory elements in Berduc are akin to that of the CI-chondrite, indicates that they were not mobilised from Berduc parent mass. The unfractionated pattern exhibited by the refractory and moderately volatile trace elements resembles that of an unequilibrated ordinary chondrite. Berduc parent body seems to have had a particular behaviour, as an open system allowing a substantial loss of the highly volatile elements and as a closed-system during and after the peak thermal metamorphism. [ABSTRACT FROM AUTHOR]

The spectroscopic characterization of plasma generated in meteorite samples during Laser-Induced Breakdown Spectroscopy (LIBS) shows the emission spectrum of elements present and also allows one to rapidly identify the elemental composition without any sample preparation and with good accuracy compared to some other methods. In addition, LIBS has other advantages, such as multi-elemental response, micro–nano gram level of destructiveness and portability of the instrument. Since the presence of Rare Earth Elements (REEs) in meteorites is usually in trace levels or not at all, LIBS can be used as a potential alternative method for the meteorite fragment analysis which, in turn, gives valuable clues on its origin as well as the origin of the solar system and its impact on life on Earth, particularly on the presence of REEs. The elemental analysis results for a few of the selected samples, such as iron meteorites, lunar meteorites, eucrites and impact glass, are presented and discussed. The LIBS analysis was supplemented by Principal Component Analysis (PCA) with which it was possible to classify the samples into different classes according to their chief constituents, structure and origin. [ABSTRACT FROM AUTHOR]

The physical and chemical characterisation of meteorites is of paramount importance in the study of the formation of the Solar System. In this work we show the feasibility of a complete set of non-destructive measurements to perform such a characterisation using a stony meteorite as a mock-up sample. The identification of the sample as a meteorite was performed by means of gamma ray spectrometry, which identified the presence of cosmogenic 26Al. Time-of-Flight Neutron Diffraction (ToF-ND) enabled the mineralogical phase quantification and the analysis of the presence of strains and substitutions in each mineral. Neutron Resonance Capture Analysis (NRCA), Neutron Resonance Transmission Imaging (NRTI) and Muonic Atom X-Ray Spectroscopy (MAXRS) allowed a study of the presence and the space distribution of certain elements. Furthermore, micro-Raman Spectroscopy (μRS) and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) were also considered in order to validate the protocol. [ABSTRACT FROM AUTHOR]

The Chelyabinsk superbolide, the largest in XXI century, which exploded on 15 February 2013 over snowy fields of Southern Urals was a historic event not just only because of its massive scale and explosive power. High-temperature, high-pressure conditions in the front shock wave caused intense ablation of the asteroid material and formation of huge amount of meteoritic dust dispersed in the atmosphere during the flyby. Massive snowfalls just few days before and after the event conserved precipitated meteoritic dust in thin layer of snow which was collected and studied later. The most intriguing and challenging material discovered in the dust was closed-shell 10–70 µm exotic polygonal graphitic carbon microcrystals of undisclosed nature. Using optical and electron microscopy and Raman spectroscopy the atomic structure of closed-shell microcrystals was thoroughly studied and their graphitic nature was revealed. It was found that some of the particles formed by multilayer graphitic polygonal shells have extensive hollows inside. Comparative microscopic and spectroscopic analysis of meteorite exotic carbon microcrystals with different graphite species, carbon onions, and diamond revealed two distinctively different closed-shell carbon particles. The first type of the particles can be attributed to carbon onions with characteristic graphite nanocrystalline basic structural units (BSU) of 49 nm lateral size and less and, probably, BSU heteroatomic termination necklace with oxygen content comparable to 1.1% and more. It was shown that the second type of unique graphitic carbon particles of a convex shape and perfect hexagonal symmetry with lateral dimensions of 14 µm correspond to multiply twinned closed-shell graphite microcrystals with polyhexacyclooctadecane (–C18–)n core wrapped by multiple layers of carbon honeycombs with low (<1%) content of oxygen termination necklace. [ABSTRACT FROM AUTHOR]

Recent findings, in vitro and in silico, are strengthening the idea of a simpler, earlier stage of genetically encoded proteins which used amino acids produced by prebiotic chemistry. These findings motivate a re-examination of prior work which has identified unusual properties of the set of twenty amino acids found within the full genetic code, while leaving it unclear whether similar patterns also characterize the subset of prebiotically plausible amino acids. We have suggested previously that this ambiguity may result from the low number of amino acids recognized by the definition of prebiotic plausibility used for the analysis. Here, we test this hypothesis using significantly updated data for organic material detected within meteorites, which contain several coded and non-coded amino acids absent from prior studies. In addition to confirming the well-established idea that "late" arriving amino acids expanded the chemistry space encoded by genetic material, we find that a prebiotically plausible subset of coded amino acids generally emulates the patterns found in the full set of 20, namely an exceptionally broad and even distribution of volumes and an exceptionally even distribution of hydrophobicities (quantified as logP) over a narrow range. However, the strength of this pattern varies depending on both the size and composition the library used to create a background (null model) for a random alphabet, and the precise definition of exactly which amino acids were present in a simpler, earlier code. Findings support the idea that a small sample size of amino acids caused previous ambiguous results, and further improvements in meteorite analysis, and/or prebiotic simulations will further clarify the nature and extent of unusual properties. We discuss the case of sulfur-containing amino acids as a specific and clear example and conclude by reviewing the potential impact of better understanding the chemical "logic" of a smaller forerunner to the standard amino acid alphabet. [ABSTRACT FROM AUTHOR]

Ordinary chondrites account for the majority of the described meteorites on Earth. To expand the toolbox of analytical techniques available to describe such specimens, this study evaluates the application of a previously described fayalite determination method by X‐ray diffraction (XRD) to equilibrated ordinary chondrites. A suite of ordinary chondrites, ranging from petrologic type 4 to 6, and types H, L, and LL were analyzed by both XRD and electron probe microanalysis. A comparison of the results shows good agreement between the two methods with an R2 of 0.95 and better agreement for homogenous ordinary chondrites above petrographic grade 4. The differences between the two methods can largely be attributed to analytical uncertainty, as well as differences between point and bulk sampling techniques. These differences were used to identify two polymict breccia samples, Peace River and Northwest Africa 10946. Of note is the effect of exposure of the ordinary chondrites to room temperature and humidity conditions after sample preparation (powdering) and the impact on measured fayalite content by XRD. As such, it is recommended that XRD analyses of meteorites be performed immediately after sample preparation. [ABSTRACT FROM AUTHOR]

We performed scanning electron microscopy and electron microprobe analysis on the eucritic meteorites Errachidia 002 and Northwest Africa 11911, with a focus on the metallic iron disseminated in them, in order to constrain the processes involved in its formation, and discuss its implication for their parent body collisional history. Errachidia 002 is a polymict eucrite that consists of basaltic and noritic (diogenite) clasts set in a fragmental matrix. Fe-metals in this meteorite contain <0.04 wt% Ni, and 0.06 wt% Co, and they are mostly associated with silica in pyroxene. This suggests formation by decomposition of troilite, which generated S-vapors (S 2) that subsequently reacted with FeO in pyroxene during an impact event, producing pure Fe-metal and silica, with escape of SO 2 from the rock. The presence of late-stage phases in proximity of a few Fe-metal grains, as well as low Fe/Mn coupled with high Fe/Mg in pyroxene indicate a different scenario in which pure Fe-metal in this meteorite formed by reduction from a residual melt. NWA 11911 is also a polymict eucrite composed mainly of unequilibrated and equilibrated eucritic clasts set in a clastic groundmass. Here, metallic iron is either enclosed in the fragmental matrix, or within a vitrophyric impact melt clast. Its Ni and Co contents are ∼2.8 and 0.6 wt%, implying an exogenous origin, namely contamination by an iron-bearing impactor. Our results point out the major role impacts played in controlling the surface features and mineral compositions of early formed bodies in the solar system such as (4) Vesta. [Display omitted] • We investigate metallic iron in two brecciated eucrites to constrain the collisional history of the asteroid (4) Vesta. • The polymict eucrite Errachidia 002 is a breccia within a breccia consisting of various eucritic and noritic fragments. • The polymict eucrite NWA 11911 is composed mainly of eucritic clasts and impact melts. • Fe-metal in Errachidia 002 formed through reduction of FeO in pyroxene, or by reduction from a residual melt. • The presence of Fe Ni metal in NWA 11911 indicates contamination by metal-bearing impactors. [ABSTRACT FROM AUTHOR]

Determining how and when Mars formed has been a long-standing challenge for planetary scientists. The size and orbit of Mars are difficult to reproduce in classical simulations of planetary accretion, and this has inspired models of inner solar system evolution that are tuned to produce Mars-like planets. However, such models are not always coupled to geochemical constraints. Analyses of Martian meteorites using the extinct hafnium–tungsten (Hf–W) radioisotopic system, which is sensitive to the timing of core formation, have indicated that the Martian core formed within a few million years of the start of the solar system itself. This has been interpreted to suggest that, unlike Earth's protracted accretion, Mars grew to its modern size very rapidly. These arguments, however, generally rely on simplified growth histories for Mars. Here, we combine likely accretionary histories from a large number of N -body simulations with calculations of metal–silicate partitioning and Hf–W isotopic evolution during core formation to constrain the range of conditions that could have produced Mars. We find that there is no strong correlation between the final masses or orbits of simulated Martian analogs and their 182W anomalies, and that it is readily possible to produce Mars-like Hf–W isotopic compositions for a variety of accretionary conditions. The Hf–W signature of Mars is very sensitive to the oxygen fugacity (f O 2) of accreted material because the metal–silicate partitioning behavior of W is strongly dependent on redox conditions. The average f O 2 of Martian building blocks must fall in the range of 1.3–1.6 log units below the iron–wüstite buffer to produce a Martian mantle with the observed Hf/W ratio. Other geochemical properties (such as sulfur content) also influence Martian 182W signatures, but the timing of accretion is a more important control. We find that while Mars must have accreted most of its mass within ∼5 million years of solar system formation to satisfy the Hf–W isotopic constraints, it may have continued growing afterwards for over 50 million years. There is a high probability of simultaneously matching the orbit, mass, and Hf–W signature of Mars even in cases of prolonged accretion if giant impactor cores were poorly equilibrated and merged directly with the proto-Martian core. [ABSTRACT FROM AUTHOR]

Asteroid 2018 LA, discovered around eight hours earlier on the morning of 2018 June 2, crashed into earth's atmosphere at 16h44 UT. With a size of about 1.6 metres and travelling at 17 km/second it produced a bright fireball which disintegrated over Botswana. A number of fireball reports were submitted to the ASSA webpage, and security video footage was posted on several social media sites, including the Sterre en Planete Facebook page. These played an important role in an international investigation of the fall and the subsequent recovery of fragments from asteroid 2018 LA. After an exhaustive analysis of the meteorites, a report on the findings was published in Meteoritics and Planetary Science on April 23, 2021. The collective finds have now been classified as the Motopi Pan (MP) meteorite, which is found to be a eucrite-rich howardite, part of the howardite-eucrite-diogenite (HED) class with a likely origin at asteroid 4 Vesta. ASSA participated in this study. This article describes the timeline of events, procedures followed in order to analyse the various videos and reports in order to define the location of the strewn field for the initial search in June 2018, and the subsequent search for meteorites in October 2018. Video footage was also calibrated in order to measure the brightness of the fireball which reached absolute magnitude -23 at disintegration. Suggestions are made on how the investigation of future very bright fireball events can be improved in order to recover other potential meteorites. [ABSTRACT FROM AUTHOR]

Asteroid 4 Vesta is the only largely preserved differentiated asteroid and thus is an excellent proxy to study early magmatism occurring on planets and moons. In this study, we focus on eucrite Pecora Escarpment (PCA) 82502, a medium‐ to fine‐grained eucrite which chemical analyses suggest belongs to the main howardite–eucrite–diogenite clan, albeit with some peculiarities. We carried out backscattered electron and electron backscattered diffraction microscopy analyses of the meteorite along with step‐heating 40Ar/39Ar dating analyses of various types of groundmass aliquots. We show that Pecora Escarpment 82502 is composed of medium‐grained igneous crystalline clasts and smaller fractured satellite clasts surrounded by approximately 50 µm wide impact melt veins of the same composition. Our results show that the large crystalline clasts and fine‐grained veins both display little evidence of shock processes. Six groundmass aliquots from large crystalline clasts returned concordant plateau (>70% of 39Ar) or mini‐plateau (50–70% of 39Ar) 40Ar/39Ar ages with a weighted mean of 4531 ± 6 Ma (P = 0.67). Thermodynamic cooling and 40Ar diffusion models suggest that the K/Ar system recorded and preserved the igneous age despite subsequent infiltration of hot and quickly quenched melt veins. Our new igneous age, combined with evidence for four other young volcanic and plutonic eucrites of similar age, shows that Vesta was still magmatically active around 4531 Ma. The lack of younger ages suggests that this age might well represent the end of the magmatic activity in the upper crust of Vesta. When combined with existing paleomagnetic constraints, our data suggest that 4 Vesta had an active dynamo that was still active ~35 Ma after accretion. [ABSTRACT FROM AUTHOR]

Earth's habitability is closely tied to its late-stage accretion, during which impactors delivered the majority of life-essential volatiles. However, the nature of these final building blocks remains poorly constrained. Nickel (Ni) can be a useful tracer in characterizing this accretion as most Ni in the bulk silicate Earth (BSE) comes from the late-stage impactors. Here, we apply Ni stable isotope analysis to a large number of meteorites and terrestrial rocks, and find that the BSE has a lighter Ni isotopic composition compared to chondrites. Using first-principles calculations based on density functional theory, we show that core-mantle differentiation cannot produce the observed light Ni isotopic composition of the BSE. Rather, the sub-chondritic Ni isotopic signature was established during Earth's late-stage accretion, probably through the Moon-forming giant impact. We propose that a highly reduced sulfide-rich, Mercury-like body, whose mantle is characterized by light Ni isotopic composition, collided with and merged into the proto-Earth during the Moon-forming giant impact, producing the sub-chondritic Ni isotopic signature of the BSE, while delivering sulfur and probably other volatiles to the Earth. Based on Nickel isotope analysis of meteorites and terrestrial rocks, the authors suggest that the Bulk Silicate Earth has a sub-chondritic Nickel isotope composition. This signature is thought to result from the impact and accretion of a Mercury-like impactor which originated from the innermost Solar System. [ABSTRACT FROM AUTHOR]

The article offers information on unusual meteorite crashed in a Costa Rican rainforest. Topics include examines the perennial criticism of the Murchison finds by ensuring the molecules discovered inside were native, and not contamination from Earth's own microbes; and reports that Murchison also contained nucleobases, the building blocks of genetic molecules such as RNA, and in November 2019, researchers found a major component of RNA's backbone, the sugar molecule ribose.

The formation of the rubidium resonance lines is considered by taking into account the effects of departures from local thermodynamic equilibrium (LTE). A rubidium model atom has been constructed using 29 Rb I levels and the Rb II ground level. Non-LTE calculations have been performed for a grid of model atmospheres with from 3500 to 6500 K, from 1.0 to 5.0, [Fe/H] from to , km s , and a relative rubidium abundance . It is shown that disregarding the non-LTE effects can lead to significant errors in the abundance of this element. The non-LTE corrections for dwarf stars with effective temperatures below 4000 K depend critically on the inclusion of collisional interactions with hydrogen atoms. The differences in rubidium abundance when using quantum-mechanical calculations and Drawin's theoretical approximation to take into account the collision rates of atoms with hydrogen atoms can reach 0.17 dex. The rubidium abundance has been determined from its lines in the solar spectrum, , which virtually coincides with the rubidium abundance deduced from the analysis of meteorites, . [ABSTRACT FROM AUTHOR]

Raman imaging is an emerging tool for the analysis of meteorites, as it is capable of describing mineralogy, carbon composition/speciation, and crystal orientation all within a petrographic context. Adequately examining the heterogeneous composition of a meteorite often requires long image collection times on the timescale of days. However, the wavenumber calibration of the Raman spectrometer drifts over long timescales resulting in low wavenumber precision for the Raman spectra comprising a large Raman image. This decrease in wavenumber precision can compromise the analysis of geological markers that can provide important information on a meteorite sample. We examine, in detail, the change in bandwidth and wavenumber of the Raman bands and Hg–Ar emission lines in our Raman images as a function of time and laboratory temperature. To overcome the drift in calibration, we utilize a commercial WITec Raman instrument with a built‐in Hg–Ar calibration lamp to individually calibrate each spectrum in the Raman image. We show that using the Hg–Ar calibration, we can improve the wavenumber precision for the spectra in our Raman images from ~±0.15 to ~±0.05 cm−1 for Raman spectra collected over multiple days. This is important as it improves measurements of mineral chemistry, latent strain, and other features that are dependent upon accurate peak position determination. We also examine the spectral signal‐to‐noise ratio needed to minimize the wavenumber error when fitting bands to Gaussian/Lorentzian profiles. We then use our results to suggest a general method for calibrating the wavenumber of Raman spectra in large Raman images. [ABSTRACT FROM AUTHOR]

Here we present results from pulsed laser irradiation of troilite samples in an effort to simulate space weathering on airless bodies via micrometeorite impacts. We find that the spectral trends observed in directly irradiated samples and samples with a vapor‐deposited coating are different than those found in silicate minerals previously studied. For instance, direct laser irradiation causes our troilite samples to initially brighten, but continued irradiation causes darkening and a decrease in spectral slope. In contrast, our samples with a vapor‐deposited coating show a continuous increase in spectral slope and overall albedo as the deposit thickness increases. Observation using both digital imaging and electron microscopy of our directly irradiated samples leads us to conclude that topography effects likely become important after a relatively high number of laser pulses in our directly irradiated samples, causing the apparent darkening and decrease in spectral slope. Thus, we conclude that the spectral changes observed relevant to space weathering via micrometeorite impacts are an increase in spectral slope and an increase in the albedo of troilite. Future studies will investigate whether these trends are generally representative of other sulfide‐bearing minerals and of weathering trends in other components found in the asteroid regolith. Plain Language Summary: Carbonaceous asteroids are the most common asteroid found in our solar system. While it is generally accepted that the surfaces of these objects are altered over time by impacts via energetic particles, it is not currently understood how this alteration will change the spectral properties of the surface. In this study, we investigated how the spectral reflectance of troilite (FeS), one component that will likely be found on the surface of these types of asteroids, was altered by pulsed laser irradiation, which is used to mimic micrometeorite impacts that are regularly occurring on asteroid surfaces. The main finding in our study that is different from what has been found in previous studies with other relevant minerals, such as silicates, is that the overall reflectance spectrum brightens as the sample is altered. These results, combined with previous ones, will help astronomers interpret reflectance spectra taken of carbonaceous asteroids and possibly other extraterrestrial objects containing troilite. Key Points: Spectral changes observed in directly irradiated FeS samples and those with a vapor‐deposited coating are differentDirect laser irradiation induces topography effects, which can alter the reflectance spectrum of FeSSpectral changes induced in FeS that are relevant to space weathering are an increase in the albedo and increase in spectral slope [ABSTRACT FROM AUTHOR]

Although meteorites are now considered as scientific objects, they still bear a strong and powerful symbolic meaning due to their extraterrestrial provenance. The present article focuses on their legal status, in other words the collection of rules, very diverse in nature, which are applicable to them. Despite a growing international market, the question of meteorites is often ignored or regarded as a detail in international relations and is rarely taken explicitly into account in negotiations and treaties. This relative neglect explains why a non‐State player, the Meteoritical Society, has taken methodological initiatives into meteoritic science and has effectively become a regulator of meteorite naming and acceptance, with a global scope. We show that to understand the legal status of meteorites, it is necessary to consider them under the prism of public international law, transnational law, and national law. We conclude that, despite the universality of meteorites as extraterrestrial objects, the variability of legal rules applicable to meteorites depending onto which territory they fall or where they are found. We note, however, that there is a trend toward regulatory uniformity in the scientific analysis of meteorites, which frames the practices of researchers and regulates traders' activities. Finally, we contend that a meteorite remains a badly defined legal object, because it can be viewed under many angles: as an object susceptible to private appropriation, as a "common thing" (res communis), or as an element of national heritage. [ABSTRACT FROM AUTHOR]

A non-destructive approach to the sample treatment during the analytical process is one of the crucial advantages of the particle induced X-ray emission technique. Rare and precious environmental and space samples can be analyzed in order to evaluate concentrations of individual elements presented in specimens. A non-destructive analysis of two meteorite samples was carried out using 3 MeV protons incident in a narrow ion beam (1.5 mm diam.). GUPIXWIN software package was used for spectra evaluation. Concentrations of several elements (Fe, Ni, Cu and Zn) were determined and quantitative surface elemental distribution maps were constructed. [ABSTRACT FROM AUTHOR]

Meteorites have been arousing the curiosity of mankind since antiquity. However, the interest in these objects goes far beyond mere curiosity in the study of such materials, which has great importance due essentially to the information they can provide. The importance of studying meteorites is associated about the earliest conditions and processes during the formation and earliest history of the solar system. So, in this study, the characterization of two meteorite fragments was performed using X-ray computed microtomography (micro-CT) and X-ray microfluorescence (micro-XRF). These techniques were used for their non-destructive characteristics and the ability to provide information about the structure and composition the meteorites. The micro-CT images showed encrusted structures within both samples. However, while in Lunar meteorites spheroidal structures very similar to small grains internally grouped in clusters were found, in the Martian meteorite a very peculiar structure was identified. Besides that, the micro-CT it was also possible to evaluate the different density materials that compose the samples. The micro-XRF results accounted for the presence of the elements Si, Ca, Ti, Cr, Mn, Fe, Ni and Sr in the Lunar sample, as well as of Si, S, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Sr and Y in the Martian sample. The results obtained are effective for the characterization of meteorites, proving thus that it is possible to obtain important information about the chemical composition, as well as about the distribution and the internal structure of these materials, evaluating aspects such as density and porosity. [ABSTRACT FROM AUTHOR]

Almost three years since the entry of asteroid 2018 LA into the atmosphere over Botswana on June 2, 2018, the scientific results generated by sixty-six authors, collectively known as the '2018 LA Consortium', and after an in-depth analysis of the recovered meteorites from 2018 LA, are now out in an article in Meteoritics and Planetary Science. [ABSTRACT FROM AUTHOR]

NASA's strategy in exploring Mars has been to follow the water, because water is essential for life, and it has been found that there are many locations where there was once liquid water on the surface. Now perhaps, to narrow down the search for life on a barren basalt‐dominated surface, there needs to be a refocusing to a strategy of "follow the nutrients." Here we model the entry of metallic micrometeoroids through the Martian atmosphere, and investigate variations in micrometeorite abundance at an analogue site on the Nullarbor Plain in Australia, to determine where the common limiting nutrients available in these (e.g., P, S, Fe) become concentrated on the surface of Mars. We find that dense micrometeorites are abundant in a range of desert environments, becoming concentrated by aeolian processes into specific sites that would be easily investigated by a robotic rover. Our modeling suggests that micrometeorites are currently far more abundant on the surface of Mars than on Earth, and given the far greater abundance of water and warmer conditions on Earth and thus much more active weather system, this was likely true throughout the history of Mars. Because micrometeorites contain a variety of redox sensitive minerals including FeNi alloys, sulfide and phosphide minerals, and organic compounds, the sites where these become concentrated are far more nutrient rich, and thus more compatible with chemolithotrophic life than most of the Martian surface. Plain Language Summary: NASA's exploration program has allowed the scientific community to demonstrate clearly that Mars had a watery past, so the search for life needs to move on to identifying the places where water and nutrients coincided. We have investigated the relative abundance of micrometeorites on Mars compared to the Earth because these contain key nutrients that the earliest life forms on Earth used, and because their contained minerals can be used to investigate past atmospheric chemistry. We suggest that micrometeorites should be far more abundant on the Martian surface than on Earth's, and that wind‐driven modification of sediments is expected to concentrate micrometeorites, and their contained nutrients, in gravel beds and cracks in exposed bedrock. Key Points: Micrometeorites are predicted to be far more abundant on Mars than on EarthMicrometeorites are concentrated in the residue of aeolian sediment removal, such as at bedrock cracks and gravel accumulationsMicrometeorite accumulation sites are enriched in key nutrients for primitive microbes: reduced phosphorus, sulfur, and iron [ABSTRACT FROM AUTHOR]

Recent research suggests that major meteorite impact events into a Late Hesperian/Early Amazonian ocean likely produced a mega‐tsunami that would have resurfaced coastal areas in northwestern Arabia Terra. The orientations of the associated lobate deposits, a conspicuous type of landforms called Thumbprint Terrain, suggests that if an impact event triggered the mega‐tsunami, the most likely location of the source crater is within the northern plains regions situated north of Arabia Terra. This study focuses on the identification of impact craters that impacted into the ocean and are likely to have produced the tsunami. We selected 10 complex impact craters, based on their diameters, location, and geomorphic characteristics. Of those, the Late Hesperian ~120‐km‐diameter Lomonosov crater exhibits a unique topographic plan view asymmetry (compared to other similar‐sized and similar‐aged craters in the northern plains such as Micoud, Korolev, and Milankovic). We attribute its broad and shallow rim, in part, to an impact into a shallow ocean as well as its subsequent erosion from the collapsing transient water cavity. The likely marine formation of the Lomonosov crater, and the apparent agreement in its age with that of the Thumbprint Terrain unit (~3 Ga), strongly suggests that it was the source crater of the tsunami. These results have implications for the stability of a late northern ocean on Mars. Key Points: Unusual morphometric characteristics of Lomonosov crater in comparison to the other northern complex cratersLomonosov crater was probably due to the presence of a shallow ocean of liquid water at the time of the impactAgreement of the Lomonosov age with that of the Thumbprint Terrain unit (~3 Ga) suggests that it was the source crater of the tsunami [ABSTRACT FROM AUTHOR]

The textures and accretion ages of chondrites have been used to argue that their parent asteroids never differentiated. Without a core, undifferentiated planetesimals could not have generated magnetic fields through dynamo activity, so chondrites are not expected to have experienced such fields. However, the magnetic remanence carried by the CV chondrites is consistent with dynamo‐generated fields, hinting that partially differentiated asteroids consisting of an unmelted crust atop a differentiated interior may exist. Here, we test this hypothesis by applying synchrotron X‐ray microscopy to metallic veins in the slowly cooled H6 chondrite Portales Valley. The magnetic remanence carried by nanostructures in these veins indicates that this meteorite recorded a magnetic field over a period of tens to hundreds of years at ∼100 Myr after solar system formation. These properties are inconsistent with external field sources such as the nebula, solar wind, or impacts, but are consistent with dynamo‐generated fields, indicating that the H chondrite parent body contained an advecting metallic core and was therefore partially differentiated. We calculate the thermal evolution of the chondritic portions of partially differentiated asteroids that form through incremental accretion across 105 to 106 years, finding this can agree with the measured ages and cooling rates of multiple H chondrites. We also predict that the cores of these bodies could have been partially liquid and feasibly generating a dynamo at 100 Myr after solar system formation. These observations contribute to a growing body of evidence supporting a spectrum of internal differentiation within some asteroids with primitive surfaces. Plain Language Summary: Asteroids formed during the first few million years of the solar system through the accretion of billions of millimeter‐sized solids. If this process occurred within the first ∼2 Myr of the solar system, the asteroid is thought to have partially melted, while if it occurred after this time, the asteroid is thought to have remained completely unmelted. Partial melting is an easy mechanism allowing an asteroid to differentiate into a rocky mantle and metallic core. Recently, this discrete nature of asteroid melting has been challenged by magnetic measurements of a group of unmelted meteorites that suggest they experienced magnetic fields generated in an asteroid core, hinting that their parent asteroid contained both melted and unmelted material and was therefore partially differentiated. Here, we show that a previously unmeasured type of unmelted meteorite recorded a magnetic field over a period of tens to hundreds of years at ∼100 million years after solar system formation. These timings make this a particularly robust observation that some unmelted meteorites experienced dynamo fields and originate from partially differentiated asteroids. This observation favors the episodic formation of some asteroids, potentially impacting our understanding of the thermal and structural history of the first planetary bodies in our solar system. Key Points: The Portales Valley H6 chondrite experienced a magnetic field with properties consistent with dynamo fields at  100 Myr after CAI formationThis observation indicates that the H chondrite parent body contained an advecting metallic core, so was partially differentiatedWe model the thermal evolution of such bodies, finding that they can reproduce the measured ages and cooling rates of multiple H chondrites [ABSTRACT FROM AUTHOR]

The capabilities of the ICAP-6500 Duo high-resolution echelle spectrometer (Thermo Scientific) for the elemental analysis of geochemical materials and extraterrestrial matter have been investigated. The features of the determination of elements in chondritic meteorites are studied, and appropriate procedures, including sample preparation, are developed. Main (including phosphorus and sulfur) and impurity elements are determined in four fragments of chondritic meteorites: Kainsaz, Zhovtnevyi Khutor, Saratov, and Allende. The data are compared with the average concentration of elements in ordinary chondrites. The composition of the available sample of the Allende chondritic meteorite is characterized for using it as an intralaboratory reference sample. [ABSTRACT FROM AUTHOR]

The study of shock-metamorphic features of the Zagami meteorite revealed pseudotachylite-like melt veins with inhomogeneous chemistry and schlieren structure of silica-glass and alkali feldspar melt glass. The feldspar occurs as diaplectic glass in the interstitial area indicating short-time (few seconds) quenching of shock pressure during the impact event, with post-shock annealing. At several locations, apatite needles were identified, which are formed by fluids (cold water with dissolved ions) after the crystallization of cumulate magmatic minerals. Phosphates also could form in impact melts due to circulation of fluids after the impact event. The other signature for the high shock temperature is the presence of Ca-Ti-rich pyroxenes and titanomagnetite, which indicate temperature above 1,200 °C. The formation of silica-rich melt in interstitial area has two scenarios: (a) fractional melting of the Martian crust or (b) formation by pseudotachylite-like impact melting. According to textural observations (schlieren pattern), we propose an impact origin of the large amount of silica-rich melt in this meteorite. Pseudotachylite-like textures were mentioned earlier in terrestrial impact craters; however, we first propose them to form in a Martian meteorite based on their similarity of texture with terrestrial pseudotachylites. [ABSTRACT FROM AUTHOR]

Highlights • Space weathering of a carbonaceous chondrite simulated via pulsed laser irradiation. • Reflectance spectra of the melt and vapor deposits show strong reddening. • The reflectance spectrum of the irradiated meteorite surface is darkened. • TEM analyses reveal a compositionally diverse nanoparticle population. • Results suggest a departure from lunar-style space weathering. Abstract We performed pulsed-laser irradiation of a chip of the CM2 Murchison carbonaceous chondrite meteorite to simulate micrometeorite impacts on carbonaceous asteroids. Optical reflectance spectroscopy and transmission electron microscopy were performed to characterize the unirradiated and irradiated samples and vapor and melt deposits collected on a glass slide ∼7 mm from the surface of the sample. The spectrum of the deposit on the glass slide shows a red slope between 0.35–2.5 µm, while the irradiated surface of the meteorite shows only slight darkening over the same spectral range. We identified predominant melt products and vesiculated textures in the glass slide deposit, in the fine-grained matrix of the meteorite, and in individual mineral phases of the meteorite chip. Extracted focused ion beam (FIB) sections from the matrix material, an olivine grain, a pentlandite grain, and from the glass slide deposit were analyzed by scanning transmission electron microscopy (STEM). Microstructural and chemical analyses based on the STEM observations show widespread melting and the formation of Fe-bearing nanoparticles (including prevalent Fe–Ni–sulfides) across the surface of the meteorite. The section extracted from the glass slide revealed nanoparticles embedded in a chemically and microstructurally complex deposit, which likely formed as a result of both melting and vaporization processes. These analyses reveal a significantly more compositionally diverse population of nanoparticles compared to what is observed in lunar or ordinary chondritic space weathered samples. We discuss the implications these results have for the space weathering of carbonaceous asteroids and their importance for understanding the surface processes on primitive bodies. [ABSTRACT FROM AUTHOR]

Highlights • This article provides the context for "Ceres mineralogical mapping special issue". • We describe the global mineralogy of Ceres. • A summary of all the special issue papers is reported. Abstract Ceres' surface composition is of special interest because it is a window into the interior state and the past evolution of this dwarf planet. Disk-integrated telescopic spectral observations indicated that Ceres' surface is hydroxylated, similar to but not exactly the same as some of the carbonaceous chondrite classes of meteorites. Furthermore, Ceres' bulk density is low, suggesting significant water content. The Dawn mission in orbit around Ceres provided a new and much larger set of observations on the mineralogy, molecular and elemental composition, and their distributions in association with surface features and geology. The set of articles contained in this special issue is the first treatment of the entire surface composition of Ceres using the complete High Altitude Mapping Orbit (HAMO) Dawn Ceres data set and the calibrations from all the Dawn instruments. Most articles here treat the different geologic quadrangles of Ceres within the context of the entire body. There also are articles that treat global or technical topics. As a whole, these articles provide a current and comprehensive view of Ceres' surface composition. Ceres' surface composition shows a fairly uniform and widespread distribution of NH 4 - and Mg-phyllosilicates and carbonates, mixed with a dark component and with some exposures of salts and water-ice on Ceres' surface, all indicative of the presence of aqueous alteration processes that involved the entire dwarf planet. There is also likely some contamination by low velocity infall, as seen on Vesta, but it is more difficult to distinguish this infall from native Ceres material, unlike for the Vesta case. This article introduces and provides the context for the following papers, presents a summary of the various findings, and integrates them into some general conclusions. [ABSTRACT FROM AUTHOR]

Instrumental neutron activation analysis (INAA), inductively coupled plasma atomic emission spectrometry (ICP-AES) and ICP mass spectrometry (ICP-MS) (hereafter, ICPs) were applied to meteorite samples for the determination of elemental content. The analytical applicability and suitability of the three methods have been compared. Those comparisons led to the refinement of our analytical procedures for INAA and ICPs, yielding more reliable data. Our INAA data proved to be reliable enough for classifying meteorites, while the ICPs, especially ICP-MS, can characterize elemental abundance features in detail, as demonstrated by REE abundance patterns for the Allende meteorite. In this manner, INAA and ICPs can be used in a complementary fashion in cosmochemical studies. [ABSTRACT FROM AUTHOR]

We develop a full methodology to measure the complex relative permittivity of planetary regolith analog materials in vacuum and up to 120 °C over a broad range of frequencies (400 MHz to 8.5 GHz or wavelengths 18.8–3.5 cm). We demonstrate our method with measurements of analog regolith materials appropriate for asteroid (101955) Bennu, the target of National Aeronautics and Space Administration's OSIRIS‐REx mission: individual and mixed components of UCF/DSI‐CI‐2, a new carbonaceous asteroid regolith simulant produced by Deep Space Industries based on CI chondrite meteorite mineralogy. We measure, for the first time, the effect of carbonaceous material on the complex relative permittivity of asteroid regolith analogs by measuring the powdered serpentine component of the simulant mixed with varying amounts of carbonaceous material in vacuum at 25 and 40 °C. We find that at a bulk density of 1.60 g/cm3 and wavelength of 12.6 cm, serpentine with 5 wt% carbonaceous material has εr′ = 3.30 ± 0.01 and tanδ = 0.016 ± 0.003 and that carbonaceous material increases the attenuation of electromagnetic energy in our samples. Ground‐based radar (at 12.6‐ and 3.5‐cm wavelengths) has previously been used to investigate carbonaceous asteroid (101955) Bennu. Our measurements provide new constraints on the attenuation of radar energy in granular carbonaceous materials. Plain Language Summary: We measure the electrical parameters that are responsible for absorbing and reflecting radar waves in powders that have been mixed to resemble the composition of the regolith of the asteroid Bennu. Regolith is powdered rock material that covers the surfaces of most rocky planetary bodies. Bennu is the target of National Aeronautics and Space Administration's OSIRIS‐REx mission, which is a spacecraft that will return regolith from the surface of Bennu to Earth. Radar has been used from Earth to look at Bennu, so it is important to understand how the electrical parameters of the regolith on Bennu affect radar signals. Bennu's regolith is thought to contain organic carbon. We have measured the effect of adding organic carbon to our samples and found that adding carbon increases absorption of radar waves. Key Points: We present methods for measuring the complex relative permittivity of regolith analog materialsWe measure carbonaceous asteroid analog materials in vacuum between 400 MHz and 8.5 GHz at 25 and 40 °CThese measurements provide new constraints on the attenuation of radar waves in granular carbonaceous materials [ABSTRACT FROM AUTHOR]