^1,2Shuya Tan,^1,3,4Yasuhito Sekine,²Takazo Shibuya
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008591]
¹Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, Tokyo, Japan
²Institute for Extra-cutting-edge Science and Technology Avantgarde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
³Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Japan
⁴Planetary Plasma and Atmospheric Research Center, Tohoku University, Sendai, Japan
Published by arrangement with John Wiley & Sons

Enceladus’ ocean could support methanogenic life in terms of the availability of chemical energy (H2 and CO2) and nutrients (N and P). However, excess energy and nutrients in the ocean raise the question of why they remain abundant if Enceladus is inhabited. Terrestrial methanogens require trace metals, such as Co, Ni, Cu, Zn, and Mo, for their enzyme activation; nevertheless, the availability of these trace metals is largely unknown in Enceladus’ ocean. Here, we investigate concentrations of dissolved trace metals in Enceladus based on hydrothermal experiments and thermodynamic equilibrium calculations in order to understand the minerals that control their concentrations in water-rock interactions. Our results show that Ni and Co concentrations in hydrothermal fluids can be controlled by dissolution of a sulfide mineral, pentlandite, in chondritic rocks. In a pH range for Enceladus’ ocean, our calculations show that hydrothermal environments would be the source of dissolved Ni and Co. Given a suggested range of water chemistry (pH and dissolved species) of Enceladus’ ocean, Ni, Zn, and Mo concentrations in hydrothermal fluids would be comparable to the levels required for terrestrial methanogens. However, both Co and Cu concentrations would be depleted compared with the levels required for terrestrial methanogens. We suggest that if methanogenic life in Enceladus requires trace metals at the same levels as for terrestrial methanogens, the availability of Co and Cu could control the activity of methanogenesis, possibly leaving excess chemical energy and nutrients in the ocean.

¹Sohei Wada,¹Ken-ichi Bajo,^1,2Tomoya Obase,¹Hisayoshi Yurimoto
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14346]
¹Department of Natural History Sciences, Hokkaido University, Sapporo, Hokkaido, Japan
²Department of Earth and Planetary Sciences, Institute of Science Tokyo, Meguro, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Solar wind (SW) is preserved in meteorites as abundant solar noble gases. We performed in situ 4He isotope imaging of mineral grains in the CR2 chondrite matrix of Northwest Africa 801 using time-of-flight secondary neutral mass spectrometry with strong-field post ionization. 4He+ signals were detected along the surfaces of individual grains of Fe-Ni metal, ferrihydrite, olivine, pyroxene, and troilite. The high 4He concentrations along the surfaces indicate implantation of SW into the mineral grains. We determined the SW-4He fluence of eight mineral grains from the line profiles across the grain boundaries. SW-4He fluence ranged from 2.7 × 1016 to 58 × 1016 atoms cm−2. These fluences were then used to calculate the SW irradiation durations. Assuming irradiation occurred at 4 astronomical units, the durations ranged from 3.8 to 82 kyr. These durations correspond to the residence time of individual mineral grains on the surface of the parent body. The variation in residence time for the mineral grains suggests variable durations for local mixing and burial processes on the parent body. The SW exposure ages provide insights into the gardening rate driven by small-scale impact mixing processes on the parent body.

^1,2Peter Jenniskens et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14337]
¹SETI Institute, Mountain View, California, USA
²NASA Ames Research Center, Moffett Field, California, USA
Published by arrangement with John Wiley & Sons

The Aguas Zarcas (Costa Rica) CM2 carbonaceous chondrite fell during nighttime in April 2019. Security and dashboard camera videos of the meteor were analyzed to provide a trajectory, light curve, and orbit of the meteoroid. The trajectory was near vertical, 81° steep, arriving from an ~109° (WNW) direction with an apparent entry speed of 14.6 ± 0.6 km s−1. The meteoroid penetrated to ~25 km altitude (5 MPa dynamic pressure), where the surviving mass shattered, producing a flare that was detected by the Geostationary Lightning Mappers on GOES-16 and GOES-17. The cosmogenic radionuclides were analyzed in three recovered meteorites by either gamma-ray spectroscopy or accelerator mass spectrometry (AMS), while noble gas concentrations and isotopic compositions were measured in the same fragment that was analyzed by AMS. From this, the pre-atmospheric size of the meteoroid and its cosmic ray exposure age were determined. The studied samples came from a few cm up to 30 cm deep in an object with an original diameter of ~60 cm that was ejected from its parent body 2.0 ± 0.2 Ma ago. The ejected material had an argon retention age of 2.9 Ga. The object was delivered most likely by the 3:1 or 5:2 mean motion resonances and, without subsequent fragmentation, approached the Earth from a low i < 2.8° inclined orbit with a perihelion distance q = 0.98 AU close to the Earth’s orbit. The steep entry trajectory and high strength resulted in deep penetration in the atmosphere and a relatively large fraction of surviving mass.

¹Yves Marrocchi, ²Tahar Hammouda, ²Maud Boyet, ³Guillaume Avice, ^4,5Alessandro Morbidelli
Earth and Planetary Science Letters 659, 119337 Link to Article [https://doi.org/10.1016/j.epsl.2025.119337]
¹Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France
²CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, Université Clermont Auvergne, 63000 Clermont-Ferrand, France
³Institut de physique du globe de Paris, CNRS, Université de Paris, Paris 75005, France
⁴Laboratoire Lagrange, Centre National de la Recherche Scientifique, Observatoire de la Côte d’Azur, Université Côte d’Azur, 06304 Nice, France
⁵Collège de France, Centre National de la Recherche Scientifique, Université Paris Sciences et Lettres, Sorbonne Université, 75014 Paris, France
Copyright Elsevier

The nature and origin of the Earth’s building blocks remain intensely debated. While enstatite chondrites (ECs) were formed from a reservoir with an isotopic composition of major elements similar to that of the Earth, they nevertheless exhibit significant chemical differences. Specifically, the Earth is enriched in refractory elements and depleted in moderately volatile elements compared to ECs. By reevaluating the budget of rare earth elements in enstatite chondrites, we show that EC chondrule precursors correspond to early condensates formed in the inner protoplanetary disk. Taking condensation models into account, we propose that these condensates consist primarily of olivine, which was subsequently transformed into enstatite due to gas-melt interactions during chondrule formation. We show that the accretion of the Earth from olivine-rich EC chondrules, which underwent shorter gas-melt interactions compared to those present in ECs, satisfactorily reproduces its chemical ratios (i.e., Mg/Si, Al/Si, Na/Si, Ti/Si, Ca/Si) and oxygen isotopic composition. This difference in the duration of gas-melt interactions in the protoplanetary disk had thus major consequences on the chemical composition of the planetesimals accreted by planetary embryos. Our approach thus addresses the chemical divergence between Earth and ECs without altering their isotopic compositions, while also supporting planet formation models involving large embryos formed in the inner protoplanetary disk.

¹Xue Su, ¹Youxue Zhang, ²Yang Liu
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.03.026]
¹Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
Copyright Elsevier

Our recent investigations have discovered inward diffusion (in-gassing) of moderately volatile elements (MVEs; e.g., Na, K and Cu) from volcanic gas into volcanic beads/droplets. In this work, we examine the distribution of sulfur in lunar orange glass beads. Our analyses reveal that sulfur exhibits a non-uniform distribution across the beads, forming “U” or “W” shaped profiles typical of in-gassing. A model developed to assess sulfur contributions from different sources (original magmatic sulfur versus atmospheric in-gassed sulfur) in the orange beads indicates that atmospheric sulfur in-gassed during eruption contributes approximately 9–24 % to the total sulfur content of an orange bead, averaging around 16 %. This in-gassed sulfur is derived from the eruption plume, where atmospheric sulfur could undergo photochemical reactions induced by UV light, leading to mass independent fractionation and a distinct sulfur isotope signature.
Interestingly, a recent study discovered a small mass independent isotope fractionation of sulfur in lunar orange glass beads in drive tube 74002/1 and a lack of such mass independent isotope fractionation in black glass beads in the same lunar sample. This finding contrasts with sulfur in lunar basalts, which typically exhibit mass dependent fractionation. With our work, the observed mass independent fractionation signal in sulfur isotopes of orange beads can be attributed to the in-gassing of photolytic sulfur in the optically thin part of the eruption plume where UV light can penetrate. Using the sulfur isotope data of lunar orange beads, we estimate that the Δ33S value of atmospheric sulfur is approximately −0.18 ‰. Our study provides new insights into the complex dynamics of volatile elements in lunar volcanic processes, highlighting the role of in-gassing in shaping sulfur isotope signatures in volcanic glass beads.

¹Franz Brandstätter,^2,3Niels J. de Winter,⁴Alessandro Migliori,⁴Roman Padillia-Alvarez,¹Dan Topa,⁵Seerp Visser,⁴Steven Goderis,⁴Philippe Claeys,⁵Christian Koeberl
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14340]
¹Natural History Museum Vienna, Vienna, Austria
²Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
³Archaeology, Environmental Changes and Geo-Chemistry Group, Vrije Universiteit Brussel, Brussels, Belgium
⁴Department of Nuclear Sciences and Applications, International Atomic Energy Agency, Vienna International Centre, Vienna, Austria
⁵Bellevuedreef 40, Antwerp, Belgium
⁶Department of Lithospheric Research, University of Vienna, Vienna, Austria
Published by arrangement with John Wiley & Sons

The “Weltmuseum Wien” owns a large collection of kris daggers from Indonesia. These objects are famous for their metal blades consisting of numerous layers made by a complicated forging process involving repeated folding and welding of the individual layers. There is a widespread belief that some krises were manufactured by adding meteoritic nickel–iron from the Prambanan meteorite that fell in Central Java and is known since the late 18th century. In our study, we investigated a selection of five Ni-rich krises from this collection with the aim to identify in their blades nickel–iron from Prambanan or another iron meteorite source. To obtain a better insight into the forging process, we investigated analog objects that were produced by a forging procedure similar to the one applied in the production of original krises and by using iron meteorite material from the meteorites Campo del Cielo and Gibeon as admixture. These investigations were performed by nondestructive analytical techniques, including handheld X-ray fluorescence (HH-XRF) analysis, scanning electron microscopy (SEM), and electron microprobe (EMP) analysis. The original daggers were investigated by HH-XRF and micro-X-ray fluorescence (μ-XRF) analysis, as well as by portable laser ablation (pLA) subsampling followed by trace element analysis using inductively coupled plasma mass spectrometry (ICP-MS). By comparing the data obtained for both materials, we demonstrate that the main difficulties in identifying the presence of a meteoritic component in the kris daggers are due to the exclusive use of (quasi-)nondestructive methods in combination with locally varying surface heterogeneities, resulting from contamination, corrosion, and etching features. We also show that the presence of significant amounts of Ni and Co (in the wt% range) in a premodern kris dagger does not imply that it was manufactured with an admixture of meteoritic metal. We found that among the five krises investigated, only a single dagger (no. 900382) was manufactured with the possible admixture of nickel–iron from the Prambanan iron meteorite, as it contains high concentrations of siderophile elements and has a Ni/Co ratio comparable to that of the meteorite.

¹Yuanyuan He, ²Flavio Siro Brigiano, ³Michel Sablier, ¹Nadezda Khodorova, ⁴David Boulesteix, ⁴Arnaud. Buch, ²Peter Reinhardt, ¹Sylvain Bernard,¹Laurent Remusat
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.03.017]
¹Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Sorbonne Université, 75005 Paris, France
²Laboratoire de Chimie Théorique, Sorbonne Université, 75005 Paris, France
³Laboratoire Sciences Analytiques, Bioanalytiques et Miniaturisation ESPCI CNRS UMR CBI 8231, 10 rue Vauquelin, 75005 Paris, France
⁴Laboratoire Génie des Procédés et Matériaux, LGPM, CentraleSupélec, University of Paris-Saclay, 91190 Gif-sur-Yvette, France
Copyright Elsevier

Amino acids detected in carbonaceous chondrites are commonly enriched in heavy isotopes of hydrogen compared to terrestrial counterparts. This is interpreted as the consequence of synthesis processes happening in cold extraterrestrial environments. However, the magnitude of this enrichment is variable among classes of chondrites and among individual amino acid in a given chondrite. In this study, we investigated the evolution of the D/H isotope ratio of amino acids experimentally exposed to pure D2O at 150 °C. We observed that not all the hydrogen-specific sites are prone to deuterium-hydrogen exchange under hydrothermal conditions. Ab-initio modeling pinpoints the higher acidity of the carbon in α position (Cα) leading to a site-specific preferential D-H exchange, affecting the hydrogen atoms bonded to Cα (α-H). This explains the low exchange rate of 2-aminoisobutyric acid and isovaline, these branched amino acids lacking α-H, and the rather high exchange rate of glycine, a-alanine and β-alanine, their α-H exchanging faster. By extrapolating these results, it can be assumed that chondritic amino acids lacking α-H and containing only primary hydrogen (i.e., –CH3 group) have better retained their pre-accretional D/H values despite hydrothermal alteration on the parent body.

¹A. Emran, ¹K.M. Stack
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116576]
¹NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
Copyright Elsevier

Hollows on Mercury are small depressions formed by volatile loss, providing important clues about the volatile inventory of the planet’s surface and shallow subsurface. We investigate the composition of hollows in various phases of devolatilization at Dominici crater. By applying a machine learning approach to MESSENGER Mercury Dual Imaging System data, we defined surface units within the study area and extracted their reflectance spectra. We applied linear (areal) spectral modeling using laboratory sulfides, chlorides, graphite, and silicate mineral spectra to estimate the composition of hollows and their surrounding terrains. At Dominici, the hollow on the crater rim/wall is interpreted to be active, while that in the center of the crater is interpreted as a waning hollow. We find that the active hollow predominantly comprises silicates (augite and albite), with a trace amount of graphite and CaS. In contrast, waning hollows contain marginally elevated sulfides (MgS and CaS) and graphite, but slightly lower silicates than the active hollow. The spectra of low reflectance terrain surrounding the hollows appear to be dominated by graphite and sulfides, which contribute to its darker appearance. We suggest that hollow at the crater forms due to thermal decomposition of sulfides, primarily MgS possibly mixed with CaS, as well as possible the depletion of graphite. As devolatilization wanes, a mixture of predominantly silicate minerals remains in the hollows — impeding further vertical growth.

^1,2Roshan Nath et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14342]
¹Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh, India
²Physical Research Laboratory, Ahmedabad, Gujarat, India
Published by arrangement with John Wiley & Sons

Meteorites, remnants of asteroids that successfully survive their passage through the Earth’s atmosphere, hold critical information about the evolution and history of the solar system. Traditional methods of analyzing these rare and precious specimens often involve destructive geochemical techniques, which deplete the sample and limit subsequent analyses. The accurate classification of meteorites, typically determined through petrological examination, is crucial before any further analytical steps. Reflectance spectroscopy, which interprets a sample’s characteristics by analyzing reflected light, has emerged as a nondestructive alternative with significant potential for meteorite classification. In this technique, apparently, sometimes we do not need to process the sample. This technique allows for the examination of spectral features such as absorption bands, symmetry, band centers, inflection points, and overall slope. In this study, we employed spectral reflectance data from 1781 meteorite samples to develop and fine-tune a deep learning model capable of accurate classification. The model was trained on 75% of the dataset and validated on the remaining 25%, achieving a validation accuracy of 93%. These results demonstrate the efficiency of using deep learning and reflectance spectroscopy for meteorite classification, offering a nondestructive and accurate alternative to traditional methods.

^1,2Zhi Cao et al. (>10)
Earth and Planetary Science Letters 658, 119327 Link to Article [https://doi.org/10.1016/j.epsl.2025.119327]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China
²Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-Sen University, 519082 Zhuhai, China
Copyright Elsevier

The space weathering processes modify the microstructure and physicochemical properties of the surface of regolith mineral grains. We report microcraters and space-weathered rims on the surface of plagioclase, pyroxene, olivine, ilmenite and troilite grains in Chang’e-5 scooped lunar soil by electron microscopy. Micro-analysis shows that low-speed secondary impact events indicated by microcraters dominated the evolution of Chang’e-5 regolith materials, which may have driven the formation of a potential microscale redox environment under a special mineral combination. Solar wind and cosmic ray irradiation lead to significant differences in space-weathered rims of mineral surfaces. This indicates the correlation between the nature of different space-weathered rims and the inherent structure and composition of minerals. According to the statistical correlation between space-weathered rim width and track density, the average exposure ages of plagioclase and olivine in Chang’e-5 lunar soil are 2.180−0.222+0.229 Ma and 0.842−0.469+1.120 Ma, respectively. This rule applies to regolith materials with short exposure time. The in situ mineralogical evidence clarifies that compared with Apollo mature lunar soil, Chang’e-5 lunar soil seems to have undergone weaker space weathering modification and shorter exposure history, and the essence is a weakly space-weathered lunar soil from young basalt. The nature of the space-weathered rims on the mineral surface of Chang’e-5 lunar soil reflects the response of regolith material to space weathering in a short exposure history, which is of great significance for the interpretation of spectral data of returned samples.