¹Gurpreet Kaur Bhatia
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2023.105783]
¹Department of Physics, MM Engineering College, Maharishi Markandeshwar (Deemed to be University), Mullana-Ambala, Haryana, 133207, India

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

¹Lingqi Zeng,¹Jochen Gätjen,¹Manuel Reinhardt,^2,3,4Michael E. Böttcher,¹Andreas Reimer,¹Volker Karius,¹Volker Thiel,¹Gernot Arp
Geochmica et Cosmochimica acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.10.013]
¹Geoscience Center, University of Göttingen, D-37077 Göttingen, Germany
²Geochemistry and Isotope Biogeochemistry, Leibniz Institute for Baltic Sea Research (IOW), D-18119 Warnemünde, Germany
³Marine Geochemistry, University of Greifswald, D-17489 Greifswald, Germany
⁴Interdisciplinary Faculty, University of Rostock, D-18059 Rostock, Germany
Copyright Elsevier

In impact crater lakes, the lacustrine sedimentary records may not solely reflect climatic changes but also potential erosional effects from lithologically distinct impactite formations. The hydrochemical and biogeochemical processes during the deposition of the Nördlinger Ries impact crater lake, which fall in the range of the mid-Miocene Climate Transition, were studied by analysing microcrystalline authigenic carbonates in a drill core succession, using stable oxygen and carbon isotopes in conjunction with biomarkers. These investigations revealed an early sulfidic interval characterized by thiophenes, iso- and anteiso-C15:0 acids derived from sulfate reducing bacteria, and dolomites with low to intermediate δ13Ccarb values. The subsequent distinctive interval is characterized by extremely 13C-enriched dolomite (δ13Ccarb up to +20.93 ± 0.05 ‰ V-PDB), decline of iso- and anteiso-C15:0 acids and is rich in an Archaea-derived archaeol that is 13C-enriched (-14.7‰), indicating extensive methanogenesis in sulfate-depleted lake porewater during early diagenesis. The sulfate decline results from successive sulfate reduction when replenishment of sulfate-bearing runoff water is limited. The carbonates exhibit enriched 18O due to pronounced evaporation in a long-resided water body and enriched 13C by methanogenesis. A change in provenance of water derived from the sulfur-rich suevite (impact melt-bearing breccia) and crystalline source rocks to the sulfur-poor Bunte Breccia (continuous ejecta blanket) is required. Intermittently high Si/Al and Zr/Al at the high δ13C interval suggests sporadic short-term runoff increase, leading to fluctuating physiochemical lake conditions. A subsequent decline in both δ13Ccarb and archaeol indicates a decreasing lake level with intermittent subaerial exposure events, supported by bioturbation and mud cracks. The concomitant lake oxygenation is well supported by increasing Pr/Ph ratios and lipids derived from aerobic methanotrophs (13C-depleted 3-methyl-hopanoids). In the youngest unit, allochthonous lignites and biomarkers from lacustrine/soil sources appear, high total sulphur contents and thiophenes recur, and stable C and O isotope values decrease again. These observations suggest another major provenance change of the inflowing solutes, with increasing influx from weathered pyrite-bearing Jurassic claystones. These findings demonstrate that the climatic record expected from the stable carbon and oxygen isotopes of the Ries carbonates is strongly overprinted by hydrochemical and biogeochemical processes due to changing ion influx from substrate rocks, along the course of the successive ejecta erosion and catchment changes. Such an intrinsic control of lacustrine biogeochemical processes is also expected for other hydrologically closed impact crater lake basins, where catchment rocks with distinctively different lithologies are present.

¹Lydie Bonal et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115826]
¹Institut de Planétologie et d’Astrophysique, Université Grenoble Alpes, 38000 Grenoble, France
Copyright Elsevier

This paper is focused on the characterization of the thermal history of C-type asteroid Ryugu through the structure of the polyaromatic carbonaceous matter in the returned samples determined by Raman spectroscopy. Both intact particles and extracted Insoluble Organic Matter (IOM) from the two sampling sites on Ryugu have been characterized. The main conclusions are that (i) there is no structural difference of the polyaromatic component probed by Raman spectroscopy between the two sampling sites, (ii) in a manner similar to type 1 and 2 chondrites, the characterized Ryugu particles did not experience significant long-duration thermal metamorphism related to the radioactive decay of elements such as 26Al; (iii) some structural variability is nevertheless observed within our particle set. It can be interpreted as some particles having experienced some short-duration and weak heating (R3 in the scale defined by Quirico et al. 2018 and TII or lower according to the scale defined by Nakamura, 2005).

^1,2Elias Wölfer,^2,3Gerrit Budde,^1,2Thorsten Kleine
Geochimica et Cosmochmica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2023.10.010]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
³Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
Copyright Elsevier

The carbonaceous Bencubbin-like (CB), high-metal (CH), and Renazzo-like (CR) chondrites are metal-rich chondrites that have been suggested to be genetically linked and are sometimes grouped together as the CR chondrite clan. Of these, the CB and CH chondrites are thought to have formed in an impact-generated vapor-melt plume from material that may be isotopically akin to CR chondrites. We report Mo, Ti, Cr, and Hf-W isotopic data for CB and CH chondrites in order to determine their formation time, to assess whether these chondrites are genetically related, and to evaluate their potential link to CR chondrites. An internal Hf-W isochron for the CH chondrite Acfer 182 yields an age of 3.8±1.2 Ma after formation of Ca-Al-rich inclusions, which is indistinguishable from the mean Hf-W model age for CB metal of 3.8±1.3 Ma. The Mo isotopic data for CB and CH chondrites indicate that both contain some of the same metal and silicate components, which themselves are isotopically distinct. As such, the different Mo isotopic compositions of bulk CB and CH chondrites reflect their distinct metal-to-silicate ratios. CR metal exhibits the same Mo isotopic composition as CB and CH metal, but CR silicates have distinct Mo and Ti isotopic compositions compared to CB and CH silicates, indicating that CB/CH chondrites may be genetically related to CR metal, but not to CR silicates. Together, the new isotopic data are consistent with formation of CB and CH chondrites in different regions of a common impact-generated vapor-melt plume and suggest that the CB and CH metal may derive from a metal-rich precursor genetically linked to CR chondrites. The Hf-W systematics of CH and CB chondrites indicate that the impact occurred at 3.8±0.8 Ma after the formation of Ca-Al-rich inclusions and, hence, up to ∼1 Ma earlier than previously inferred based on Pb-Pb chronology.

¹Nicolas Dauphas,¹Timo Hopp,²David Nesvorný
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115805]
¹Origins Lab, The University of Chicago, 5734 South Ellis Ave, Chicago, IL 60637, USA
²Department of Space Studies, Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, USA
Copyright Elsevier

Elements with differing siderophile affinities provide insights into various stages of planetary accretion. The isotopic anomalies they exhibit offer a deeper understanding of the materials responsible for the formation of terrestrial planets. By analyzing new iron isotopic anomaly data from Martian meteorites and drawing insights from published data for O, Ca, Ti, Cr, Fe, Ni, Sr, Zr, Mo, Ru, and Si, we scrutinize potential changes in the isotopic composition of the material accreted by Mars and Earth during their formation. Our methodology employs a Bayesian inference method, executed using a Markov Chain Monte Carlo (MCMC) algorithm.

The Bayesian method helps us balance the task of emulating the compositions of the terrestrial planets (reflected in the likelihood) with the flexibility to explore the isotopic compositions of mixing components within permissible intervals (indicated by the priors of the nuisance parameters). A Principal Component Analysis of isotopic anomalies in meteorites identifies three main clusters (forming the three parts of the isotopic trichotomy): CI, CC=CM + CO + CV + CR, and NC = EH + EL + H + L + LL. We adopt CI, COCV, O, and E as endmember compositions in the mixtures. We are concerned here with explaining isotopic anomalies in Mars and Earth, not their chemical compositions. Previous studies have shown that Earth’s chemical composition could not be well explained by solely considering undifferentiated meteorites, as it requires incorporation of a refractory component enriched in forsterite. The endmember chondrite components considered here are assumed to be representative of isotopic reservoirs that were present in the solar nebula, but the actual building blocks could have had different chemical compositions, and we use cursive letters to denote those putative building blocks

Because Earth’s mantle composition is an endmember for some isotopic systems, it cannot be reproduced exactly by considering known chondrite groups only and requires involvement of a component that is missing from meteorite collections but is likely close to enstatite meteorites. With this caveat in mind, our results suggest that Earth is primarily an isotopic mixture of ~92%, 6%, and < 2% and . Mars, on the other hand, appears to be a mixture of ~65% , 33% , and < 2% and . We establish that Earth’s contribution substantially increased during the latter half of its accretion. Mars began accreting a mix of and but predominantly accreted later. Mars’ changing isotopic makeup during accretion can be explained if it underwent gas-driven type I migration from its origin near the – boundary to a location well within the region during the first few million years of solar system history. Earth’s later increased contribution may be attributed to the stochastic impact of an interloper carbonaceous embryo that moved inside the inner solar system region while nebular gas was still present, and subsequently participated in the stage of chaotic growth. The discovery that a significant portion of Earth’s building blocks closely resembles enstatite chondrites contrasts with recent findings of Si isotopic anomalies in enstatite chondrites when compared to terrestrial rocks. We suggest this discrepancy likely stems from insufficient correction for high-temperature equilibrium isotopic fractionation, whether of nebular or planetary origin. With appropriate adjustments for this influence, both the silicate Earth and enstatite chondrites exhibit comparable Si isotopic anomalies, reaffirming a genetic link between them.

¹Peter L. Olson,¹Zachary D. Sharp
Earth and Planetary Science Letters 622, 118418 Link to Article [https://doi.org/10.1016/j.epsl.2023.118418]
¹Earth and Planetary Sciences, University of New Mexico, United States of America
Copyright Elsevier

We combine calculations of pebble accretion and accretion by large and giant impacts to quantify the effects of pebbles on the hafnium-tungsten system during Earth formation. Our models include an early pebble accretion phase lasting 4–6 Myr with a global magma ocean and core segregation, a 20–50 Myr phase of large impacts, and a late giant impact representing the Moon-forming event. We consider various mass additions during each accretion phase, vary the metal-silicate partition coefficient for tungsten over a wide range, and track Hf180, Hf182, W182 and W184 in proto-Earth and impactor models over time using standard chondritic values for these isotopes in the pebbles. We find that an early phase of pebble accretion is compatible with the tungsten anomaly of Earth’s early mantle as well as the present-day Hf/W ratio, but under restricted conditions. In particular, the pebble mass of proto-Earth is limited to 0.7 Earth masses or less, the average metal-silicate partition coefficient for tungsten is 30–50, and because the metal-silicate equilibration efficiency for giant impacts is low, the equilibration efficiency must be high for the large impactors.

¹David R. Frank,¹Gary R. Huss,²Michael E. Zolensky,¹Kazuhide Nagashima,³Loan Le
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14083]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i, USA
²Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas, USA
³Jacobs JETS, Houston, Texas, USA
Published by arrangement with John Wiley & sons

Cosmochemists have relied on CI carbonaceous chondrites as proxies for chemical composition of the non-volatile elements in the solar system because these meteorites are fine-grained, chemically homogeneous, and have well-determined bulk compositions that agree with that of the solar photosphere, within uncertainties. Here we report the discovery of a calcium-aluminum-rich inclusion (CAI) in the Ivuna CI chondrite. CAIs are chemically highly fractionated compared to CI composition, consisting of refractory elements and having textures that either reflect condensation from nebular gas or melting in a nebular environment. The CAI we found is a compact type A CAI with typical 16O-rich oxygen. However, it shows no evidence of 26Al, which was present when most CAIs formed. Finding a CAI in a CI chondrite raises serious questions about whether CI chondrites are a reliable proxy for the bulk composition of the solar system. Too much CAI material would show up as mismatches between the CI composition and the composition of the solar photosphere. Although small amounts of refractory material have previously been identified in CI chondrites, this material is not abundant enough to significantly perturb the bulk compositions of CI chondrites. The agreement between the composition of the solar photosphere and CI chondrites allows no more than ~0.5 atom% of CAI-like material to have been added to CI chondrites. As the compositions of CI chondrites, carbonaceous asteroids, and the solar photosphere are better determined, we will be able to reduce the uncertainties in our estimates of the composition of the solar system.

¹Alexander N. Krot,²Tasha L. Dunn,³Michail I. Petaev,⁴Chi Ma,¹Kazuhide Nagashima,⁵Jutta Zipfel
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14080]
¹Hawai’i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai’i at Mānoa, Honolulu, Hawaii, USA
²Department of Geology, Colby College, Waterville, Maine, USA
³Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁵Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany
Published by arrangement with John Wiley & Sons

We report on the primary and secondary mineralogies of three coarse-grained igneous calcium-aluminum-rich inclusions (CAIs) (Compact Type A [CTA], Type B [B], and forsterite-bearing type B [FoB]) from the Northwest Africa (NWA) 5343 (CK3.7) and NWA 4964 (CK3.8) carbonaceous chondrites, compare them with the mineralogy of igneous CAIs from the Allende (CV3.6) chondrite, and discuss the nature of the alteration processes that affected the CK and CV CAIs. The primary mineralogy and mineral chemistry of the CK3 CAIs studied are similar to those from Allende; however, primary melilite and anorthite are nearly completely absent. Although the secondary minerals identified in CK CAIs (Al-diopside, andradite, Cl-apatite, clintonite, forsterite, ferroan olivine, Fe,Ni-sulfides, grossular, ilmenite, magnetite, plagioclase, spinel, titanite, and wadalite) occur also in the Allende CAIs, there are several important differences: (i) In addition to melilite and anorthite, which are nearly completely replaced by secondary minerals, the alteration of CK CAIs also affected high-Ti pyroxenes (fassaite and grossmanite) characterized by high Ti³⁺/Ti⁴⁺ ratio and spinel. These pyroxenes are corroded and crosscut by veins of Fe- and Ti-bearing grossular, Fe-bearing Al,Ti-diopside, titanite, and ilmenite. Spinel is corroded by Fe-bearing Al-diopside and grossular. (ii) The secondary mineral assemblages of grossular + monticellite and grossular + wollastonite, commonly observed in the Allende CAIs, are absent; the Fe-bearing grossular + Fe-bearing Al-diopside ± Fe,Mg-spinel, Fe-bearing grossular + Fe,Mg-olivine ± Fe,Mg-spinel, and Ca,Na-plagioclase + Fe-bearing Al-diopside + Fe-bearing grossular assemblages are present instead. These mineral assemblages are often crosscut by veins of Fe-bearing Al-diopside, Fe,Mg-olivine, Fe,Mg-spinel, and Ca,Na-plagioclase. The coarse-grained secondary grossular and Al-diopside often show multilayered chemical zoning with distinct compositional boundaries between the layers; the abundances of Fe and Ti typically increase toward the grain edges. (iv) Sodium-rich secondary minerals, nepheline and sodalite, commonly observed in the peripheral portions of the Allende CAIs, are absent; Ca,Na-plagioclase is present instead. We conclude that coarse-grained igneous CAIs from CK3.7–3.8 s and Allende experienced an open-system multistage metasomatic alteration in the presence of an aqueous solution–infiltration metasomatism. This process resulted in localized mobilization of all major rock-forming elements: Si, Ca, Al, Ti, Mg, Fe, Mn, Na, K, and Cl. The metasomatic alteration of CK CAIs is more advanced and occurred under higher temperature and higher oxygen fugacity than that of the Allende CAIs.

¹Kevin Zahnle,²James F. Kasting
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2023.09.023]
¹NASA Ames Research Center, Mails Stop 245-3, Moffett Field, 94043, CA, USA
²The Pennsylvania State University, State College,, PA, USA
Copyright Elsevier

We develop a new model of diffusively modulated hydrodynamic escape to predict oxygen isotopic fractionations caused by the loss of water from a steam atmosphere of Venus. The chief technical advance over previous work is including CO₂ as a major species. We find that ordinary (�18O) and mass-independent (Δ17O) fractionations depend mostly on the extent of lithospheric buffering and the ferocity of EUV heating when escape took place, and relatively little on the size of the lost ocean(s). It is likely that Δ17O evolved significantly from its birth state, not only in the atmosphere but also in the silicates of the crust and upper mantle. If both �18O and Δ17O of Venus are identical to Earth and Moon, we may conclude that Venus and Earth accreted from a common pool. But differences in �18O and Δ17O can be attributed to escape rather than to genetics. If the differences are large enough, they can be used to constrain when escape took place and the extent of volatile exchange with the lithosphere. Neon and argon systematics are most consistent with minimal escape, especially if an Ar-rich source, possibly derived from comets, is added. However, we also find a novel class of solutions in which Ne and Ar of Venus, Earth, and Mars are evolved from a common source material subject to different vigors of hydrodynamic escape, least extreme for Earth and most extreme for Mars. These alternative models require that Venus was always rather dry (<10% of an Earth ocean) and its water lost very early (before <100 Myrs). The two styles of escape – minimal or extreme – should be readily distinguished by an unambiguous measurement of the Ar/Kr ratio. Finally, we find that predicted D/H enrichments are of order 100 for almost all model parameters. This result, a direct consequence of diffusion-limited escape of H and D, provides support for the overall scenario.

^1,2Elizaveta Kovaleva, ³Hassan Helmy, ^4,5Said Belkacim,²Anja Schreiber, ²Franziska D.H. Wilke,²Richard Wirth
American Mineralogist 108, 1906-1923 Link to Article [http://www.minsocam.org/msa/ammin/toc/2023/Abstracts/AM108P1906.pdf]
¹Department of Earth Sciences, University of the Western Cape, Robert Sobukwe Road, 7535 Bellville, South Africa
²Helmholtz Centre Potsdam—GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam, Germany
³Department of Geology, Minia University, 61519-Minia, Egypt
⁴LAGAGE Laboratory, Department of Geology, Faculty of Sciences, Ibn Zohr University, P.O. Box 28/S, 80 000, Agadir, Morocco
⁵Research Institute on Mines and Environment (RIME), Université du Québec en Abitibi-Témiscamingue, 445 Boul. Université, Rouyn-Noranda, Québec J9X 5E4, Canada
Copyright: The Mineralogical Society of America

The origin of Libyan Desert Glass (LDG) found in the western parts of Egypt close to the Libyan
border is debated in planetary science. Two major theories of its formation are currently competing:
(1) melting by airburst and (2) formation by impact-related melting. While mineralogical and textural
evidence for a high-temperature event responsible for the LDG formation is abundant and convincing, minerals and textures indicating high shock pressure have been scarce. This paper provides a
nanostructural study of the LDG, showing new evidence of its high-pressure and high-temperature
origin. We mainly focused on the investigation of Zr-bearing and phosphate aggregates enclosed within
LDG. Micro- and nanostructural evidence obtained with transmission electron microscopy (TEM) are
spherical inclusions of cubic, tetragonal, and orthorhombic (Pnma or OII) zirconia after zircon, which
indicate high-pressure, high-temperature decomposition of zircon and possibly, melting of ZrO2. Inclusions of amorphous silica and amorphous Al-phosphate with berlinite composition (AlPO4) within
mosaic whitlockite and monazite aggregates point at decomposition and melting of phosphates, which
formed an emulsion with SiO2 melt. The estimated temperature of the LDG melts was above 2750 °C,
approaching the point of SiO2 boiling. The variety of textures with different degrees of quenching immediately next to each other suggests an extreme thermal gradient that existed in LDG through radiation
cooling. Additionally, the presence of quenched orthorhombic OII ZrO2 provides direct evidence of
high-pressure (>13.5 GPa) conditions, confirming theory 2, the hypervelocity impact origin of the LDG.