^1,2Bo-Lun Huang, ³Zhen-Zhao Tao, ^1,2Tong-Jie Zhang
The Astrophysical Journal, 1006, 9
Open Access Link to Article [DOI: 10.3847/1538-4357/ae742c]
¹Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, People’s Republic of China
²School of Physics and Astronomy, Beijing Normal University, Beijing 100875, People’s Republic of China
³College of Computer and Information Engineering, Dezhou University, Dezhou 253023, People’s Republic of China

We present a meteorite-calibrated Bayesian framework for searching archival abundance records for chemical technosignatures—operationally, compositional patterns better explained by an idealized “processed” template (endmember) than by the empirical distribution of natural rocks. We fit a multimodal natural-composition reference using 3493 whole-rock meteorite analyses, and for each of 697 star–paper abundance sets—spanning at least 397 distinct objects once Gaia-designated repeats are consolidated—we compare the Bayesian evidence for (i) natural material and (ii) a mixture of natural material with a fixed siderophile-enriched template, parameterized by a Ca-normalized mixing fraction α. Strong support for the processed template is uncommon: in the atmospheric compilation (atm) 8/697 records have BF > 10 (4/697 have BF > 100), and in the diffusion-adjusted steady-state subset (acc_ss; 148 records spanning at least 94 objects) 6/148 have BF > 10. We report the highest-evidence candidate records and infer the fraction of records detectably favoring the mixture model, with posterior medians π̃ = 0.011 (atm) and π̃ = 0.041 (acc_ss). We calibrate the analysis with end-to-end injection–recovery experiments matched to each record’s coverage and censoring. The calibration shows that discrimination is driven mainly by chemical information, typically requires ≳5 detected elements for decisive support, and—for the siderophile template—is strongest for exact, five-element panels that include Fe, Mg, Cr, and Ti together with Ni, Si, or Na. These results constrain the detectable incidence of the tested processed-composition class in current data and set observational requirements for future multielement surveys and expanded template families.

^1,2Patrick Cordier et al. (>10)
The Astrophysical Journal, 1005, 87
Open Access Link to Article [DOI: 10.3847/1538-4357/ae71bd]
¹Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207—UMET—Unité Matériaux et Transformations, F-59000 Lille, France
²Institut Universitaire de France, 1 rue Descartes, F-75005 Paris, France

Olivine is one of the most abundant silicate minerals in cosmic environments, occurring largely in amorphous form in the interstellar medium before crystallizing within protoplanetary disks. The kinetics and mechanisms governing this transition are central to understanding the thermal and chemical evolution of silicate dust. To investigate these processes at high spatial and structural resolution, we conducted an in situ transmission electron microscopy study on amorphous olivine thin films produced by pulsed laser deposition. Structural and chemical evolution during heating was monitored using selected-area electron diffraction, pair distribution function analysis, automated crystal orientation mapping, electron energy-loss spectroscopy, and aberration-corrected high-resolution transmission electron microscopy. The amorphous material begins to chemically reorganize at ∼400 °C, where Fe²⁺ is oxidized to Fe³⁺ and nanoscale crystallites—presumably hematite—form within the glassy matrix. These crystallites appear to act as nucleation sites that promote subsequent olivine crystallization. Full crystallization occurs near 800 °C, yielding grains 50–150 nm in size. These observations provide direct nanoscale evidence for iron-assisted nucleation in amorphous olivine and offer constraints on the temperatures and pathways governing the crystallization of interstellar and protoplanetary silicate dust.

^1,2I. Psaradaki et al. (>10)
The Astrophysical Journal, 1005, 53
Open Access Link to Article [DOI: 10.3847/1538-4357/ae78dd]
¹MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139, USA
²European Space Agency (ESA), European Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

We present results on X-ray absorption and the dust grain chemistry in the diffuse interstellar medium, based on a new Cycle 25 Chandra High Energy Transmission Grating Spectrometer (HETGS) observational campaign targeting the black hole transient GX 339–4. The X-ray source offers an optimal combination of moderate hydrogen column density and high X-ray flux, enabling the first detailed simultaneous fitting of the photoabsorption edges of Fe, O, Si, and Mg, which are key elemental constituents of interstellar dust. We perform a joint spectral analysis of Chandra/HETGS data and archival observations from the Reflection Grating Spectrometer on board XMM-Newton. We find that the dust grain chemical composition along this diffuse Galactic line of sight is best described by the silicate Mg-rich amorphous pyroxene (Mg_0.75Fe_0.25SiO₃) and metallic iron. We also discuss the elemental abundances and depletions of Fe, O, Si, and Mg, and the presence of absorption features in the X-ray spectrum of this source associated with highly ionized plasma.

¹Yao Liu et al. (>10)
The Astrophysical Journal, 1004, 162
Open Access Link to Article [DOI: 10.3847/1538-4357/ae6a94]
¹School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, People’s Republic of China

Infrared spectroscopy provides a powerful diagnostic for probing the mineralogical properties of dust grains in the terrestrial planet–forming regions of protoplanetary disks. The Upper Scorpius association offers an excellent laboratory for studying disk evolution because it represents an evolved stage (5–10 Myr) compared with younger star-forming regions such as the Taurus molecular cloud (1–3 Myr). In this work, we present mid-infrared spectra of 11 disks in Upper Scorpius that were obtained with the Mid-Infrared Instrument aboard the James Webb Space Telescope. We derive emission feature indices for crystalline olivine and pyroxene centered at ∼9.2 and ∼11.1 μm, as well as perform spectral decomposition to quantify dust crystallinity and characteristic grain size. These results are compared with those measured from Spitzer/IRS spectra of 31 disks in Taurus with similar stellar types. We find no significant difference in dust crystallinity between the two groups, suggesting that crystallization is largely established at early stages of disk evolution. Our analysis indicates that the average grain size in Upper Scorpius disks is systematically larger than that in Taurus disks, aligning with theories of dust evolution. We also observe a trend of increasing grain size towards later-type stars, as well as a correlation between crystallinity, grain size, and the flux ratio F₂₄/F₈, which serves as a measure of dust settling. These results suggest that dust processing proceeds in tandem with disk evolution.

^1,4Pengyue Wang, ^2,4Edward Cloutis, ^3,4Ye Su, ¹Xian Shi, ¹Man-to Hui
The Astrophysical Journal Supplement Series, 284, 61
Open Access Link to Article [DOI: 10.3847/1538-4365/ae644a]
¹Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, People’s Republic of China
²Department of Geography, University of Winnipeg, Winnipeg, Canada
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, People’s Republic of China

To date, the parent body of mesosiderites remains uncertain. Some candidate bodies have been proposed, including 4 Vesta and 16 Psyche. In this study, we performed a comprehensive spectroscopic survey of mesosiderites and pyroxene+metal mixtures to determine the factors that control their reflectance spectra in the 0.3–2.5 μm region and to help better identify possible parent bodies. We also applied these results to several well-known parent-body targets. We found that the mesosiderite powder and pyroxene powder on a metal slab both show significant differences in their spectra compared to Psyche. Although the spectra of the 10:90 orthopyroxene+metal powder was similar to that of Psyche, this does not necessarily mean that there is only a small amount (∼10%) of pyroxene on the surface of Psyche. Taking into account the density of Psyche, we infer that there might be a large amount of low-iron pyroxene on its surface. Looking in more detail at the spectral metrics, we note that some forms of some mesosiderites match some aspects of Psyche. Since some spectral metrics and ferrosilite content of howardites, diogenites, and mesosiderites are similar, the possibility of Vesta being a mesosiderite parent body cannot be ruled out either. However, the higher metal content of mesosiderites favors them, over howardites and diogenites, being linked to Psyche.

¹Viacheslav V. Klimenko, ¹Varsha P. Kulkarni, ²Monique C. Aller
The Astrophysical Journal, 1003, 129
Open Access Link to Article [DOI: 10.3847/1538-4357/ae5659]
¹Department of Physics & Astronomy, University of South Carolina, Columbia, SC 29208, USA
²Department of Biochemistry, Chemistry, & Physics, Georgia Southern University, Statesboro, GA 30458, USA

We present results from a mini-survey of dust spectral features arising in galaxies at redshifts 0.5 < z < 1.2 in our James Webb Space Telescope (JWST) mid-infrared spectra of physically unrelated background quasars. We analyze the JWST Mid-infrared Instrument Medium-Resolution Spectrometer spectra of five quasars presented in Klimenko et al. (Paper I) to determine the best-fit silicate mineralogies. Template profile fits to the 10 μm feature suggest the possible presence of crystalline silicates in three of the galaxies. This contrasts with the predominately amorphous silicate grains in the Milky Way diffuse interstellar medium (ISM). We also measure the extinction curves using existing data from UV to mid-IR. Combining our results with past Spitzer IRS studies, we find the following: (i) the 10 μm silicate peak optical depth (τ 10 diffuse ISM over the range A V =0.1–2.0, with τ 10 /A V ) is about 3 times stronger than expected for the local =0.17 ± 0.09. (ii) The relative strength of the UV bump is similar to that in the local ISM. However, the ratio τ 10 approaching the Galactic ISM value (∼0.1) at A V /A 2175 is larger (∼0.1–1), and appears to decrease with A ∼1.5–2. (iii) There is no significant correlation of τ R V . (iv) τ 10 is strongly correlated with the gas-phase Mg II V , 10 /A V with absorption strength for the quasar sightlines. Possible interpretations include that some quasar sightlines probe dust in the circumgalactic medium (CGM), and that dust grains may have been significantly reprocessed in the ISM and CGM under conditions that may differ from those in the local ISM.

¹J. Gattacceca et al. (>10)
Meteoritics & Planetary Science (in Press)
Open Access Link to Article [DOI: 10.1111/maps.70233]
¹CEREGE, CNRS, Aix-Marseille Univ, IRD, INRAE, Aix-en-Provence, France

Published by arrangement with John Wiley & Sons

A minor fraction of meteorites contains xenoliths, that is, clasts that were formed on a different parent body than that of the host lithology. The occurrence of xenoliths is direct evidence for the exchange of material between asteroids, including exchanges between asteroids from the carbonaceous (CC) and non-carbonaceous (NC) reservoirs. Overall xenolith population statistics may therefore inform us about the dynamical mixing of these two asteroid reservoirs. Xenoliths are also intrinsically interesting because they may sample parent bodies that are not represented in the meteorite collection. In this work, we conducted a critical and exhaustive review of xenoliths described in the literature and performed a new large-scale search for macroscopic lithic xenoliths. We identify 89 xenolith-bearing meteorites in the literature, and report 18 new ones. We expand the diversity of known host/xenolith pairs with occurrence that had not been reported before: a CM clast in a L chondrite, a CO3 clast in a eucrite, a pallasite and H clasts in howardites, and two CO-CM breccias. Based on our observations, we reinterpret a number of previously described xenoliths. In particular, many “CI-like” xenoliths should rather be classified as ungrouped C1 or C2 chondrite xenoliths. At least a third of xenoliths do not belong to the known meteorite groups, suggesting that they represent a flux of meteoroids different from the present-day one that is dominated by the products of recent (~<50 Ma) collisions. Although xenoliths are present in only 0.14% of meteorites, the statistics of the total data set of 107 xenolith-bearing meteorites can be discussed in relation with the asteroid population. Xenoliths are more abundant in the regolith breccias of large asteroids, in agreement with their ability to maintain an old and mature regolith. Chondritic xenoliths represent 95% of xenolith occurrence, in line with a higher number of chondritic asteroids with respect to achondritic ones. Xenoliths from the CC and NC reservoirs are found in host meteorites from both reservoirs, and a majority was implanted at low collisional speed (below about 2 km s⁻¹). The low proportion of CC meteorites with NC xenoliths can be related to the fact that the present-day outer asteroid belt that hosts the majority of CC asteroids is depleted in NC asteroids. The broad agreement between the xenolith population and the present-day architecture of the asteroid belt, as well as the low collisional speed between CC and NC materials suggest that the implantation of most xenoliths occurred after the main scattering event of the asteroids triggered by the formation of Jupiter a few Myr after the formation of the solar system. Conversely, CV, CK, and CO chondrites contain only xenoliths from a meteorite group of their own meteorite clan suggesting that these intra-clan xenoliths were implanted while their parent bodies were still orbiting in a narrow range of heliocentric distance, that is, before the main scattering event of the asteroids triggered by the formation of Jupiter. Eventually, a few xenoliths were incorporated in asteroids that were still accreting. Therefore, xenolith implantation seems to have been a universal and protracted phenomenon, active for most of solar system history.

¹Robert Huber, ²Hans Lauterbach, ³Robert Darga
Meteoritics & Planetary Science (in Press) Open Access Link to Article [DOI: 10.1111/maps.70255]
¹MARUM—Center for Marine Environmental Sciences, Universität Bremen, Bremen, Germany
²Independent Researcher, Traunreut, Germany
³MammutMuseum Siegsdorf, Siegsdorf, Germany

Published by arrangement with John Wiley & Sons

Public fascination with impact craters often drives bold speculations, but rigorousverification is critical. In southeastern Bavaria, numerous depressions have been proposed torepresent impact craters associated with a catastrophic event in Celtic times (between 900 BCand 600 BC)—the so called “Chiemgau Impact.” To date, the evidence presented in supportof the proposed Chiemgau Impact has not been independently validated as diagnostic of aconfirmed impact event, and this interpretation has been repeatedly challenged in thescientific literature. More recently, numerous newly identified, predominantly small-scalestructures have been presented as further evidence supporting this claim. Many, however,lack precise geographic information, complicating independent verification. We localized andcritically examined these structures in the field as well as using publicly availablehigh-resolution LIDAR data, aerial imagery (historic and recent), and development plans.The majority of these images show structures which are demonstrably anthropogenic,including gravel pits, WWII bomb craters, retention basins, and—most notably—golf coursefeatures such as bunkers and ponds. Other depressions correspond to glacial landformscharacteristic of the Inn-Chiemsee foreland. None of the structures examined exhibitcharacteristics that would support a formation by a cosmic impact. The repeatedmisinterpretation of recently constructed golf course elements as impact craters highlights astriking lack of methodological rigor and illustrates how extraordinary claims can arise fromneglecting simple cross-checks with publicly available geospatial and planning data andindicates that the postulated impact in Chiemgau belongs to the realm of myths.

^1,2Subhasmita Swain, ³Enrico Mugnaioli, ³Anna Musolino, ⁴Markus Patzek, ^5,6Beda Hofmann, ^1,2,7Surya Snata Rout
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70245]
¹School of Earth and Planetary Sciences, National Institute of Science Education and Research (NISER), Jatni, Khurda, India
²Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, India
³Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
⁴Institut für Planetologie, University of Münster, Münster, Germany
⁵Institute of Geology, University of Bern, Bern, Switzerland
⁶Natural History Museum Bern, Bern, Switzerland
⁷Centre for Interdisciplinary Sciences (CIS), National Institute of Science Education and Research (NISER), Jatni, Khurda, India

Published by arrangement with John Wiley & Sons

Volatile-rich xenolithic clasts in different meteoritic breccias represent primitivesolar system material. Here, we report the mineralogy and organic maturity of C1, C2, andCM-like clasts present within five polymict ureilites, two polymict eucrites, one howardite,and one CR chondrite. Of all the clasts, the C1s are the most abundant, and the majorityhave mineralogy and organic maturity similar to the CI chondrites. Two C1 clasts show theleast altered polyaromatic organic matter, similar to Bells, Essebi, and a CR chondrite.A few C1 clasts have unique mineralogy with abundant Fe-rich olivine surroundingmagnetite grains. Such clasts show a Raman signature of mild to moderate heating effectsrelated to impact-shock processing. The Fe-rich olivine within these clasts formed aroundmagnetite grains from an aqueous fluid at a water/rock ratio of 0.1–0.2, T > 150 °C, andhigh activity of SiO 2 and Fe. Additionally, the Fe-rich olivine could have also formedthrough the reduction of magnetite by H 2 gas and SiO 2 (aq). The CM-like clasts are foundonly in the studied HED meteorites and have mineralogy and organic maturity similar to theCM chondrites. Only one CM-like clast shows unique Raman signatures, either due tothermal effects or the presence of unique organic precursor material. The C2 clasts showsimilarities with other C2 clasts in CH/CB chondrites. None of the studied clasts showsignatures of high degrees of thermal metamorphism like the subtype ≥3.1 chondrites.

^1,2Robert W. Nicklas, ^3,4Aratz Beranoaguirre, ²Dylan M. Seal, ⁵James M. D. Day, ²Ethan F. Baxter, ⁶Anthony B. Love
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70254]
¹Lunar and Planetary Institute, USRA, Houston, Texas, USA
²Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, Massachusetts, USA
³Institut für Geowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
⁴Frankfurt Isotope and Element Research Center (FIERCE), Goethe-Universität Frankfurt, Frankfurt am Main, Germany
⁵Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA
⁶Department of Geological and Environmental Sciences, Appalachian State University, Boone, North Carolina, USA

Published by arrangement with John Wiley & Sons

Brachinites and brachinite-like achondrites record melting processes at moreoxidizing conditions than many other achondrite meteorites, attested by relatively Fe-richsilicate phases. Here, new major-, trace-, and highly siderophile-element (Os, Ir, Ru, Pt, Pd,Re) abundances, as well as Re-Os and Rb-Sr isotope data are reported for the brachinite ElMedano 395 and for the anomalously apatite-rich (~1.26% modal) brachinite-like achondriteNorthwest Africa (NWA) 12,532. Both meteorites have Rb-Sr and Re-Os isotope systematicsthat have been significantly affected by terrestrial alteration, reflecting variable addition of Srand variable loss of Rb and Re. Brachinite-like achondrite NWA 12532 experienced lateaddition of metallic phases and apatite on its parent body, having nearly chondriticabundances of Os, Ir, Ru, Pt, and Pd. The apatite in NWA 12532 gives an age of4491.3 14.1 Ma, overlapping with apatite U-Pb ages for ordinary chondrites, as well asfor other brachinites and brachinite-like achondrites. This age is significantly younger thanavailable Mn-Cr ages for brachinite silicate phases. The young U-Pb ages of brachinites andbrachinite-like achondrites likely reflect significant impact shock resetting events at ~4.43 to4.49 Ga across the solar system, also recorded in ordinary chondrites. These resetting eventsmay be related to a significant dynamical reorganization at that time.