¹Emmanuel Jacquet
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13896]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS, CP52, 57 rue Cuvier, 75005 Paris, France
Published by arrangement with John Wiley & Sons

The current meteorite taxonomy, a result of two centuries of meteorite research and tradition, entangles textural and genetic terms in a less than consistent fashion, with some taxa (like “shergottites”) representing varied lithologies from a single putative parent body while others (like “pallasites”) subsume texturally similar objects of multifarious solar system origins. The familiar concept of “group” as representative of one primary parent body is also difficult to define empirically. It is proposed that the classification becomes explicitly binominal throughout the meteorite spectrum, with classes referring to petrographically defined primary rock types, whereas groups retain a genetic meaning, but no longer tied to any assumption on the number of represented parent bodies. The classification of a meteorite would thus involve both a class and a group, in a two-dimensional fashion analogous to the way Van Schmus and Wood decoupled primary and secondary properties in chondrites. Since groups would not substantially differ, at first, from those in current use de facto, the taxonomic treatment of “normal” meteorites, whose class would bring no new information, would hardly change. Yet classes combined with high- or low-level groups would provide a standardized grid to characterize petrographically and/or isotopically unusual or anomalous meteorites—which make up the majority of represented meteorite parent bodies—for example, in relation to the carbonaceous/noncarbonaceous dichotomy. In the longer term, the mergers of genetically related groups, a more systematic treatment of lithology mixtures, and the chondrite/achondrite transition can further simplify the nomenclature.

¹Sergey E. Kichanov,^1,2Bekhzodjon A. Abdurakhimov,¹Ivan Yu Zel,¹Andrei K. Kirillov,¹Denis P. Kozlenko,³Irina K. Lapina,³Yulii L. Mentsin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13903]
¹FLNP, Joint Institute for Nuclear Research, 141980 Dubna, Russia
²Institute of Nuclear Physics, Academy of Sciences of the Republic of Uzbekistan, 100214 Tashkent, Uzbekistan
³Museum of the History of Astronomy, Sternberg Astronomical Institute, Lomonosov Moscow State University, 119992 Moscow, Russia
Published by arrangement with John Wiley & Sons

We present the results of neutron methods, specifically neutron diffraction and neutron tomography, in studying the structural organization of a Kunya-Urgench chondrite fragment. The major phases of the meteorite fragment and variation of the phase content across the studied volume were revealed using neutron diffraction. The 3-D model of the spatial distribution of metal and silicate phases inside the meteorite volume was obtained using neutron tomography. The distributions of volumes, average sizes, and shape-related parameters of kamacite and silicate phases were analyzed. Shape preferred orientations of the kamacite particles were observed and the origins of shape fabric of these particles were discussed.

^1,2Brendt C. Hyde,¹Desmond E. Moser,²Kimberly T. Tait,³James R. Darling,⁴Qing-Zhu Yin,⁴Matthew E. Sanborn,^1,2Neil R. Banerjee,^1,2Arshad Ali,¹Iffat Jabeen,³Hugo Moreira
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13897]
¹Department of Earth Sciences, University of Western Ontario, London, Ontario, N6A 5B7 Canada
²Department of Natural History, Royal Ontario Museum, Toronto, Ontario, M5S 2C6 Canada
³School of the Environment, Geography and Geosciences, University of Portsmouth, Portsmouth, PO13QL UK
⁴Department of Earth and Planetary Sciences, University of California Davis, One Shields Avenue, Davis, California, 95616 USA
Published by arrangement with John Wiley & Sons

Detailed textural and geochemical analyses of the carbonaceous achondrites Northwest Africa (NWA) 7680 and NWA 6962 support a rapid progression of thermal events, by similar processes, on the same parent body. The achondrites have olivine compositions of Fa44.8 and Fa47.4 for NWA 7680 and NWA 6962, respectively. Replicate oxygen isotope analyses of grains and bulk powders from NWA 7680 yielded average Δ17O values of −1.04 ± 0.03‰ and −1.00 ± 0.05‰, respectively, which is identical to that reported for NWA 6962. The whole rock ɛ54Cr compositions are also equivalent for NWA 7680 and NWA 6962 (1.36 ± 0.05 and 1.30 ± 0.05, respectively). Both meteorites are plagioclase-rich, and NWA 7680 is also Fe-metal-rich, suggesting they both formed via differentiation processes that resulted in the pooling of partial melt products. Major element geochemical trends show that both rocks could be formed through the melting of chondritic material on a CR chondrite-like parent body. This is consistent with oxygen isotope and chromium isotope compositions. Intrusion of a late-stage melt is evident in both meteorites and the crystallization products include silica-rich, alkali-deficient nepheline. The late-stage liquid has partially melted and mixed with primary plagioclase in NWA 6962. In contrast, the late-stage liquid was often restricted to grain boundaries in NWA 7680, leaving some of the primary plagioclase crystals intact. In situ dating of NWA 7680 phosphate minerals (merrillite and fluorapatite) reveals that it has not experienced long duration thermal metamorphism, or impact-related Pb loss and age resetting since 4578 ± 17 Ma (207Pb/206Pb age ± 2σ, within error of solar system age). Phosphates associated with the late-stage melt in NWA 6962 yield a 207Pb/206Pb age of 4556.6 ± 8.0 Ma (2σ) within 2σ of the NWA 7680 age. These early dates indicate that the observed chromium isotope signatures in these meteorites were not introduced by a later high-temperature event, such as late impact accretion processes. These data are consistent with a rapid separation of inner and outer solar system chemical reservoirs, planetesimal melting, differentiation, and cooling, all within several million years of calcium-aluminum-rich inclusion formation.

^1,2John Carter,³Lucie Riu,¹François Poulet,¹Jean-Pierre Bibring,¹Yves Langevin,¹Brigitte Gondet
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115164]
¹Institut d’Astrophysique Spatiale (IAS), CNRS/Paris-Saclay University, France
²Laboratoire d’Astrophysique de Marseille (LAM), CNRS/Aix-Marseille University, France
³ESA-ESAC, Madrid, Spain
Copyright Elsevier

We describe the completion of the MOCAAS project providing a global repository of secondary minerals formed through interaction with water on Mars. This work is based on the analysis of orbital imaging spectroscopy data from the OMEGA/Mars Express and CRISM/MRO near-infrared instruments. A database and a set of high-resolution global maps (200 m/pix) are produced which provide a large collection of these “aqueous” secondary mineral deposits, most of which were not previously reported. Several aqueous mineral classes are discriminated including hydrated silicates, hydrated silica, sulfate and carbonate salts. A preliminary statistical analysis on the database of aqueous mineral deposits is carried out, revealing significantly more widespread and diverse aqueous alteration on Noachian and Hesperian Mars than previously seen. Higher resolution local scale studies are also carried out over current and prospective rover landing sites on Mars, providing enhanced sensitivity to mineral detection and reachable science targets. Collectively, the data presented here at all scales is expected to foster synergy between orbital and landed missions, particularly for future missions and to pinpoint prospective resources for human exploration.

¹Alessandro Pisello,²Marco Ferrari,²Simone De Angelis,^1,2,3Francesco P.Vetere,¹Massimiliano Porreca,²Stefania Stefani,¹Diego Perugini
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115222]
¹Department of Physics and Geology, University of Perugia, I-06123 Perugia, Italy
²Institute for Space Astrophysics and Planetology, INAF, Rome, Italy
³Department of Physical Sciences, Earth and Environment, University of Siena, 53100, Italy
Copyright Elsevier

Volcanic phenomaena shaped the surface of all terrestrial planets in the solar system, and silicate glasses represent a major component in pyroclastic deposits and lavas. Spectral features of silicate glasses therefore influence spectral characteristics of large portions of planetary surfaces.

In this study, experimental petrology techniques have been used to produce 19 silicate glass samples having natural chemical composition corresponding to four of the most common magmatic series on planet Earth. Reflectance of such products was investigated in the mid-infrared region (MIR) to observe the evolution of their spectral characteristics with changing degree of evolution (expressed as silica content) and alkaline content. We have observed how chemical features have a clear influence in shifting the spectral features (to lower wavelengths with increasing silica, such as for previously studied volcanic rocks) and on the spectral shape, which is substantially different between mafic and highly silicic products. This allowed us to propose a model to retrieve chemical information (SiO2 and SiO2 + Al2O3 + TiO2 content) from the wavelength at which spectral features (CF and RBpeak) occur. Moreover, by comparing our results with previous MIR studies we have observed that our model can be applied, to a certain extent, to interpret chemical fingerpint volcanic rocks in general. Here, it is also shown how granulometry influences spectral shape, but does not affect spectral shift.

This study will be useful to interpret planetary information and assess how amorphous silicate phases influence spectral characteristics of volcanic areas on planetary surfaces.

¹S.A.Crowther,¹P.L.Clay,¹S.Edwards,²H.Busemann,¹K.H.Joy,¹A.A.Early,¹R.Burgess,³A.R.Butcher,⁴M.Humay,¹J.D.Gilmour
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2022.08.002]
¹Department of Earth and Environmental Sciences, The University of Manchester, UK
²ETH Zürich, Institut für Geochemie und Petrologie, Zürich, Switzerl
³Geological Survey of Finland GTK, Espoo, Finland
⁴National High Magnetic Field Laboratory and Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, USA
Copyright Elsevier

The martian meteorite Northwest Africa (NWA) 8114 is a regolith breccia grouped with the NWA 7034 (‘Black Beauty’) stone and others. The meteorite, with its complex rock and mineral load, records over 4.4 billion years of martian geological and atmospheric history. In this work we present new analyses of noble gases in NWA 8114, and consider the constraints they impose on the evolution of the martian atmosphere over the past 4 billion years. We also report a petrographic overview, halogen abundances, and an argon isotope age, which provide context for interpreting the noble gas data.

The krypton and xenon elemental signature of NWA 8114 is elementally fractionated with respect to the present-day martian atmosphere as measured in shergottite glasses; there is no requirement for a contribution from the ancient martian atmosphere in our data. The xenon isotopic composition incorporates (i) a component enriched in 129Xe (maximum 129Xe/132Xe = 2.450 ± 0.045 compared with a solar ratio of ∼1), which is similar to the present day martian atmosphere, (ii) a cosmic-ray spallation component dominated by production from barium, and (iii) a fission component. We estimate a cosmic ray exposure (CRE) age of 5.7 ± 1.3 Myr from cosmogenic 21Ne and 38Ar.

Understanding how the martian atmosphere has changed through the planet’s history is a key part of understanding the planet’s geological history and evolution. We develop a model for the evolution of the martian atmosphere constrained by the amount of spallation-derived xenon in the atmosphere today and the evolution of the 129Xe/132Xe ratio over time. A baseline model in which the early atmosphere collapsed 3.7 Gyr ago (and assuming no further loss) requires a constant degassing of the crustal budget of spallation xenon of 0.034 % Myr-1 to accumulate sufficient spallation-derived xenon in the atmosphere. Combining constraints imposed by the 129Xe/132Xe ratio with the spallation budget requires loss of xenon from the martian atmosphere over the last 3.7 Gyr, with the present day budget being as little as 20 % of that at the start of this period.

Due to conferences and technical issues, the will be another short Summer Break.

^1,2G.Caravaca et al. (>10)
Journal of Geophysical Research (Planets) Open Access Link to Article [https://doi.org/10.1029/2021JE007093]
¹UMR 5277 CNRS, UPS, CNES Institut de Recherche en Astrophysique et Planétologie, Université Paul Sabatier Toulouse III, Toulouse, France
²UMR 6112 CNRS Laboratoire de Planétologie et Géosciences, Nantes Université, Université d’Angers, Nantes, France
Published by arrangement with John Wiley & Sons

Between January 2019 and January 2021, the Mars Science Laboratory team explored the Glen Torridon region in Gale crater (Mars), known for its orbital detection of clay minerals. Mastcam, MAHLI and ChemCam data are used in an integrated sedimentological and geochemical study to characterize the Jura member of the upper Murray formation and the Knockfarril Hill member of the overlying Carolyn Shoemaker formation in northern Glen Torridon. The studied strata show a progressive transition represented by interfingering beds of fine-grained, recessive mudstones of the Jura member and coarser-grained, cross-stratified sandstones attributed to the Knockfarril Hill member. Whereas the former are interpreted as lacustrine deposits, the latter are interpreted as predominantly fluvial deposits. The geochemical composition seen by the ChemCam instrument show K2O-rich mudstones (∼1-2 wt.%) vs MgO-rich sandstones (>6 wt.%), relative to the average composition of the underlying Murray formation. We document consistent sedimentary and geochemical datasets showing that low-energy mudstones of the Jura member are associated with the K-rich endmember, and that high-energy cross-stratified sandstones of the Knockfarril Hill member are associated with the Mg-rich endmember, regardless of stratigraphic position. The Jura to Knockfarril Hill transition therefore marks a significant paleoenvironmental change, where a long-lived and comparatively quiescent lacustrine setting progressively changes into a more energetic fluvial setting, as a consequence of shoreline regression due to either increased sediment supply or lake-level drop.

¹A.C.McAdam et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2022JE007179]
¹NASA Goddard Space Flight Center, Greenbelt, MD, USA
Published by arrangement with John Wiley & Sons

Evolved gas analysis (EGA) data from the Sample Analysis at Mars (SAM) instrument suite indicated Fe-rich smectite, carbonate, oxidized organics, Fe/Mg sulfate, and chloride in sedimentary rocks from the Glen Torridon (GT) region of Gale crater that displayed phyllosilicate spectral signatures from orbit. SAM evolved H2O data indicated that the primary phyllosilicate in all GT samples was an Fe-rich dioctahedral smectite (e.g., nontronite) with lesser amounts of a phyllosilicate such as mixed layer talc-serpentine or greenalite-minnesotaite. CO2 data supported the identification of siderite in several samples, and CO2 and CO data was also consistent with trace oxidized organic compounds such as oxalate salts. SO2 data indicated trace and/or amorphous Fe sulfates in all samples and one sample may contain Fe sulfides. SO2 data points to significant Mg sulfates in two samples, and lesser amounts in several other samples. A lack of evolved O2 indicated the absence of oxychlorine salts and Mn3+/ Mn4+ oxides. The lack of, or very minor, evolved NO revealed absent or very trace nitrate/nitrite salts. HCl data suggested chloride salts in GT samples. Constraints from EGA data on mineralogy and chemistry indicated that the environmental history of GT involved alteration with fluids of variable redox potential, chemistry and pH under a range of fluid-to-rock ratio conditions. Several of the fluid episodes could have provided habitable environmental conditions and carbon would have been available to any past microbes though the lack of significant N could have been a limiting factor for microbial habitability in the GT region.

¹Randy L. Korotev
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13900]
¹Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, Saint Louis, Missouri, 63130 USA
Published by arrangement with John Wiley & Sons

Bulk composition data for 24 chemical elements are presented for regolith samples (<1 mm fines) from each of the 62 half-centimeter dissection intervals along the 31 cm length of the 76001 vertical drive tube collected by astronauts at the base of the North Massif at station 6 of the Apollo 17 landing site. The core regolith is nearly uniform in composition with depth although the concentrations of Sc and Sm, for example, decrease from 28.5 μg g−1 Sc and 5.93 μg g−1 Sm at the top 2.5 cm to 26.9 μg g−1 Sc and 5.55 μg g−1 Sm at the bottom 2.5 cm. This change reflects an increase with depth in the relative abundance of Sm-poor, feldspathic material, from 48.4% at the top to 50.1% at the bottom. On the basis of compositional mass balance, the feldspathic (nonmare) material of the station 6 regolith requires a substantial proportion of an Mg-rich lithology, ~27% when modeled as troctolite sample 76535. The remaining 73% is nominally Sm-poor anorthositic norite in composition. No such Mg-rich component is required to account for the composition of the regolith of the South Massif (stations 2 and 3). The total feldspathic component of the North Massif regolith, normatively an anorthositic troctolite (74 vol% plagioclase, olivine:pyroxene = 55:45, Mg′ = 78%), is very similar to that of the nonmare component of the Luna 20 regolith collected 910 km to the southeast on the Crisium ejecta deposit. We also present new composition data for 21, 25, and 16 small lithic fragments (0.1–3.9 mg each) from the regoliths of the Luna 16, 20, and 24 missions.