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On Earth, carbonate minerals are widely used as recorders of the geological environments in which they formed. Here, we present a method designed to retrieve the crystal chemistry of Fe‐Mg carbonate minerals using infrared remote sensing or Raman spectroscopy. We analyzed a suite of well‐characterized Fe‐Mg carbonate minerals for which Raman spectra were obtained in two different laboratories, and IR spectra were measured in reflectance and transmission from the visible range to 25‐μm. We built calibration lines for the dependence of fundamental and harmonic vibrational modes position to the Mg# (defined as Mg# = 100 × Mg/(Mg + Fe + Ca + Mn)). These calibrations should enable retrieval of Mg# based on spectroscopic observations with a typical accuracy of 10. We discuss the framework of applicability of these calibrations and apply them to a typical CRISM spectrum of carbonates from the Nilli Fossae region of Mars. Key Points: Fundamental FeMg carbonate mode position have a linear dependence to Mg# for Fe‐Mg carbonate mineralHarmonic bands at 2.3 and 2.5 also have a linear dependence of their position with Mg# for Fe‐Mg carbonate mineralsWe present calibration curves of Mg# versus fundamental and harmonic vibration position than can be used to retrieve crystal chemistry [ABSTRACT FROM AUTHOR]

The Hayabusa2 mission sampled Ryugu, an asteroid that did not suffer extensive thermal metamorphism, and returned rocks to the Earth with no significant air exposure. It therefore offers a unique opportunity to study the redox state of carbonaceous Cb‐type asteroids and evaluate the overall redox state of the most primitive rocks of the solar system. An analytical framework was developed to investigate the iron mineralogy and valence state in extraterrestrial material at the micron scale by combining x‐ray diffraction, conventional Mössbauer (MS), and nuclear forward scattering (NFS) spectroscopies. An array of standard minerals was analyzed and cross‐calibrated between MS and NFS. Then, MS and NFS spectra on three Ryugu grains were collected at the bulk and the micron scales. In Ryugu samples, iron is essentially accommodated in magnetite, clay minerals (serpentine–smectite), and sulfides. Only a single set of Mössbauer parameters was necessary to account for the entire variability observed in MS and NFS spectra, at all spatial scales investigated. These parameters therefore make up a fully consistent iron mineralogical model for the Ryugu samples. As far as MS and NFS spectroscopies are concerned, Ryugu grains are overall similar to each other and share most of their mineralogical features with CI‐type chondrites. In detail however, no ferrihydrite is found in Ryugu particles even at the very sensitive scale of Mössbauer spectroscopy. The typical Fe3+/Fetot of clay minerals is much lower than typical redox ratios measured in CI chondrites (Fe3+/Fetot = 85%–90%). Furthermore, magnetite from Ryugu is stoichiometric with no significant maghemite component, whereas up to 12% of maghemite was previously identified in the Orgueil's so‐called magnetite. These differences suggest that most CI meteorites suffered terrestrial alteration and that the preterrestrial composition of these carbon‐rich samples was less oxidized than previously measured. However, it is not clear yet whether or not the parent bodies of CI chondrites were as reduced as Ryugu. Finally, the high spatial resolution of NFS allows to disentangle the redox state and the crystal chemistry of iron accommodated in serpentine and smectite. The most likely polytype of serpentine is lizardite, containing <35% of Fe3+, a fraction of which being tetrahedrally coordinated. Smectite is more oxidized (Fe3+/Fetot > 65%) and mainly contains octahedral ferric iron. This finding implies that these clays formed from highly alkaline fluids and the spatial variability highlighted here may suggest a temporal evolution or a spatial variability of the nature of this fluid. [ABSTRACT FROM AUTHOR]

The Hayabusa2 mission from the Japan Aerospace Exploration Agency (JAXA) returned to the Earth samples of carbonaceous asteroid (162173) Ryugu. This mission offers a unique opportunity to investigate in the laboratory samples from a C‐type asteroid, without physical or chemical alteration by the terrestrial atmosphere. Here, we report on an investigation of the mineralogy and the organo‐chemistry of Hayabusa2 samples using a combination of micro‐ and nano‐infrared spectroscopy. Particles investigated with conventional FTIR spectroscopy have spectra dominated by phyllosilicate‐related absorption, as observed for samples of CI‐chondrites, selected ungrouped carbonaceous chondrites, and selected hydrated micrometeorites. Ryugu samples show smaller sulfate‐related absorption than CI‐chondrites. Our samples that were only briefly exposed to the Earth atmosphere show absorptions related to molecular water, revealing fast terrestrial contamination of the spectral signature at 3 μm. Overall, our FTIR data are in agreement with other work done on Ryugu samples, revealing a low degree of mineralogical variability across Ryugu samples. AFM‐IR mapping of the grains shows the presence of a micrometer‐sized organic globule in one of our analyzed grains. The AFM‐IR spectra obtained on this globule are similar to IR spectra obtained on IOM suggesting that it is constituted of refractory organic matter. This globule may host silicate in its interior, with a different mineralogy than bulk Ryugu phyllosilicate. The shape, presence of peculiar silicate, and the nature of organic constituting the globule point toward a pre‐accretionary origin of this globule and that at least part of Ryugu organics were inherited from the protosolar nebulae or the interstellar media. Altogether, our results show the similarities between Ryugu samples and CI chondrites. [ABSTRACT FROM AUTHOR]

We report a Fourier transform infrared analysis of functional groups in insoluble organic matter (IOM) extracted from a series of 100–500 μm Ryugu grains collected during the two touchdowns of February 22 and July 11, 2019. IOM extracted from most of the samples is very similar to IOM in primitive CI, CM, and CR chondrites, and shows that the extent of thermal metamorphism in Ryugu regolith was, at best, very limited. One sample displays chemical signatures consistent with a very mild heating, likely due to asteroidal collision impacts. We also report a lower carbonyl abundance in Ryugu IOM samples compared to primitive chondrites, which could reflect the accretion of a less oxygenated precursor by Ryugu. The possible effects of hydrothermal alteration and terrestrial weathering are also discussed. Last, no firm conclusions could be drawn on the origin of the soluble outlier phases, observed along with IOM in this study and in the preliminary analysis of Ryugu samples. However, it is clear that the HF/HCl residues presented in this publication are a mix between IOM and the nitrogen‐rich outlier phase. [ABSTRACT FROM AUTHOR]

The Mars 2020 Perseverance rover has explored fluvio‐lacustrine sedimentary rocks within Jezero crater. Prior work showed that igneous crater floor Séítah and Máaz formations have mafic mineralogy with alteration phases that indicate multiple episodes of aqueous alteration. In this work, we extend the analyses of hydration to targets in the Jezero western fan delta, using data from the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) Raman spectrometer. Spectral features, for example, sulfate and hydration peak positions and shapes, vary within, and across the crater floor and western fan. The proportion of targets with hydration associated with sulfates was approximately equal in the crater floor and the western fan. All hydrated targets in the crater floor and upper fan showed bimodal hydration peaks at ∼3,200 and ∼3,400 cm−1. The sulfate symmetric stretch at ∼1,000 cm−1 coupled with a hydration peak at ∼3,400 cm−1 indicate that MgSO4·nH2O (2 < n ≤ 5) is a likely hydration carrier phase in all units, perhaps paired with low‐hydration (n ≤ 1) amorphous Mg‐sulfates, indicated by the ∼3,200 cm−1 peak. Low‐hydration MgSO4·nH2O (n = 1–2) are more prevalent in the fan, and hydrated targets in the fan front only had one peak at ∼3,400 cm−1. While anhydrite co‐occurs with hydrated Mg‐sulfates in the crater floor and fan front, hydrated Ca‐sulfates are observed instead at the top of the upper fan. Collectively, the data imply aqueous deposition of sediments with formation of salts from high ionic strength fluids and subsequent aridity to preserve the observed hydration states. Plain Language Summary: The Mars 2020 Perseverance rover has explored a fan delta deposit in the Jezero crater where a lake was present in the past. In this work, we use the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) Raman spectroscopy instrument on the rover to determine the minerals that contain water in the form of H2O and/or OH. These hydrated minerals are indicators of interactions of rock with water and inform us how the environmental conditions and the habitability of Jezero crater evolved over time. Hydrated Mg‐sulfates MgSO4·nH2O (2 < n ≤ 5) are observed in both the crater floor and the western fan. Mg‐sulfates of lower hydration degree (n = 1–2) are more commonly found in the western fan, particularly the fan front. Hydrated Ca‐sulfate is found only close to the top of the fan. These changes in sulfate degree of hydration and/or cations from the floor to the fan are evidence of multiple past fluid events and chemistries at Jezero crater. Key Points: MgSO4·nH2O (2 < n ≤ 5) are found in the Jezero fan and floor while low‐hydration MgSO4·nH2O (n = 1–2) are more commonly found in the fanHydrated Ca‐sulfates are found only in the upper fanThe diverse phases imply salt formation from high ionic strength fluids and subsequent aridity to preserve the observed hydration states [ABSTRACT FROM AUTHOR]

Renazzo‐type (CR) chondrites are a relatively rare group of carbonaceous chondrites with the vast majority having escaped thermal alteration. This means that CRs are composed of relatively unprocessed material, depending on the extent of aqueous alteration they have experienced. Hydration in CRs ranges from incipient alteration of matrix glass, up to nearly complete replacement of the rock by hydration products. The extent of secondary processes is often difficult to assess in these meteorites, due to their heterogeneity and diversity of alteration products. Yet, this is crucial in order to understand the extent of geological processing that occurred on the primary parent body. Additionally, the parent asteroids of CRs remain a mystery, mainly because terrestrial oxyhydroxide signatures dominate the reflectance spectra of CRs. In this work, we have conducted optical and IR reflectance and transmission spectra of 25 CR chondrites in order to (i) better evaluate the extent of aqueous alteration that occurred on the CR parent body, and (ii) find possible parent body candidates. Terrestrial oxyhydroxides were removed from 12 samples, as these tend to interfere with the optical‐IR spectra of CRs. Our results suggest, among other, that (i) aqueous alteration in most of our CRs was limited to the matrix and (ii) most CRs may stem from a continuum of X‐to‐C complex asteroids, depending on their extent of aqueous alteration. More specifically, the endmembers being Xk/Xn types and Cgh/Ch types. This has strong implication in regard to what we can expect from the Psyche mission. [ABSTRACT FROM AUTHOR]

Impact melt rocks formed during hypervelocity impact events are ideal for studying impact structures. Here, we describe impact melt rock samples collected proximal to the 31 km wide 58 Ma Hiawatha impact structure, northwest Greenland, which is completely covered by the Greenland Ice Sheet. The melt rocks contain diagnostic shock indicators (e.g., planar deformation features [PDF] in quartz and shocked zircon) and form three groups based on melt textures and chemistry: (i) hypocrystalline, (ii) glassy, and (iii) carbonate‐based melt rocks. The exposed foreland directly in front of the structure consists of metasedimentary successions and igneous plutons; however, the carbonate‐based impactites indicate a mixed target sequence with a significant carbonate‐rich component. Well‐preserved organic material in some melt rocks indicates that North Greenland at the time of impact was host to abundant organic material, likely a dense high‐latitude temperate forest. Geochemical signatures of platinum‐group elements in selected samples indicate an extraterrestrial component and support previous identification of a highly fractionated iron impactor in glaciofluvial sand. Our results illustrate the possibility to study impact structures hidden beneath a thick ice sheet based on transported samples and this opens a new avenue for identifying other potential impact craters in Greenland and Antarctica. [ABSTRACT FROM AUTHOR]

Meteorite matrices from primitive chondrites are an interplay of ingredients at the sub‐µm scale, which requires analytical techniques with the nanometer spatial resolution to decipher the composition of individual components in their petrographic context. Infrared spectroscopy is an effective method that enables the probing of vibrations at the molecule atomic scale of organic and inorganic compounds but is often limited to a few micrometers in spatial resolution. To efficiently distinguish spectral signatures of the different constituents, we apply here nano‐infrared spectroscopy (AFM‐IR), based on the combination of infrared and atomic force microscopy, having a spatial resolution beyond the diffraction limits. Our study aims to characterize two chosen meteorite samples to investigate primitive material in terms of bulk chemistry (the CI chondrite Orgueil) and organic composition (the CR chondrite EET 92042). We confirm that this technique allows unmixing the IR signatures of organics and minerals to assess the variability of organic structure within these samples. We report an investigation of the impact of the widely used chemical HF/HCl (hydrogen fluoride/hydrochloric acid) extraction on the nature of refractory organics (insoluble organic matter [IOM]) and provide insights on the mineralogy of meteorite matrices from these two samples by comparing to reference (extra)terrestrial materials. These findings are discussed with a perspective toward understanding the impact of post‐accretional aqueous alteration and thermal metamorphism on the composition of chondrites. Last, we highlight that the heterogeneity of organic matter within meteoritic materials extends down to the nanoscale, and by comparison with IOMs, oxygenated chemical groups are not affected by acid extractions. [ABSTRACT FROM AUTHOR]

Miller Range (MIL) 07687 is a peculiar carbonaceous chondrite officially classified as a CO3. However, it has been found to display unique petrographic properties that are atypical of this group. Moreover, Raman spectra of its polyaromatic carbonaceous matter do not reflect a structural order consistent with the metamorphic history of a type 3 chondrite. As a result, it has been suggested to be an ungrouped C2 chondrite with CO affinities, although it has not been fully excluded as a CO chondrite. The ambiguity of the meteorite's classification is the motivation behind the present study. We conclude that MIL 07687 is a unique carbonaceous chondrite with possible affinities to CO, CM, and/or some ungrouped carbonaceous chondrites. The difficulty in classifying this meteorite stems from (1) its heavily weathered nature, which interferes with the interpretation of our oxygen (O‐)isotopic measurements; (2) the overlap in the petrographic and O‐isotopic descriptions of various COs, CMs, and ungrouped meteorites in the Meteoritical Society Database. Optical and infrared spectra are consistent with the meteorite's unequilibrated nature and indicate that it is probably mildly aqueously altered. Despite traces of aqueous alteration having previously been described in MIL 07687, this is the first time that the presence of hydrated amorphous silicates is reported. In fact, our results show that its present hydration is beyond that of most CO3s, less than most CM2s, and comparable to primitive CR2s. Consequently, we support the meteorite's C2‐ung label, although a CO2 or CM2 classification cannot be fully excluded. [ABSTRACT FROM AUTHOR]

The Piancaldoli ordinary chondrite fell in northern Italy on August 10, 1968. Preliminary studies led to its classification as an LL3.4 unequilibrated ordinary chondrite. However, recent developments in classification procedures have prompted us to re‐examine its mineralogical, petrographic, spectroscopic, chemical, and isotopic features in a multi‐technique study. Raman spectra and magnetic properties indicate that Piancaldoli experienced minimal thermal metamorphism, consistent with its high bulk hydrogen content and the Cr contents of ferroan olivines in its type II chondrules. In combination with findings of previous studies, our data thus confirm the variability of Cr contents in ferroan olivines in type II chondrules as a proxy of thermal metamorphism. Furthermore, our results reveal that Piancaldoli is less altered than previously reported and should be reclassified as an LL3.10 unequilibrated ordinary chondrite. Our results also imply that the bulk deuterium enrichment, as observed in Piancaldoli (LL3.10), Bishunpur (LL3.15), and Semarkona (LL3.00), is a specific signature of the most primitive unequilibrated ordinary chondrites. Based on our results, we propose that, to date, Piancaldoli is the second least‐altered unequilibrated ordinary chondrite fall after Semarkona. This work reiterates the importance of meteorite collections worldwide as fundamental resources for studying the formation conditions and evolution of our solar system. [ABSTRACT FROM AUTHOR]

A set of high‐fidelity simulated asteroid materials, or simulants, was developed based on the mineralogy of carbonaceous chondrite meteorites. Three varieties of simulant were developed based on CI1 chondrites (typified by Orgueil), CM2 chondrites (typified by Murchison), and CR2/3 chondrites (multiple samples). The simulants were designed to replicate the mineralogy and physical properties of the corresponding meteorites and anticipated asteroid surface materials as closely as is reasonably possible for bulk amounts. The simulants can be made in different physical forms ranging from larger cobbles to fine‐grained regolith. We analyzed simulant prototypes using scanning electron microscopy, X‐ray fluorescence, reflectance spectroscopy at ambient conditions and in vacuum, thermal emission spectroscopy in a simulated asteroid environment chamber, and combined thermogravimetry and evolved gas analysis. Most measured properties compare favorably to the reference meteorites and therefore to predicted volatile‐rich asteroid surface materials, including boulders, cobbles, and fine‐grained soils. However, there were also discrepancies, and mistakes were made in the original mineral formulations that will be updated in the future. The asteroid simulants are available to the community from the nonprofit Exolith Lab at UCF, and the mineral recipes are freely published for other groups to reproduce and modify as they see fit. [ABSTRACT FROM AUTHOR]

Here, we evaluate the extent of aqueous alteration among five pristine specimens of the ungrouped Tagish Lake carbonaceous chondrite (TL5b, TL11h, TL11i, TL4, and TL10a) using thermogravimetric analysis (TGA) and infrared (IR) transmission spectroscopy. Both TGA and IR spectroscopy have proven to be reliable methods for determining the extent of aqueous alteration among different carbonaceous chondrites, in particular the CM chondrites (e.g., Garenne et al. 2014), with which Tagish Lake shares some affinities. Using these two methods, our goal is to incorporate TL4 and TL10a into the known alteration sequence of TL5b < TL11h < TL11i (Herd et al. 2011; Blinova et al. 2014a). This study highlights the compositional variability of the Tagish Lake specimens, which we ascribe to its brecciated nature. Our TGA and IR spectroscopy results are congruent with the reported alteration sequence, allowing us to introduce the TL4 and TL10a specimens in the following order: TL4 < TL5b ≤ TL10a < TL 11h < TL11i. Notably, these two specimens appear to be similar to the least altered lithologies previously reported, and the alteration of Tagish Lake is similar to that experienced by lesser altered members of the CM chondrites (>CM1.6). Based on these findings, Tagish Lake could be considered a 1.6–2.0 ungrouped carbonaceous chondrite. Visible and near‐IR reflectance measurements of Tagish Lake were also acquired in this study to revisit the Tagish Lake parent body connection. While other studies have paired Tagish Lake with D‐ and T‐type asteroid parent bodies, the reflectance spectra acquired in this study are variable among the different Tagish Lake specimens in relation to their alteration sequences; results match with spectra characteristic of C‐, X‐, Xc‐, and D‐type asteroids. The heterogeneity of Tagish Lake coupled with its low albedo makes the parent body connection a challenge. [ABSTRACT FROM AUTHOR]

Northwest Africa 7533, a polymict Martian breccia, consists of fine-grained clast-laden melt particles and microcrystalline matrix. While both melt and matrix contain medium-grained noritic-monzonitic material and crystal clasts, the matrix also contains lithic clasts with zoned pigeonite and augite plus two feldspars, microbasaltic clasts, vitrophyric and microcrystalline spherules, and shards. The clast-laden melt rocks contain clump-like aggregates of orthopyroxene surrounded by aureoles of plagioclase. Some shards of vesicular melt rocks resemble the pyroxene-plagioclase clump-aureole structures. Submicron size matrix grains show some triple junctions, but most are irregular with high intergranular porosity. The noritic-monzonitic rocks contain exsolved pyroxenes and perthitic intergrowths, and cooled more slowly than rocks with zoned-pyroxene or fine grain size. Noritic material contains orthopyroxene or inverted pigeonite, augite, calcic to intermediate plagioclase, and chromite to Cr-bearing magnetite; monzonitic clasts contain augite, sodic plagioclase, K feldspar, Ti-bearing magnetite, ilmenite, chlorapatite, and zircon. These feldspathic rocks show similarities to some rocks at Gale Crater like Black Trout, Mara, and Jake M. The most magnesian orthopyroxene clasts are close to ALH 84001 orthopyroxene in composition. All these materials are enriched in siderophile elements, indicating impact melting and incorporation of a projectile component, except for Ni-poor pyroxene clasts which are from pristine rocks. Clast-laden melt rocks, spherules, shards, and siderophile element contents indicate formation of NWA 7533 as a regolith breccia. The zircons, mainly derived from monzonitic (melt) rocks, crystallized at 4.43 ± 0.03 Ga (Humayun et al. ) and a 147Sm-143Nd isochron for NWA 7034 yielding 4.42 ± 0.07 Ga (Nyquist et al. ) defines the crystallization age of all its igneous portions. The zircon from the monzonitic rocks has a higher Δ17O than other Martian meteorites explained in part by assimilation of regolith materials enriched during surface alteration (Nemchin et al. ). This record of protolith interaction with atmosphere-hydrosphere during regolith formation before melting demonstrates a thin atmosphere, a wet early surface environment on Mars, and an evolved crust likely to have contaminated younger extrusive rocks. The latest events recorded when the breccia was on Mars are resetting of apatite, much feldspar and some zircons at 1.35-1.4 Ga (Bellucci et al. ), and formation of Ni-bearing pyrite veins during or shortly after this disturbance (Lorand et al. ). [ABSTRACT FROM AUTHOR]

Northwest Africa ( NWA) 5958 is a carbonaceous chondrite found in Morocco in 2009. Preliminary chemical and isotopic data leading to its initial classification as C3.0 ungrouped have prompted us to conduct a multitechnique study of this meteorite and present a general description here. The petrography and chemistry of NWA 5958 is most similar to a CM chondrite, with a low degree of aqueous alteration, apparently under oxidizing conditions, and evidence of a second, limited alteration episode manifested by alteration fronts. The oxygen isotopic composition, with ∆'17O = −4.3‰, is more 16O-rich than all CM chondrites, indicating, along with other compositional arguments, a separate parent body of origin. We suggest that NWA 5958 be reclassified as an ungrouped carbonaceous chondrite related to the CM group. [ABSTRACT FROM AUTHOR]

An overview of several innovations regarding in situ laser-heating techniques in the diamond anvil cell at the high-pressure beamline ID27 of the European Synchrotron Radiation Facility is presented. Pyrometry measurements have been adapted to allow simultaneous double-sided temperature measurements with the installation of two additional online laser systems: a CO2 and a pulsed Nd:YAG laser system. This reiteration of laser-heating advancements at ID27 is designed to pave the way for a new generation of state-of-the-art experiments that demand the need for synchrotron diffraction techniques. Experimental examples are provided for each major development. The capabilities of the double pyrometer have been tested with the Nd:YAG continuous-wave lasers but also in a time-resolved configuration using the nanosecond-pulsed Nd:YAG laser on a Fe sample up to 180 GPa and 2900 K. The combination of time-resolved X-ray diffraction with in situ CO2 laser heating is shown with the crystallization of a high-pressure phase of the naturally found pyrite mineral MnS2 (11 GPa, 1100-1650 K). [ABSTRACT FROM AUTHOR]