^{1,2 3}M.Millan et al. (>10)
Joournal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007107]
¹Department of Biology, Georgetown University, Washington, DC, USA
²NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD, USA
³Laboratoire Atmosphère, Observations Spatiales (LATMOS), LATMOS/IPSL, UVSQ Université Paris-Saclay, Sorbonne Université, CNRS, Guyancourt, France
Published by arrangement with John Wiley & Sons

The Sample Analysis at Mars (SAM) suite instrument on board NASA’s Curiosity rover has characterized the inorganic and organic chemical composition of seven samples from the Glen Torridon clay-bearing unit. A variety of organic molecules were detected with SAM using pyrolysis (up to ∼850°C) and wet chemistry experiments coupled with evolved gas analysis (EGA) and gas chromatography-mass spectrometry (GCMS). SAM EGA and GCMS analyses revealed a greater diversity and abundance of sulfur-bearing aliphatic and aromatic organic compounds in the sediments of this Gale crater unit than earlier in the mission. We also report the detection of nitrogen-containing, oxygen-containing, and chlorine-containing molecules, as well as polycyclic aromatic hydrocarbons found in Glen Torridon (GT), although the sources of some of these organics may be related to the presence of chemical reagents in the SAM instrument background. However, sulfur-bearing organics released at high temperature (>600°C) are likely derived from martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources and consistent with the presence of recalcitrant organic materials in the sample. The SAM measurements of the GT clay-bearing unit expand the inventory of organic matter present in Gale crater and is also consistent with the hypothesis that clay minerals played an important role in the preservation of ancient refractory organic matter on Mars. These findings deepen our understanding of the past habitability and biological potential of Gale crater.

¹G. Schmidt,²E. Luzzi,²A.P. Rossi,³M. Pondrelli,¹A. Apuzzo,¹F. Salvini
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2022JE007320]
¹Department of Science, Università degli studi Roma Tre, Rome, Italy
²Department of Physics and Earth Sciences, Jacobs University Bremen, Bremen, Germany
³International Research School of Planetary Sciences, Università d’Annunzio, Pescara, Italy
Published by arrangement with John Wiley & Sons

The formation of layered mounds on Mars remains a major topic of debate, with the relationship between their deposition and chemical alteration a major aspect still to be constrained. The association these deposits have with hydrated minerals indicates aqueous processes were active in their past, however the extent and duration of this aqueous period has yet to be fully realized. We studied compositional, stratigraphical, and structural characteristics of two separate layered deposits within Becquerel crater, Arabia Terra, to constrain their origins and the intensity of past aqueous activity. We find that due to key differences in composition, layering, and deformation between the two deposits, the timing of important depositional changes within Becquerel can be identified. We propose a scenario involving differences in fluid expulsion intensity and water level between the two layered deposits, in which diverse depositional and post-depositional environments were able to form. Furthermore, internal collapsing and deformation of the main mound might reflect that fluid upwelling persisted below the mound after formation. Determining the relationship between these two deposits is an important step in unraveling the past climate of Arabia Terra, and more broadly Mars. The evidence of protracted fluid expulsion represents a unique opportunity for future missions searching for signs of past life.

¹Yazhou Yang,²Te Jiang,¹Yang Liu,¹Yuchen Xu,^2,3Hao Zhang,⁴Heng-Ci Tian,⁴Wei Yang,¹Yongliao Zou
Journal of Geophysical Research (Planets)(In Press) Link to Article [https://doi.org/10.1029/2022JE007453]
¹State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, China
²Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, China
³CAS Center for Excellence in Comparative Planetology, Hefei, China
⁴Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

The Chang’e-5 (CE-5) mission has successfully returned samples from a site that is much younger than the sites of all previous lunar sampling missions. Sample analysis results reported so far have revealed a more complex sampling area than previously thought, casting uncertainties over the interpretation of remote sensing spectral data and the U and Th abundance derived from the orbital data. Laboratory spectral measurement of the returned samples can serve as validation of remote sensing observations and thus help refine our understanding of the geological evolution of the landing region. In this study we report detailed micro mid-infrared (MIR) spectral characteristics of individual soil grains of CE-5 samples. The spectral analysis results show that the CE-5 olivine grains have low Fo (molar Mg/[Mg + Fe] × 100) consistent with previous studies, indicating a Fe-rich source region of the mantle or a highly evolved magma. These olivine grains show high level of crystallinity, implying low degree of space weathering. Most of the CE-5 glasses analyzed are spectrally consistent with mare impact glasses, despite that a few of them may have a volcanic origin. These laboratory spectral analysis of CE-5 samples in the MIR wavelengths at a micro scale, together with the derived MIR optical constants of the olivine, pyroxene, plagioclase, and glass grains, provide important input for the modeling and interpretation of thermal remote sensing data of the Moon.

¹A.Rudolph et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2021JE007098]
¹Purdue University, West Lafayette, United States
Published by arrangement with John Wiley & Sons

Glen Torridon (GT) is a recessive-trough feature on the northwestern slope of “Mt. Sharp” in Gale crater, Mars with the highest Fe-/Mg-phyllosilicates abundances detected by the Curiosity rover to date. Understanding the origin of these clay minerals and their relationship with diagenetic processes is critical for reconstructing the nature and habitability of past surface and subsurface environments in Gale crater. We aim to constrain the distribution and extent of diagenesis using compositional and morphological trends observed by visible-to-near infrared reflectance spectra in GT from Mastcam and ChemCam, supported by high-resolution images from the Mars Hand Lens Imager. Spectral features consistent with nontronite and fine-grained red hematite are ubiquitous throughout lower GT, and are strongest where diagenetic features are limited, suggesting that both were formed early, before burial. Diagenetic features increase in both abundance and diversity farther up-section, and we observe morphologic evidence for multiple episodes of diagenesis, with the edge of a diagenetic front partially preserved in the middle stratigraphic member, Knockfarril Hill. Near the contact between GT and the overlying Greenheugh pediment capping unit, we observe a lack of clay minerals with signatures consistent instead with coarse-grained gray hematite, likely formed through late-diagenetic alteration. We hypothesize that the sandstone-dominant Stimson formation acted as a conduit for diagenetic fluid flow into the area and that the clay-rich impermeable GT slowed the flow of those fluids, leading to enhanced alteration surrounding the clay-rich portions of GT, including within the nearby Vera Rubin ridge.

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.