^1,2Zhang, Ai-Cheng, ³He, Huai-Yu, ⁴Hu, Sen, ³Li, Xian-Hua, ⁴Lin, Yang-Ting,⁵Qin, Li-Ping,⁶Wang, Gui-Qin,⁷Xiao, Zhi-Yong
Space: Science and Technology 4, 0170 Open Access Link to Article [DOI10.34133/space.0170]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
⁴Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
⁵CAS Key Laboratory of Crust-Mantle Materials and Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China
⁶State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
⁷Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China

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¹Mireia Leon-Dasi, ²Sebastien Besse, ³Lauren M. Jozwiak, ⁴Erica R. Jawin, ¹Alain Doressoundiram
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.11642]
¹LESIA, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, Meudon, 92195, France
²European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, Villanueva de la Cañada, 28692, Spain
³Planetary Exploration Group, Johns Hopkins University Applied Physics Laboratory, 1101 Johns Hopkins Road, Laurel, 20723, MD, United States
⁴Smithsonian Institution, National Air and Space Museum, 600 Independence Ave, Washington, 20560, DC, United States
Copyright Elsevier

Explosive volcanic activity on Mercury extended after the end of the widespread effusive volcanism era. While prior research has recognized a prolonged period of explosive volcanic activity, the specific eruption timing for individual pyroclastic deposits remains unknown. In this study, we explore the evolution of explosive volcanism by examining the relationship between the morphological degradation of the vents and spectral changes in the associated deposits. We find a diverse range of spectral properties in pyroclastic deposits, which are typically characterized by increased brightness, a red spectral slope, and a higher curvature compared to the average surface. Rather than presenting a unique spectral signature, these deposits exhibit spectral parameters that span the range of most units on Mercury. We observe a trend between the deposit spectra and the vent degradation characterized by a rapid initial darkening and flattening over time followed by stabilization. The oldest deposits reach a steady state with no further spectral changes. To explain these temporal variations in spectral properties, we propose three potential processes: space weathering, mixing with the background and changes in pyroclast size over time. We examine the implications of space weathering on spectral properties and discuss the eruption timeline for each scenario. The saturation of spectral changes induced by space weathering acts over a period of 1 Gyr. We suggest that a large portion of the pyroclastic deposits identified to date, which have a marked spectral contrast with the surrounding terrain, have been emplaced by recent explosive volcanic eruptions.

¹B.G. Rider-Stokes, ¹S.L. Jackson, ^2,3T.H. Burbine, ¹L.F. White, ¹R.C. Greenwood, ⁴E.M. MacLennan, ¹M. Anand, ⁵A. Yamaguchi, ¹M.M. Grady
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116429]
¹School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
²Department of Astronomy, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA
³Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719, USA
⁴Department of Physics, University of Helsinki, Finland
⁵National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
Copyright Elsevier

It is hypothesized that the Solar System was once populated by Moon to Mars-sized planetary embryos, however, resulting debris from their disruptions is not easily discernible in the modern-day Solar System. Angrites are among the oldest differentiated materials in our Solar System, recording prolonged magmatism, and their parent body is expected to have been Moon to Mars-sized. Even so, no parent body in the modern-day Solar System has been identified. Our UV–Vis-NIR spectra of ten angrites, compared with 712 asteroids, reveal multiple candidates with spectral similarities through curve matching and band-structure analysis. Asteroid (246) Asporina provides the best analog for the angrite meteorites, potentially representing a fragment of a long-lost Moon to Mars-sized body that once resided in the inner Solar System, which was subsequently incorporated into the growing terrestrial planets.

¹José San Martin et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116403]
¹Technische Universität Bergakademie Freiberg, 09599 Freiberg, Germany
Copyright Elsevier

Martian Simulants are an essential part of in situ resource utilization (ISRU) technology development and testing, and aid in providing new astrobiology insights regarding Mars’s past habitability. This study proposes a new method involving average and standard deviation (ASD), complementary to Figures of Merit (FOM) simulant evaluation methods, for geochemical prospection and evaluation of simulant feedstock using portable XRF (pXRF) and whole-rock (ICP-OES) analyses. It also presents Simulant Modification Calculations (SMC) that integrate multiple approaches used in simulant production and design, and provides theoretical mineral recipes (estimated mineral composition) and their estimated geochemical compositions for FOM evaluation of an intended target composition. These methods were used to prospect simulant material in volcanic-subvolcanic outcrops at the SW edge of the Atacama Desert in Chile, and to evaluate their potential for standard and enhanced simulant development. Through ASD (pXRF data) and FOM (ICP-OES data) evaluation, this resulted in the presentation of the first Chilean basic Martian bedrock simulant that can be used for Biomining applications, which is tentatively labeled as Chilean Atacama Desert 1 (CAD-1). An Excel file with the applied prospection method and database is also available for simulant feedstock prospection (Supplementary section). Applying these methods will provide more base materials and components for simulant development and allow flexibility in their design for general and specific applications.

¹C. H. Seeger,¹J. P. Grotzinger
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008531]
¹Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

The diversity and abundance of diagenetic textures observed in sedimentary rocks of the clay-sulfate transition recorded in the stratigraphic record of Gale crater are distinctive within the rover’s traverse. This study catalogs all textures observed by the MAHLI instrument, including their abundances, morphologies, and cross-cutting relationships in order to suggest a paragenetic sequence in which multiple episodes of diagenetic fluid flow were required to form co-occurring color variations, pits, and nodules; secondary nodule populations; and two generations of Ca sulfate fracture-filling vein precipitation. Spatial heterogeneities in the abundance and diversity of these textures throughout the studied stratigraphic section loosely correlate with stratigraphic unit, suggesting that grain size and compaction controls on fluid pathways influenced their formation; these patterns are especially prevalent in the Pontours member, where primary stratigraphy is entirely overprinted by a nodular fabric, and the base of the stratigraphic section, where increased textural diversity may be influenced by the underlying less permeable clay-bearing rocks of the Glen Torridon region. Correlations between quantitative nodule abundance and subtle variations in measured bulk rock chemistry (especially MgO and SO3 enrichment) by the Alpha Particle X-Ray Spectrometer instrument suggest that an increase in Mg sulfate upsection is linked to precipitation of pore-filling diagenetic cement. Due to a lack of sedimentological evidence for widespread evaporite or near-surface crust formation of these Mg sulfates, we propose three alternative hypotheses for subsurface groundwater-related remobilization of pre-existing sulfates and reprecipitation at depth in pore spaces.

¹D.C. Rubie, ²K.I. Dale, ³G. Nathan, ⁴M. Nakajima, ⁵E.S. Jennings, ¹G.J. Golabek, ³S.A. Jacobson, ^2,6A. Morbidelli
Earth and Planetary Science Letters 651, 119139 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2024.119139]
¹Bayerisches Geoinstitut, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany
²Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
³Department of Earth & Environmental Sciences, Michigan State University, 288 Farm Lane, East Lansing, MI 48823, USA
⁴Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester, NY 14627, USA
⁵School of Natural Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
⁶Collège de France, CNRS, PSL Univ., Sorbonne Univ., Paris, 75014, France
Copyright Elsevier

The Hf-W isotopic system is the reference chronometer for determining the chronology of Earth’s accretion and differentiation. However, its results depend strongly on uncertain parameters, including the extent of metal-silicate equilibration and the siderophility of tungsten. Here we show that a multistage core-formation model based on N-body accretion simulations, element mass balance and metal-silicate partitioning, largely eliminates these uncertainties. We modified the original model of Rubie et al. (2015) by including (1) smoothed particle hydrodynamics estimates of the depth of melting caused by giant impacts and (2) the isotopic evolution of ¹⁸²W. We applied two metal-silicate fractionation mechanisms: one when the metal delivered by the cores of large impactors equilibrates with only a small fraction of the impact-induced magma pond and the other when metal delivered by small impactors emulsifies in global magma oceans before undergoing progressive segregation. The latter is crucial for fitting the W abundance and ¹⁸²W anomaly of Earth’s mantle. In addition, we show, for the first time, that the duration of magma ocean solidification has a major effect on Earth’s tungsten isotope anomaly. We re-evaluate the six Grand Tack N-body simulations of Rubie et al. (2015). Only one reproduces ε¹⁸²W=1.9 ± 0.1 of Earth’s mantle, otherwise accretion is either too fast or too slow. Depending on the characteristics of the giant impacts, results predict that the Moon formed either 143–183 Myr or 53–62 Myr after the start of the solar system. Thus, independent evaluations of the Moon’s age provide an additional constraint on the validity of accretion simulations.

^1,2W. Abouchami, ¹F. Wombacher, ²S.J.G. Galer
Geochimica et Cosmochimica (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.12.001]
¹Institute of Geology and Mineralogy, University of Cologne, Köln, Germany
²Max Planck Institute for Chemistry, Climate Geochemistry Department, Mainz, Germany
Copyright Elsevier

Early pioneering studies of Apollo lunar soils revealed a geochemical dichotomy reflecting a dominance of mare and highland lithologies, with variable additions of Procellarum KREEP Terrane material. Here, we use the moderately volatile element cadmium to identify the sources and processes responsible for mass-dependent Cd stable isotope variations in the lunar regolith. In addition, capture of thermal neutrons by 113Cd, resulting from galactic cosmic rays (GCR) impacting the lunar surface, provides a means of reconstructing the exposure history of the regolith.
We report TIMS double spike Cd stable isotope data on samples from the Apollo 12, 16 and 17 missions, consisting of twelve soils of varying maturity, two ferroan anorthosites, and orange glass 74220. Cadmium abundances are generally lower in mare (12 to 79 ng/g) than highland soils (∼70 to 95 ng/g). Cadmium stable isotope compositions, expressed as ε112/110Cd, display a larger range in mare (∼0 to + 106) and highland (+60 to + 97) soils. The two anorthosites exhibit contrasting ε112/110Cd values (−107 vs. + 47) and Cd concentrations similar to those of highland soils. Orange glass 74,220 is Cd-rich (290 ng/g) and has a light Cd isotopic composition (ε112/110Cd = -27) due to condensation of Cd vaporized during lava fountaining.
A broad trend of decreasing Cd abundance and increasing heavy isotope enrichment with increasing maturity is observed for mare soils but is not apparent for the highland soils. These characteristics might arise from space weathering, including micrometeorite bombardment, but simple mass balance indicates that meteoritic addition has a negligible effect on the lunar regolith Cd. Likewise, neutron capture on 113Cd tends to increase with maturity in mare soils while being greater and relatively uniform in highland soils, reflecting a longer exposure history and more extensive reworking of the highland regolith. Neutron capture effects were not resolved for immature mare soils, orange glass and one anorthosite, indicating these samples experienced only short near-surface exposure to GCR.
The relationships between Cd abundances and isotope effects reveal three distinct correlations for the highland soils and the mature and immature mare soils, respectively. These are best explained by simple binary mixing between isotopically distinct components. The “heavy” Cd components of mare and highland soils have variable but overall low Cd contents while the cadmium-rich component is always isotopically “light”, and common, at least, to all mare soils. The strong correlation between Cd stable isotopic composition and neutron capture effects in mare soils constrains the ε112/110Cd of the neutron capture-free component to be −4.9 ± 2.3, that is marginally lighter than that of the Bulk Silicate Earth (0.01 ± 0.94). This component is predominantly found in immature, KREEP-rich soils that were not exposed to GCR. This supports an origin as exhumed material, possibly from the relatively recent Copernicus Crater, and/or as vapor re-distributed over the lunar surface. The ubiquitous presence on the Moon of a cadmium-rich reservoir and its apparent isotopic similarity with the BSE requires further scrutiny for a critical evaluation of its significance and implications for the bulk Moon composition.

¹Maggie McAdam,²Cristina Thomas,²Lauren McGraw,³Andrew Rivkin,²Joshua Emery
Planetary Science Journal 5, 254 Open Access Link to Article [DOI 10.3847/PSJ/ad888d]
¹NASA Ames Research Center, PO Box 1, Moffett Field, CA 94035, USA
²Northern Arizona University, DAPS: Room 209, Building 19, Physical Sciences, 527 S. Beaver Street, Flagstaff, AZ 86011, USA
³Johns Hopkins University’s Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA

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¹Du Zhimao,¹ Li Shaolin,¹Shan Xingmei,¹Lin Qing
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14291]
¹Shanghai Astronomy Museum (branch of Shanghai Science & Technology Museum), Shanghai, China
Published by arrangement with John Wiley & Sons

The Shanghai Astronomy Museum (SAM) has opened its meteorite collections to the planetary science community. Inaugurated in July 2021, SAM is recognized as the world’s largest astronomical museum and currently houses a collection of 97 meteorites weighing a total of 469 kg. These meteorites come from over 40 nations and encompass a diverse array of 37 different groups. Among them, 70 meteorites are displayed in the museum. The museum also features a series of interactive exhibition areas showcasing the internal structure of meteorites, engaging games introducing meteorite identification, and simulating the formation process of asteroid impact craters. This comprehensive range of offerings enables public access to extensive scientific knowledge about meteorites, making the museum a pivotal platform for disseminating meteoritics to the public.

¹K. I. Ridenhour,¹V. Reddy, A. Battle,¹D. Cantillo,²N. C. Pearson, ²J. A. Sanchez
Planetary Science Journal 5, 256 Open Access Link to Article [DOI 10.3847/PSJ/ad7116]
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA; kayceer@arizona.edu
²Planetary Sciences Institute, Tucson, AZ 85719, USA

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