¹M. J. Burchell,¹P. J. Wozniakiewicz
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14152]
¹Centre for Astrophysics and Planetary Science, School of Physics and Astronomy, University of Kent, Kent, UK
Published by arrangement with John Wiley & Sons

This paper considers how space missions that fly through the plumes known, or suspected, to erupt naturally from some icy ocean worlds (IOW), such as Enceladus, or that aim to intercept icy ejecta from impact cratering processes on such bodies can sample the water and ice within the plumes. The mechanics of how grains (either in the plumes or the ejecta) would interact with a passing spacecraft (i.e., impact speeds, shock pressures, etc.) are introduced. The impact speeds are estimated and vary with both the mass of the IOW and the orbital parameters of a space mission. This can lead to large differences in impact speeds (and hence collection methods) at bodies such as Enceladus and Europa. The implications of these different impact speeds (a few hundred m s−1 to several km s−1, and even greater than 10 km s−1) for the collection of organic materials from the plumes are shown to be significant.

¹Bailiang Liu,^1,2,3Jingnan Guo,¹Mikhail I. Dobynde,⁴Jia Liu,^1,2Yingnan Zhang,^1,2Liping Qin
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008069]
¹Deep Space Exploration Laboratory/School of Earth and Space Sciences, University of Science and Technology of China, Hefei, PR China
²CAS Center for Excellence in Comparative Planetology, USTC, Hefei, PR China
³Collaborative Innovation Center of Astronautical Science and Technology, Harbin, China
⁴Deep Space Exploration Laboratory, Institute of Deep Space Science, Hefei, China
Published by arrangement with John Wiley & Sons

The nucleosynthetic Cr isotope anomalies provides useful information to trace the source and origin of extraterrestrial samples, but it is usually influenced by high-energy cosmic rays, and evaluating such effect of cosmic rays in lunar samples is especially important. Those cosmic radiation particles (primary particles) can react with lunar materials, creating many secondary particles. Both primary and secondary particles can produce cosmogenic nuclides on the Moon. Radiation Environment and Dose at the Moon (REDMoon) is a novel GEANT4 Monte-Carlo model built to simulate the interactions of space particles with the lunar surface and subsurface content. Using this model, we simulate the production of cosmogenic Cr isotopes (50Cr, 52Cr, 53Cr, 54Cr) at different depths of lunar surface, and compare the contribution of different reactions generating these nuclides. The results suggest that spallation reactions are the most important process producing cosmogenic Cr isotopes. We also analyze the relationship between 53Cr/52Cr and 54Cr/52Cr predicted by our model and compare it with different Apollo samples. As previously studied, we also find an approximate linear relationship between ɛ53Cr and ɛ54Cr, where ɛ53Cr (or ɛ54Cr) is the relative deviation from the standard 53Cr/52Cr ratio (or 54Cr/52Cr ratio), normalized to 1/10,000. Furthermore, we reveal a change of this linear relationship in different depths of lunar surface. Besides, we investigate how the slopes can be influenced by exposure age and the Fe/Cr ratio. With these additional factors carefully considered, the comparison between our modeled results and the measurements is better than previous studies.

¹Matthew Varnam,¹Christopher W. Hamilton,^2,3Igor Aleinov,¹Jessica J. Barnes
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116009]
¹Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85716, USA
²Center for Climate Systems Research, Columbia University, New York, NY, USA
³NASA Goddard Institute for Space Studies, New York, NY, USA
Copyright Elsevier

Lunar volcanic volatiles are crucial for understanding eruption dynamics on the Moon as well as the potential formation, life span, and dissipation of a lunar secondary atmosphere. We review literature concerning volatile content, degassing extent, and speciation during the mare eruption period on the Moon from 4.0 to 1.2 Ga, providing a realistic summary of degassed compositions for the traditional volcanic elements C-O-H-S-F-Cl. The most reliable estimates of lunar volcanic volatiles come from high‑titanium (high-Ti) glass beads sampled during the Apollo 17 mission. Analysis of these samples demonstrates that hydrogen is the most abundant element by mole in erupted volcanic gases, so a hydrogen species should be the most abundant molecule in the lunar gas, rather than carbon monoxide. This hydrogen is expected to speciate mostly as H2, rather than H2O, at the predicted oxygen fugacity for lunar magma. This difference is important because H2 more easily escapes from the Moon, whereas H2O could freeze out on the lunar surface, and potentially persist within permanently shadowed regions near the poles. We also find that sulfur, rather than carbon, is the third most abundant element in lunar volcanic gas, after hydrogen and oxygen.

^1,2Chanud N. Yasanayake,¹Brett W. Denevi,³Takahiro Hiroi,⁴Brad. L. Jolliff,¹Anna C. Martin,^3,5Annabelle L. Gao,^6,7Margaret L. Zhang,^8,9Lucas M. Bloom,¹⁰Samuel J. Lawrence
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008115]
¹Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
²Johns Hopkins University, Baltimore, MD, USA
³Brown University, Providence, RI, USA
⁴Washington University in St. Louis, St. Louis, MI, USA
⁵Marriotts Ridge High School, Marriottsville, MD, USA
⁶University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
⁷Mount Hebron High School, Ellicott City, MD, USA
⁸University of Alabama, Tuscaloosa, AL, USA
⁹Severna Park High School, Severna Park, MD, USA
¹⁰NASA Johnson Space Center, Houston, TX, USA
Published by arrangement with John Wiley & Sons

The lunar surface evolves over time due to space weathering, and the visible–near-infrared spectra of more mature (i.e., heavily weathered) soils are lower in reflectance and steeper in spectral slope (i.e., darker and redder) than their immature counterparts. These spectral changes have traditionally been attributed to the space-weathered rims of soil grains (and particularly nanophase iron therein). However, understudied thus far is the spectral role of agglutinates—the agglomerates of mineral and lithic fragments, nanophase iron, and glass that are formed by micrometeoroid impacts and are ubiquitous in mature lunar soils. We separated agglutinates and non-agglutinates from six lunar soils of varying maturity and composition, primarily from the 125–250 μm size fraction, and measured their visible–near-infrared reflectance spectra. For each soil, the agglutinate spectra are darker, redder, and have weaker absorption bands than the corresponding non-agglutinate and unsorted soil spectra. Moreover, greater soil maturity corresponds to darker agglutinate spectra with weaker absorption bands. These findings suggest that agglutinates (rather than solely the space-weathered rims) play an important role in both the darkening and reddening of mature soils—at least for the size fractions examined here. Comparisons with analog soils suggest that high nanophase iron abundance in agglutinates is likely responsible for their low reflectance and spectrally red slope. Additional studies of agglutinates are needed both to more comprehensively characterize their spectral properties (across size fractions and in mixing with non-agglutinates) and to assess the relative roles of agglutinates and rims in weathering-associated spectral changes.

^1,2J. Martell et al. (>10)
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008222]
¹Department of Geology, Lund University, Lund, Sweden
²LINXS Institute of Advanced Neutron and X-ray Science, Lund, Sweden
Published by arrangement with John Wiley & Sons

With several upcoming sample return missions, such as the Mars Sample Return Campaign, non-destructive methods will be key to maximizing their scientific output. In this study, we demonstrate that the combination of neutron and X-ray tomography provides an important tool for the characterization of such valuable samples. These methods allow quantitative analyses of internal sample features and also provide a guide for further destructive analyses with little to no sample treatment, which maintains sample integrity, including minimizing the risk of potential contamination. Here, we present and review the results from four case studies of terrestrial impactites and meteorites along with their analytical setup. Using combined X-ray and neutron tomography, a Ni-Fe silicide spherule, that is, projectile material, was located within a Libyan Desert Glass sample and the distribution of hydrous phases was pinpointed in selected impactite samples from the Chicxulub IODP-ICDP Expedition 364 drill core and the Luizi impact structure, as well as in the Miller Range 03346 Martian meteorite.

¹Kathleen C. Benison et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008155]
¹Department of Geology and Geography, West Virginia University, Morgantown, WV, USA
Published by arrangement with John Wiley & Sons

The Mars 2020 Perseverance rover has examined and sampled sulfate-rich clastic rocks from the Hogwallow Flats member at Hawksbill Gap and the Yori Pass member at Cape Nukshak. Both strata are located on the Jezero crater western fan front, are lithologically and stratigraphically similar, and have been assigned to the Shenandoah formation. In situ analyses demonstrate that these are fine-grained sandstones composed of phyllosilicates, hematite, Ca-sulfates, Fe-Mg-sulfates, ferric sulfates, and possibly chloride salts. Sulfate minerals are found both as depositional grains and diagenetic features, including intergranular cement and vein- and vug-cements. Here, we describe the possibility of various sulfate phases to preserve potential biosignatures and the record of paleoenvironmental conditions in fluid and solid inclusions, based on findings from analog sulfate-rich rocks on Earth. The samples collected from these outcrops, Hazeltop and Bearwallow from Hogwallow Flats, and Kukaklek from Yori Pass, should be examined for such potential biosignatures and environmental indicators upon return to Earth.

¹Tom Seccull,^2,3Wesley C. Fraser,⁴Dominik A. Kiersz,⁵Thomas H. Puzia
The Planetary Science Journal 5, 42 Open Access Link to Article [DOI 10.3847/PSJ/ad16dd]
¹Gemini Observatory/NSF’s NOIRLab, 670 N. A’ohoku Place, Hilo, HI 96720, USA; tom.seccull@proton.me
²Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
³Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2, Canada
⁴Independent Researcher, Belfast, UK
⁵Institute of Astrophysics, Pontificia Universidad Católica de Chile, Av. Vicuña MacKenna 4860, 7820436, Santiago, Chile

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

^1,2Seann J. McKibbin,³Lutz Hecht,¹Christina Makarona,⁴Matthew Huber,³Hermann Terryn, ¹Philippe Claeys
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14147]
¹Analytical-, Environmental-, and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
²Geowissenschaftliches Zentrum, Abteilung Isotopengeologie, Georg-August-Universität Göttingen, Göttingen, Germany
³Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
⁴Department of Earth Science, University of the Western Cape, Bellville, South Africa
⁵Research Group of Electrochemical and Surface Engineering, Vrije Universiteit Brussel, Brussels, Belgium
Published by arrangement with John Wiley & Sons

The occurrence of forsteritic olivine in EH enstatite chondrites is indicative of bulk disequilibrium. In MgO-rich magmatic systems, forsterite can either crystallize as a liquidus phase or be produced during peritectic melting of enstatite. Because diffusion of divalent cations through forsterite is relatively rapid, it records peak melting (i.e., chondrule-forming events) and is also sensitive to subsequent metamorphism in the EH chondrite parent body. Here, we report the major and minor element geochemistry of olivine in EH chondrites across petrologic types 3 and 4. In all cases, olivine meets the technical definition of forsterite (>90 mole% Mg2SiO4). For unequilibrated EH chondrites, minor elements identify CaO-Al2O3-TiO2-rich (refractory forsterite), MnO-rich (“LIME” forsterite), and FeO-bearing (forsteritic olivine) endmember components, the latter with Cr2O3-rich and Cr2O3-poor varieties. At higher petrologic type, minor element concentrations become restricted and compositions approach pure forsterite, while grain sizes reduce strongly with peak metamorphic temperatures. These changes reflect diffusive equilibration with enstatitic groundmass and dissolution reaction with free silica. The global geochemical distribution of forsteritic olivine in EH chondrites is, perhaps unexpectedly, more similar to those in low-FeO type I chondrules and associated objects in carbonaceous chondrites (CCs), rather than equivalent objects in ordinary (H, L, LL), low-FeO (or HH), or Kakangari (K) chondrites. Among achondrites, there is similarity between pure forsterite in aubrites and EH4 chondrites arising due to subsolidus equilibration in both settings, while Cr2O3-poor forsteritic olivine in EH3 and CCs is similar to magnesian xenocrystic olivine in angrites. This might reflect CaO-rich and SiO2-poor magmatic sources across multiple early solar system reservoirs.

^1,2Robert W. Nicklas,³Kathryn G. Gardner-Vandy,¹James M. D. Day
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14142]
¹Scripps Institution of Oceanography, UniRobert W. Nicklas, Department of Earth and Environmental Sciences,
²Boston College, Chestnut Hill, MA 02467, USA.versity of California San Diego, La Jolla, California, USA
³Aviation and Space, Oklahoma State University, Stillwater, Oklahoma, USA
Published by arrangement with John Wiley & Sons

Highly siderophile elements (HSE) strongly partition into metal phases over silicate minerals and so offer important constraints on nebular and core formation processes acting on early planetesimals. Abundances of the HSE are also an important tool for constraining relationships between metal-rich meteorites. The first bulk rock and in situ HSE abundance and 187Re-187Os data are reported for the ungrouped metal-rich achondrite Tafassasset to examine models of its petrogenesis and origin. Bulk rock and metal grain HSE abundances are elevated at ~2 and ~15 times CI chondrite abundances, respectively, and are largely unfractionated from one another. Metal within Tafassasset is therefore likely to have quenched shortly after partial melting without significant fractional crystallization. Metal grain HSE abundances can be used to calculate a metal fraction of 14 ± 4 wt%, overlapping with the parent bodies of CC iron meteorites, which have also been related to Tafassasset using nucleosynthetic isotope anomalies. Despite such similarities, HSE systematics of bulk rock Tafassasset are not equivalent to any known chondrites, and metal grains do not overlap with iron meteorites or chondrite metal grains, precluding a direct genetic relationship.

¹Hunter Vannier,¹Briony Horgan,²Julie D. Stopar,^3,4,5Marie Henderson
Journal of Geophysical Researhc (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008108]
¹Purdue University, West Lafayette, IN, USA
²Lunar and Planetary Institute, USRA, Houston, TX, USA
³Center for Space Sciences and Technology, University of Maryland, Baltimore, MD, USA
⁴Solar System Exploration Division, NASA/GSFC, Greenbelt, MD, USA
⁵Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD, USA
Published by arrangement with John Wiley & Sons

Irregular mare patches (IMPs) are enigmatic volcanic features on the Moon’s surface, whose lack of cratering and crisp appearance imply they formed <100 Ma ago, ∼1 Ga after the expected turnoff of lunar volcanism. Multiple contrasting formation hypotheses have been put forth to explain their young appearance, including recent emplacement via eruptions of juvenile volcanic material or outgassing, versus ancient volcanic deposits that were emplaced billions of years ago but only appeared young due to highly porous material. If IMPs formed recently, this would require a reinterpretation of lunar thermal evolution. To help constrain formation hypotheses, we provide a comprehensive mineralogical analysis of IMPs using visible to near infrared hyperspectral data from the Moon Mineralogy Mapper. IMPs appear spectrally dominated by high-calcium pyroxene and are spectrally similar to their host mare and fresh craters. IMPs do not show clear indications of significant glass, implying that pyroclastic eruption was not significant in IMP formation. Based on spectral comparisons to terrestrial magma foam, we find that this also contradicts the glassiness expected for a magma foam exposed at the surface. Thus, we find it is unlikely that IMPs are composed of recently erupted material and may instead be the result of recent or ongoing surface modification of materials similar in composition and likely contemporaneously emplaced with the mare. We favor previous hypotheses that collapse processes or drainage into subsurface voids or porous materials may have been the major drivers of IMP surface rejuvenation, supported by their proximity to collapse features.