¹E.S. Kite et al. (>10)
Earth and Planetary Science Letters 660, 119347 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2025.119347]
¹University of Chicago, Chicago, IL, USA
Copyright Elsevier

Early Mars was habitable, at least intermittently, but major questions remain about how much water flowed and for how long. The paleoclimate evolution of Mars is captured by the stratigraphic record in Gale crater (Milliken et al. 2010). Climbing through mostly aeolian deposits reflecting arid conditions within Gale crater, the Mars Science Laboratory Curiosity rover encountered wave-rippled lake sediments of the basin-spanning Amapari Marker Band (AMB) that have very high metal enrichments (Fe, Mn, Zn). What caused the association between relatively wet primary depositional environment, and metal enrichment? Tentative, but reasonable extrapolation of rover metal data across the AMB suggests an excess Fe mass of 0.2 Gt. Transporting this Fe likely required ∼10,000 km³ of water flow, much more than the volume of the lake, across >10³ yr. Deposition of the Fe could be due to a redox or pH front within or just beneath the lake. One possible basin-scale synthesis involves a climate excursion consisting of initial cooling then subsequent warming: initial cooling permits wind scour in Gale basin and ice build-up on Gale’s rim, while subsequent melting fills the lake and mobilizes Fe. Alternatively, the data can be explained by water-table fluctuations. In either case, the metal enrichment likely contributed to the hardness of these rocks, aiding wave-ripple preservation.

¹Simon Turner,²Bernard Wood,³Tim Johnson,⁴Craig O’Neill,⁵Bernard Bourdon
Nature 640, 390–394 Link to Article [DOI https://doi.org/10.1038/s41586-025-08719-3]
¹School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
²Department of Earth Sciences, University of Oxford, Oxford, UK
³School of Earth and Planetary Sciences, Curtin University, Perth, Western Australia, Australia
⁴School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
⁵Laboratoire de Géologie de Lyon Terre Planète Environnement, ENS Lyon, CNRS and Université Lyon I, Lyon, France

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^1,2S. Iannini Lelarge, ^1,3M. Masotta, ^1,3L. Folco, ⁴T. Ubide, ^1,5M.D. Suttle, ^6,7L. Pittarello
Geochemistry (Chemie der Erde)(in Press) Link to Article [https://doi.org/10.1016/j.chemer.2025.126293]
¹Dipartimento di Scienze della Terra, Università di Pisa, Via Santa Maria 53, 56126 Pisa, Italy
²Institute of Geosciences and Earth Resources, Consiglio Nazionale delle Ricerche, Via Moruzzi 1, 56124 Pisa, Italy
³CISUP, Centro per l’Integrazione della Strumentazione Università di Pisa, Lungarno Pacinotti 43, Pisa 56126, Italy
⁴School of Earth and Environmental Sciences, The University of Queensland, Brisbane 4102, QLD, Australia
⁵School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
⁶Naturhistorisches Museum, Mineralogisch-Petrographische Abteilung, Burgring 7, 1010 Vienna, Austria
⁷Department of Lithospheric Research, University of Vienna, Josef-Holaubek-Platz 2,1090 Vienna, Austria
Copyright Elsevier

We conducted high-pressure (1 GPa) melting experiments (1100–1400 °C) on the equilibrated ordinary chondrite DAV 01001 (L6) to investigate partial melting scenarios of planetary embryo in the early solar system. At 1100 °C, no melting of the silicate phase is observed, and the initial chondritic texture is preserved, but the metallic-sulphidic phases formed two immiscible Fesingle bondNi and S-rich liquids. Melting of silicate minerals began at 1200 °C, progressing from plagioclase to high-Ca and low-Ca pyroxene and olivine. As melting advanced, the formation of new olivine and low-Ca pyroxene resulted in the production of trachy-andesitic melt at 1200 °C, basaltic trachy-andesitic melt at 1300 °C, and andesitic melt at 1400 °C. These silicate melts have chemical similarities with some anomalous achondrites (e.g., GRA 60128/9). At the same time, minerals of new formation resemble those of primitive achondrites (e.g., brachinites, ureilites, IAB silicate inclusions, acapulcoites and lodranites). The rapid mineral-liquid re-equilibration suggests that basaltic liquids can form only above 1400 °C and that relatively high degrees of melting (>20 %) and crystallisation are necessary to explain the observed diversity of achondritic lithologies. These findings suggest that partial melting and recrystallization processes within planetary embryos could have played a critical role in the early solar system, contributing to the early differentiation of planetary bodies and the diversity of achondritic lithologies, including (but not limited to) alkali-rich achondrites.

¹Lee Saper,¹Yang Liu,²Michael A. Kipp,¹David Burney,³Chi Ma,²Francois L. H. Tissot,⁴Edward Young,³Jonathan Treffkorn,³Kenneth A. Farley
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14345]
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
²The Isotoparium, Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA
³Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁴Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, California, USA
Published by arrangement with John Wiley & Sons

Northwest Africa 13134 is a coarse-grained gabbro with an oxygen isotopic composition consistent with a Martian origin and is classified as an enriched shergottite based on its bulk trace element abundances and bulk La/Yb ratio of 1.53. The meteorite is composed of a framework of large pyroxene rods up to 6 mm in longest dimension (64% by area) with interstitial maskelynite (formerly plagioclase; 28% by area). Minor phases include merrillite and apatite, Fe-Ti oxides, and Fe-sulfides; trace phases such as baddeleyite, tranquillityite, fayalitic olivine, silica, and a felspathic phase are observed in evolved mesostasis pockets and partially crystallized magmatic inclusions in minerals. Individual pyroxene rods display a distinctive patchy Ca zoning pattern of juxtaposed low-Ca (pigeonite) and high-Ca (augite) patches with a common crystallographic orientation indicating epitaxial growth. Low-Ca pigeonite is the volumetrically dominant pyroxene phase (~70% of exposed pyroxene) and was the primary liquidus phase, followed closely by augite. Plagioclase crystallized along with the other minor phases from the residual melt between cumulus pyroxene rods. Pyroxenes display ubiquitous exsolution lamellae with typical widths and spacings of 1–2 μm. Sulfide grains are characterized by flame-shaped lamellar intergrowths of hexagonal pyrrhotite (Fe0.90S) and slightly metal-deficient pyrrhotite (Fe0.98S), along with minor pentlandite and chalcopyrite. The pyroxene and sulfide microtextures suggest that the gabbro experienced slow and protracted subsolidus cooling. Ilmenite-oxide pairs imply an oxygen fugacity of ~1 log unit below the fayalite–magnetite–quartz buffer at a closure T ≈ 875°C. Collectively, the texture and bulk composition suggest that Northwest Africa 13134 represents a slowly cooled and coarsely crystalline portion of a solidified magma body similar to the source of the enriched basaltic shergottites. Magnetite occurs locally as veins crosscutting pyrrhotite grains and in oxide–phosphate symplectites observed at merrillite–apatite phase boundaries. The presence of magnetite in the sample suggests that at various stages of cooling, the gabbro interacted with relatively oxidized fluids, which could be of deuteric or exogeneous origin. A cosmic-ray exposure age of 2.8–4.0 Ma was calculated based on 3He measured in pyroxene grain separates and overlaps with other shergottites. Finally, we present the first bulk uranium isotope measurement of a Martian meteorite: δ238U = −0.22 ± 0.10‰ and δ234Usec = +9.57 ± 0.35‰. These values indicate slight excesses in heavy U but overlap with the distribution of U isotope compositions of the Earth and other solar system materials.

¹Mireia Leon-Dasi, ²Sebastien Besse, ³Camille Cartier, ⁴Océane Barraud, ⁴Alessandro Maturilli, ¹Alain Doressoundiram, ⁵Johannes Benkhoff, ^3,6Laurie Llado
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116582]
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 Canada, 28692, Spain
³Centre de Recherches Pétrographiques et Géochimiques, Université de Lorraine, 15 Rue Notre Dame des Pauvres, Vandœuvre-lès-Nancy, 54501, France
⁴German Aerospace Center DLR, Institute of Planetary Research, Rutherfordstr. 2, Berlin, 12489, Germany
⁵European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, Noordwijk, 2200 AG, The Netherlands
⁶Department of Geology, University of Liège, 4000 Sart Tilman, Belgium
Copyright Elsevier

The temperature of Mercury varies greatly across different latitudes due to the planet’s spin/orbit resonance, leading to modifications in the surface spectral properties. The upcoming BepiColombo mission will map the surface of the planet in the UV-TIR range, providing a more comprehensive understanding of the surface alteration. However, comparing the spectral measurements between BepiColombo and the past MESSENGER mission could be challenging due to the large differences in observation geometry. Laboratory experiments with close surface analogs in viewing conditions similar to the space-based observations are necessary to understand the effect of the space environment and interpret the orbital spectral measurements. This study presents the UV-NIR spectroscopy of a Mercury simulant to understand the impact of observation geometry and temperature on the spectral properties of the planet’s surface. The simulant (a mixture of aubrites, albite, and synthetic sulfides) and its endmembers are measured under six geometries that sample the viewing conditions of both missions. The samples are measured fresh and after heating to 450 °C during three cycles. This study finds that the observation geometry modifies the reflectance spectrum of the samples differently depending on the wavelength and composition. The analog presents a darkening, reddening, and flattening with increasing phase angle in the UV-NIR domain. The heated samples present a brightening and reddening, with a deepening of absorption bands. The spectral changes associated with observation geometry and heating are stronger with increasing Mg abundance.

^1,2Laura Noel García,³Frederic Danoix,⁴Martina Ávalos,⁵Pouyan Shen,¹María Eugenia Varela
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14352]
¹Instituto de Ciencias Astronómicas, de la Tierra y del Espacio, Universidad Nacional de San Juan, CONICET, San Juan, Argentina
²Instituto de Mecánica Aplicada, Universidad Nacional de San Juan, San Juan, Argentina
³Groupe de Physique des Matériaux, UMR CNRS 6634, Saint Etienne du Rouvray, France
⁴Instituto de Física Rosario, Universidad Nacional de Rosario, CONICET, Rosario, Argentina
⁵Department of Materials and Optoelectronic Science, National Sun Yat-sen University, Kaohsiung, Taiwan, ROC
Published by arrangement with John Wiley & Sons

The presence of spheroidized plessite (SP) in mesosiderites was recently reported in the literature. This finding coupled with the poor understanding of this plessite variant, motivated us to investigate its formation process and evaluate its implications in assessing the previous proposals concerning mesosiderites’ genesis and cooling history. SP consists of spherulitic taenite particles irregularly distributed, usually surrounded by carbides, and embedded in a kamacite matrix. It has been reported in iron meteorites containing graphite, carbides, and pearlitic plessite (PP), especially in the IAB main group and the sLL and sLH subgroups. From the combination of X-ray tomography, electron backscatter diffraction, energy-dispersive spectrometry, and atom probe tomography in three samples of Vaca Muerta mesosiderite (A1, low to moderate metamorphism) from the ICATE (Argentina) collection of meteorites, we were able to identify a common crystallographic orientation between spheroids and retained taenite, the absence of PP and the carbon depletion in the metallic portion contiguous to the spheroids, and the high volumetric connectivity of the metallic portion. Based on these findings: (i) SP likely grew at the expense of pearlite lamellae, with their absence resulting from complete consumption after an extraordinarily slow cooling rate, probably succeeding a deep burial in a breccia of rock fragments. (ii) Carbon introduction would have followed plessite formation in mesosiderites at a temperature low enough to prevent carbon solid-state diffusion. (iii) Metal would have been poured in silicates, which favors the collision model between a differentiated asteroid and a molten core for mesosiderite genesis.

¹Thomas J. Barrett, ¹James F.J. Bryson, ²Kalotina Geraki
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116588]
¹Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
²Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
Copyright Elsevier

Despite being pivotal to the habitability of our planet, the process by which Earth gained its present-day hydrogen budget is unclear. Due to their isotopic similarity to terrestrial rocks across a range of elements, the meteorite group that is thought to best represent Earth’s building blocks is the enstatite chondrites (ECs). Because of ECs’ nominally anhydrous mineralogy, these building blocks have long been presumed to have supplied negligible hydrogen to the proto-Earth. However, recent bulk compositional measurements suggest that ECs may unexpectedly contain enough hydrogen to readily explain Earth’s present-day water abundance. Together, these contradictory findings mean the contribution of ECs to Earth’s hydrogen budget is currently unclear. As such, it is uncertain whether appreciable hydrogen is a systematic outcome of Earth’s formation. Here, we explore the amount of hydrogen in ECs as well as the phase that may carry this element using sulfur X-ray absorption near edge structure (S-XANES) spectroscopy. We find that hydrogen bonded to sulfur is prevalent throughout the meteorite, with fine matrix containing on average almost 10 times more Hsingle bondS than chondrule mesostasis. Moreover, the concentration of the Hsingle bondS bond is linked to the abundance of micrometre-scale pyrrhotite (Fe1-xS, 0 < x < 0.125). This sulfide can sacrificially catalyse a reaction with H2 from the disk at high temperatures to create H2S, which could be dissolved in adjoining molten silicate-rich material. Upon rapid cooling, this assemblage would form pyrrhotite encased in submicron silicate-rich glass that carries trapped H2S. These findings indicate that hydrogen is present in ECs in higher concentrations than previously considered and could suggest that this element may have a systematic, rather than stochastic, origin on our planet.

^1,2Y. Zheng,^1,2X. Yang,¹M. Valdes,^1,2,3A. M. Davis,^1,2P. R. Heck
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14351]
¹Robert A. Pritzker Center of Meteoritics and Polar Studies, Negaunee Integrative Research Center, Field Museum of Natural History, Chicago, Illinois, USA
²Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA
³Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
Published by arrangement with John Wiley & Sons

In this paper, we introduce a method for volume measurement of microparticles that includes scanning electron microscope photogrammetry with 3-D model construction. Our results show that our method limits the volume uncertainty to ±10%, which is a significant improvement compared to previous methods (which likely overestimated volume by 100%–200%). We also discuss how the size, morphology, and porosity of the sample can affect the uncertainty of volume measurement. We find that our method can have a significant impact on cosmic ray exposure age determinations based on noble gas concentration, with implications for our understanding of cosmic ray irradiation of refractory minerals in the early solar system and presolar grains in the interstellar medium.

¹Axel Wittmann,²Marc Biren
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14350]
¹Eyring Materials Center, Arizona State University, Tempe, Arizona, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

Circa 300 years ago, a ~15-m iron asteroid impacted sand dunes in the Empty Quarter of Saudi Arabia, creating the Wabar craters and fragments of the IIIAB Wabar iron meteorite. A significant portion of the asteroid dissolved into the sand, forming a wide range of impactites including glassy Wabar pearls, dumbbells, and dark scoria-like material. In this study, we report the discovery of ~60–1400 nm nuggets of refractory highly siderophile elements (HSEs) dominated by Pt, Os, Ru, Ir, Re, and Rh in Wabar impact glass. These HSEs were distributed in the IIIAB iron at low parts per million and became concentrated up to ×44,000 in the nano-nuggets. The petrologic context of the nano-nuggets is consistent with the rapid dissolution of the iron meteorite into the dune sand target triggered by the impact shockwave, followed by the separation of immiscible HSEs from the silicate impact melt at 1900°C to over 2700°C. This research provides new insights into the formation processes of HSE nano-nuggets in impact glass and predicts the potential for similar findings at other impact sites.

²Larbi Zennouri,^1,2Hasnaa Chennaoui Aoudjehane,^3,4Luigi Folco,¹Taha Shisseh,⁵Abderrazak El Albani,⁵Arnaud Mazurier,¹Mohamed Hassan Leili
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14349]
¹GAIA Laboratory, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, Casablanca, Morocco
²ATTARIK Foundation for Meteoritics and Planetary Science, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, Casablanca, Morocco
³Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
⁴Centro per la Integrazione della Strumentazione della Università di Pisa, CISUP, Pisa, Italy
⁵Université de Poitiers, CNRS, IC2MP, Poitiers, France
Published by arrangement with John Wiley & Sons

Tamdakht meteorite is the most massive observed fall in Morocco with a total recovered mass of ~500 kg. Most of the specimens investigated in this study are covered by a well-developed primary fusion crust with thickness that reaches up to 12 mm. Macroscopic investigations reveal the development of complex fusion crust features indicative of unusual entry conditions. In some specimens, pieces of the primary fusion crust are missing, and the newly exposed areas developed a thinner fusion crust, which suggests that the former were removed during the late stages of the meteoroid’s flight. Meteorite fragments are enclosed in the primary fusion crust, implying a potential intershower debris transfer prior to the dark flight and that the broken pieces were retained by the viscous fusion crust. X-ray tomographic and backscattered electron imaging shows that the primary fusion is irregular in thickness and consists of three layers. The outer layer is mainly composed of magnetite that formed as a result of the reaction of atmospheric oxygen with Fe in the melt produced by heating. The middle layer consists of zoned olivine phenocrysts, large vesicles, and metal and sulfide grains. The innermost layer displays a lower degree of melting and contains tiny vesicles, as well as metal and iron sulfides in the form of blebs and veins invading the substrate. The textural, mineralogy, and the compositional variation of Tamdakht’s fusion crust imply a change in the degassing degree, temperature, and reaction with atmospheric oxygen from the surface inward.