¹Y.Y.He et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.09.035]
¹Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Sorbonne Université, 75005, Paris, France
Copyright Elsevier

Carbonaceous chondrites contain amino acids, with variable abundances and isotope compositions between and within carbonaceous chondrites. The parent body processes, and the presence of clay minerals may explain those differences. Here, we experimentally investigate the evolution of 6 amino acids (glycine, β-alanine, α-alanine, 2-aminoisobutyric acid, γ-aminobutyric acid, and isovaline) exposed to hydrothermal conditions in the presence or absence of silicates. We determined the chemical nature and isotopic composition of the organic compounds of the soluble and solid fractions of the residues using X-ray diffraction, spectroscopy, and mass-spectrometry methods. Glycine and α-alanine exhibit a rather high stability, which is consistent with the measured abundances of α-alanine and glycine in chondrites having experienced various degrees of aqueous alteration. In the meantime, the evolution of β-alanine under hydrothermal conditions leads to the formation of a new compound, which likely results from the decarboxylation and deamination of β-alanine followed by recombination. More than 95 % of γ-ABA was transformed into 2-pyrrolidione though self-cyclization during the aqueous alteration. The solid residues of the experiments conducted in the presence of clay minerals contain organic material, with abundances varying depending on the amino acid used for the experiments (TOC isovaline > 2-aminoisobutyric acid > γ-aminobutyric acid > glycine > α-alanine > β-alanine). Clay minerals thus preferentially trap branched amino acids over chained amino acids, likely within their interlayer spaces as suggested by XRD data. The δ13C values of amino acids have not changed significantly during the experiments, even with the presence of silicates. Thus, the δ13C values of amino acids reported in CR and CM chondrites likely relate to synthetic conditions or the origin of their precursors (i.e. inherited from the pre-accretion processes).

¹Emmanuel Jacquet,¹Béatrice Doisneau
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14270]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS; CP52, Paris, France
Published by arrangement with John Wiley & Sons

The multiplication of decimal petrologic schemes for different or the same chondrite groups evinces a lack of unified guiding principle in the secondary classification of type 1–3 chondrites. We show that the current OC, R and CO classifications can be a posteriori unified, with only minor reclassifications, if the decimal part of the subtype is defined as the ratio m = FaI/FaII of the mean fayalite contents of type I and type II chondrules, rounded to the nearest tenth (with adaptations from Cr systematics for the lowest subtypes following the past literature). This parameter is more efficiently evaluable than the oft-used relative standard deviation of fayalite contents and defines a general metamorphic scale from M0.0 to M1, where the suffixed number is the rounded m. Type 3 chondrites thus span the range M0.0–M0.9 (i.e. subtypes 3.0–3.9) and M1 designates type 4. Corresponding applications are then proposed for other chondrite groups (with, e.g., CV secondary classification reduced to essentially three grades from M0.0 to M0.2, that is, subtypes 3.0–3.2). Known type 1 and 2 chondrites are at M0.0 (i.e. the metamorphic grade of type 3.0 chondrites), even so-called “CY” chondrites, since our metamorphic scale is insensitive to brief heating. Independently, we define an aqueous alteration scale from A0.0 to A1.0, where the suffixed number is the (rounded) phyllosilicate fraction (PSF). For CM and CR chondrites, the alteration degrees can be characterized in terms of the thin-section-based criteria of previous schemes which are thus incorporated in the present framework, if in a coarser, but hereby more robust form. We propose their corresponding petrologic subtype to be 3-PSF, rounded to the nearest tenth (so that type 1 would correspond to subtypes 2.0 and 2.1). Since nonzero alteration and metamorphic degrees remain mutually exclusive at the level of precision chosen, a single petrologic subtype ≈3+m-PSF indeed remains a good descriptor of secondary processes for all unequilibrated chondrites, obviating the explicit mention of our separate scales unless finer subdivisions are adopted for the most primitive chondrites.

^1,2E. K. Leask,¹B. L. Ehlmann,³M. M. Dundar
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008259]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
³Indiana University-Purdue University, Indianapolis, IN, USA
Published by arrangement with John Wiley & Sons

Terra Sirenum, a region of Noachian highlands southwest of the Tharsis volcanic complex, is unique in the number, proximity, and diversity of orbital detections of secondary minerals, as the sole region found to date hosting large-scale deposits of all of Mars’ major salts (chlorides, sulfates, carbonates) as well as diverse hydrated silicates. We combine mineralogical information, high-resolution imagery, and elevation models to investigate the geologic context of these secondary minerals to understand the sources of water and ions for each type of deposit and their spatial/temporal relationships. Carbonates, where present, are part of Noachian basement rocks exposed through cratering and do not appear associated with evaporative sequences. Numerous small detections of the acid sulfate minerals alunite and jarosite mirror the dominant clay cation in the localities they are found—Al phyllosilicates and Fe phyllosilicates, respectively—suggesting in situ formation. We interpret a previously discovered kaolinite-rich unit overlying Fe/Mg clays across northeast Terra Sirenum as remnants of a widespread ash unit rather than a pedogenic weathering sequence. Sulfate and chloride detections are decoupled, with sulfates in topographic lows likely precipitated from volcanism-associated groundwaters, while chloride detections are consistent with surface water runoff, in some instances clearly post-dating volcanic units capping sulfate detections. Volcanic resurfacing of craters in the region is progressively younger from west to east, and crater statistics-based ages indicate localized sulfate- and chloride-forming processes continue to occur from ∼3.5 to ∼1.4 Ga. We hypothesize that their decoupling points to disconnected, episodic surface and groundwater reservoirs, perhaps separated by a permafrost layer.

¹B. Sutter,¹P. D. Archer,²P. B. Niles,²D. W. Ming,³D. Hamara,³W. V. Boynton
Journalof Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008335]
¹Jacobs/JETSII, NASA Johnson Space Center, Houston, TX, USA
²NASA Johnson Space Center, Houston, TX, USA
³Lunar Planetary Laboratory, University of Arizona, Tucson, AZ, USA
Published by arrangement with John Wiley & Sons

The Thermal Evolved Gas Analyzer (TEGA) analysis of surface and icy subsurface Phoenix landing site soils consisted of low (300–700°C) and high (>700°C) temperature CO2 evolutions that were attributed to organic carbon (83–1,484 μgC/g) and Ca-rich carbonate (1.1–2.6 wt.%). Total carbon abundances ranged from 1,143 to 4,905 µgC/g, which is the highest soil carbon concentration so far detected on Mars. Low temperature CO2 was attributed to oxidized organic C (e.g., oxalates, acetates), while hydrocarbon combustion was indicated in two soils by the detection of coevolved CO2 and O2 (perchlorate). Combustion reactions may have prevented the detection of hydrocarbon masses in the Phoenix landing site soils. Organic C was likely derived from meteoritic and igneous/hydrothermal sources, but microbiological sources cannot be excluded. CO2 evolved at high temperatures was consistent with Ca-rich carbonate along with possible minor contributions from macromolecular organic carbon and mineral/glass vesicle CO2. Carbon detected in the Phoenix landing site soil and other landing site soils and sands (e.g., Gale/Jezero craters) would be consistent with global organic C and carbonate in soils and sand across Mars. However, oxidizing water thin films derived from the near-surface ice in the Phoenix soils favor Ca-carbonate over Fe-carbonate, which is likely more stable in the ice-free regions of Mars (e.g., Gale/Jezero craters). The global carbon budget on Mars inferred from these results emphasizes that Mars Sample Return should yield carbon bearing soil/rock that would allow the identification of the origin of carbon and any possible connections to ancient martian microbiology.

¹Sanchez, Juan A.,²Reddy, Vishnu,³Thirouin, Audrey,⁴Bottke, William F.,³Kareta, Theodore,⁵De Florio, Mario,⁶Sharkey, Benjamin N. L.,²Battle, Adam,²Cantillo, David C.,¹Pearson, Neil
The Planetary Science Journal 5, 131 Open Access Link to Article [DOI 10.3847/PSJ/ad445f]
¹Planetary Science Institute, 1700 East Fort Lowell Road, Tucson, 85719, AZ, United States
²Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson, 85721-0092, AZ, United States
³Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, 86004, AZ, United States
⁴Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, 80302, CO, United States
⁵Division of Applied Mathematics, Brown University, 170 Hope Street, Providence, 02906, RI, United States
⁶Department of Astronomy, University of Maryl, 4296 Stadium Drive PSC (Building 415), Room 1113, College Park, 20742-2421, MD, United States

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Y.Y. He et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.09.035]
¹Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Muséum
Copyright Elsevier

Carbonaceous chondrites contain amino acids, with variable abundances and isotope compositions between and within carbonaceous chondrites. The parent body processes, and the presence of clay minerals may explain those differences. Here, we experimentally investigate the evolution of 6 amino acids (glycine, β-alanine, α-alanine, 2-aminoisobutyric acid, γ-aminobutyric acid, and isovaline) exposed to hydrothermal conditions in the presence or absence of silicates. We determined the chemical nature and isotopic composition of the organic compounds of the soluble and solid fractions of the residues using X-ray diffraction, spectroscopy, and mass-spectrometry methods. Glycine and α-alanine exhibit a rather high stability, which is consistent with the measured abundances of α-alanine and glycine in chondrites having experienced various degrees of aqueous alteration. In the meantime, the evolution of β-alanine under hydrothermal conditions leads to the formation of a new compound, which likely results from the decarboxylation and deamination of β-alanine followed by recombination. More than 95 % of γ-ABA was transformed into 2-pyrrolidione though self-cyclization during the aqueous alteration. The solid residues of the experiments conducted in the presence of clay minerals contain organic material, with abundances varying depending on the amino acid used for the experiments (TOC isovaline > 2-aminoisobutyric acid > γ-aminobutyric acid > glycine > α-alanine > β-alanine). Clay minerals thus preferentially trap branched amino acids over chained amino acids, likely within their interlayer spaces as suggested by XRD data. The δ¹³C values of amino acids have not changed significantly during the experiments, even with the presence of silicates. Thus, the δ¹³C values of amino acids reported in CR and CM chondrites likely relate to synthetic conditions or the origin of their precursors (i.e. inherited from the pre-accretion processes).

¹Hitoshi Miura
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116317]
¹Graduate School of Science, Nagoya City University, Yamanohata 1, Mizuho-cho, Mizuho-ku, Nagoya, 467-8501, Aichi, Japan
Copyright Elsevier

In this study, we propose a novel numerical method to simulate the growth dynamics of an olivine single crystal within an isolated, multicomponent silicate droplet. We aimed to theoretically replicate the solidification textures observed in chondrules. The method leverages the phase-field model, a well-established framework for simulating alloy solidification. This approach enables the calculation of the solidification process within the ternary MgO–FeO–SiO
system. Furthermore, the model incorporates the anisotropic characteristics of interface free energy and growth kinetics inherent to the crystal structure. Here we investigated an anisotropy model capable of reproducing the experimentally observed dependence of the growth patterns of the olivine single crystal on the degree of supercooling under the constraints of two-dimensional modeling. By independently adjusting the degree of anisotropies of interface free energy and growth kinetics, we successfully achieved the qualitative replication of diverse olivine crystal morphologies, ranging from polyhedral shapes at low supercooling to elongated, needle-like structures at high supercooling. This computationally driven method offers a unique and groundbreaking approach for theoretically reproducing the solidification textures of chondrules.

¹Yang Liu,²Chi Ma
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2024JE008444]
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
²Division of Geology and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

Identification of the mineral species of vapor condensates on the surface of lunar pyroclastic beads, formed during the flights of beads in the lunar volcanic plume, helps to constrain the physical and chemical conditions of the lunar volcanic plume. We conducted nanomineralogy studies of vapor condensates on the surface of pristine black beads from a clod that was extracted from the recently opened Apollo drive tube 73001. This drive tube had been sealed under vacuum since its collection on the Moon and thus represents the most pristine sample in allocatable Apollo collection. Vapor condensates observed on the surface include patches made of ZnS nanocrystals and possible rare scattered NaCl nanocrystals. ZnS nanocrystals were previously found on Apollo 15 green and yellow beads, but NaCl nanocrystals are unique to black beads. Both ZnS and NaCl nanocrystals are absent in Apollo 17 74220 orange beads. Although orange and black beads are of similar chemistry, black beads in the clod 73001, 226 could form from a different environment.

¹Elias N. Mansbach et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008505]
¹Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
Published by arrangement with John Wiley & Sons

Although Mars today does not have a core dynamo, magnetizations in the Martian crust and in meteorites suggest a magnetic field was present prior to 3.7 billion years (Ga) ago. However, the lack of ancient, oriented Martian bedrock samples available on Earth has prevented accurate estimates of the dynamo’s intensity, lifetime, and direction. Constraining the nature and lifetime of the dynamo are vital to understanding the evolution of the Martian interior and the potential habitability of the planet. The Perseverance rover, which is exploring Jezero crater, is providing an unprecedented opportunity to address this gap by acquiring absolutely oriented bedrock samples with estimated ages from ∼2.3 to >4.1 Ga. As a first step in establishing whether these samples could contain records of Martian paleomagnetism, it is important to determine their ferromagnetic mineralogy, the grain sizes of the phases, and the forms of any natural remanent magnetization. Here, we synthesize data from various Perseverance instruments to achieve those goals and discuss the implications for future laboratory paleomagnetic analyses. Using the rover’s instrument payload, we find that cored samples likely contain iron oxides enriched in Cr and Ti. The relative proportions of Fe, Ti, and Cr indicate that the phases may be titanomagnetite or Fe-Ti-Cr spinels that are ferromagnetic at room temperature, but we cannot rule out the presence of non-ferromagnetic ulvöspinel, ilmenite, and chromite due to signal mixing. Importantly, the inferred abundance of iron oxides in the samples suggests that even <1 mm-sized samples will be easily measurable by present-day magnetometers.