¹Camille R. Butkus,²Alexandra O. Warren,²Edwin S. Kite,^3,4Santiago Torres,^3,4Smadar Naoz,⁵Jennifer B. Glass
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115580]
¹School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA
²Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
³Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, CA, USA
⁴Mani L. Bhaumik Institute for Theoretical Physics, Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA, USA
⁵School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
Copyright Elsevier

Methane is a promising gaseous biosignature on rocky exoplanets, given a suitable context. Establishing the robustness of methane biosignatures on rocky exoplanets requires assessing potential “false positive” production pathways that could yield large fluxes of methane of abiotic origin. Here we modeled the flux of abiotic methane production from graphite hydrogenation on the surface of Mercury, where a relatively carbon-rich crust and bombardment by solar protons might favor this reaction. We calculated negligible methane flux from this abiotic reaction compared to biological methane flux on Earth. Graphite hydrogenation would only be expected to yield significant methane fluxes on exoplanets with high temperatures and ion fluxes that would preclude habitability for life as we know it. Thus, graphite hydrogenation by stellar wind can likely be ruled out as a potential “false positive” methane biosignature source.

¹Dominik Talla,¹Gerald Giester,¹Manfred Wildner
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115583]
¹Institut für Mineralogie und Kristallographie, Universität Wien, Josef-Holaubek-Platz 2, 1090 Wien, Austria
Copyright Elsevier

The presence and importance of sulfates in our solar system have become common knowledge among the dedicated scientific community, as well as their crucial role in governing the water budget of planets such as Mars. The formation of subsurface oceans and cryovolcanism on icy moons of Jupiter and Saturn owe their existence to melting equilibria influenced by sulfate hydrates in the deeper parts of these celestial bodies. In such a setting, it cannot be ruled out that lower-hydrated sulfates including kieserite, MgSO4·H2O, are also present, given their stability under geologic pressures relevant even down to the lower mantle of the icy satellites. With regard to the composition of the water-soluble fraction in C1 and C2 chondritic meteorites presumed to correspond to that of the rocky cores of the Jovian moons, local kieserite may contain significant amounts of Mn in addition to Ni (and also some Fe). Minor Mn contents are probable even in kieserite occurring on the surface of Mars. Substantial lattice parameter changes and spectral band shifts between kieserite and its isostructural Mn-analogue szmikite, MnSO4·H2O, are well known, nevertheless neither the existence of a potential Mgsingle bondMn solid solution series nor its crystal chemical and spectroscopic behavior has yet been investigated.

This work provides the first evidence for such a continuous solid solution, describes its structural properties, and gives a detailed insight into the position changes of prominent bands in FTIR- and Raman spectra of synthetic samples, as the Mn/Mg ratio increases, with the measurement having been performed both at ambient and low temperatures relevant for Mars and the icy satellites. It reveals that contents of Mn do not cause any significant shift in the H2O stretching vibrational bands, yet influence the position of sulfate-related vibrations much in the same way as the incorporation of other relevant transition metal cations, such as Ni. The contrasting behavior of the ν3 and ν1 stretching vibrations of the H2O molecule in case of Mn- (no shift) and Ni-incorporation (significant shift to lower wavenumber) along with their comparable influence on the position of sulfate bands allow to deduce the chemical composition of kieserite in a ternary Mg–Mn–Ni system based on spectroscopic remote sensing or in situ data from celestial bodies. The assessment of chemical composition from vibrational spectra is facilitated by the observed Vegard-type behavior, where lattice parameters as well as the spectral band positions change along linear trends with increasing substitution of Mg, regardless if by Mn, Fe, or Ni. The observed shift of mainly the H2O stretching vibrations to lower wavenumber values as temperature decreases (in contrast to the bands related to the sulfate group) match thermal behavior observed in other binary solid solutions of sulfate monohydrate phases isostructural with kieserite.

^1,2,3C.K. Shearer,^4,5,6D.P. Moriarty,¹S.B. Simon,⁴N. Petro,^1,2J.J. Papike
Journal Geophysical Research (Planets) Link to Article [https://doi.org/10.1029/2022JE007409]
¹Institute of Meteoritics, University of New Mexico, Albuquerque, NM, 87131 United States
²Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, 87131 United States
³Lunar and Planetary Institute, Houston, TX, 77058 United States
⁴NASA Goddard Space Flight Center, Greenbelt, MD, 20771 United States
⁵University of Maryland, College Park, MD, 20742 United States
⁶Center for Research and Exploration in Space Science and Technology, College Park, MD, 20742 United States
Published by arrangement with Jon Wiley & Sons

Remote sensing observations have been interpreted to indicate that the Crisium basin-forming event excavated deep crust and upper mantle. Samples from the highlands adjacent to the Crisium basin returned by Luna 20 (L-20) bring a unique perspective for evaluating this concept. The magmatic lithologies returned from the noritic Hilly and Furrowed Terrain (nHFT) by L-20 are coarse-grained feldspar (>300 µm) with inclusions of pyroxene, and a finer-grained norites, troctolites, spinel troctolites, and gabbros (<100 µm). These two suites represent ferroan anorthosites (FANs) and the Mg-suite, respectively. There is limited evidence for mantle or deep crustal material within the nHFT samples. Ultramafic rocks such as dunites and orthopyroxenites are absent, and Mg-rich olivine- and orthopyroxene-bearing-assemblages are derived from magmatic rocks emplaced in the shallow crust. These lithic fragments represent pre-Crisium episodes of magmatism and lunar magma ocean products. The lack of deep lithologies at the L-20 site seems contradictory to excavation models for Crisium. Mineralogical-chemical differences suggest a higher FAN component in the rim and that this represents FANs excavated from the deep lunar crust. If it exists, the Mg-rich olivine previously identified within the Crisium rim is most likely related to deep, complementary versions of the Mg-suite rocks from L-20. The material associated with the Crisium basin is not derived from the lunar mantle but represents crustal lithologies from the shallow to deep crust, a substantial mantle component may have been incorporated into the Crisium basin impact melt sheet, or that our “Earth-analog” for the lunar upper mantle is incorrect.

¹Huanxin Liu,²Richard D. Ash,³Yan Luo,³D. Graham Pearson,¹Jingao Liu
Earth and Planetary Science Letters 612, 118162 Link to Article [https://doi.org/10.1016/j.epsl.2023.118162]
¹State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
²Department of Geology, University of Maryland, College Park, MD 20742, USA
³Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
Copyright Elsevier

Metal phases in primitive chondrites contain important information for understanding early Solar System processes. Northwest Africa (NWA) 12273 is an ungrouped chondrite and, due to its preternatural high modal abundance of metal grains (>60%), provides a unique perspective on the formation and evolution of primitive planetesimals. To investigate the formation of metal phases in early solar system materials we report detailed petrography, siderophile geochemistry and Hf-W isotope geochronology for NWA 12273. The primitive textures and heterogeneous mineral chemistry of chondrules, as well as siderophile element compositions of Ni-rich metal, all indicate an affinity of NWA 12273 to unequilibrated (type 3.8) ordinary chondrites that experienced limited thermal metamorphism. Modeling shows that crucial inter-element fractionations among refractory siderophile elements for kamacite in NWA 12273, were most likely caused by solid metal-liquid metal partitioning, for example during partial melting of Fe-Ni metal containing ∼3.9 wt.% of S. Analysis of the metal fractions within NWA 12273 gives a Hf-W model age of ∼2.4 Ma after CAI formation (), older than metal formation in most of H chondrites and IIE irons. In comparison with published data for chondrites and ‘non-magmatic’ iron meteorites, siderophile element data suggest that the metal phases in NWA 12273 may have originated from similar precursor materials and/or accreted in adjacent nebular locations to IIE irons and H chondrites. These primary planetesimals experienced impact-related evaporation and mixing followed by rebuilding of the secondary body. This scenario is consistent with that proposed for IIE and other silicate-bearing iron meteorites, indicating that the building blocks of some chondrite parent bodies were not entirely primitive (undifferentiated) materials.

¹M.S.Rice et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2022JE007548]
¹Western Washington Univ, Bellingham, WA, United States
Published by arrangement with John Wiley & Sons

NASA’s Mars-2020 Perseverance rover spent its first year in Jezero crater studying the mafic lava flows of the Máaz formation and the ultramafic cumulates of the Séítah formation, both of which have undergone minor alteration and are variably covered by coatings, dust and/or soil deposits. Documenting the rock and soil characteristics across the crater floor is critical for establishing the geologic context of Perseverance’s cached samples – which will eventually be returned to Earth – and for interpreting the deposition and modification of the Máaz and Séítah formations. Mastcam-Z, a pair of multispectral, stereoscopic zoom-lens cameras, provides broadband red/green/blue and narrowband visible to near-infrared images (VNIR, 440-1020 nm). From multipsectral observations from sols 0-380, we compiled a database of ∼2400 representative Mastcam-Z spectra. We analyzed principal components, spectral parameters and laboratory spectra of pure minerals and natural rock surfaces to interpret the spectral diversity of rocks and soils. We define eight spectral classes of rocks: Dusty, Hematite-like, Coated, Low-Ca Pyroxene-like, Olivine-like, Weathered Olivine-like, Fe-rich Pyroxene-like, and Dark Oxide-like. The variability of soil spectra in the Jezero crater floor is controlled primarily by the amount of dust and indicates a largely consistent soil mineralogy across the traverse, with the exception of the area disturbed by the landing event. In comparison to rock spectra from the Curiosity rover’s Mastcam instrument in Gale crater, rocks on the Jezero crater floor are generally less spectrally diverse, but the Olivine-like rocks within the Séítah formation represent new spectral classes in Mars surface exploration.

¹Yoko Kebukawa et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115582]
Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
Copyright Elsevier

Primitive carbonaceous xenolithic clasts found in sturdy metamorphosed meteorites often provide opportunities to reach labile volatile-rich materials which are easily destroyed during atmospheric entry and materials which we do not have sampled as individual meteorites. Among them, a xenolithic carbonaceous clast in the Zag H3–6 ordinary chondrite has been providing us with the opportunity to analyze a possible sample from D/P-type asteroids. Here we performed a new suite of coordinated analyses of organic matter in the Zag clast using the atomic force microscope infrared spectroscopy (AFM-IR) combined with nanoscale secondary ion mass spectrometer (NanoSIMS), X-ray absorption near-edge spectroscopy (XANES) coupled with scanning transmission X-ray macroscope (STXM), Raman, and (scanning) transmission electron microscopy [(S)TEM] on adjacent ultramicrotomed thin sections from a single sample grain. We successfully demonstrated the practicality of coordinated analyses using AFM-IR, Raman and NanoSIMS on the same sample area, as well as STXM/XANES on adjacent (and nearly identical) thin sections to those used for AFM-IR. The AFM-IR map and STXM maps provided consistent and complementary results. We found that at least two types of organics were closely mixed in this specimen. One was deuterium-rich, Cdouble bondO rich organics with likely smaller aromatic domains, possibly originating in relatively oxidized environments from D-rich precursors. The other type was less deuterium-rich, but aromatic-rich organics, possibly produced in relatively reduced and higher temperature environments with less deuterium-rich precursors. These characteristics point to complex mixtures of materials with different origins and sampling a wide heliocentric range of the Solar System before accretion in the parent body of the clast.

¹B.E.Clark et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115563]
Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
Copyright Elsevier

This paper summarizes the evidence for the optical effects of space weathering, as well as the properties of the surface that control optical changes, on asteroid (101955) Bennu. First, we set the stage by briefly reviewing what was known about space weathering of low-albedo materials from telescopic surveys, laboratory simulations, and sample return analysis. We then look at the evidence for the nature of space weathering on Bennu from recent spacecraft imaging and spectroscopy observations, including the visible to near-infrared and thermal infrared wavelengths, followed by other measurements such as normal albedo measurements from LIDAR scans. We synthesize these different lines of evidence in an effort to describe a general model of space weathering processes and resulting color effects on dark C-complex asteroids, with hypotheses that can be tested by analyzing samples returned by the mission.

A working hypothesis that synthesizes findings thus far is that the optical effects of maturation in the space environment depend on the level of hydration of the silicate/phyllosilicate substrate. Subsequent variations in color depend on surface processes and exposure age. On strongly hydrated Bennu, in color imaging data, very young craters are darker and redder than their surroundings (more positive spectral slope in the wavelength range 0.4–0.7µm) as a result of their smaller particle sizes and/or fresh exposures of organics by impacts. Solar wind, dehydration, or migration of fines may cause intermediate-age surfaces to appear bluer than the very young craters. Exposed surfaces evolve toward Bennu’s moderately blue global average spectral slope. However, in spectroscopic and LIDAR data, the equator, the oldest surface on Bennu, is darker and redder (wavelength range 0.55–2.0
µm) than average and has shallower absorption bands, possibly due to dehydration and/or nanophase and/or microphase opaque production.

Bennu is a rubble pile with an active surface, making age relationships, which are critical for determining space weathering signals, difficult to locate and quantify. Hence, the full story ultimately awaits analyses of the Bennu samples that will soon be delivered to Earth.

¹A.Dugdale et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115568]
¹AstrobiologyOU, School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
Copyright Elsevier

The phyllosilicate-bearing martian plain, Oxia Planum, is the proposed landing site for the Rosalind Franklin rover mission, scheduled to launch in 2028. Rosalind Franklin which will search for signs of past or present life on Mars. Terrestrial analogue sites and simulants can be used to test instruments analogous to those on Rosalind Franklin, however no simulant for Oxia Planum currently exists. In anticipation of this mission, a simulant – SOPHIA (Simulant for Oxia Planum: Hydrated, Igneous, and Amorphous) – representative of the local mineralogy at Oxia Planum has been developed for biosignature and mineralogy experiments, which will assist in interpreting data returned by the rover. The simulant is derived from orbital observations of Oxia Planum and its catchment area. As no in situ data is available for Oxia Planum, mineralogy from other comparable sites on Mars was used to design the simulant including orbital data from Arabia Terra and Mawrth Vallis and in situ data collected from Gale crater. The mineralogy, chemistry and physical properties of the simulant were characterised using standard laboratory techniques (SEM-EDS, XRF, XRD).Techniques analogous to rover instruments (Raman spectroscopy, Near-IR spectroscopy analogous to the Raman laser spectrometer and ISEM and MicrOmega instruments) were also used. The simulant is rich in Fe/Mg phyllosilicates with additional primary igneous and other alteration minerals and is an appropriate spectral and mineralogical analogue for Oxia Planum.

^1,2Dennis HARRIES,³Xuchao ZHAO,³Ian FRANCHI
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.13980]
¹Department of Analytical Mineralogy, Institute of Geoscience, Friedrich Schiller University Jena, Carl-Zeiss-Promenade 10,07745 Jena, Germany
²European Space Resources Innovation Centre, Luxembourg Institute of Science and Technology, 41 rue du Brill, L-4422Belvaux, Luxembourg
³School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
Published by arrangement with John Wiley & Sons

Hydroxyl defects in nominally anhydrous minerals (NAMs) were potential carriers ofwater in the early Solar System and might have contributed to the accretion of terrestrial water.To better understand this, we have conducted a nanoscale secondary ion mass spectrometrysurvey of water contents in olivine and orthopyroxene from a set of equilibrated ordinarychondrites of the L and LL groups (Baszk ́owka, Bensour, Kheneg Ljouˆad, and Tuxtuac) andseveral ultramafic achondrites (Zakøodzie, Dhofar 125, Northwest Africa [NWA] 4969, NWA6693, and NWA 7317). For calibration, we used terrestrial olivine and orthopyroxene with H2Ocontents determined by Fourier transform infrared. Our 99.7% (~3SD) detection limits are 3.6–5.4 ppmw H2O for olivine and 7.7–10.9 ppmw H2O for orthopyroxene. None of the meteoriticsamples studied consistently shows water contents above the detection limits. A few exceptionsslightly above the detection limits are suspected of terrestrial contamination by ferricoxyhydroxides. If the meteorite samples investigated accreted in the presence of small amountsof water ice, the upper limits of water contents provided by our survey suggest that the retentionof hydrogen during thermal metamorphism and differentiation was ineffective. We suggest thatloss occurred through combinations of low internal pressures, high permeability along grainboundaries, and speciation of hydrogen into reduced compounds such as H2and methane,which are less soluble in NAMs than in water.

^1,2Amanda Tosi et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13976]
¹LABSONDA/IGEO/UFRJ, Instituto de Geociências, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos, 274, Cidade Universitária, 21941-972 Rio de Janeiro, RJ, Brazil
²LABET/MN/UFRJ, Laboratório Extraterrestre, Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão, 20940-040 Rio de Janeiro, RJ, Brazil
Published by arrangement with John Wiley & Sons

On August 19, 2020, at 13:18—UTC, a meteor event ended as a meteorite shower in Santa Filomena, a city in the Pernambuco State, northeast Brazil. The heliocentric orbital parameters resulting from images by cameras of the weather broadcasting system were semimajor axis a = 2.1 ± 0.1 au, eccentricity e = 0.55 ± 0.03, and inclination i = 0.15o ± 0.05. The data identified the body as an Apollo object, an Earth-crossing object with a pericenter interior to the Earth’s orbit. The chemical, mineralogical, and petrological evaluations, as well as the physical analysis, followed several traditional techniques. The meteorite was identified as a H5-6 S4 W0 ordinary chondrite genomict breccia. The large amount of metal in the meteorite made a metallographic evaluation based on the opaque phases possible. The monocrystalline kamacite crystals suggest a higher petrological type and the distorted Neumann lines imply at least two different shock events. The absence of the plessite phase shows that the meteorite did not reach the highest shock levels S5 and S6. The well-defined polycrystalline taenite is indicative of petrologic types 4 and 5 due to the conserved internal tetrataenite rim at the boundaries. The presence of polycrystalline taenites and the characteristics of the Agrell Effect suggest that the Santa Filomena meteorite did not reheat above 700°C. The absence of martensite confirms reheating temperatures <800°C and a slow cooling rate. The Ni contents and sizes of the zoned taenite particles indicate a slow cooling rate ranging from 1 to 10 K Myr−1.