¹A.N.Nguyen,¹K.Nakamura-Messenger,¹L.P.Keller,¹S.Messenger
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.09.005]
¹Astromaterials Research and Exploration Science, NASA Johnson Space Center, 2101 NASA Parkway, Houston, TX 77058, USA
Copyright Elsevier

A coordinated TEM and NanoSIMS isotopic imaging study of microtome sections of three anhydrous interplanetary dust particles (IDPs) revealed a diverse collection of primitive materials having disparate origins and histories. Presolar silicate grains that likely originated in asymptotic giant branch (AGB) stars were present in each IDP at abundances ranging from 140 (+320/-120) ppm to 2000 (+4600/-1700) ppm. A unique compound presolar grain was identified that consisted of a crystalline spinel core and amorphous silicate mantle having heterogeneous Fe content. This compound grain traces the changing conditions in the circumstellar region during condensation and is the first identified presolar spinel in an IDP. A presolar SiC grain, also rare in IDPs, was found to be enriched in 13C, 14N, and 28Si, consistent with mainstream SiC that originated in ∼solar metallicity AGB stars. We determine presolar spinel and presolar SiC abundances of 760 (+1700/-630) ppm and 190 (+440/-160) ppm, respectively, in the individual IDPs.

Two elongate whisker-like enstatite grains and one platy enstatite were found to have near-terrestrial O isotopic compositions (δ18O = -17 – 18 ‰) and show chemical evidence of equilibrium condensation from a high temperature gas. Two highly 16O-rich silicates with near-solar O isotopic compositions (δ18O = -79 ‰ and -83 ‰) were also identified and may represent the primordial dust reservoir. These silicates were crystalline equilibrated aggregates. The wide range of isotopic compositions observed in these silicate grains suggests they condensed from isotopically diverse reservoirs in the protoplanetary disk in different locations and/or times. The 16O-rich grains likely condensed in the inner solar system and were subsequently transported to the outer solar system, while grains having terrestrial O isotopic compositions likely condensed from the gas phase in the terrestrial planet forming region or beyond.

The IDPs showed bulk 15N enrichments (δ15N = 15 – 129 ‰) and contained 15N-rich hotspots up to 1150 ‰, consistent with the presence of molecular cloud material. IDPs U2015D21 and W7013E17 had bulk O isotopic compositions that were offset from the carbonaceous chondrite anhydrous minerals line by ∼10 ‰ to more 17O-rich compositions. This 17O enrichment cannot be explained by the observed abundance of 17O-rich presolar grains in these particles and the source remains unknown. IDP W7027E6 had an unusual isotopically heavy bulk O isotopic composition (δ17,18O = 39 ‰, Δ17O = 19 ‰). W7027E6 lacked hydrous phases and was therefore not likely altered by isotopically heavy primordial water. We propose that the high temperature mineral assemblage in W7027E6 condensed in the inner solar system from an 16O-poor reservoir that existed prior to O isotope homogenization in the early nebula and was subsequently transported to the outer solar system.

¹C. C. Zurkowski,¹J. Yang,¹S. Chariton,²V. B. Prakapenka,¹Y. Fei
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2022JE007344]
¹Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
²Center for Advanced Radiation Sources, The University of Chicago, Lemont, IL, USA
Published by arrangement with John Wiley & Sons

Super-Earths ranging up to 10 Earth masses (ME) with Earth-like density are common among the observed exoplanets thus far, but their measured masses and radii do not uniquely elucidate their internal structure. Exploring the phase transitions in the Mg-silicates that define the mantle-structure of super-Earths is critical to characterizing their interiors, yet the relevant terapascal conditions are experimentally challenging for direct structural analysis. Here we investigated the crystal chemistry of Fe3O4 as a low-pressure analog to Mg2SiO4 between 45–115 GPa and up to 3000 K using powder and single crystal X-ray diffraction in the laser-heated diamond anvil cell. Between 60–115 GPa and above 2000 K, Fe3O4 adopts an 8-fold coordinated Th3P4-type structure (I-43d, Z = 4) with disordered Fe2+ and Fe3+ into one metal site. This Fe-oxide phase is isostructural with that predicted for Mg2SiO4 above 500 GPa in super-Earth mantles and suggests that Mg2SiO4 can incorporate both ferric and ferrous iron at these conditions. The pressure-volume behavior observed in this 8-fold coordinated Fe3O4 indicates a maximum 4% density increase across the 6- to 8-fold coordination transition in the analog Mg-silicate. Reassessment of the FeO—Fe3O4 fugacity buffer considering the Fe3O4 phase relationships identified in this study reveals that increasing pressure and temperature to 120 GPa and 3000 K in Earth and planetary mantles drives iron toward oxidation.

¹S. Gwizd et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2022JE007280]
¹Department of Earth and Planetary Sciences, University of Tennessee at Knoxville, Knoxville, TN, USA
Published by arrangement with John Wiley & Sons

This study utilizes instruments from the Curiosity rover payload to develop an integrated paleoenvironmental and compositional reconstruction for the 65-m thick interval of stratigraphy comprising the Hartmann’s Valley and Karasburg members of the Murray formation, Gale crater, Mars. The stratigraphy consists of cross-stratified sandstone (Facies 1), planar-laminated sandstone (Facies 2), and planar-laminated mudstone (Facies 3). Facies 1 is composed of sandstone showing truncated sets of concave-curvilinear laminae stacked into cosets. Sets are estimated to be meter-to sub-meter-scale, consistent with low-height dunes. Thin stratigraphic intervals of Facies 1 and stacking patterns with Facies 2 and 3 support a wet aeolian dune interpretation. Meter-thick packages of planar-laminated sandstone (Facies 2) are interpreted to represent interfingering dune-interdune strata. Facies 3 consists of meter-thick packages of planar-laminated mudstone interpreted to represent lacustrine deposition with persistent standing water. Integration of geochemistry with each facies reveals some compositional control based on the depositional process. Models for source rock composition from Alpha Particle X-Ray Spectrometer measurements show that facies derived from a basaltic source. Alteration indices and geochemical trends provide evidence that moderate chemical weathering occurred before compositional changes due to diagenesis. Differences in wt% FeO(T) and TiO2 between facies are minimal, though trends point to sediment sorting in transport. Comparisons to terrestrial basaltic sedimentary systems indicate that the Hartmann’s Valley and Karasburg facies reflect deposition in an environment where diverse subaqueous and subaerial facies persisted adjacent to a long-lived body of water.

¹Bojun Jia,^1,2,3Wenzhe Fa,¹Mingwei Zhang,⁴Kaichang Di,⁵Minggang Xie,¹Yushan Tai,^7,3Yang Li
Earth and Planetary Science Letters 596, 117791 Link to Article [https://doi.org/10.1016/j.epsl.2022.117791]
¹Institute of Remote Sensing and Geographical Information System, School of Earth and Space Sciences, Peking University, Beijing, China
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
³Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
⁴State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, China, Beijing, China
⁵College of Science, Guilin University of Technology, Guilin, China
⁶Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Copyright Elsevier

China’s Chang’E-5 (CE-5) mission has collected 1.731 kg samples from a young mare basalt unit (named P58/EM4) in the northeastern Oceanus Procellarum region of the Moon. Accurate tracing of the provenance of returned samples is essential for understanding their laboratory measurements, which can provide critical information about the Moon and the inner Solar System. In this article, the provenance, chemical composition, formation, and evolution processes of the regolith at the CE-5 landing site are analyzed by using remote sensing observations and crater ejecta deposition models. A comprehensive search based on crater ejecta thickness model shows that 1892 impact craters in P58 likely deposited ∼0.56 m of primary ejecta at the landing site, whereas 4 impact craters outside P58 deposited 0.05 m of distal ejecta that further excavated and reworked ∼0.5 m thick local mare basalt. Twelve craters within 1 km from the CE-5 landing site are estimated to contribute ∼0.49 m (~88%) of the ejecta materials, and their ejecta source regions are investigated using the Maxwell Z model. Among these 12 craters, Xu Guangqi and a smaller crater near the landing site are the two most volumetrically significant contributors (~0.3 m and ∼0.12 m). Craters more than 1 km distant from the landing site deposited fewer exotic materials, but some of them could have delivered low-Ti materials to the sampling site. Finally, the regolith stratigraphy at the landing site is investigated based on the identified and assumed impact sequence by using a Monte Carlo-based ejecta ballistic sedimentation model. The results reveal a depth-varying FeO/TiO2 abundance profile at the landing site, suggesting that the sedimentation of distant ejecta can reduce FeO/TiO2 abundance of the underlying layer by ∼1 wt.% at ∼0.5 m depth. Our results provide key information on sample provenance and regolith stratigraphy of the landing site, which is crucial to deciphering the returned CE-5 samples.

¹Xiaohui Fu,¹Chengxiang Yin,²Bradley L.Jolliff,¹Jiang Zhang,¹Jian Chen,¹Zongcheng Ling,¹Feng Zhang,³Yang Liu,³Yongliao Zou
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115254]
¹Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Institute of Space Sciences, Shandong University, Weihai, Shandong, China
²Department of Earth and Planetary Sciences and The McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO, USA
³State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
Copyright Elsevier

Chang’E-5 (CE-5) mission returned 1731 g of lunar soil from northeastern Oceanus Procellarum. This study begins by comparing the mineralogy and geochemistry of CE-5 soil with Apollo and Luna soils. CE-5 soil shares similar mineral components with Apollo mare soils. Geochemically, CE-5 soil is characterized by high-FeO, intermediate-TiO2, and elevated incompatible elements. The new returned CE-5 soil represents a unique type of mare soil that expands the diversity of returned lunar samples. Its bulk chemical compositions suggest that CE-5 soil consists of pulverized local mare basalt. Nonmare materials are thought to be negligible while meteoroid contamination is <1%. CE-5 soil provides an additional iron-rich basaltic end-member composition and extends the chemical ranges of the existing calibration soils for lunar remote sensing. CE-5 soil, together with the landing site, can serve as new ground truth both in mineralogy and geochemistry. Based on bulk chemical data of CE-5 soils and pyroxene compositions of CE-5 mare basalt clasts, we infer that CE-5 mare basalt has a fractional crystallization history similar to the Apollo high-Ti basalts. These CE-5 mare basalt clasts analyzed in recent studies, possibly derive from a single lava flow that experienced strong fractional crystallization.

¹Laura M.Barge,¹Erika Flores,¹Jessica M.Weber,¹Abigail A.Fraeman,^1,2Yuk L.Yung,³David VanderVelde,⁴Eduardo Martinez,¹Amalia Castonguay,¹Keith Billings,⁴Marc M.Baum
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.08.038]
¹NASA Jet Propulsion Laboratory, California Institute of Technology
²Division of Geological and Planetary Sciences, California Institute of Technology
³Department of Chemistry, California Institute of Technology
⁴Department of Chemistry, Oak Crest Institute of Science
Copyright Elsevier

Iron minerals are highly reactive drivers of abiotic / prebiotic organic chemistry, and in the presence of ammonia (NH3/NH4+) or other reduced nitrogen (N) compounds, have been shown to promote amino acid synthesis from organic precursors. On early Mars, oxidized nitrogen species (NOx-) such as NO3- and/or NO2- may have been present, which could be reduced by Fe(II) to form various species including N2O and/or NH3/NH4+. The production of NH3/NH4+ from Fe(II)-driven NO3- or NO2- reduction may be able to feed into prebiotic organic reactions including amino acid formation. In this study, we tested whether iron mineral-driven reduction of NO3- or NO2- could provide a source of NH3/NH4+ to form amino acids from two prebiotically relevant precursors (pyruvate and glyoxylate); or, whether an exogeneous source of NH3/NH4+ would be required. We observed that pyruvate and glyoxylate reacted with Fe-oxyhydroxide minerals in NOx–containing experiments to form reduced hydroxy acid products; and in experiments containing only NH3/NH4+, amino acids were also formed. However, significant amino acid formation was not observed in any experiments containing NO3- or NO2- unless sufficient NH4+ was also added; furthermore, colorimetric analysis did not show any generation of NH4+ from NO3- / NO2- reduction at these conditions. NO2- was observed to be highly reactive with Fe2+ and Fe(II)-bearing minerals, resulting in Fe oxidation during mineral precipitation and the formation of oxidized mineral phases (hematite). The Fe(II)/Fe(III) ratio in oxyhydroxide minerals is an important parameter for determining organic product distributions from pyruvate and glyoxylate; therefore, Fe-mediated NOx- reduction does impact organic chemistry. However, amino acid formation, at least under these conditions, would also require an exogenous source of NH3/NH4+ or other reduced N species. These results have implications for organic-N chemistry on early Mars, as well as for some early Earth origin of life scenarios regarding organic synthesis in mineral-containing systems.

^1,2Bing Yang,¹Jiuxing Xiad,^1,2Xuan Guo,^1,Huaiwei Ni,³Anat Shahar,³Yingwei Fei,³Richard W.Carlson,^1,2Liping Qin
Earth and Planetary Science Letters 595, 117701 Link to Article [https://doi.org/10.1016/j.epsl.2022.117701]
¹CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
²CAS Center for Excellence in Comparative Planetology, China
³Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
⁴Institute of Geology and Geophysics, School of Earth Sciences, Zhejiang University, Hangzhou, Zhejiang 310027, China
Copyright Elsevier

Core formation may modify the stable isotopic signatures for both the mantles and cores of differentiated planetary bodies. We performed high P-T experiments with a piston-cylinder apparatus at 1 GPa and 1873-2073 K to determine the Cr isotopic fractionation factor during metal-silicate segregation. Experimental results consistently indicate that the metal phase is isotopically heavier than the coexisting silicate phase, with Cr_{metal-silicate} up to 0.3‰ at the investigated experimental conditions. Oxygen fugacity, silicate composition, and S content in the metal phase do not have significant effects on the Cr isotopic fractionation factor. By contrast, increasing Ni content in the metal increases the Cr_{metal-silicate} value, implying that the Ni content of the core could influence planetary isotopic signatures. We conclude that heavier Cr isotopes enter the core preferentially during planetary core formation. The Cr value of the terrestrial mantle could be lowered by up to ∼0.02‰ by core formation, despite that this is within current analytical uncertainty of chondritic Cr isotopic composition. For smaller bodies such as the Moon, Mars, and Vesta, the lower core formation temperatures could potentially generate a resolvable core-mantle Cr isotopic fractionation. However, the Moon’s small core size would limit the change in the Cr isotopic composition of the lunar mantle compared to chondritic. For Vesta and Mars, core formation could lower the Cr values of their mantles by ∼0.01-0.02‰, which is trivial relative to the analytical uncertainty. On the other hand, core formation could increase the Cr values of the cores of the parent bodies of iron meteorites by up to ∼0.2‰ at 1873 K. Therefore, the significantly heavy Cr isotopic composition (up to 2.85‰) of iron meteorites cannot be explained by equilibrium fractionation between the core and the mantle of the parent bodies of iron meteorites.

^1,2Jan Render,^1,2Gregory A.Brenneck,¹Christoph Burkhardt,^1,3Thorsten Kleine
Earth and Planetary Science Letters 595, 117748 Link to Article [https://doi.org/10.1016/j.epsl.2022.117748]
¹Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, Münster, 48149 Germany
²Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA, USA
³Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
Copyright Elsevier

Nucleosynthetic isotope signatures in meteorites provide key insights into the structure and dynamics of the solar protoplanetary disk and the accretion history of the planets. We present high-precision Zr isotopic data of a comprehensive suite of non-carbonaceous (NC) and carbonaceous (CC) meteorites, and find that various meteorite groups, including enstatite chondrites, exhibit ⁹⁶Zr enrichments, whereas there is no resolved ⁹¹Zr and ⁹²Zr variability. These new Zr isotope data reveal the same fundamental NC-CC dichotomy observed for several other elements, where CC meteorites are more anomalous compared to NC meteorites and are shifted towards the isotopic composition of Ca-Al-rich inclusions (CAIs). For Zr and other elements, the CC composition is reproduced as a mixture of materials with CAI-like and NC-like isotopic compositions in approximately constant proportions, despite these elements exhibiting disparate nucleosynthetic origins or different cosmo- and geochemical behaviors. These constant mixing proportions are inconsistent with an origin of the dichotomy by thermal processing or selective dust-sorting in the disk but indicate mixing of isotopically distinct materials with broadly solar chemical compositions. This corroborates models in which the NC-CC dichotomy reflects time-varied infall from an isotopically heterogeneous molecular cloud. Among NC meteorites, the isotope anomalies in Zr are linearly correlated with those of other elements, which likewise reflects primordial mixing. Lastly, the new Zr isotope data reinforce the notion that Earth incorporated s-process enriched material from the innermost Solar System, which is not represented by known meteorites. By contrast, contributions to Earth and Mars from outer Solar System CC-like materials were limited, indicating that these planets did not form by pebble accretion, which would have led to high CC fractions.

¹A.-M.Seydoux-Guillaume,²T.de Resseguier,³G.Montagnac,⁴S.Reynaud,⁵H.Leroux,³B.Reynard,⁶A.J.Cavosie
Earth and Planetary Science Letters 595, 117727 Link to Article [https://doi.org/10.1016/j.epsl.2022.117727]
¹Univ Lyon, UJM, UCBL, ENSL, CNRS, LGL-TPE, F-42023 Saint Etienne, France
²PPRIME, CNRS-ENSMA-Université de Poitiers, 1 avenue Clément Ader, 86961 Futuroscope, France
³Univ Lyon, ENSL, UCBL, UJM, CNRS, LGL-TPE, F-69007 Lyon, France
⁴Université de Lyon, UJM-Saint-Etienne, CNRS, Institut d’Optique Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023 Saint-Etienne, France
⁵Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 – UMET – Unité Matériaux et Transformations, F-59000 Lille, France
⁶The Space Science and Technology Centre (SSTC) and the Institute for Geoscience Research (TIGeR), School of Earth and Planetary Science, Curtin University, Perth, WA 6102, Australia
Copyright Elsevier

Impact-related damage in minerals and rocks provides key evidence to identify impact structures, and deformation of U-Th-minerals in target rocks, such as monazite, makes possible precise dating and determination of pressure-temperature conditions for impact events. Here a laser-driven shock experiment using a high-energy laser pulse of ns-order duration was carried out on a natural monazite crystal to compare experimentally produced shock-deformation microstructures with those observed in naturally shocked monazite. Deformation microstructures from regions that may have experienced up to ∼50 GPa and 1000 °C were characterized using Raman spectroscopy and transmission electron microscopy. Experimental results were compared with nanoscale observations of deformation microstructures found in naturally shocked monazite from the Vredefort impact structure (South Africa). Raman-band broadening observed between unshocked and shocked monazite, responsible for a variation of ∼3 cm−1 in the FWHM, is interpreted to result from the competition between shock-induced distortion of the lattice, and post-shock annealing. At nanoscale, three main plastic deformation structures were found in both naturally and experimentally shocked monazite: deformation twins, mosaïcism, and deformation bands. The element Ca is enriched along host-twin boundaries, which further confirms that the laser shock loading experiment produced both comparable styles of crystal-plastic deformation, and also localized element mobility, as that found in natural shock-deformed monazite. Deformation twins form in the experiment were only along the (001) plane, an orientation which is not considered diagnostic of shock deformation. However, both mosaïcism and deformation, expressed in SAED patterns as streaking of spots, and the presence of extra spots (more or less pronounced), are interpreted as unambiguous nano-scale signatures of shock metamorphism in monazite. Experimentally calibrated deformation features, such as those documented here at TEM-scale, provide new tools for identifying evidence of shock deformation in natural samples.

¹Maryjo Brounce,²Jeremy W.Boyce,²Francis M.McCubbin
Earth and Planetary Science Letters 595, 117784 Link to Article [https://doi.org/10.1016/j.epsl.2022.117784]
¹Department of Earth and Planetary Sciences, University of California Riverside, Riverside, CA 92521, USA
²Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, TX 77058, USA
Copyright Elsevier

Estimates of the oxygen fugacity (fO2) recorded by the Martian nakhlite meteorites from direct observations of the main igneous phenocryst assemblages range from values similar to that recorded by the quartz-fayalite-magnetite oxygen buffer to ∼two orders of magnitude lower. Inferences of changes in fO2 during the late stages of crystallization, volcanic degassing, and emplacement of the nakhlite cumulate pile have been made based on variable sulfide and apatite chemistry. We present S-XANES measurements of the oxidation state of sulfur in apatite and associated mesostasis glass in Nakhla to place direct constraints on the magnitude of changes in fO2 experienced by the Nakhla portion of the nakhlite cumulate pile during apatite crystallization. Nakhla apatites range from containing dominantly S2− to containing dominantly S6+. This, together with correlations between S2−, Cl, and FeO in the mesostasis glass near these apatites, suggest that our measurements capture directly the oxidation of the interstitial late-stage Nakhla magmas as the result of Cl-saturation and degassing. As the result of this degassing, at least part of the nakhlite cumulate pile experienced an increase in fO2 of ∼1.5–2.5 orders of magnitude during apatite crystallization and final mesostasis cooling. Based on these measurements, the sulfur oxidation states of apatites in the other nakhlite meteorites are predicted to range from exclusively S2−-bearing to exclusively S6+-bearing.