^1,2Dominik C. Hezel,³Knut Metzler,⁴Mara Hochstein
Meteoritics & Plantary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14336]
¹Institut für Geowissenschaften, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
²Department of Mineralogy, Natural History Museum, London, UK
³Institut für Planetologie, University of Münster, Münster, Germany
⁴Department of Geology and Mineralogy, University of Cologne, Köln, Germany
Published by arrangement with John Wiley & Sons

Chondrule size–frequency distributions provide important information to understand the origin of chondrules. Size–frequency distributions are often obtained as apparent 2-D size–frequency distributions in thin sections, as determining a 3-D size–frequency distribution is notoriously difficult. The relationship between a 2-D size–frequency distribution and its corresponding 3-D size–frequency distribution has been previously modeled; however, the results contradict measured results. Models so far predict a higher mean of the 2-D size–frequency distribution than the corresponding mean of the 3-D size–frequency distribution, while the measurements of real chondrule populations show the opposite. Here, we use a new model approach that agrees with these measurements and at the same time offers a solution, why models so far predicted the opposite. Our new model provides a tool with which the 3-D chondrule size–frequency distribution can be determined from the fit of a measured 2-D chondrule size–frequency distribution.

¹R.K. Williams, ¹J.P. Emery
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116554]
¹Northern Arizona University, Flagstaff, AZ, United States
Copyright Elsevier

Material remaining from the formation of the outer Solar System congregated in the Kuiper Belt. Studying this material has provided key information about the formation of the Solar System, the distribution of planetary materials, and the compositions of different objects. Additional spectra of objects in the Kuiper Belt will provide further insight into Solar System formation and evolution. An important question is whether, and in what quantity, hydrated material formed in the outer Solar System. We address this question here with visible spectra of three Kuiper Belt Objects (KBOs) and one Centaur. We find moderately red spectral slopes for these four bodies, with no clear evidence for the 7000 Å feature due to Fe-rich phyllosilicates. These results extend the overall lack of detection of hydrated materials among KBOs and Centaurs. Although it is clear that hydrated silicates are not common in the outer Solar System, some hydration might be expected, and further observations will continue to refine its prevalence.

¹Masahisa Yanagisawa, ¹Yuki Uchida, ¹Seiya Kurihara, ²Shinsuke Abe, ²Ryota Fuse, ³Satoshi Tanaka, ⁴Keisuke Onodera, ⁵Taichi Kawamura, ⁶Ryuhei Yamada
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.11648]
¹Department of Engineering Science, The University of Electro-Communications, Japan
²Department of Aerospace Engineering, Nihon Univ., Japan
³Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
⁴Earthquake Research Institute, The University of Tokyo, Japan
⁵Institut de Physique du Globe de Paris, University of Paris Diderot, France
⁶School of Computer Science and Engineering, The University of Aizu, Japan
Copyright Elsevier

Lunar impact flashes are observed at collisions of meteoroids against the non-sunlit lunar surface. They appear suddenly and usually last only 0.1 s or less in visible light. Using our spectral video cameras, we made observations to obtain their low dispersion spectra from Oct. 2017 to Dec. 13, 2018. We detected five flashes confirmed by multiple site observations and eight unconfirmed flashes. The spectra of the confirmed flashes in the 400–800 nm wavelengths are continuous and red. The best-fitted single blackbody spectra to these spectra show temperatures of 2200–4000 K. The spectrum at the beginning of the brightest confirmed flash may show the optical radiation from the impact-generated vapor plume. The rapid cooling of the impact-generated fine droplets could explain the decrease in brightness and temperature between the subsequent two video frames. The temperature of this flash remained above 2300 K, even 80 ms (milliseconds) after the flash appearance, indicating the existence of coarse incandescent ejecta that cools slowly. This flash’s spectral evolution would show the following three processes of meteoroids’ impact phenomena on the moon: vapor plume generation, rapid cooling of fine droplets that would be later the lunar spherical glasses, and the ejection of incandescent coarse particles probably melt and solid particle aggregates.

Xiangyu Zhang, Gregory M. Green
Science 387:1209-1214 Link to Article [DOI 10.1126/science.ado9787]
Galaxies and Cosmology Department, Max Planck Institute for Astronomy, Heidelberg, Germany

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

^a,bDel Rio, ^a,cL. Folco, ^a,cE. Mugnaioli, ^dS. Goderis. ^a,cM. Masotta
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.03.005]
^aDipartimento di Scienze ella Terra, Università di Pisa, Via Santa Maria, 53, 56126 Pisa, Italy
^bDipartimento di Matematica, Informatica e Geoscienze, Università di Trieste, Via Weiss, 2, 34128 Trieste, Italy
^cCenter for the Instrument Sharing of the University of Pisa, CISUP, Lungarno Pacinotti 43/44, 56126 Pisa, Italy
^dArchaeology, Environmental Changes & Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, BE-1050 Brussels, Belgium
Copyright Elsevier

Recent studies on alkali metals, Ar-, Fe- and K-isotope distribution in Australasian microtektites have revealed the complex interplay of multiple fractionation processes in establishing their moderately volatile elements record, particularly in those deposited in Antarctica, most distal from the hypothetical source crater. To provide a better understanding of moderately volatile elements fractionation during microtektite formation, we studied the distribution of K, Na, Rb and Cs in twenty-seven Australasian microtektites from Antarctica ranging in size from 180 to 680 µm. Compositional profiles were determined using electron probe microanalyses (major elements) and laser ablation-inductively coupled plasma-mass spectrometry (trace elements), following a petrographic study at the nanoscopic scale by means of scanning and transmission electron microscopy. The Australasian microtektites from Antarctica contain nanometer-sized, partly digested lechatelierite inclusions and rare vesicles, and record significant moderately volatile elements depletion (Na₂O = 0.30 ± 0.07 (1σ) wt%; K₂O = 0.94 ± 0.25 (1σ) wt%) relative to: i) upper continental crust (Na₂O = 3.46 wt%; K₂O = 3.45 wt%), ii) microtektites from deep sea sediments (Na₂O = 1.15 ± 0.43 (1σ) wt%; K₂O = 2.47 ± 0.82 (1σ) wt%), and iii) Australasian tektites (Na₂O = 1.20 ± 0.19 (1σ) wt%; K₂O = 2.43 ± 0.24 (1σ) wt%). They are also characterized by moderately volatile elements enrichments at their rims (up to ∼ 2.7x for K₂O; ∼1.6x for Na₂O), and the enrichment factor typically decreases with increasing diameter. Lastly, there is an inverse correlation between bulk Na₂O content (but not K₂O) and diameter. We propose that the most distal Antarctic microtektites originated as impact melt droplets and not as vapor condensate spherules. Their moderately volatile elements geochemical budget was established through three subsequent stages of fractionation in the context of a hypervelocity impact. 1) Gross Na and K and other moderately volatile elements loss which occurred during the melting and vaporization of the target precursor materials. 2) Re-accretion of Na, K and other moderately volatile elements from the condensation of a hot gas envelope of vaporized target materials onto volatile depleted droplets cores. 3) Size-controlled partial evaporation of (mainly) Na, caused by aerodynamic drag heating, during deceleration from high ejection velocities either during the decoupling from the hot gas envelope in ambient air, or during atmospheric re-entry, as suggested by alkalis and Fe-isotope data in the literature. The late accretion of K vapor also provides plausible explanations for the contamination by extraneous Ar and K-isotopic systematics reported in the literature.

^aO.L. Kafka, ^aN.H. Moser, ^aA.N. Chiaramonti, ^aE.J. Garboczi, ^bR.P. Wilkerson, ^aD.L. Rickman
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116542]
¹Applied Chemicals and Materials Division, MS647, National Institute of Standards and Technology, Boulder, CO 80305, USA
¹Sigma-1: Fabrication Manufacturing Science, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
²Jacobs Engineering, Inc., Huntsville, AL, 35812, USA
Copyright Elsevier

Lunar regolith simulants are manufactured in order to provide a higher volume, much less expensive and more available source of material, compared to real lunar regolith material, with which to test various instruments and machines designed to operate on the lunar surface. The particle size distribution and mineralogy of these materials is engineered but not the particle shape, although particle shape does play an important role in many engineering applications. Thus, the three-dimensional (3D) shape of these materials has rarely been characterized and never compared to each other and to real lunar regolith material. The focus of this paper is to provide 3D shape and size distribution of 17 different simulants, use this data to compare these materials against each other and provide these data in a NIST database. Over 1.1 M particles are in this database, with their 3D shape stored as STL files. The particle size range considered is roughly 7 μm to 1 mm. With the recent publication of 3D characterizations of lunar regolith material from the Apollo 11 and Apollo 14 missions, these characterizations are also compared to equivalent data for the real lunar regolith material. Both mare and highland simulants are studied using graphical comparisons as well as size and shape figure of merit analysis. This kind of 3D characterization provides the information that new engineering manufacturing techniques will need to enable the engineering of particle shape for new lunar regolith simulants, since the ability to make particle shape measurements relevant to manufacturing and use is a prerequisite for any such engineering. This database can also serve as a source of “digital twins” or “virtual simulants” for modeling studies both of individual particle properties and of packed particle geometry and properties.

S. Charnoz, A. Limare, E.D.A. Pereira, R. Caracas, F. Moynier Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116462]
Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, Paris, F-75005, France
Copyright Elsevier

¹Lingzhi Sun et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14332]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Manoa, Honolulu, Hawaii, USA
Published by arrangement with John Wiley & Sons

The double drive tube 73001/2 is a regolith core and was collected on the Light Mantle at Station 3 during the Apollo 17 mission. This core preserves an in situ record of space weathering and compositional stratigraphy, providing insights to the thickness of the Light Mantle and the local regolith reworking time scale. We measured the dissection passes 2–3 of core 73002 and passes 1–3 of core 73001 using a high-spatial resolution multispectral imaging system, and analyzed the space weathering products on individual soil grains from pass 2 of 73002 using transmission electron microscopy analysis. Our results indicate that the double drive tube 73001/2 contains a zone of submature to mature soil overlying a zone of immature soil. The top more mature zone is about 6–7 cm thick, corresponding to the local regolith reworking depth. On the basis of this depth, the estimated regolith reworking time scale for core 73001/2 is approximately 9–13 million years. Due to mixing with basaltic materials from the central valley, the top mature zone exhibits an FeO content 1–3 wt% higher than the underlying immature soils. Spectral images indicate that the double drive tube failed to penetrate the bottom of the Light Mantle but may have reached the edge of the landslide-valley material mixing zone. The local landslide deposit is thicker than the maximum sampling depth of the double drive tube, which is about 70 cm.

^1,2*Craig R. Walton, ³Mahesh Anand, and ¹Maria Schönbächler
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14333]
¹Department of Earth Sciences, Institute f€ur Geochemie und Petrologie, ETH Zurich, Zurich, Switzerland
²Institute of Astronomy, University of Cambridge, Cambridge, UK
³School of Physical Sciences, Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

The majority of ordinary chondrite (OC) meteorites record some amount of textural evidence for impact-induced deformation. Melt veins in some shocked samples have been compared to terrestrial impact-related pseudotachylites, which form by frictional melting of host rock. However, lacking in situ context, the role of friction in driving impact-related melting in meteorites remains unclear. Here, we present evidence for an important role for shear deformation and friction in complementing shock melting of OC material. We find microfaults directly associated with textural evidence for quenched frictional shock melt in samples of a broad range of bulk shock stages and across all three classes studied (LL, L, or H). Microfaults occur in 20% of our studied samples. We identify examples of both individual microfaults and, in rare cases, microfault networks, complete with subsidiary shear structures. Our observations indicate that friction plays an important role in melt generation in weakly to moderately shocked samples and may also be relevant for strongly shocked meteorites. Microfault structures may be of underestimated significance in chondrites in general—both with regard to their general abundance and their possible utility for elucidating the geological settings sampled by meteoritic impactites.

¹Christina M. Verhagen et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14331]
¹Department of Earth and Planetary Sciences, Rutgers University, Piscataway Township, New Jersey, USA
Published by arrangement with John Wiley & Sons

Large terrestrial impacts may produce vast subsurface hydrothermal systems, capable of generating conditions favorable to the origin of life. Modeling suggests that these systems may persist for >1 million years for basin-sized craters; however, direct experimental constraints on hydrothermal system duration are needed. Paleomagnetism may be used as a tool to study the nature and duration of the postimpact hydrothermal system generated within the upper peak ring of the 200 km diameter Chicxulub crater (Yucatán Peninsula, México). Previous work observed that upper peak ring suevite samples contained characteristic remanent magnetizations with negative and positive inclinations, with most samples having a magnetic inclination close to −44°, the expected paleoinclination at the crater at the time of the impact. This magnetic record was at the time interpreted as chemical remanent magnetization (CRM) acquired over a period of at least 150 thousand years, from the time of the impact in geomagnetic Chron C29r into Chron C29n. We conducted further paleomagnetic and rock magnetic studies of upper peak ring rocks and found that, while most samples likely contain CRM acquired during Chron C29r, the dispersion of magnetic inclinations within suevite subunits is more likely attributed to pre-depositional remanence held within clasts than the recording of magnetic reversals. Therefore, the paleomagnetic record of the peak ring suevites is non-ideal for inferring the duration of the Chicxulub postimpact hydrothermal system.