¹Patrick J. Gasda et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007097]
¹Los Alamos National Laboratory, Los Alamos, New Mexico, USA
Published by arrangement with John Wiley & Sons

The clay-rich Glen Torridon region of Gale crater, Mars, was explored between sols 2300 and 3007. Here, we analyzed the diagenetic features observed by Curiosity, including veins, cements, nodules, and nodular bedrock, using the ChemCam, Mastcam, and Mars Hand Lens Imager instruments. We discovered many diagenetic features in Glen Torridon, including dark-toned iron- and manganese-rich veins, magnesium- and fluorine-rich linear features, Ca-sulfate cemented bedrock, manganese-rich nodules, and iron-rich strata. We have characterized the chemistry and morphology of these features, which are most widespread in the higher stratigraphic members in Glen Torridon, and exhibit a wide range of chemistries. These discoveries are strong evidence for multiple generations of fluids from multiple chemical endmembers that likely underwent redox reactions to form some of these features. In a few cases, we may be able to use mineralogy and chemistry to constrain formation conditions of the diagenetic features. For example, the dark-toned veins likely formed in warmer, highly alkaline, and highly reducing conditions, while manganese-rich nodules likely formed in oxidizing and circumneutral conditions. We also hypothesize that an initial enrichment of soluble elements, including fluorine, occurred during hydrothermal alteration early in Gale crater history to account for elemental enrichment in nodules and veins. The presence of redox-active elements, including Fe and Mn, and elements required for life, including P and S, in these fluids is strong evidence for habitability of Gale crater groundwater. Hydrothermal alteration also has interesting implications for prebiotic chemistry during the earliest stages of the crater’s evolution and early Mars.

¹Kenneth J. Orr,¹Lucy V. Forman,²Kai Rankenburg,²Noreen J. Evans,²Bradley J. McDonald,³Belinda Godel,^1,4,5Gretchen K. Benedix
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13816]
¹Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, GPO Box 1987, Perth, Western Australia, 6845 Australia
²School of Earth and Planetary Science/John de Laeter Centre, Curtin University, GPO Box 1987, Perth, Western Australia, 6845 Australia
³CSIRO Mineral Resources, ARRC, Kensington, Western Australia, Australia
⁴Department of Earth and Planetary Science, Western Australia Museum, Locked Bag 49, Welshpool, Western Australia, 6986 Australia
⁵Planetary Science Institute, 1700 E. Fort Lowell, Suite 106, Tucson, Arizona, 85719 USA
Published by arrangement with John Wiley & Sons

Martian meteorites are rare; therefore, the discovery of new meteorites has the potential to significantly expand our current understanding of Mars. In this study, we describe four new shergottites, all found within the past 5 yr, in Northwest Africa (NWA): NWA 10441, NWA 10818, NWA 11043, and NWA 12335. To determine the geochemical and mineralogical composition of these new shergottites, a number of traditional and nontraditional analytical techniques were utilized, such as high-resolution X-ray computed tomography (for 3-D modal abundance determination) and electron backscattered diffraction (for identification of shock features). This enabled a comprehensive, nondestructive investigation of the in situ and bulk characteristics of these meteorites. From the results, we confirm the preliminary classifications of NWA 10441 and NWA 12335 as basaltic (diabasic), and NWA 10818 and NWA 11043 as poikilitic, shergottites. Chondrite-normalized rare earth element (REE) patterns of shergottites distinguish likely source reservoirs in the Martian mantle. NWA 10441 and NWA 12335 have bulk enriched REE patterns. NWA 10818 has an intermediate REE pattern, being slightly depleted in the light REE. Although published data for bulk rock REE in NWA 11043 indicate an enriched pattern, here we show that targeted in situ analyses of unaltered minerals reveal an intermediate REE pattern, suggesting that terrestrial weathering combined with shock processes experienced by these meteorites on ejection may affect the bulk analysis. Extensive fracturing in NWA 11043 likely acted as conduits for terrestrial alteration products. We suggest that in situ spot checking of REE in meteorites will constrain any weathering effect on the REE pattern of the bulk rock.

¹V. E. Di Cecco,^1,2B. C. Hyde,¹K. T. Tait,¹R. I. Nicklin
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13824]
¹Department of Natural History – Mineralogy, Royal Ontario Museum, Toronto, Ontario, M5S 2C6 Canada
²Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario, K7L 2N8 Canada
Published by arrangement with John Wiley & Sons

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.

¹Victoria E.Hamilton,²Hannah H.Kaplan,^3,4Harold C.ConnollyJr,⁵Cyrena A.Goodrich,⁶Neyda M.Abreu,²Amy A.Simon
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115054]
¹Southwest Research Institute, Boulder, CO, United States of America
²NASA Goddard SpaceFlight Center, Greenbelt, MD, United States of America
³Rowan University, Glassboro, NJ, United States of America
⁴American Museum of Natural History, New York, NY, United States of America
⁵Lunar and Planetary Institute, USRA, Houston, TX, United States of America
⁶NASA Langley Research Center, Hampton, VA, United States of America
Copyright Elsevier

Orbital spectra collected of asteroid (101955) Bennu by NASA’s Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS–REx) spacecraft have identified ungrouped C, CI, and CM meteorites having petrologic types 1, 1/2, and 2 as the best mineralogical analogues to Bennu to date. Here we present spectral evidence that Grosvenor Mountains (GRO) 95,577, a CR1, is a better analogue for Bennu’s bulk surface mineralogy. CR-like parent bodies are targets of interest because they contain some of the most pristine materials from the solar nebula and can contain substantial amounts of H2O and OH− in addition to exotic organics. Unfortunately, terrestrial weathering makes constraining their indigenous mineralogy and organics challenging. Analysis of samples retrieved directly from an asteroid would help us disentangle the effects of terrestrial weathering and asteroidal aqueous alteration and hence whether some of the exotic organics and large populations of presolar grains were affected by terrestrial processes in meteorites. If Bennu is comprised of CR1(−like) material, in whole or in part, the OSIRIS–REx returned sample represents a tremendous opportunity to explore in depth what is currently a unique material among carbonaceous chondrites.

¹M.Fastelli,¹P.Comodi,²B.Schmitt,²P.Beck,²O.Poch,³P.Sassi,¹A.Zucchini
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115055]
¹Department of Physics and Geology, University of Perugia, I-06123 Perugia, Italy
²Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di sotto 8, 06123 Perugia, Italy
Copyright Elsevier

It has been proposed that ammonium-bearing minerals are present in a varying amount in icy planetary bodies. Their observation at the surface of large objects was related to the upwelling and cryovolcanism of ammoniated water from possible subsurface oceans forming ammonium-bearing minerals (NH₄⁺) mixed with ice at the surface. We analyzed the temperature evolution of the near-infrared spectra of a selected number of anhydrous and hydrated ammonium-bearing minerals containing different anions and water content. Reflectance spectra were collected in the 1–4.8 μm spectral range at cryogenic temperatures ranging from 293 K to ~65 K and the effect of sample’s grain size between 32 and 150 μm was also investigated at room temperature. Reflectance spectra of anhydrous samples show well-defined absorption bands in the 1–2.5 μm range. The bands located at ~1.06, 1.3, 1.56, 2.02, and 2.2 μm could be useful to discriminate these salts and their characteristics are examined in detail in this work. On the other hand, the reflectance spectra of water-rich samples show H₂O fundamental absorption bands strongly overlapping the NH₄⁺ bands, thus dominating the spectra from 1 to 2.8 μm and fully saturating above 2.8 μm. The position of the absorption bands changes with temperature and grain size, shifting to higher frequencies as temperature decreases. The low-temperature spectra also reveal a fine structure compared to the room temperature ones and display narrower and more defined absorption bands. Granulometry mainly affects the band depth and band area parameters. Moreover, mascagnite, salammoniac, ammonium phosphate, tschermigite, and ammonium nitrate are subjected to a reversible low-temperature phase transition, which is manifested in the spectra by a progressive growth and shift of the bands towards shorter wavelengths with an abrupt change in their depth. This new set of spectra at cryogenic temperatures can be directly compared with remote sensing data to detect the presence of ammonium-bearing minerals on the surface of icy bodies. Their identification can impact our knowledge of the internal composition and dynamics of these bodies as well as their potential habitability.

¹Patrick M. Shober et al. (>10)
Meteoritics & Plantetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13813]
¹Space Science & Technology Centre, School of Earth and Planetary Sciences, Curtin University, Bentley, Western Australia, 6102 Australia
Published by arrangement with John Wiley & Sons

On June 1, 2019, just before 7:30 p.m. local time, the Desert Fireball Network (DFN) detected a −9.3 magnitude fireball over South Australia near the Western Australia border. The event was observed by six fireball observatories, and lasted for 5 s. One station was nearly directly underneath the trajectory, greatly constraining the trajectory solution. This trajectory’s backward numerical integrations indicate that the object originated from the outer main belt with a semimajor axis of 2.75 au. A light curve was also extracted and showed that the body experienced very little fragmentation during its atmospheric passage. A search campaign was conducted with several DFN team members and other volunteers. One 42 g fragment was recovered within the predicted fall area based on the dark flight model. Based on measurements of short-lived radionuclides, the fragment was confirmed to be a fresh fall. The meteorite, Arpu Kuilpu, has been classified as an H5 ordinary chondrite. This marks the fifth fall recovered in Australia by the DFN, and the smallest meteoroid (≃2 kg) to ever survive entry and be recovered as a meteorite.

¹Chelsea D.Willett,¹William S.Cassata,¹Naomi E.Marks
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.04.017]
¹Nuclear and Chemical Science Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA
Copyright Elsevier

Novel analytical approaches to determining the trapped 38Ar/36Ar ratio of gases contained within Martian meteorites are presented and applied to the Martian regolith breccia Northwest Africa (NWA) 7034 and paired stone NWA 11220. The resulting data indicate that extensive mass-dependent fractionation of atmospheric Ar may have occurred within 150 million years of planetary formation, ostensibly as a result of diffusion-limited hydrodynamic escape. The inferred fractional loss of Ar and lighter atmospheric constituents exceeds 50%. These data suggest that volatiles derived from planetary outgassing and/or impactors may dominate the present abundance of atmospheric Ar.

¹Tamara E. Koch,¹Dominik Spahr,¹Beverley J. Tkalcec,²Oliver Christ,¹Philomena-Theresa Genzel,¹Miles Lindner,¹David Merges,³Fabian Wilde,¹Björn Winkler,^1,4Frank E. Brenker
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13815]
¹Institute of Geosciences, Goethe University Frankfurt, Altenhoeferallee 1, 60438 Frankfurt am Main, Germany
²Department of Geoscience, University of Padua, Via Gradenigo 6, 35131 Padua, Italy
³Helmholtz-Zentrum Hereon, Max-Planck Strasse 1, 21502 Geesthacht, Germany
⁴Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, 1680 East-West Road, Honolulu, Hawaii, 96822 USA
Published arrangement with John Wiley & Sons

In order to gain further insights into early solar system aggregation processes, we carried out an experiment on board the International Space Station, which allowed us to study the behavior of dust particles exposed to electric arc discharges under long-term microgravity. The experiment led to the formation of robust, elongated, fluffy aggregates, which were studied by scanning electron microscopy, electron backscatter diffraction, and synchrotron micro-computed tomography. The morphologies of these aggregates strongly resemble the typical shapes of fractal fluffy-type calcium-aluminum-rich inclusions (CAIs). We conclude that a small amount of melting could have supplied the required stability for such fractal structures to have survived transportation and aggregation to and compaction within planetesimals. Other aggregates produced in our experiment have a massy morphology and contain relict grains, likely resulting from the collision of grains with different degrees of melting, also observed in some natural CAIs. Some particles are surrounded by igneous rims, which remind in thickness and crystal orientation of Wark–Lovering rims; another aggregate shows similarities to disk-shaped CAIs. These results imply that a (flash-)heating event with subsequent aggregation could have been involved in the formation of different morphological CAI characteristics.

¹Svetlana N. Teplyakova,¹Cyril A. Lorenz,¹Marina A. Ivanova,²Munir Humayun,¹Nataliya N. Kononkova,³Sergey E. Borisovsky,¹Alexander V. Korochantsev,⁴Ian A. Franchi,⁵Nina G. Zinovieva
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13814]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, 119991 Russia
²National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, Florida, 32310 USA
³Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry RAS, Staromonetnyi per, 35, Moscow, 119017 Russia
⁴Planetary and Space Sciences Research Institute, Open University, Milton Keynes, MK7 6AA UK
⁵Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991 Russia
Published by arrangement with John Wiley & Sons

Karavannoe is a pallasite found in Russia in 2010. The mineralogy, chemistry, and oxygen isotopic composition indicate that Karavannoe is a member of the Eagle Station Pallasite (ESP) group. Karavannoe contains mostly olivine and subdued interstitial Fe,Ni-metal. Zoned distribution of FeO in small, rounded grains of olivine and FeO and Al2O3 in chromite shows that the cooling rate of the melt was fast during the crystallization of the round olivine grains. Siderophile element distribution and correlations of Au-As and Os-Ir concentrations in Karavannoe and the other ESP metal record its magmatic origin. FeO-rich composition of olivine, low W and Ga, and high Ni abundances in the Karavannoe metal indicate the formation of the metal from an oxidized chondrite precursor. Model calculations demonstrate that the ESPs’ metal compositions correspond to the solids of the fractional crystallization of CV- or CO-chondrite-derived metallic liquids. The Karavannoe metal composition corresponds to the solid fraction crystallized after ~40% fractional crystallization. The Mg/(Mg+Fe) atom ratio of complementary silicate liquid corresponds to Fo70, possibly indicating that the olivine is not in equilibrium with the metal and could have been a product of the late evolutionary processes in the Karavannoe parent body mantle. In any ESP genesis Karavannoe was not in equilibrium with its metal and is a product of mantle differentiation processes. Olivine of Karavannoe and ESPs is similar in composition, while the metal is different. We propose a model of ESP formation involving an impact-induced intrusion of liquid core metal into a basal mantle layer, followed by fractional crystallization of the metal. The metal textures and chemical zoning of Karavannoe minerals point to remelting and rapid cooling due to a later impact event.

¹Yang He,¹Xiao-Wen Liu,¹Ai-Cheng Zhang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13817]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 China
Published by arrangemnt with John Wiley & Sons

In this study, we report the petrography and mineralogy of a brecciated eucrite Northwest Africa (NWA) 8021, which shows a locally layered texture with one layer containing graphic clasts and Si,Ti-rich regions. The graphic clasts contain rod-like grains of silica phases, augite, K-feldspar, and Ca-phosphate minerals included in anorthite. Some of the clasts contain relatively coarse grains of quartz, K-feldspar, and augite, which are chemically different from the rod-like phases, indicating different origins. All of the augite grains in the graphic clasts have rare earth element (REE) concentrations higher than those in typical eucrites. The bulk Na2O+K2O contents of the graphic clasts are higher than typical eucrites. All of these chemical features indicate that the graphic clasts were probably derived from an evolved parent rock. Low-degree partial melting of the eucritic crust (<10%) is required to generate a melt equilibrated with the REE-rich rod-like pyroxene from the graphic clasts. The Si,Ti-rich regions contain high abundances of silica phases (~52 vol%) and ilmenite (~9 vol%), probably derived from an evolved Si,Ti-rich rock (dacite). The evolved components observed in NWA 8021 are different from other evolved components observed in howardites and indicate more diverse evolution in the eucrite parent body than previously thought.