^1,2,3Wladimir Neumann,⁴Robert Luther,²Mario Trieloff,⁵Philip M. Reger,⁶Audrey Bouvier
The Planetary Science Journal 4 196 Open Access Link to Article [DOI 10.3847/PSJ/acf465]
¹Institute of Geodesy and Geoinformation Science, Technische Universität Berlin, Kaiserin-Augusta-Allee 104-106, D-10553 Berlin, Germany
²Klaus-Tschira-Labor für Kosmochemie, Institut für Geowissenschaften, Universität Heidelberg, Im Neuenheimer Feld 234-236, D-69120 Heidelberg, Germany
³Institute of Planetary Research, German Aerospace Center (DLR), Rutherfordstr. 2 D-12489 Berlin, Germany
⁴Museum für Naturkunde—Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, D-10115 Berlin, Germany
⁵Department of Earth Sciences, Institute of Earth and Space Exploration, University of Western Ontario, London, ON N6A 5B7, Canada
⁶Bayerisches Geoinstitut, University of Bayreuth, D-95447 Bayreuth, Germany

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^1,2P. Beck et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115840]
¹Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France
²Univ. Grenoble Alpes, ISTerre, F-38000 Grenoble, France
Copyright Elsevier

Onboard NASA’s Curiosity rover, the ChemCam LIBS instrument has provided a wealth of information on the chemistry of rocks within Gale crater. Here, we use ChemCam in order to search for carbonates among the >3500 individual targets analyzed by this instrument. Because the carbon-lines are a combination of signal from the CO2-rich atmosphere and possible carbon from the targets, we developed a laboratory-based univariate calibration obtained under Mars-like atmosphere. We measured different type of carbon-bearing samples (sediments, coals, carbonates) and their mixture with a basaltic powder. Based on this work, the preferred approach to qualitatively assess carbon under a CO2-rich atmosphere is to use a ratio to an oxygen line (777 nm) and the estimated limit of detection for carbon in a single LIBS point are found to be of 4.5 wt% and 6.9 wt% for reduced and organic carbon, respectively. Considering carbonate, this LOD correspond to about 50 wt% carbonate in the analyzed volume.

Analysis of data obtained on Mars by ChemCam up to sol 3350 reveals the presence of a correlation between the intensity of carbon and oxygen lines, as observed in the laboratory, confirming that most carbon signal is related to ionization of the atmosphere. Some variability in the carbon signal appears related to the physical state of the atmosphere (density, temperature).

Based on a combined analysis of carbon lines and major element compositions (Ca, Fe, Mg), there was no detection of carbonate in the ChemCam dataset up to sol 3355. Therefore, we conclude that carbonate was not present as a major constituent (>50%) in the ChemCam LIBS targets, and that soils are not enriched in carbon beyond the limit of detection. The dominant salts present are sulfate, chlorides, and the lack of carbonates in Gale, while observed in Jezero, may at least partly be related to a difference in protolith.

¹M. S. Huber,^1,2E. Kovaleva,³A. S. P. Rae,^4.5N. Tisato,^4,5,6S. P. S. Gulick
Journal Geophysical Research (Planets) (in Press) Open Access Link to Article [10.1029/2022JE007721]
¹Department of Earth Science, University of the Western Cape, Bellville, South Africa
²Helmholtz Centre Potsdam, GFZ, Potsdam, Germany
³Department of Earth Sciences, University of Cambridge, Cambridge, UK
⁴Department of Geological Sciences, Jackson School of Geoscience, University of Texas at Austin, Austin, TX, USA
⁵Center for Planetary Systems Habitability, University of Texas at Austin, Austin, TX, USA
⁶Institute for Geophysics, Jackson School of Geoscience, University of Texas at Austin, Austin, TX, US
Published by arrangement with John Wiley & Sons

The record of terrestrial impact events is incomplete with no Archean impact structures discovered, despite the expected abundance of collisions that must have occurred. Because no Archean impact structures have been identified, the necessary conditions to preserve an impact structure longer than 2 Byr are unknown. One significant effect of shock metamorphism is that the physical properties of the target rocks change, resulting in distinctive geophysical signatures of impact structures. To evaluate the preservation potential of impact structures, we evaluate the deeply eroded Proterozoic Vredefort impact structure to examine the changes in physical properties and the remnant of the geophysical signature and compare the results with the well-preserved Chicxulub impact structure. The major structural features of Vredefort are similar to the expected profile of the Chicxulub structure at a depth of 8–10 km. The Vredefort target rocks, while shocked, do not preserve measurable changes in their physical properties. The gravity signature of the impact structure is minor and is controlled by the remnant of the collapsed transient crater rim and the uplifted Moho surface. We anticipate that erosion of the Vredefort structure by an additional 1 km would remove evidence of impact, and regardless of initial size, erosion by >10 km would result in the removal of most of the evidence for any impact structure from the geological record. This study demonstrates that the identification of geologically old (i.e., Archean) impact structures is limited by a lack of geophysical signatures associated with deeply eroded craters.

^1,2Zhang, ChuanTong,^1,2Wang, XiaoRui,^1,2Miao, BingKui,^1,2Xia, ZhiPeng,^1,2Chen, GuoZhu
Yanshi Xuebao/Acta Petrologica Sinica 39, 205 – 216 Open Access Link to Article [DOI 10.18654/1000-0569/2023.01.14]
¹Institution of Meteorites and Planetary Materials Research, Key Laboratory of Planetary Geological Evolution, Universities of Guangxi Province, Guilin University of Technology, Guilin, 541006, China
²Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin, 541006, China

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^1,2,3J. Greer,⁴B. Zhang,⁵D. Isheim,⁵D.N. Seidman,⁶A. Bouvier,^1,2P.R. Heck
Geochemical Perspectives Letters (in Press) Open Access Link to Article [https://doi.org/10.7185/geochemlet.2334]
¹Robert A. Pritzker Center for Meteoritics and Polar Studies, Negaunee Integrative Research Center, Field Museum of Natural History, 1400 South DuSable Lake Shore Drive, Chicago, Illinois 60605-2496, USA
²Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637-1468, USA
³School of Geographical & Earth Sciences, University of Glasgow, G12 8QQ, Glasgow, UK
⁴Department of Earth, Planetary, and Space Sciences, University of California, 595 Charles Young Dr. E, Los Angeles, California 90095-1567, USA
⁵Northwestern University Center for Atom Probe Tomography, Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, Illinois
60208-3108, USA
⁶Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany

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¹David C. Cantillo,¹Vishnu Reddy,¹Adam Battle,¹Benjamin N. L. Sharkey,²Neil C. Pearson,^1,3Tanner Campbell,¹Akash Satpathy,⁴Mario De Florio,^3,4Roberto Furfaro,²Juan Sanchez
The Planetary Science Journal 4, 177 Open Access Link to Article [DOI 10.3847/PSJ/acf298]
¹Lunar & Planetary Laboratory, The University of Arizona, Tucson, AZ, USA
²Planetary Science Institute, Tucson, AZ, USA
³Department of Aerospace & Mechanical Engineering, The University of Arizona, Tucson, AZ, USA
⁴Department of Systems & Industrial Engineering, The University of Arizona, Tucson, AZ, USA

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¹Thomas Smith,^1,2,3Huaiyu He,⁴Shijie Li,¹Fei Su
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14085]
¹State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
²Institutions of Earth Science, Chinese Academy of Sciences, Beijing, China
³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
⁴Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Published by arrangement with John Wiley & Sons

We report light noble gas (He, Ne, and Ar) concentrations and isotopic ratios in 11 achondrites, Tafassasset (unclassified primitive achondrite), Northwest Africa (NWA) 12934 (angrite), NWA 12573 (brachinite), Jiddat al Harasis (JaH) 809 (ureilite), NWA 11562 (ungrouped achondrite), four lodranites (NWA 11901, NWA 7474, NWA 6685, and NWA 6484), NWA 2871 (acapulcoite), and Sahara 02029 (winonaite), most of which have not been previously studied for noble gases. We discuss their noble gas isotopic composition, determine their cosmogenic nuclide content, and systematically calculate their cosmic ray exposure (CRE) and gas retention ages. In addition, we estimate their preatmospheric radii and preatmospheric masses based on the shielding parameter (22Ne/21Ne)cos. None of the studied meteorites shows evidence of contribution from solar cosmic rays (SCRs). JaH 809 and NWA 12934 show evidence of 3He diffusive losses of >90% and 40%, respectively. The winonaite Sahara 02029 has lost most of its noble gases, either during or before analysis. The average CRE age of Tafassasset of ~49 Ma is lower than that reported by Patzer et al. (2003), but is consistent with it within the uncertainties; this confirms that Tafassasset and CR chondrites are not source paired, CR chondrites having CRE ages from 1 to 25 Ma (Herzog & Caffee, 2014). The ureilite JaH 809 has a CRE age of ~5.4 Ma, which falls into the typical range of exposure ages for ureilites; the angrite NWA 12934 has a CRE age of ~49 Ma, which is within the main range of exposure ages reported for angrites (0.2–56 Ma). We calculate a CRE age of ~2.4 Ma for the brachinite NWA 12573, which falls into a possible “cluster” in the brachinite CRE age histogram around ~3 Ma. Three lodranites (NWA 11901, NWA 7474, and NWA 6685) have CRE ages higher than the average CRE ages of lodranites measured so far, NWA 11901 and NWA 6685 having CRE ages far higher than the CRE age already reported by Li et al. (2019) on NWA 8118. The measured 40K-40Ar gas retention ages fit well into established systematics. The gas retention age of Tafassasset is consistent, within respective uncertainties, with that previously calculated by Patzer et al. (2003). Our study indicates that Tafassasset originates from a meteoroid with a preatmospheric radius of ~20 cm, however discordant with the radius of ~85 cm inferred in a previous study (Patzer et al., 2003).

¹Minoru Uehara,¹Jérôme Gattacceca
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14087]
¹CNRS, IRD, INRAE, CEREGE, Aix Marseille Univ, Aix-en-Provence, France
Published by arrangement with John Wiley & Sons

We developed a simple, handheld, and user-friendly magnetic susceptibility meter specialized for the identification of meteorites. The measurement is based on an LC resonance circuit. When provided with a rough estimate of the sample mass, the instrument displays directly the mass-normalized magnetic susceptibility expressed in logχm (with χm in 10−9 m3 kg−1), a parameter that is widely used in the classification of meteorites. Moreover, the measurement of the impedance of the LC resonator provides a proxy of the electrical conductivity (C-index) that can be helpful to distinguish metal-bearing samples from magnetite-bearing samples. This C-index offers an additional diagnostic for the identification of meteorites. Our tests demonstrate that the precision and the accuracy of this instrument called “Meteorite meter” (MetMet) are sufficient to allow distinguishing most meteorites from most terrestrial rocks, for a minimum recommended sample mass of 5 g. The distinction of some meteorite groups is also possible, in particular the separation of the three ordinary chondrite groups. Meteorite hunters, collectors, and curators and non-specialists, including children, can use this instrument as a guidance in the identification and classification of meteorites. This kind of instrument has an immense advantage over the widely used testing of meteorites with magnets, as it does not affect the paleomagnetic records of meteorites that are highly valuable for scientists.

^1,2Massa, Giuseppe,²Longobardo, Andrea,²Palomba, Ernesto,^1,2Angrisani, Marianna,^1,2Gisellu, Chiara,Dirri, Fabrizio,²De Sanctis, Maria Cristina,²Raponi, Andrea,²Carrozzo, Filippo Giacomo,²Ciarniello, Mauro
Universe 9, 296 Open Access Link to Article [DOI 10.3390/universe9060296]
¹INAF Istituto di Astrofisica e Planetologia Spaziali, Rome, 00133, Italy
²Department of Information Engineering, Electronics and Telecommunications, University of Rome “Sapienza”, Rome, 00185, Italy

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¹Toshiki Koga,¹Yoshinori Takano,²Yasuhiro Oba,³Hiroshi Naraoka,¹Naohiko Ohkouchi
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.10.024]
¹Biogeochemistry Research Center (BGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan
²Institute of Low Temperature Science (ILTS), Hokkaido University, N19W8, Kita-ku, Sapporo, Hokkaido 060-0189, Japan
³Department of Earth and Planetary Sciences, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Fukuoka, 819-0395, Japan
Copyright Elsevier

Extraterrestrial nucleobases are of key interest owing to their implications for the chemical evolution of primordial molecules in the solar system and their potential contributions to prebiotic chemistry on the early Earth. Recent advances in analytical techniques capable of detecting femto-mole-order nucleobases have allowed us to identify all five exogenous nucleobases—uracil, cytosine, thymine, adenine, and guanine—in carbonaceous chondrites and to quantify uracil obtained from the carbonaceous asteroid (162173) Ryugu. In this study, we optimized the analytical method using hot-water extraction followed by 6 M hydrochloric acid (HCl) extraction from a sample of the CM2 Murchison meteorite to reassess the abundances and distributions of extraterrestrial nucleobases. The target analyses performed using high-performance liquid chromatography paired with electrospray-ionization, high-resolution mass spectrometry revealed that purine nucleobases were substantially more enriched in the subsequent 6 M HCl extract (951 ± 104 parts per billion, ppb) than in the hot-water extract (199 ± 3 ppb). The most abundant nucleobase was guanine (649 ± 103 ppb in total). The 6 M HCl extract not only contained canonical nucleobases but also included rare nucleobase analogs from the purine family, such as 8-substituted purines. Unlike purines, we preferentially detected pyrimidine nucleobases in the hot-water extract and the acid hydrolysate (185 ± 17 ppb and 297 ± 5 ppb, respectively) rather than in the 6 M HCl extract (51 ± 4 ppb). The disparate distributions of purine and pyrimidine bases in the Murchison meteorite suggests that purines are more robustly incorporated than pyrimidines into meteoritic matrices and/or insoluble macromolecular organic matter. We propose a unified formation mechanism for purine nucleobases—which involves the synthesis of 5-aminoimidazole derivatives from hydrogen cyanide and its related molecules—that can account for the molecular distributions of the extraterrestrial purine nucleobases found in the Murchison meteorite.