¹Satoru Yamamoto,¹Moe Matsuoka,²Hiroshi Nagaoka,³Makiko Ohtake,¹Ayame Ikeda
Journal of Geophysical Research (Planets) (in Press) Link to Artice [https://doi.org/10.1029/2024JE008663]
¹Geological Survey of Japan (GSJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
²Earth and Space Exploration Center, Ritsumeikan University, Kusatsu Shiga, Japan
³School of Computer Science and Engineering, The University of Aizu, Aizuwakamatsu, Japan
Published by arrangement with John Wiley & Sons

We studied the global distribution and geological features of lunar surface sites whose spectra indicate an ilmenite-rich composition. Hyperspectral data obtained by the Kaguya Spectral Profiler were used for data mining to identify diagnostic features of a 1- and 2-μ
m spectral reflectance of ilmenite, revealing the global distribution of sites showing ilmenite-rich spectra. The results show that regions with ilmenite-rich spectra are concentrated at the margins of impact basins on the lunar nearside, whereas no such regions are identified in the Feldspathic Highland Terrain or the South Pole-Aitken basin. Using multiband images and a digital terrain model obtained by the Kaguya Multiband Imager and Terrain Camera, we examined the geological features of each site showing ilmenite-rich spectra and found that most of the sites are distributed on pyroclastic deposits overlying highland materials. Spectra interpreted as glass-rich material are prevalent in and around areas having ilmenite-rich spectra. However, sites showing ilmenite-rich spectra do not correspond to mare regions with
-rich basalts. These results may indicate that the concentration of ilmenite in pyroclastic deposits is high enough to exhibit diagnostic features of 1- and 2-μ
m spectral reflectance of ilmenite, whereas the concentration in mare regions with
-rich basalt is not. Since pyroclastic deposits are expected to be extensive, deep unconsolidated deposits of relatively block-free debris, resulting in high processing efficiency in the hydrogen reduction processes, our data may be useful for developing an efficient exploration strategy for ilmenite as a lunar resource.

^1,2Huanyu Wu,^1,2Yuan Zou,³Chi Zhang,³Wei Yang,^2,4Bo Wu,^2,5Kai-Leung Yung,^1,2Qi Zhao
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008787]
¹Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China
²Research Centre for Deep Space Explorations, The Hong Kong Polytechnic University, Hong Kong, China
³Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
⁴Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong, China
⁵Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong, China
Published by arrangement with John Wiley & Sons

Chang’e-5 (CE-5) lunar regolith samples were scanned using X-ray micro-computed tomography (micro-CT), and over 0.7 million particles were extracted from the images through machine learning-based segmentation. This is the largest three-dimensional (3D) image data set on lunar regolith particles to date, offering a unique opportunity to study the key characteristics of the lunar regolith. The image intensity was correlated with mineral density, allowing for the assessment of the bulk density (1.58 g/cm3), true density (3.17 g/cm3), and mineralogy of the lunar regolith. Glass and plagioclase contributed 45.6 wt.% of the samples, while pyroxene and olivine made up 49.7 wt.%, and ilmenite accounted for 4.7 wt.%. The median grain size of CE-5 was 57.5 μm, smaller than the Apollo 11, 16 and Luna 16, 20 and 24 samples. Spherical harmonic (SH) analysis and aspect ratio (AR) measurement revealed that the CE-5 lunar regolith particles have more complex shapes than two common terrestrial soils and exhibit less spherical shapes than Apollo 11, 16 and Luna 16, 20 and 24 samples. We recommend using size and shape characteristics cautiously when inferring the lunar regolith maturity because the intrinsic crystal size of the protolith and complex lunar surface weathering can cause significant size and shape variations. Additionally, characterizing particle shapes requires a large sample size (>1,000) to prevent skewed results from outliers. Our non-destructive examination method offers a novel and appealing approach for analyzing critical physical, mineralogical, and morphological properties of million-scale extraterrestrial soil particles, paving the way for future deep space explorations.

^1,2Peter Jenniskens,³Hadrien A. R. Devillepoix
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14321]
¹SETI Institute, Mountain View, California, USA
²NASA Ames Research Center, Moffett Field, California, USA
³Space Science and Technology Centre and International Centre for Radio Astronomy Research, Curtin University, Perth, Western Australia, Australia
Published by arrangement with John Wiley & Sons

With the goal to determine the origin of our meteorites in the asteroid belt, video and photographic observations of meteors have now tracked 75 meteorite falls. Six years ago, there were just hints that different meteorite types arrived on different orbits, but now, the number of orbits (N) is high enough for distinct patterns to emerge. In general, 0.1–1-m sized meteoroids do not arrive on similar orbits as the larger ~1-km sized near-Earth asteroids (NEA) of corresponding taxonomic class. Unlike larger NEA, a group of H chondrite meteoroids arrived on low-inclined orbits from a source just beyond the 5:2 mean-motion resonance with Jupiter (N = 12), three of which have the 7 Ma cosmic ray exposure (CRE) age from a significant collision event among H chondrites. There is also a source of H chondrites low in the inner main belt with a ~35 Ma CRE age (N = 8). In contrast, larger H-like taxonomic S-class NEA arrive from high-inclined orbits out of the 3:1 resonance. Some H chondrites do so also, four of which have a 6 Ma CRE age and two have an 18 Ma CRE age. L chondrites arrive from a single source low in the inner main belt, mostly via the ν6 secular resonance (N = 21), not the 3:1 resonance as most L-like NEA do. LL chondrites arrive too from the inner main belt (N = 5), as do larger LL-like NEA. CM chondrites are delivered from a low i < 3° inclined source beyond the 3:1 resonance (N = 4). Source asteroid families for these meteorite types are proposed, many of which have the same CRE age as the asteroid family’s dynamical age. Also, two HED achondrites are now traced to specific impact craters on asteroid Vesta.

^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