Month: September 2025

Delivery of carbonaceous materials to the Moon

Posted by

0

Linxi Lia,b,d, et al. (>10)

Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116802]
aState Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Copyright Elsevier

Asteroidal impacts play an important role in creating new lithology, shaping the morphology, and transporting water to the inner Solar System planets. Massive impact records have been preserved on the Moon; however, exogenous impactors have not been adequately identified in lunar samples. Here we carried out petrological and geochemical investigations on the newly lunar samples returned by Chang’e-6 (6CE) to estimate the source of impactors to the Moon. One spinel-bearing troctolite-like clast was identified in the 6CE soils. This clast displays porphyritic texture and is mainly composed of olivine (32 %), plagioclase (31 %), and mesostasis (34 %) with minor troilite (2 %) and spinel (1 %), and rare Fesingle bondNi metal, in area%. The sample olivines have a forsterite variation range of 75–85 and a Fe/Mn atomic ratio of 55–80. The trace element concentrations of Co (113–223 μg.g−1), Ni (121–938 μg.g−1), Cr (1191–4832 μg.g−1), and P (827–1645 μg.g−1) in olivines are notable higher than the typical lunar samples. Furthermore, these olivines exhibit notable 16O depletion features (δ18O: +10.7 ‰ to +16.7 ‰ and δ17O: +5.9 ‰ to +9.5 ‰). The investigated clast has a bulk Ir content of 51 ng.g−1, significantly higher than local lunar materials. The unusual texture, mineral chemistry, trace element concentrations, and oxygen isotopic compositions suggest this clast was likely derived from an impact event created by a CI- or CY-like carbonaceous chondrite. Such chemical and isotopic features are correlated with textures, indicating that some olivine have relict cores originated from the impactor. Such an impact event could have produced a new lithology of spinel-bearing troctolite on the Moon. Meanwhile, the carbonaceous chondritic impactor would have delivered a great amount of water and volatiles to the Moon.

Regolith without age? High-resolution regolith depth measurements across lunar maria

Posted by

0

Elizabeth F.M. Atang
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116790]
University of Idaho, Department of Physics, 875 Perimeter Dr. MS 0903, Moscow, ID 83844-0903, USA
Copyright Elsevier

In this work, we test the established hypothesis that lunar regolith depth increases with time because the surface is continually exposed to meteorite bombardment. If this hypothesis is correct, younger surfaces should have thinner regolith than older surfaces. Because many of the regolith depth studies in the literature are for surfaces older than 3 Gy, in this paper, we study Mare regions with a wide range of ages between 1.33 Gy and 3.88 Gy. To measure regolith depths, we used the small crater morphology method based on the work by Oberbeck & Quaide. We found median regolith depths between 1.6 m to 4.0 m across our study sites. Importantly, we did not find any correlation between the thickness of the regolith and the age of the surface within the Mare units we studied. We conclude by discussing whether this result represents a true lack of correlation, which would imply an incomplete understanding of regolith formation.

Condensation of major and trace elements in dust-rich environments

Posted by

0

Marwane Mokhtari, Bernard Bourdon

Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116801]
Laboratoire de Géologie de Lyon, Terre Planètes Environnement, ENS de Lyon, CNRS, Université Lyon 1. 46 Allée d’Italie, 69007 Lyon, France
Copyright Elsevier

Recent astronomical observations have shown that dust can get locally concentrated in protoplanetary disks, forming ring structures. The thermal processing of such regions could lead to dust evaporation and local enrichment of the solar gas in condensable elements. Previous studies focusing on major element behavior have shown that condensation of such dust-enriched gas could lead to the formation of a silicate melt with compositions resembling that of chondrules. However, previous studies focusing on dust-enriched environments were restricted to a limited set of elements. To study the mineralogical and chemical composition of condensates in these conditions, we have performed equilibrium calculations using the FactSage™ software for a dust-enriched solar gas. The calculations were done with dust-enrichment factors of 1 (solar composition), 10 and 100 at pressures ranging from 10−6 bar to 10−3 bar, for a CI-chondrite dust and a H-chondrite dust. The trace element condensation was accurately modelled with newly calculated activity coefficients in different solid and melt solutions. The available gas phase database was completed with new trace element species that are important to consider in oxidized conditions. The mineralogical sequence, melt composition and condensation temperature for all condensable elements were then quantified.
Our calculations show that the iron contents of olivine in equilibrium with a gas that is x100 enriched in CI-dust is consistent with that of amoeboid olivine aggregates and chondrules. Furthermore, our estimated temperature at which fayalite can form in these conditions is higher than what was previously proposed, enabling diffusion and homogenization of iron in olivine. The calculated composition of refractory metals for a x10 and x100 CI-dust enriched gas at 10−4 bar is consistent with the measured compositions of refractory metal nuggets. The possibility for these grains to have fractionated in an H2O ice-enriched gas can be ruled out as the calculated fractionation patterns in this case did not match the observed compositions.

Trends in planetary science research in the Puna and Atacama Desert regions: Underrepresentation of local scientific institutions?

Posted by

0

1A. Tavernier,2,3G. A. Pinto,4,5,6M. Valenzuela,1A. Garcia,1C. Ulloa,7R. Oses,8,9,10,11B. H. Foing
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13972]
1Instituto de Investigaciones Científicas y Tecnológicas, IDICTEC, Laboratorio de Investigacion de la Criosfera y Aguas, Universidad de Atacama, UDA, Copiapó, Chile
2Instituto de Investigación en Astronomía y Ciencias Planetarias, INCT, Universidad de Atacama, UDA, Copiapó, Chile
3Centre de Recherches Pétrographiques et Géochimiques, CRPG, Université de Lorraine, Nancy, France
4Departamento de Ciencias Geológicas, Universidad Católica del Norte, UCN, Antofagasta, Chile
5Millennium Institute of Astrophysics, MAS, Santiago, Chile
6Center for Excellence in Astrophysics and Associated Technologies, CATA, Santiago, Chile
7Centro Regional de Investigacion y Desarrollo Sustentable de Atacama, CRIDESAT, Universidad de Atacama, UDA, Copiapó, Chile
8Instituto de Investigación en Astronomía y Ciencias Planetarias, INCT, Universidad de Atacama, UDA, Copiapó, Chile
9International Lunar Exploration Working Group, ILEWG, EuroMoonMars, Noordwijk, The Netherlands
10Vrije Universiteit Amsterdam, VUA, Amsterdam, The Netherlands
11Universiteit Leiden, Leiden, The Netherlands
Published by arrangement with John Wiley & Sons

In 2019, while launching a multidisciplinary research project aimed at developing the Puna de Atacama region as a natural laboratory, investigators at the University of Atacama (Chile) conducted a bibliographic search identifying previously studied geographic points of the region and of potential interest for planetary science and astrobiology research. This preliminary work highlighted a significant absence of local institutional involvement in international publications. In light of this, a follow-up study was conducted to confirm or refute these first impressions, by comparing the search in two bibliographic databases: Web of Science and Scopus. The results show that almost 60% of the publications based directly on data from the Puna, the Altiplano, or the Atacama Desert with objectives related to planetary science or astrobiology do not include any local institutional partner (Argentina, Bolivia, Chile, and Peru). Indeed, and beyond the ethical questioning of international collaborations, Latin-American planetary science deserves a strategic structuring, networking, as well as a road map at national and continental scales, not only to enhance research, development, and innovation, but also to protect an exceptional natural heritage sampling extreme environmental niches on Earth. Examples of successful international collaborations such as the field of meteorites, terrestrial analogs, and space exploration in Chile or astrobiology in Mexico are given as illustrations and possible directions to follow to develop planetary science in South America. To promote appropriate scientific practices involving local researchers, possible responses at academic and institutional levels will eventually be discussed.

A comprehensive study of comet 67P/Churyumov-Gerasimenko in the 2021/2022 apparition. I. Photometry, spectroscopy, morphology

Posted by

0

Vera Rosenbusha,b, et al. (>5)

Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116799]
aAstronomical Observatory of Taras Shevchenko National University of Kyiv, 3 Observatorna St., Kyiv 04053, Ukraine
Copyright Elsevier

We present observations of comet 67P/Churyumov–Gerasimenko during its 2021/22 apparition, aiming to investigate its dust and gas environment and compare the results with those obtained in 2015/16 using the same telescope. Quasi-simultaneous photometric, spectroscopic, and polarimetric observations were carried out at the 6-m BTA SAO telescope. The comet was observed on 6 October 2021, 31 days before perihelion, with g-sdss and r-sdss filters, and on 6 February 2022, 96 days after perihelion, using narrowband cometary filters: BC (λ4450/62 Å), RC (λ6839/96 Å), and CN(λ3870/58 Å). These were complemented by images from the 2-m Liverpool Telescope (La Palma). On 6 October 2021, a sunward jet and long dust tail were detected. By 6 February 2022, the dust coma morphology had changed noticeably, revealing a bright sunward neckline structure superimposed on the projected dust tail, along with two jets at position angles of 133° and 193°. Spectra showed strong CN emission, with relatively weak C₂, C₃, and NH₂ emissions. The dust production rate Afρ did not exceed 200 cm (uncorrected for phase angle) in both epochs. An unusual CN coma morphology was observed, with evidence of an additional CN source associated with dust jets. Geometric modeling of the jets’ dynamics indicated an active area at latitude −70° ± 4° with a jet opening angle of 20° ± 6° on 6 October 2021, and two active areas at latitudes −58° ± 5° and − 53° ± 10°, separated by longitude 150° ± 20°, producing the observed jets on 6 February 2022. The average particle velocity in the jets was about 0.32 ± 0.04 km s−1.

The YORP effect for meter-sized asteroids

Posted by

0

Conor J. Benson, Daniel J. Scheeres

Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116794]
University of Colorado Boulder, 3775 Discovery Drive, Boulder, CO 80303, USA
Copyright Elsevier

The spin states of meter-sized asteroids should evolve rapidly due to the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect. While these asteroids are very challenging to observe, artificial geosynchronous (GEO) satellites are convenient analogues given that they are driven primarily by solar torques, evolve rapidly, and are easy to observe. These artificial objects could provide insight about the evolution of their natural counterparts. Recent studies of YORP for defunct GEO satellites with full and tumbling-averaged models have uncovered rich dynamical structure with tumbling cycles, angular momentum sun-tracking, and tumbling resonances. Applying the tumbling-averaged YORP models to meter-sized pseudo asteroids, we find that the solar torque structure yields sun-tracking precession in many cases, particularly for asteroids with at least some elongation. Precession about the sun line results in the long-term obliquity averaging to roughly 90°. As a result, the sun-tracking behavior could potentially shut off Yarkovsky drift for these asteroids and thereby limit their mobility out of the main asteroid belt. For some asteroid shapes, tumbling cycles with alternating spin up and spin down are also observed. These tumbling cycles offer a possible avenue to prevent spin-driven disruption of meteoroids.

Geological mapping and chronology of lunar landing sites: Apollo 15

Posted by

0

I.W. Iqbal1, J.W. Head IIIb, L. Wuellera, H. Hiesingera, C.H. van der Bogerta, D.R. Scottb,c

Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116791]
aInstitut für Planetologie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
bDepartment of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
aApollo 15 Commander, USA
Copyright Elsevier

Apollo 15 was the first extended exploration mission to the Moon. The data acquired from the Apollo 15 mission constitutes a comprehensive geological dataset, significantly enhancing our understanding of volcanic, impact and other geological processes, and the chronological and thermal evolution of the Moon. Moreover, the Apollo 15 data provide a critical calibration point for the lunar cratering chronology function. This chronology is established through the systematic correlation of crater size-frequency distributions (CSFDs) with radioisotopic ages of samples from the Apollo, Luna, and Chang’e landing sites. Establishing this link between samples and CSFDs necessitates a thorough understanding of the geology of the landing sites. In this study, we present a newly developed, detailed regional geological map of the Apollo 15 landing site, utilizing modern data. Our new geological map enables the identification of homogeneous regions suitable for new CSFD measurements, from which updated N(1) values (i.e., the cumulative number of craters with diameters ≥1 km) can be derived for the corresponding geological units. Furthermore, this geological map addresses outstanding scientific questions, which have been outlined as objectives for the 500-day Hadley Max design reference mission (DRM) (Daniti et al., 2024). The new calibration point obtained from comparing these updated N(1) values with sample ages was found to be consistent with the lunar chronology proposed by Neukum (1983). This consistency, in conjunction with our previous research, reinforces the validity of Neukum’s lunar cratering chronology. We summarize the key outstanding scientific questions identified by the new geologic map as a basis for future human and robotic lunar exploration of the Moon.

Century-scale effect of climate change on meteorite falls

Posted by

0

Eloy PENA-ASENSIO1,2, Denis VIDA3,4, Ingrid CNOSSEN5 , and Esteban FERRER2
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70046]
1Department of Geosciences, University of Arizona Geosciences, Tucson, Arizona, USA
2School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
3Lawrence Livermore National Laboratory, Livermore, California, US
Published by arrangement with John Wiley & Sons

Climate change is inducing a global atmospheric contraction above the tropopause (~10 km), leading to systematic decrease in neutral air density. The impact of climate change on small meteoroids has already been observed over the last two decades, with documented shifts in their ablation altitudes in the mesosphere (~50–85 km) and lower thermosphere (~85–120 km). This study evaluates the potential effect of these changes on meteorite-dropping fireballs, which typically penetrate the stratosphere (~10–50 km). As a case study, we simulate the atmospheric entry of the fragile Winchcombe carbonaceous chondrite under projected atmospheric conditions for the year 2100 assuming a moderate future emission scenario. Using a semi-empirical fragmentation and ablation model, we compare the meteoroid’s light curve and deceleration under present and future atmospheric density profiles. The results indicate a modest variation of the ablation heights, with the catastrophic fragmentation occurring 300 m lower and the luminous flight terminating 190 m higher. The absolute magnitude peak remains unchanged, but the fireball would appear 0.5 dimmer above ~120 km. The surviving meteorite mass is reduced by only 0.1 g. Our findings indicate that century-scale variations in atmospheric density caused by climate change moderately influence bright fireballs and have a minimal impact on meteorite survival.

Trace element analyses of plagioclase from troctolite 76535 and implications for the petrogenesis of the lunar highlands Mg-suite

Posted by

0

Isaiah SPRING1, Ananya MALLIK1, Jason KIRK1, Pranabendu MOITRA1, Richard HERVIG2, and Lars BORG3
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70047]
1Department of Geosciences, University of Arizona Geosciences, Tucson, Arizona, USA
2School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
3Lawrence Livermore National Laboratory, Livermore, California, US
Published by arrangement with John Wiley & Sons

We used trace element analyses of plagioclase from Mg-suite troctolite 76535 to estimate the Rare Earth Element (REE) concentrations of its parental liquid and assess the feasibility of an urKREEP contribution to the Mg-suite parental liquid. We measured 33 trace elements in 76535 plagioclase separates. Our measurements revealed enrichments in incompatible elements consistent with previous analyses. Using the measured REE concentrations, we estimated the REE concentrations of the unfractionated Mg-suite parental liquid using a RhyoliteMELTS-based forward model. Compared to chondritic concentrations, the Mg-suite parental liquid is ~100 times more enriched in light REEs and ~10 times more enriched in heavy REEs. We sought to explore the feasibility of reproducing these enrichments in the parental liquid through assimilation of urKREEP by a partial melt of rising LMO cumulates during cumulate mantle overturn. We show that these enrichments can be reproduced by a 30%–50% addition of fully molten urKREEP to the LMO cumulate melt, if the LMO cumulate melt and urKREEP are in thermal equilibrium with each other. However, the Mg# of these mixtures (57–68) is too low to produce the most Mg-rich olivine (Fo 91) observed in Mg-suite troctolites. Alternatively, assuming that the LMO cumulate melt and urKREEP are in thermal disequilibrium, we reproduced both the REE abundances and Mg# of the Mg-suite parental liquid with only a 10% addition of the urKREEP partial melt. These results support the feasibility of urKREEP assimilation as a mechanism for generating the incompatible element enrichments in Mg-suite magmas while preserving their major element chemistry.

Secondary corundum in CAIs from CK3 carbonaceous chondrites dates metasomatic alteration of CK chondrites

Posted by

0

A. N. KROT1, K. NAGASHIMA1 , S. EBERT2, M. I. PETAEV3, C. MA4, J. HAN5, and T. L. DUNN6
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70044]
1Hawai’i Institute of Geophysics & Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at
Manoa, Honolulu, Hawaii, USA
2Institut für Planetologie, University of Münster, Münster, Germany
3Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
4Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
5Amentum, NASA Johnson Space Center, Houston, Texas, USA
16Department of Geology, Colby College, Waterville, Maine, USA
Published by arrangement with John Wiley & Sons

We report on the mineralogy, petrography, and oxygen and aluminum-magnesium isotopic systematics of the corundum-bearing Ca,Al-rich inclusions (CAIs) from the CK3 (Karoonda-type) carbonaceous chondrites NWA (Northwest Africa) 4964-#1 and -Homer, NWA 5343-#1, and LAR (Larkman Nunatak) 12002-#1. These CAIs experienced extensive metasomatic alteration: melilite and possibly anorthite and AlTi-diopside are nearly completely replaced by secondary corundum, grossular, CaNa-plagioclase, FeAl-diopside, and FeO-rich spinel; perovskite is largely replaced by ilmenite. Two types of corundum grains occur in the NWA 4964 CAIs: (1) compact, FeO-poor grains zoned in cathodoluminescent (CL) images and (2) FeO-bearing (up to 1.5 wt% FeO), porous grains showing no detectable CL; the porous corundum grains overgrow the compact ones. Corundum grains in CAIs from LAR 12002 and NWA 5343 belong to the first and second types, respectively. Hibonite, primary spinel, and rare perovskite inclusions in spinel retained the original, 16O-rich compositions (Δ17O ~ −24 ± 2‰), whereas melilite, most perovskite grains, and secondary corundum and spinel are 16O-depleted (Δ17O ~ −5 ± 2‰). Hibonite and melilite have excesses of radiogenic 26Mg (26Mg*) corresponding to approximately the canonical initial 26Al/27Al ratio [(26Al/27Al)0] of ~5 × 10−5 suggesting that corundum-bearing CAIs studied belong to a population of the canonical inclusions, dominant in most chondrite groups. Corundum grains in LAR 12002-#1, NWA 4964-#1, NWA 4964-Homer, and NWA 5343-#1 show resolvable 26Mg* correlated with 27Al/24Mg ratio which corresponds to much lower than the canonical (26Al/27Al)0: (3.10 ± 0.48) × 10−6, (3.03 ± 0.23) × 10−6, (2.72 ± 0.19) × 10−6, and (3.5 ± 1.2) × 10−7, respectively. Porous Fe-bearing corundum grains in NWA 4964 CAIs Homer and #1 have low 26Mg* not correlated with 27Al/24Mg ratio. We conclude that compact corundum grains in the CK3 CAIs studied are secondary parent body products that resulted from metasomatic alteration of the host inclusions by hydrothermal fluid ~3−5 Ma after their crystallization. Porous corundum grains may have formed by dehydration of diaspore [AlO(OH)] during subsequent thermal metamorphism.