¹Melissa De Andrade Nunes,¹Ricardo I. F. Trindade,¹João Pedro Rodriguez Pinto,²Alvaro P. Crósta,³Gabriel G. Silva,⁴Ludovic Ferrière,¹Camila R. Sales,¹Giovanna M. Tosi
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70155]
¹Institute of Astronomy, Geophysics and Atmospheric Sciences, University of Sao Paulo, Sao Paulo, Brazil
²Institute of Geosciences, University of Campinas, Campinas, Brazil
³Institute of Chemistry, University of Sao Paulo, Sao Paulo, Brazil
⁴Natural History Museum Abu Dhabi, Abu Dhabi, United Arab Emirates
Published by arrangement with John Wiley & Sons

Geraisites are a newly recognized class of tektite from Brazil. They occur as centimeter-sized, elongated to subspherical bodies scattered across surface gravel and shallow subsurface layers within a ~90-km-long strewn field extending between the municipalities of São João do Paraíso and Curral de Dentro, near the border between the states of Minas Gerais and Bahia. This study presents a rock magnetic characterization of geraisites, aimed at understanding their magnetic mineralogy and remanent magnetization. The samples exhibit weak bulk magnetization dominated by a paramagnetic contribution, consistent with typical tektite compositions. In addition, rock magnetic analyses indicate the presence of a ferromagnetic fraction, as evidenced by demagnetization curves and hysteresis behavior. Lowrie–Fuller test and isothermal remanent magnetization decomposition indicate a dominant low-coercivity component consistent with nanoscale magnetite grains in the single-domain to pseudo-single-domain range. In some samples, the remanence behavior suggests overprinting by transient high-field processes, such as lightning-induced remanent magnetization. Furthermore, geraisites show a distinct relationship between magnetic susceptibility and iron content compared to other splash-form tektites, reflecting their relatively enhanced ferromagnetic contribution. Overall, these results provide new insights into the magnetic properties of geraisites and their comparison with other tektite populations.

¹Shivanshu Dwivedi,^1,2Jayanta Kumar Pati,³Wolf Uwe Reimold,¹Anuj Kumar Singh,⁴Gordon Robert John Cooper,¹Dhananjay Mishra,⁵Álvaro Penteado Crósta,¹Kuldeep Prakash
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70162]
¹Department of Earth and Planetary Sciences, Nehru Science Centre, University of Allahabad, Prayagraj, India
²National Center of Experimental Mineralogy and Petrology, University of Allahabad, Prayagraj, India
³Institute of Geosciences, Universidade de Brasılia, Brasılia, Brazil
⁴School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
⁵Institute of Geosciences, Universidade Estadual de Campinas-UNICAMP, Campinas, Brazil
Published by arrangement with John Wiley & Sons

The Dhala structure in India, one of the oldest and most deeply eroded impact structures known on Earth, exhibits distinct morphological features. Despite decades of investigation, two fundamental attributes of the Dhala structure, its shape (variously described as rectangular, elliptical, to circular) and diameter (2.96 to ~25 km) have remained unresolved. Here, we report extensive new data pertaining to the spatial disposition of different lithounits with pre-, syn- and post-impact fabric data, and the occurrence within target granitoids of overturned fold structures related to the collapse of the central uplift, and provide an updated estimate of the current impact-melt breccia volume of ~2 km3. We propose a firm constraint on the size of the transient crater based on the extent of shock effects within target rocks and drill cores of the crater floor and below. We also provide compelling evidence for the presence of a collapsed structural uplift in the region of the Central Elevated Area (CEA), which is surrounded by a ring of monomict impact breccia exposures. Diagnostic shock deformation features in target granitoid, Giant Quartz Veins (GQVs), and samples from the breccia ring are also reported. Multispectral remote sensing, combined with digital elevation model analysis using sunshading and radial derivative techniques, reveals multiple elliptical to ovoid features around the CEA. These features, along with structural and fabric data, indicate a strong control of pre-impact basement anisotropies on the final crater geometry. We propose a revised diameter of ~10–12 km for the transient cavity and ~25 km for the final structure based on the integrated field and remote sensing data sets. The Dhala structure exhibits a distinctly elliptical morphology, with its major axis oriented in the southwest-northeast direction. The age of the Dhala impact is revised by ~400 Ma, constraining it now to the 1700 to 2100 Ma interval. The revised age constraint is derived from shock-metamorphic features identified within GQVs of approximately 2.1 Ga age, indicating the pre-impact emplacement of these reefs.

¹Gabriele Giuli,^1,2Maria Rita Cicconi,³Angela Trapananti,⁴Sigrid Griet Eeckhout,⁵Giovanni Pratesi,⁶Christian Koeberl
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70156]
¹Scuola di Scienze e Tecnologie, sez. Geologia, Universita di Camerino, Camerino (MC), Italy
²Department of Materials Science and Engineering – Inst. Glass and Ceramics, Friedrich-Alexander-Universität,Erlangen-N€urnberg, Germany
³Scuola di Scienze e Tecnologie, sez. Fisica, Universita di Camerino, Camerino, Italy
⁴European Synchrotron Radiation Facility (ESRF), Grenoble, France
⁵Dip. Scienze della Terra, Universita di Firenze, Florence, Italy
⁵Department of Lithospheric Research, University of Vienna, Vienna, Austria
Published by arrangement with John Wiley & Sons

Two thin sections of Muong Nong-type tektites from the Australasian tektite strewn field have been analyzed by Fe K-edge X-ray absorption near edge spectroscopy (XANES), using a hundreds-of-micrometers–sized beam suitable for spatially resolved analysis of the Fe oxidation state across distinct regions of the samples. Earlier analyses with an unfocused beam were inconclusive regarding different amounts of oxidized iron in the Muong Nong-type tektites, but did indicate different chemical compositions of the lighter and darker colored layers. Experimental XANES spectra are very similar in shape to those of other tektites. However, small and reproducible changes were found in the pre-edge peak involving the centroid energy: the pre-edge peak of the spectra collected within the dark layers are reproducibly 0.2 eV at higher energy than those of the spectra collected within the light matrix. This difference in energy position is four times the estimated energy reproducibility and, therefore, is significant. By comparison with pre-edge peak data of Fe model compounds, we estimate the Fe3+/(Fe2++Fe3+) ratios in the light matrix and dark layers to be 5% and 15% (±5), respectively. The heterogeneous distribution of the Fe oxidation state in Muong Nong-type tektites, as opposed to the homogeneous Fe oxidation state distribution in splash-form tektites, is consistent with previous hypotheses, based on volatile contents, of Muong Nong-type tektites resulting from melts that experienced lower temperatures compared to those of splash-form tektites.

^1,2Mark Boslough et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70140]
¹Los Alamos National Laboratory, Los Alamos, New Mexico, USA
²University of New Mexico, Albuquerque, New Mexico, USA
Published by arrangement with John Wiley & Sons

The landscape of scientific publishing and communication is changing rapidly with the accelerating growth of open-access outlets that lack rigorous peer review, revenue-driven online media, inadequately trained journalists, social media, online influencers, podcasts, celebrity endorsements of pseudoscience, anti-science political movements, and the emergence of artificial intelligence. Near-Earth objects, impacts, and airbursts—particularly when related to global catastrophes or planetary defense—often attract intense public interest and the kind of media coverage that is prone to the spread of misinformation. The field of planetary defense has profound consequences, so maintaining public trust is essential to its success. Scientists cannot afford to ignore these challenges merely because they fall outside the scope of conventional scientific discourse. This paper classifies several types of misinformation, presents representative case studies in planetary defense and planetary science, and offers practical approaches for mitigation. We consider (1) rapidly evolving news events requiring timely expert response; (2) intermediate-term cases involving inadequately reviewed publications, overpromotion, and uncritical reporting; and (3) long-term, persistent, and self-perpetuating myths that can grow organically and insidiously, even within the scientific community. We also discuss how misinformation can originate and proliferate through inadequate peer review, news releases and press conferences, exploitation of limited scientific literacy, unsubstantiated claims, and amplification of false narratives by artificial intelligence. Finally, we suggest proactive strategies for preventing and correcting misinformation, with particular attention to its implications for planetary defense.

¹S. Alwmark,¹J. Granbom,¹P. Ahlberg,¹M. Calner,¹S. Richoz,¹K. J. Gajewska,¹W. R. Hyde,¹K. Ljung,¹C. Alwmark
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70160]
¹Department of Geology, Lund University, Lund, Sweden
Published by arragement with John Wiley & Sons

Hummeln is a simple impact structure located in south-eastern Sweden. It is approximately 1.2 km in diameter and almost completely covered by a lake. Here, we present the first detailed investigation of impactites and mapping of the 164.25 m deep drill core Hummeln-1 with a focus on impact metamorphism and the impact process. We find that the drilling has penetrated a complex sedimentary succession representing syn- to postimpact crater fill. It consists of (from base to top) lithic impact breccia (Unit 1), overlain by diamictite and graywacke with an overall fining upward trend grading from sandy into silty to clayey turbidites (Units 2, 3), and, lastly, suspension dominated marine clays and limestone (Units 4, 5). The crater fill was deposited mostly as gravity slides and sediment gravity flows (debris flows, (hyper)concentrated density flows and turbidity flows), which transported sediment into the crater as a series of fan lobes prograding toward the crater center. We have identified shocked quartz in 12 samples covering the interval of 160.69–56.60 m in the drill core and in samples of polymict and suevitic breccia obtained during fieldwork. Shocked quartz grains dominantly record planar fractures (PFs), with an average of 1.5–3.5 sets per grain. We measured a total of 122 PF sets in 54 grains, with orientations parallel to the $$, (0001), and $$ orientations being most common (30%, 26%, 21%, respectively). In the same samples, we also measured and indexed 14 sets of planar deformation features (PDFs) in eight grains, oriented parallel to the basal plane (50%), as well as rhombohedral planes $$, $$, and $$ (21%, 21%, and 7%, respectively). Feather features occur associated with PFs in seven of the samples. The quartz grains with shock microstructures in the drill core occur exclusively in beige graywacke–diamictite interbedded with the basal lithic breccia unit and in distinct graywacke–diamictite beds in the late syn- to early postimpact crater fill. We suggest that Hummeln was formed just prior to the deposition of parallel bedded marine mudrock with trilobites of the species Ellipsocephalus polytomus, indicating an early “middle” Cambrian (Wuliuan) age for the impact.

^1,2Zhong-Sha Meng,^1,3Ying-Kui Xu,^1,3Shi-Jie Li,^3,4Dan Zhu,^1,2De-Liang Wang,^1,3Yang Li,^1,3Xiong-Yao Li,^1,3Jian-Zhong Liu
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70171]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²University of Chinese Academy of Sciences, Beijing, China
³Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, 230026, China
⁴State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences,Guiyang, 550081, China
Published by arrangement with John Wiley & Sons

Meteorite finds are commonly used to assess the chemical and isotopic compositions of their parent bodies. Among these, lithium (Li) isotopes in ordinary chondrites (OCs) have been applied to infer the Li abundance and isotopic characteristics of their parent bodies. However, Li is highly mobile in aqueous conditions and readily undergoes isotopic fractionation during fluid–mineral interactions. It remains uncertain whether Li isotopic compositions in meteorite finds reliably preserve their original parent-body signatures, particularly after prolonged terrestrial exposure. In this study, we investigated Li isotope behavior in Kumtag 015 (W3, L5) by conducting a series of leaching experiments. The untreated whole-rock sample yields a δ7Li value of +6.1‰, whereas all leachates exhibit heavier δ7Li values, ranging from +8.4‰ to +14.8‰, indicating the presence of weathering-related secondary components enriched in heavy Li isotopes. Combined with the petrographic observations and mass-balance results, these data suggest that the relatively heavy whole-rock δ7Li of Kumtag 015 is mainly related to the addition of heavy-δ7Li surficial fluids during terrestrial weathering, followed by the sequestration of Li into secondary minerals such as carbonates and Fe-(oxyhydr)oxides. This finding is consistent with prior work showing heavy δ7Li in carbonates. We conclude that terrestrial alteration can substantially modify Li isotope compositions in meteorite finds, highlighting the need for caution when using such samples to trace pristine planetary Li inventories.

¹Allan H. Treiman
American Mineralogist 111, 1009-2021 Link to Article [https://doi.org/10.2138/am-2025-9919]
¹Lunar and Planetary Institute (USRA), 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
Copyright: The Mineralogical Society of America

The nakhlite martian meteorites, basaltic rocks with abundant crystals of augite pyroxene, have been interpreted as cumulates, having formed as crystals of augite (and olivine) settled through basalt magma to accumulate at its bottom. Here, I show that the chemical compositions of most nakhlites are best explained if they represent magmas, and not crystal accumulates. The nakhlites Nakhla, Lafayette, and Y000593 are identified as cumulates; the rest are magmas. Among the magma nakhlites, abundances of all igneous incompatible elements are strongly correlated; abundances of highly incompatible elements are linearly correlated with the La/Yb ratio, with R2 values from 0.7 to 0.95. These close correlations are not consistent with the group being cumulates, where the proportion of cumulus augite should be mostly independent of magma composition. Instead, the correlations are consistent with the nakhlites representing magmas, with the range of compositions reflecting processes including: variable enrichment in incompatible elements (i.e., metasomatism) in the source mantle; variable degrees of partial melting of the source mantle; and mixing among such magmas. Significant crustal assimilation (for the tested elements) is excluded by the correlation of Al with La/Yb. The most Al-rich nakhlite would require assimilation of 25% mass crust into the Al-poorest, which is inconsistent with thermochemical constraints. Recognition of such augite-rich, pyroxenitic magmas requires that their mantle source be similarly pyroxenitic, which implies that the martian mantle is more heterogeneous than previously appreciated.

Cosmochemistry Papers will be on a short spring break next week, service will commence again on 01.06.

¹Simone Pascucci et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70170]
¹Institute of Methodologies for Environmental Analysis (IMAA)-Italian National Research Council (CNR), Tito Scalo, Italy
Published by arrangement with John Wiley & Sons

Asteroid compositional analysis relies on comparing reflectance spectra with laboratory data from well-characterized meteorites. To advance this comparison, we performed a comprehensive laboratory analysis on a slab of the Northwest Africa (NWA) 7317—CR6 carbonaceous chondrite. We employed high-resolution Visible-Infrared (VIS-IR) imaging spectroscopy (0.4–5.1 μm) using the SPIM hyperspectral facility, integrated with high-spatial-resolution elemental mapping via SEM-EDS and EMPA-WDS. This multi-technique approach enabled the retrieval of surface composition at high spectral and spatial resolutions. Our results, supported by ICA/PCA and K-means classification methodologies, highlight the challenges of integrating VIS-IR spectroscopy and SEM/EMPA at the micrometer scale. While both techniques consistently infer an overall poikiloblastic/metamorphic texture dominated by an olivine and pyroxene-rich matrix, their combined use requires a critical approach for robust analysis. The absence of the 3 μm absorption band indicates high temperatures during thermal metamorphism on the NWA 7317 parent body. Although FeNi metallic alloys and Fe-sulfide inclusions contribute to the VIS-IR spectroscopic signal, they are not clearly distinguishable from each other. Furthermore, minor phases like plagioclase and chromite detected via SEM/EMPA are not plainly visible in the SPIM results. We review the potential of integrating these techniques to assess the petrography, mineralogy, and terrestrial weathering of NWA 7317.

¹Christina Hamilton,²Shannon Dulin,³John Weber,²R. Douglas Elmore
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70139]
¹BP, Houston, TX, USA
²School of Geosciences, University of Oklahoma, Norman, Oklahoma, USA
³Department of Geology, Grand Valley State University, Allendale, MI, USA
Published by arrangement with John Wiley & Sons

A paleomagnetic and petrographic study of host carbonate rocks and impact breccias at the Kentland impact structure was conducted to better constrain the timing of the impact and to test for alteration by hydrothermal fluids. The Ordovician-Silurian target rocks sampled are fossiliferous wackestone/packstones with minor dolomite. Polymict impact breccias, also sampled, occur as dikes/sills and contain clasts of dolomite, host carbonate, sandstone, sphalerite, and rare coated grains which contain clays, dolomite, calcite, and hexagonal silica resembling tridymite. The host carbonates contain brecciated zones near the polymict breccias that display flow textures of aligned and elongated clasts and minerals. Authigenic minerals present include sylvite, apatite, gypsum, magnetite, and hematite. These observations suggest alteration by hydrothermal fluids, which probably had an estimated duration of ~7500 yrs after impact. Alternating field (AF) and thermal demagnetization of impact breccia and host carbonate specimens removed two post-tilting magnetic components: one with southerly declinations and moderate negative inclinations and the other with northerly declinations and positive inclinations. Demagnetization results suggest the magnetizations primarily reside in magnetite as well as hematite and possibly pyrrhotite. Petrographic and rock magnetic results are consistent with this interpretation. These magnetizations are interpreted as chemical remanent magnetizations acquired through a reversal, which formed from alteration by hydrothermal fluids generated after the impact. The paleomagnetic poles (mean pole, 75.7° N, 98.4° W) fall near the Early Jurassic part of the apparent polar wander path, which suggests the alteration in the breccias, and likely the impact, occurred in the Early Jurassic (175–185 Ma).