^1,2C. Royer,³S. Bernard,³O. Beyssac,³E. Balan,⁴O. Forni,³M. Gauthier,³M. Morand,³Y. Garino,³P. Rosier
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115894]
¹LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, Meudon, France
²Purdue University Earth, Atmospheric and Planetary Sciences department, West Lafayette, IN, USA
³Institut de Minéralogie, Physique des Matériaux et Cosmochimie, CNRS UMR 7590, Muséum National d’Histoire Naturelle, Sorbonne Université, Paris, France
⁴IRAP, CNRS, Université de Toulouse, UPS-OMP, Toulouse, France
Copyright Elsevier

Perseverance is on Mars, collecting samples which will inform about Martian paleoenvironmental conditions. However, the surface of Mars is continuously bombarded by ionizing radiation, including UVs, which may significantly alter hydrated mineral phases such as sulfates, phosphates and carbonates. To explore and constrain this effect, we experimentally exposed pellets of more or less hydrated minerals to UV radiation within a Martian chamber at a temperature relevant for the rocks at the surface of Mars. Results show that exposure to UV leads to a strong alteration of the Raman and IR signals of sulfates, phosphates and carbonates. The strong increase of the luminescence signals coupled to the decrease of the Raman signals relatively to the background and the clear attenuation of the IR signals are interpreted as caused by an increasing concentration of electronic defects. The present results have strong implications for the ongoing exploration of Mars: one should not expect to detect pristine materials, except over freshly excavated surfaces. Still, as a precaution, all the targets measured or collected on Mars should be considered as having been exposed to UV radiation to some extent.

¹D.L. Laczniak,¹M.S. Thompson,²R. Christoffersen,³C.A. Dukes,⁴R.V. Morris,⁴L.P. Keller
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115883]
¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, United States of America
²Jacobs, NASA Johnson Space Center, Mail Code X13, Houston, TX 77058, United States of America
³Laboratory for Astrophysics and Surface Physics, University of Virginia, 395 McCormick Road, Charlottesville, VA 22904, United States of America
⁴ARES, Mail Code X13, NASA Johnson Space Center, Houston, TX 77058, United States of America
Copyright Elsevier

We present results from a set of low and high flux 1 keV/amu H+ and He+ irradiation experiments performed on slabs of the Murchison CM2 carbonaceous chondrite. The low flux conditions for H+ and He+ irradiation were ~ 1–1.5 orders of magnitude lower than the high flux conditions, and each experiment was irradiated to a total fluence between ~3 × 1016 to ~6 × 1016 ions/cm2. Irradiation-induced changes in the surface chemistry and optical properties of the Murchison samples were evaluated using in situ X-ray photoelectron spectroscopy (XPS) and visible and near-infrared spectroscopy (VNIR). We characterized the microstructure and composition of ion damaged rims in focused ion beam (FIB) cross-sections extracted from olivine and matrix material in each irradiated Murchison slab using transmission electron microscopy (TEM). XPS results suggest that both low flux and high flux H+ and He+ irradiation cause minor sputtering of surface carbon as well as a reduction in the valence state of iron, from Fe3+ to Fe2+. Slope bluing is observed in VNIR spectra of the irradiated samples which may reflect carbonization and dehydrogenation of organic species and contrasts with reddening trends associated with npFe0 formation. Although we do not observe a strong flux-dependence on the crystallinity of ion-damaged olivine, TEM analyses reveal a variety of microstructures in all olivine FIB-sections, suggesting that crystallographic orientation affects amorphization efficiency. Analyses of matrix FIB-sections indicate that phyllosilicate alteration is mainly driven by He+ irradiation, where the higher incident flux leads to greater amorphization and the formation of more distinct ion-damaged layers, similar to smooth layers in returned Ryugu particles. TEM results also provide some evidence that higher ion flux leads to greater vesiculation, with He+ irradiation being more efficient at vesiculation than H+ irradiation, and that higher ion flux may promote the segregation of Mg and Si into laterally extensive lenses and layers in olivine samples. We discuss the implications of these findings for constraining the role that ion flux plays in the development of space weathering characteristics in silicate phases present in carbonaceous asteroidal regoliths. These results will be important for understanding the complexity of this process and how it operates on carbon-rich airless bodies like asteroids Bennu and Ryugu.

¹L. F. Adam,¹J. C. Bridges,²C. C. Bedford,¹J. M. C. Holt,³E. Rampe,⁴M. Thorpe,⁵K. Mason,⁵R. C. Ewing
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14105]
¹Space Park Leicester, School of Physics and Astronomy, University of Leicester, Leicester, UK
²Department of Earth, Atmospherics, and Planetary Sciences, Purdue University, West Lafayette, Indiana, USA
³NASA Johnson Space Center, Houston, Texas, USA
⁴NASA Goddard Space Flight Center, University of Maryland, Greenbelt, Maryland, USA
⁵Department of Geology and Geophysics, Texas A&M University, College Station, Texas, USA
Published by arrangement with John Wiley & Sons

The joint NASA-ESA Mars sample return campaign aims to return up to 31 sample tubes containing drilled sedimentary and igneous cores and regolith. The titanium alloy tubes will initially still be sealed when they are retrieved. Several types of measurement will be carried out on sealed samples in the pre-basic characterization phase of scientific investigation. We show that powder x-ray diffraction (XRD) analysis can be successfully carried out on sealed samples using an x-ray source at the I12 beamline of Diamond Light Source synchrotron. Our experiment used an analog sample tube and a Martian regolith analog (Icelandic basaltic sand). The titanium walls of the tube analog give strong but few diffraction peaks, making identification of the major constituent mineral phases feasible. A more significant constraint on quantification of mineral phase abundances by this XRD technique is likely to be the grain size of the sample. This technique opens up the possibility of initial mineralogical analysis of samples returned from Jezero crater without opening the sample tubes and the potential changes to the sample that entails.

¹Allan H. Treiman,²Julia Semprich
American Mineralogist 108, 2182-2192 Open Access Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/open_access/AM108P2182.pdf]
¹Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A. 2
²AstrobiologyOU, School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, U.K.
Copyright: The Mineralogical Society of America

A centimeter-sized fragment of dunite, the first recognized fragment of Moon mantle material, has
been discovered in the lunar highlands breccia meteorite Northwest Africa (NWA) 11421. The dunite
consists of 95% olivine (Fo83), with low-Ca and high-Ca pyroxenes, plagioclase, and chrome spinel.
Mineral compositions vary little across the clast and are consistent with chemical equilibration. Mineral
thermobarometry implies that the dunite equilibrated at 980 ± 20 °C and 0.4 ± 0.1 gigapascal (GPa)
pressure. The pressure at the base of the Moon’s crust (density 2550 kg/m3) is 0.14–0.18 GPa, so the
dunite equilibrated well into the Moon’s upper mantle. Assuming a mantle density of 3400 kg/m3
, the dunite equilibrated at a depth of 88 ± 22 km. Its temperature and depth of equilibration are consistent with the calculated present-day selenotherm (i.e., lunar geotherm).
The dunite’s composition, calculated from mineral analyses and proportions, contains less Al, Ti,
etc., than chondritic material, implying that it is of a differentiated mantle (including cumulates from
a lunar magma ocean). The absence of phases containing P, Zr, etc., suggests minimal involvement
of a KREEP component, and the low proportion of Ti suggests minimal interaction with late melt
fractionates from a lunar magma ocean. The Mg/Fe ratio of the dunite (Fo83) is significantly lower
than models of an overturned unmixed mantle would suggest, but is consistent with estimates of the
bulk composition of the Moon’s mantle

¹J ZhangZhou,²Yuan Li,³Proteek Chowdhury,⁴Sayan Sen,^5,6Urmi Ghosh,²Zheng Xu,⁷Jingao Liu,⁸Zaicong Wang,⁹James M.D. Day
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.11.029]
¹Key Laboratory of Geoscience Big Data and Deep Resource of Zhejiang Province, School of Earth Sciences, Zhejiang University, Hangzhou, China
²State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
³Earth, Environment and Planetary Sciences, Rice University, TX 77005, USA
⁴Zuckerberg Institute for Water Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel
⁵Environmental and Biochemical Sciences, The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
⁶Department of Geology and Geophysics, Indian Institute of Technology (IIT) Kharagpur, 721302 Kharagpur, India
⁷State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Beijing), Beijing, China
⁸State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
⁹Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0244, USA
Copyright Elsevier

The sulfur content at sulfide saturation (SCSS) of a silicate melt can regulate the stability of sulfides and, therefore, chalcophile elements’ behaviors in planetary magma oceans. Many studies have reported high-pressure experiments to determine SCSS using either linear or exponential regressions to parameterize the thermodynamics of the system. Although these empirical equations describe the effects of different parameters on SCSS, they perform poorly when predicting laboratory measurements. Here, we compiled 542 published analyses of experiments performed on a range of sulfide and silicate compositions at varying P–T conditions (<24 GPa, <2673 K). Using empirical equations, linear regression, Random Forest algorithms, and a hybrid algorithm employing empirical fits to P–T conditions and the Random Forest algorithm for compositions, we developed several SCSS models and compared them to laboratory measurements. The Random Forest and hybrid models (R² = 0.82–0.91, mean average error [MAE] < 746 ppmw S, residual mean standard error [RMSE] < 972 ppmw S), significantly outperform previous empirical models (R² = 0.28–0.69, MAE = 622–1,170 ppmw S, RMSE = 1,070–1,744 ppmw S), whereas linear regression performs moderately well, i.e., between the classic and machine learning models. We applied our hybrid model to predict SCSS during magma ocean solidification on Earth, Mars, and the Moon, and we compared our model results to expected S contents in the residual magma oceans calculated by mass balance. Our results confirm that during early accretion, sulfides precipitated from magma oceans and into the outer cores of Earth and Mars, but not the Moon. Subsequently, once the respective magma oceans began precipitating minerals with increasingly FeO-rich and SiO₂-, Al₂O₃-, and MgO-depleted compositions, the increasing S concentration in the residual magma was offset by temperature and compositional effects on SCSS, preventing sulfide precipitation during intermediate stages of crystallization. Sulfides precipitated late during magma ocean crystallization, but failed to percolate through the underlying crystalline mantle, significantly contributing to the modern bulk-silicate sulfur abundances of Earth, Mars, and the Moon. Our calculations suggest that late-stage sulfide precipitation occurred at shallow depths of 120–220 km, 40–320 km, and <10 km in the magma oceans of Earth, Mars, and the Moon, respectively.

^1,2F. Jourdan,^1,2T. Kennedy,²L. Foreman,¹C. Mayers,³E. Eroglu,^4,5A. Yamaguchi
Geoochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2023.11.027]
¹Western Australian Argon Isotope Facility, John de Laeter Centre, TIGeR, Curtin University, Australia
²Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Australia
³School of Molecular and Life Sciences, Curtin University, Australia
⁴National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
⁵Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo 190-8518, Japan
Copyright Elsevier

In this study, we investigate the 40Ar/39Ar systematics of nineteen diogenites thought to come from deep crustal levels of asteroid 4 Vesta. We applied both Electron Backscattered Diffraction (EBSD) and 40Ar/39Ar and methods to the unbrecciated diogenite LAP 031381. We obtained three plateau ages resulting in a combined weighted mean age of 4441 ± 15 Ma (P = 0.16). The EBSD analyses suggest that LAP 031381 displays minimal evidence of shock and, when combined with petrography observations, diffusion modelling and 40Ar/39Ar data, these results suggest that the crustal volume that initially contained this diogenite, reached a temperature of ca. 630 °C at ∼ 4.44 Ga. This corresponds to a linear cooling rate of ∼ 5 °C / Ma for a crystallization age of 4550 Ma. Independent thermal models suggest that these conditions were present at a depth of 60 to 65 km at 4.44 Ga.

The other eighteen diogenites yielded 40Ar/39Ar results that indicate that they have been variously shocked by impact events and seven of them yielded plateau ages ranging from 2413 ± 189 Ma to 84 ± 162 Ma. We combined these results with 40Ar/39Ar ages from eucrites and howardites and propose that the HED (Howardite, Eucrite, Diogenite) meteorites recorded impact events at the surface of Vesta until ∼ 3.4 Ga when they were then ejected during a large collision. The eucrites, diogenites and howardites were then recombined into small rubble pile asteroids which probably make up a large part of the Vestoid family. After ejection, the K/Ar system in plagioclase crystals ceased in most cases to be fully reset by impact events as the temperature spikes reached during small impacts lack enough energy to trigger significant 40Ar* diffusion. On the other hand, ultra-transient and high-temperature – sensitive pyroxene crystals kept a more systematic record of small impacts until recent time. 38Arc cosmochron cosmogenic exposure ages on diogenites mostly range from 51 ± 7 Ma to 0 ± 1 Ma and when combined with other HED cosmochron ages, suggest that almost all the HED meteorites were continuously ejected from secondary rubble pile asteroids mostly between 50 Ma and present.

^1,2Raiza R. Quintero,²Aaron J. Cavosie,^3,4Sanna Alwmark,⁵Peter W. Haines,⁶Martin Danišík,²Nicholas E. Timms,⁷David Lim
Meteoritics & Planetary Science (in Press) Link to Artticle [https://doi.org/10.1111/maps.14108]
¹Department of Geology, University of Puerto Rico at Mayagüez, Mayagüez, Puerto Rico
²Space Science and Technology Centre, School of Earth and Planetary Science, Curtin University, Perth,
Western Australia, Australia
³Department of Geology, Lund University, Lund, Sweden
⁴Niels Bohr Institute, University of Copenhagen, Copenhagen N, Denmark
⁵Geological Survey of Western Australia, East Perth, Western Australia, Australia
⁶John de Laeter Centre, Curtin University, Perth, Western Australia, Australia
⁷Maria Resources Pty. Ltd., Subiaco, Western Australia, Australia
Published by arrangement with John Wiley & Sons

The Ilkurlka structure is an ~12 km diameter buried circular aeromagnetic anomaly within the Officer Basin in Western Australia. Prior studies postulated a range of origins, including meteorite impact. We report the presence of pervasive deformation in the first drill cores from the structure. Brecciated sandstone and siltstone contain arrays of quartz grains with concussion fractures and rare shocked quartz grains with planar deformation features (PDF). Universal stage measurements of two quartz grains reveal one grain with PDF parallel to (0001) orientation and three PDF sets parallel to {10⁢1¯⁢3}. A second grain contains three PDF sets parallel to {10⁢1¯⁢3} and one set parallel to {10⁢1¯⁢4}. The shocked grains are interpreted to have formed in situ, rather than representing transported detrital shocked grains. These results suggest local shock compression of at least 10 GPa; however, preservation of primary porosity and overall paucity of shocked grains may indicate lower mean shock pressures. (U-Th)/He dating of 58 apatite grains from four samples across both cores shows a dominant age population at ~265 Ma and a minor age population at ~135 Ma. These dates overlap with regional events and thus do not provide an unambiguous impact age. An upper Carboniferous to lower Permian maximum impact age is provisionally proposed based on inferred missing target rock stratigraphy.

¹George D. Cody et al.(>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14096]
¹Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
Published by arrangement with John Wiley & Sons

This study analyzed samples of the Murchison and Sutter’s Mill carbonaceous chondrite meteorites in support of the future analysis of samples returned from the asteroid (10155) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission. Focusing specifically on the insoluble organic matter (IOM), this study establishes that a total of 1.3 g of bulk sample from a single chondritic meteorite are sufficient to obtain a wide range of cosmochemical information, including light element analysis (H, C, and N), isotopic analysis (D/H, 13C/12C, and 15N/14N), and x-ray fluorescence spectroscopy for major elemental abundances. IOM isolated from the bulk meteorite samples was analyzed by light element and isotopic analysis as described above, 1H and 13C solid-state nuclear magnetic resonance spectroscopy, Raman spectroscopy, and complete noble gas analyses (abundances and isotopes). The samples studied included a pair from Murchison (CM2), one of which had been irradiated with high-energy x-rays in the course of computed tomographic imaging. No differences between the irradiated and non-irradiated Murchison samples were observed in the many different chemical and spectroscopic analyses, indicating that any x-ray–derived sample damage is below levels of detection. Elemental, isotopic, and molecular spectroscopic data derived from IOM isolated from the Sutter’s Mill sample reveals evidence that this meteorite falls into the class of heated CM chondrites.

¹B. G. Rider-Stokes,^1,2M. Anand,¹L. F. White,³J. R. Darling,⁴R. Tartèse,⁵M. J. Whitehouse,¹I. Franchi,¹R. C. Greenwood,¹G. Degli-Alessandrini
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14102]
¹School of Physical Sciences, The Open University, Milton Keynes, UK
²Department of Mineralogy, The Natural History Museum, London, UK
³School of the Environment, Geography & Geosciences, University of Portsmouth, Portsmouth, UK
⁴Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
⁵Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
Published by arrangement with John Wiley & Sons

As some of the oldest differentiated materials in our solar system, angrite meteorites can provide unique insights into the earliest stages of planetary evolution. However, the timing of planetary mixing, as evidenced by oxygen isotope variations in the quenched angrites, and the extent of magmatism on the angrite parent body (APB) remain poorly understood. Here, we report on microstructurally guided in situ geochemical and Pb–Pb isotopic measurements on angrites aimed at better understanding of the timing and nature of magmatic processes, as well as impact events, on the APB. The quenched angrite Northwest Africa (NWA) 12320 yielded a Pb–Pb date of 4571.2 ± 9.4 Ma, which we interpret as corresponding to the timing of planetary mixing. The only known shocked quenched angrite, NWA 7203, also yielded an ancient Pb–Pb date of 4562.9 ± 9.3 Ma, which is identical to the Pb–Pb date of 4563.6 ± 7.9 Ma obtained for the texturally intermediate angrite NWA 10463. Pb–Pb analyses in phosphates in the dunitic angrite NWA 8535 yielded a much younger date of 4514 ± 30 Ma, representing the youngest Pb–Pb date ever recorded for an angrite. Based on the evidence from the lack of shock deformation, olivine major and trace element compositions, and no apparent contamination in the oxygen isotope composition of NWA 8535, our findings are consistent with prolonged magmatism on the APB. This finding is consistent with a large size for the APB.

¹Andrew Schedl
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14103]
¹Department of Chemistry and Physics, West Virginia State University, Institute, West Virginia, USA
Published by arrangement with John Wiley & Sons

Jeptha Knob is a deformed structure, 4.5 km in diameter, composed entirely of carbonate rocks in the stable craton of North America. At Jeptha Knob, conventional evidence of meteorite impact, shock metamorphism, has not been found. I used calcite twin analysis to test the hypothesis that Jeptha Knob is a meteorite impact crater. Calcite twinning gives differential stresses of >170 MPa in rocks that were 600 to ≈800 m below the surface when the rocks were deformed. Under these conditions, high differential stresses cannot be explained by tectonic processes. In addition, twin intensities are >150 twins/mm which are >50% higher than the highest twin intensities observed in limestone from a wide variety of tectonic settings. Twin intensities and differential stresses are the same magnitudes as those found at Serpent Mound, a proven impact structure. Consistent with meteorite impact, differential stresses increase toward the center of the structure. If one accepts that Jeptha Knob is a marine impact crater, then (1) the presence of high temperature (>250°C) thick twins in calcite from a resurge deposit; (2) the extensive dolomitization of the central uplift with water/rock ratios >1.0; and (3) two episodes of calcite twin recorded incremental strains, are explained.