¹A. Goodwin,¹R. Tartèse,¹R. J. Garwood,²N. V. Almeida
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE007916]
¹Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
²Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

The Martian regolith breccia Northwest Africa (NWA) 11220 and paired stones represent the only known meteorites that sample a clastic sub-surface lithology from Mars. By applying X-ray computed microtomography to monomineralic clasts, we identify three phases that can be automatically segmented by thresholding X-ray attenuation greyscale values: (A) feldspars, (B) pyroxene and apatite, and (C) iron-rich oxides and sulfides, confirmed via scanning electron microscopy and Raman spectroscopy. For these three phases, we demonstrate scale invariance in size and shape for sand-sized clasts and smaller, a characteristic commonly observed for clast populations generated by fragmentation without further sorting from sedimentary transport (e.g., Aeolian or fluvial processes). Additionally, by assessing the preferred orientation of fitted ellipses and ellipsoids to manually segmented proto-breccia clasts in two and three dimensions, we identified a weak planar fabric that likely resulted from compaction rather than impact transport. Combining clast size distribution with evidence for nested textures inside proto-breccia clasts, we propose that NWA 11220 has experienced a minimum of two hypervelocity impact events and should be considered a lithified impact ejecta lithology with little to no reworking via surface regolith processes.

^1,2G. Massa,²E. Palomba,²A. Longobardo,^1,2M. Angrisani,^1,2C. Gisellu,²F. Dirri,²M.C. De Sanctis,²A. Raponi,²F.G. Carrozzo,²M. Ciarniello
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2023.115870]
¹University of Rome “Sapienza”, Piazzale Aldo Moro 5, Rome 00185, Italy
²INAF Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere, Rome 00133, Italy
Copyright Elsevier

NASA’s Dawn mission was launched in September 2007 and orbited asteroids Vesta (2011−2012) and Ceres (2015–2018). Vesta shows surface dark units that have been suggested to be linked to exogenous materials and are therefore useful to understand the initial stages of the Solar System.

This work takes advantage of the newly calibrated data of the VIR spectrometer, which are characterized by a better signal to noise (S/N) ratio, giving us the opportunity to search for spectral features that were never seen before due to noise. Considering that hydroxyl has been shown to be present in every dark unit on Vesta and also in carbonaceous chondrites, the goals of this work are the search for and characterization of carbonates that are present in carbonaceous chondrites, i.e., the supposed darkening agents of Vesta.

The estimate of the abundances of carbonates is fundamental to identify which carbonaceous chondrite fell on Vesta; this can be crucial for the definition of an evolutionary history of Vesta and the Solar System. The study of a possible feature at 3.9 μm related to the presence of carbonates was analyzed and found to be noise-induced. Although spectral features related to carbonates were not observed, the 3.4 μm absorption band was analyzed anyway in order to fix an upper limit to the abundance of carbonates in carbonaceous chondrites on Vesta. This value is consistent with petrochemical analyses, i.e., no more than 0.2% of carbonates in carbonaceous chondrites.

¹T. A. Harvey,¹J. L. MacArthur,¹K. H. Joy,^2,3D. Sykes,⁴N. V. Almeida, R. H. Jones
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14094]
¹Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
²Henry Moseley X-Ray Imaging Facility, The Royce Institute, School of Materials, The University of Manchester, Manchester, UK
³Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
⁴Planetary Materials Group, Natural History Museum, London, UK
Published by arrangement with John Wiley & Sons

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.

¹Hugues Leroux et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14101]
¹Université de Lille, CNRS, INRAE, Centrale Lille, UMR 8207-UMET-Unité Matériaux et Transformations, Lille, France
Published by arrangement with John Wiley & Sons

Samples were recently collected from the carbonaceous asteroid (162173) Ryugu, by the Japan Aerospace Exploration Agency (JAXA) Hayabusa2 mission. They resemble CI chondrites material, thus showing clear evidence of extensive aqueous alteration attested by the widespread presence of a mixture of serpentine and saponite. We present here a scanning transmission electron microscopy study of the Ryugu dominant lithology of the phyllosilicate matrix at the nanometer scale, which we compare with that of the Orgueil CI chondrite. In both objects, the phyllosilicates are of comparable nature and texture, consisting of a mixture of small-sized crystallites of serpentine and saponite. At the micrometer scale or less, the texture is an alternation of fine and coarse domains. The fine-grained regions are dominated by saponite. In Ryugu, they enclose numerous Fe,Ni nanosulfides, whereas in Orgueil, S- and Ni-rich ferrihydrite is abundant. The coarse-grained regions contain more serpentine and no or little Fe,Ni sulfides or ferrihydrite. Scanning transmission x-ray microscopy at the Fe-L3 edge also reveals that iron valency of phyllosilicates is higher and more homogeneous in Orgueil (~70% Fe3+) than in Ryugu (<50% Fe3+). We interpret the observed textures as being mostly a consequence of aqueous alteration, likely resulting from the replacement by phyllosilicates of submicrometric components, initially agglomerated by a primary accretion. The fine-grained domains may result from the replacement of GEMS (GEMS—glass with embedded metal and sulfides) objects or from other types of nanometric assemblages of silicate and Fe-based nanophases. On the other hand, the coarse-grained regions may correspond to the replacement of anhydrous crystalline silicates of the olivine and pyroxene type. The major difference is the presence of Fe,Ni sulfides in Ryugu and of ferrihydrite and higher iron valency of phyllosilicates in Orgueil. This might be due to long-term terrestrial weathering that would have destabilized the nanosulfides. We also explore an alternative scenario involving more oxidizing hydrothermal conditions on the Orgueil parent body.

¹David Leiser,¹Christian Dürnhofer,¹Erik Poloni,¹Stefan Löhle,²Pavol Matlovič,²Juraj Tóth,³Jérémie Vaubaillon
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115867]
¹High Enthalpy Flow Diagnostics Group, Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 29, Stuttgart, 70569, Germany
²Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynská dolina F1, Bratislava, 842 48, Slovakia
³IMCCE, CNRS, Observatoire de Paris, PSL Université, Sorbonne Université, Université de Lille 1, UMR 8028 du CNRS, 77 Av. Denfert Rochereau, Paris, 75014, France
Copyright Elsevier

Ground testing meteorite samples offer in-situ measurements of known materials in conditions that occur during entry into Earth’s atmosphere. 22 meteorite samples with a wide range of origins and classifications were tested in the plasma wind tunnel facility PWK1 at the Institute of Space Systems in Stuttgart. These tests recreate the flow condition of a meteoroid during entry into earth’s atmosphere at an altitude of 78.8 km altitude and a velocity of 11.7 km s-1. Four optical diagnostic techniques were used to measure the surface temperature above 1000 K. 2-D methods showed that the surface temperature is evenly distributed over the sample surface, while time-resolved analyses show that the samples reach a steady state temperature within 0.5 s. The steady-state temperature for chondritic samples was consistent but varied significantly for achondrites and iron meteorite samples. The composition data showed a strong dependency of the surface temperature on the silicon content. The surface temperatures were shown to be dependent on the material and a database of temperatures was set up. The Planck fit methodology could be directly adapted to spectral meteor observation systems. A comparison of the method to established methods showed an offset between the methods. This data could be applied to thermal models to better understand the energy transfer processes during meteor flight.

¹Eric Quirico et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14097]
¹Institut de Planétologie et d’Astrophysique (IPAG), UMR 5274, CNRS, Université Grenoble Alpes, Grenoble, France
Published by arrangement with John Wiley & Sons

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.

¹M. Eberhart,¹S. Loehle,²J. Vaubaillon,³P. Matlovič,³J. Tóth
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115868]
¹High Enthalpy Flow Diagnostics Group, Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 29, 70569 Stuttgart, Germany
²IMCCE, Observatoire de Paris, PSL, 77 Av. Denfert Rochereau, Paris, 75014, France
³Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia
Copyright Elsevier

Experimental meteors are produced by exposing samples of meteoritic material to an air plasma flow in an arcjet driven plasma wind tunnel facility, simulating the aerothermal conditions of an entry into the Earth’s atmosphere. A plenoptic camera is used to record sequences of light field images during the tests, allowing for the first time to derive the transient evolution of the ablating and melting surface in three dimensions. Results are presented for samples of various meteorites, which show the potential of this technique for the volumetric analysis of the complex interaction between an extraterrestrial body and the upper atmosphere. Data allow to derive recession rates, heats of ablation and a shape factor, which has been redefined to meet the recorded information. Recession is found to be non-linear, with different rates for different meteorite types, with mean rates between 0.28 and 0.7 mm/s. Heats of ablation are not constant, but decrease during the experiment, with mean values between 1.7 and 10.1 MJ/kg. A fairly linear correlation is found between the materials’ iron content and both the recession rate and the heat of ablation. Shape factors decrease with time and reach a plateau after about 3 s.

¹Martin R. Lee,¹Lydia J. Hallis,^12,3Luke Daly,⁴Adrian J. Boyce
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14099]
¹School of Geographical & Earth Sciences, University of Glasgow, Glasgow, UK
²Australian Centre for Microscopy and Microanalysis, University of Sydney, Sydney, New South Wales, Australia
³Department of Materials, University of Oxford, Oxford, UK
⁴Scottish Universities Environmental Research Centre, Glasgow, UK
Published by arrangement with John Wiley & Sons

CM carbonaceous chondrites can be used to constrain the abundance and H isotopic composition of water and OH in C-complex asteroids. Previous measurements of the water/OH content of the CMs are at the higher end of the compositional range of asteroids as determined by remote sensing. One possible explanation is that the indigenous water/OH content of meteorites has been overestimated due to contamination during their time on Earth. Here we have sought to better understand the magnitude and rate of terrestrial contamination through quantifying the concentration and H isotopic composition of telluric and indigenous water in CM falls by stepwise pyrolysis. These measurements have been integrated with published pyrolysis data from CM falls and finds. Once exposed to Earth’s atmosphere CM falls are contaminated rapidly, with some acquiring weight percent concentrations of water within days. The amount of water added does not progressively increase with time because CM falls have a similar range of adsorbed water contents to finds. Instead, the petrologic types of CMs strongly influence the amount of terrestrial water that they can acquire. This relationship is probably controlled by mineralogical and/or petrophysical properties of the meteorites that affect their hygroscopicity. Irrespective of the quantity of water that a sample adsorbs or its terrestrial age, there is minimal exchange of H in indigenous phyllosilicates with the terrestrial environment. The falls and finds discussed here contain 1.9–10.5 wt% indigenous water (average 7.0 wt%) that is consistent with recent measurements of C-complex asteroids including Bennu.

^1,2A. Mojarro,³A. Buch,¹J. P. Dworkin,¹J. L. Eigenbrode,⁴C. Fressinet,¹D. P. Glavin,⁴C. Szopa,⁴M. Millan,⁵A. J. Williams,⁶R. E. Summons
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE007968]
¹NASA Goddard Space Flight Center, Greenbelt, MD, USA
²Oak Ridge Associated Universities, Oak Ridge, TN, USA
³CentraleSupélec, Université Paris-Saclay, Paris, France
⁴Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université Paris-Saclay, Paris, France
⁵Department of Geological Sciences, University of Florida, Gainesville, FL, USA
⁶Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
Published by arrangement with John Wiley & Sons

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.

^1,2Emma R. Rogers,¹Briar R. Qualizza,¹Joseph R. Heidenreich,^1,3Henry G. Dawson,¹Briony H. N. Horgan
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE007881]
¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA
²Department of Earth Sciences, Dartmouth College, Hanover, NH, USA
³Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA
Published by arrangement with John Wiley & Sons

A small basin on the Southwest (SW) margin of Melas Chasma in Valles Marineris, Mars, hosts a variety of previously identified sedimentary fans and layered strata hypothesized to have been formed by one or more paleolakes. This basin also contains light-toned layered mounds that have distinct spectral absorption bands consistent with amorphous hydrated silica (e.g., opal). While the general morphology and mineralogy of these features and the basin itself have been previously characterized, the formation mechanism of the hydrated silica features and their temporal relationships with the proposed paleolake remain to be determined. We use Compact Reconnaissance Imaging Spectrometer for Mars visible through short-wave infrared reflectance spectra (0.35–2.65 μm) and High Resolution Imaging Science Experiment digital terrain models and images to analyze the stratigraphic location and morphology of the opaline silica-bearing features in the SW Melas basin. We find that the basin hosts fourteen high-relief “mounds,” eight low-relief “patches,” and two extended layers within the sedimentary strata that are light-toned, fractured, and often exhibit hydrated silica-like spectral signatures. We hypothesize that the mounds are spring deposits formed by sub-aerial hydrothermal activity, while the patches and layers correspond to sub-lacustrine hydrothermal activity. The varied elevations of the mounds and patches indicate at least one fluctuation of lake level in the basin during its history. The combination of contemporaneous hydrothermal and lacustrine activity to form silica-cemented sedimentary deposits in a nutrient-rich subaqueous environment would have been conducive to forming and preserving biosignatures in the SW Melas basin.