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.

^1,2Yogita Kadlag,³David Haberthür,²Ingo Leya,³Ruslan Hlushchuk,⁴Klaus Mezger
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2023.105799]
¹Geosciences Division, Physical Research Laboratory, Navrangpura, 380009, Ahmedabad, India
²Space Science and Planetology, Physikalisches Institut, Universität Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
³Institut für Anatomie, Universität Bern, Baltzerstrasse 2, 3012, Bern, Switzerland
⁴Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, 3012, Bern, Switzerland

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¹P.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
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.

¹Z.E. Wilbur et al.(>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14086]
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Published by arrangement with John Wiley & Sons

In 1972, Apollo 17 astronauts returned 170.4 kg of lunar material. Within 1 month of their return, a subset of those samples was specially curated with the forethought that future analytical techniques would offer new insight into the formation and evolution of the Moon. Of interest in this work is sample 71036, a basalt collected from the rim of Steno crater in the Taurus–Littrow Valley, which was stored frozen and was processed and released for study 50 years later. We report, for the first time, the detailed mineralogy and petrology of 71036 and its companion samples 71035, 71037, and 71055 using a novel combination of 2-D and 3-D methods. We investigate lunar volatiles through in situ measurements of apatite and 3-D measurements of vesicles to understand the degassing histories of the Steno crater basalts. Our coupled 2-D petrography and 3-D tomography data sets support a model of the Steno crater basalts crystallizing in the upper crust of a mare lava flow. Apatite F and OH chemistry and the late-stage deformation of voids and formation of smaller vesicles provide evidence supporting coeval degassing of volatiles and crystallization of mesostasis apatite in Apollo 17 basalts. This work helps to close knowledge gaps surrounding the origin, magmatic evolution, emplacement, and crystallization history of high-titanium basalts.

¹E.S. Steenstra,¹C.J. Renggli,¹J. Berndt,¹S. Klemme
Earth and Planetary Science Letters 622, 118406 Link to Article [https://doi.org/10.1016/j.epsl.2023.118406]
¹Institute of Mineralogy, University of Münster, Germany
Copyright Elsevier

Volatile element abundances in magmatic iron meteorites provide fundamental insights into the processing of volatile elements in the early solar system. Although Cu, Ge and Ag concentrations of magmatic iron meteorites deviate up to 4 orders of magnitude between different magmatic iron meteorite groups, the role of evaporation on these volatile abundances is poorly constrained. Here, we experimentally assess the volatility of Cu, Ge, Ag, S, Cr, Co, Ni, Mo, Ru, Pd, W, Re and Ir from metal and sulfide melts as a function of pressure (10−4 and 1 bar), temperature (1573–1823 K) and time (5–120 min) for two end-member compositions (Fe versus FeS). These novel experiments demonstrate that the presence of S is a major parameter in establishing the volatility of Cu, Ge, Mo, Ag, Ru, W, Re and Ir. At constant P-T and time, the volatility of Ge, Mo, Ru, W, Re and Ir is greatly increased in the presence of S, whereas Cu and Ag are less volatile in the presence of S. At 1773 K and ∼0.001 bar, the volatility of S is sufficiently high that the degassed FeS liquid showed immiscibility of a S-rich sulfide and a S-poor Fe melt. Empirical equations were derived that predict the evaporative loss of Cu, Ge, Mo, Ag from Fe and/or FeS liquid as a function of temperature and time. A comparison of the newly derived volatility sequences with commonly applied 50% condensation temperature models shows that the condensation temperature models cannot be applied to sulfur-bearing Fe liquids and therefore to magmatic iron meteorites. Application of the new models on previously derived elemental depletions in the IVB parent body shows that evaporation, if it occurred, cannot have taken place under S-rich conditions. The latter would result in a depletion of Mo, which is not observed for the IVB irons. However, evaporation of a S-free or S-poor Fe liquid reproduces the observed volatility depletion trend for IVB irons under a wider range of temperature and evaporation times, demonstrating the potential importance of evaporative loss on the IVB parent body.

¹Devienne, José A. P. M.,¹Berndt, Thomas A.,²Williams, Wyn, ³Nagy, Lesleis
Geophysical Research Letters 50, e2022GL102602 Open Access Link to Article [DOI 10.1016/j.jas.2023.105827]
¹Department of Geophysics, School of Earth and Space Sciences, Peking University, Beijing, China
²School of GeoSciences, The University of Edinburgh, Edinburgh, United Kingdom
³Department of Geophysics, Ocean and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom

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^1,2Hofmann, B.A. et al. (>10)
Journal of Archaelogical Research 157, 105827 Link to Article [DOI 10.1016/j.jas.2023.105827]
¹Naturhistorisches Museum Bern, Bernastrasse 15, Bern, CH-3005, Switzerland
²Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, Bern, CH-3012, Switzerland

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¹Ngyen, Ann N. et al. (>10)
Science Advances 9, eadh1003 Open Access Link to Article [DOI 10.1126/sciadv.adh1003]
¹Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, 77058, TX, United States

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¹Huidobro J. et al. (>10)
Analytica Chimica Acta 1276, 341632 Open Access Link to Article [DOI 10.1016/j.aca.2023.341632]
¹IBeA Research Group, University of the Basque Country (UPV/EHU), Spain

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¹Liu, Weiyi, ²Zhang, Yigang, ¹Tissot, François L.H., ³Avice, Guillaume, ⁴Ye, Zhilin, ⁵Yin, Qing-Zhu
Science Advances 9, adg9213 Open Access Link to Article [DOI 10.1126/sciadv.adg9213]
¹The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, 91125, CA, United States
²Key Laboratory of Computational Geodynamics, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
³Universite Paris Cite, Institut de physique du globe de Paris, CNRS, Paris, F-75005, France
⁴Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou, 550081, China
⁵Department of Earth and Planetary Sciences, University of California, Davis, 95616, CA, United States

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