¹J.V.Clark et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008587]

¹Texas State University – Amentum JETSII Contract at NASA Johnson Space Center, Houston, TX, USA
Published by arrangement with John Wiley & Sons

The Curiosity rover explored the region between the orbitally defined phyllosilicate-bearing Glen Torridon trough and the overlying layered sulfate-bearing unit, called the “clay-sulfate transition region.” Samples were drilled from the top of the fluviolacustrine Glasgow member of the Carolyn Shoemaker formation (CSf) to the eolian Contigo member of the Mirador formation (MIf) to assess in situ mineralogical changes with stratigraphic position. The Sample Analysis at Mars-Evolved Gas Analysis (SAM-EGA) instrument analyzed drilled samples within this region to constrain their volatile chemistry and mineralogy. Evolved H2O consistent with nontronite was present in samples drilled in the Glasgow and Mercou members of the CSf but was generally absent in stratigraphically higher samples. SO2 peaks consistent with Fe sulfate were detected in all samples, and SO2 evolutions consistent with Mg sulfate were observed in most samples. CO2 and CO evolutions were variable between samples and suggest contributions from adsorbed CO2, carbonates, simple organic salts, and instrument background. The lack of NO and O2 in the data suggest that oxychlorines and nitrates were absent or sparse, and evolved HCl was consistent with the presence of chlorides in all samples. The combined rover data sets suggest that sediments in the upper CSf and MIf may represent similar source material and were deposited in lacustrine and eolian environments, respectively. Rocks were subsequently altered in briny solutions with variable chemical compositions that resulted in the precipitation of sulfates, carbonates, and chlorides. The results suggest that the clay-sulfate transition records progressively drier surface depositional environments and saline diagenetic fluid, potentially impacting habitability.

^1,2,3Chaoqun Zhang et al. (>10)
Journal of Geopyhsical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2024JE008447]
¹Key Laboratory of Deep Petroleum Intelligent Exploration and Development, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
²Laboratory for Marine Geology, Qingdao Marine Science and Technology Center, Qingdao, China
³Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, China
Published by arrangement with John Wiley & Sons

Space weathering records provide insights to better understand the formation and evolution of the lunar regolith. Ilmenite has contrasting responses to different space weathering processes. However, the atomic-scale structural modification of ilmenite induced using different space weathering processes remains poorly understood. Here, we investigate the effects of spacing weathering on lunar ilmenite grains returned from Chang’e-5 (CE-5) mission using a combination of transmission electron microscopy and thermodynamic modeling approaches. Experimental results show that melt shock induces the formation of twining structures and vein-like Si-Ca-rich nanostructures in the outermost and sub-outermost layers of ilmenite, respectively. In contrast, solar wind causes the formation of multilayered nanostructures surrounding the ilmenite grains. These structures are characterized by an outermost amorphous Si-rich vapor deposited layer, a middle layer rich in titanium (Ti) oxides and zero-valent iron (Fe0) nanoparticles, and an innermost layer hosting crystallographic orientation defect. The Ti oxides were identified as poorly crystallized anatase. Thermodynamic calculations indicate that the disruptive sputtering of solar wind and the reduction of hydrogen under lunar surface pressure conditions can promote ilmenite transformation into Fe0 and Ti oxides; nevertheless, the pressure increase associated with melt shock can lead to a rise in the decomposition temperature of ilmenite. In other words, solar wind irradiation plays a more significant role in promoting nanoparticle (such as anatase and Fe0) formation as compared to melt shock. Thus, unlike the chemical alteration of ilmenite induced by the solar wind irradiation, melt shock mainly causes physical changes in ilmenite grains.

^1,2Ye Li, ^1,3Yuting Wang, ⁴Haoxuan Jiang, ^5,6Jia Liu, ^6,5Liping Qin, ⁷Qiu-Li Li, ⁷Yu Liu, ^8,9Zhenfei Wang, ^1,2Weibiao Hsu
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.11.020]
¹Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210023, China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³School of Astronomy and Space Sciences, University of Science and Technology of China, Hefei, 230026, China
⁴School of Mechanical and Electrical Engineering, Chuzhou University, Chuzhou, 239099, China
⁵Institute of Deep Space Sciences, Deep Space Exploration Laboratory, Hefei, China
⁶CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
⁷State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
⁸International Center for Isotope Effect Research, Nanjing University, Nanjing 210023, China
⁹Frontiers Science Center for Critical Earth Material Cycling, State, Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023, China
Copyright Elsevier

Type 7 chondrites, which record a higher degree of heating process than typical type 3 to type 6 chondrites, are characterized with textures and petrography of partial melting. Understanding the timing and cooling history of incipient melting event for type 7 chondrites could provide insights into the complex thermal process of the early solar system. Here, we studied two chondrites NWA 12272 and NWA 11021. Both samples display partial melting characteristics of LL chondrites, including interconnected plagioclase/high-Ca pyroxene network, zoned plagioclase and lack of chondrules, which concurs with their classification of LL7 chondrites in the Meteoritical Bulletin Database. The 53Mn-53Cr isotopic data of NWA 12272, determined by mineral separates and bulk samples, yielded an isochron with a 53Mn/55Mn ratio of (1.40 ± 0.59) × 10-6 and a corresponding absolute age of 4558.8 ± 2.3 Ma (anchored to D’Orbigny angrite). Combined with the cooling rate estimated by the integration of REE-in-two-pyroxene thermometry and two-pyroxene thermometry, Mn-Cr isochron age of 4558.8 ± 2.3 Ma and Ca-phosphate Pb-Pb age of 4517 ± 6 Ma, we suggest that NWA 12272 experienced a two-stage cooling process after the incipient melting: it exposed to a relatively cold environment with a rapid cooling rate of ∼ 30-100°C/yr at 1150–1000 °C, and soon reburied with a slower cooling rate of ∼ 13 °C/Ma at 1000–475 °C. Although the Mn-Cr isotopic study was not conducted for NWA 11021, the average Ca-phosphate Pb-Pb age of 4509 ± 7 Ma and high-temperature cooling rate (∼1-30°C/yr) of NWA 11021 are indistinguishable from or slightly lower than those of NWA 12272. Assuming NWA 11021 cooled from the same incipient melting event as NWA 12272, it could have recorded a similar two-stage cooling process. We suggest that the studied LL7 chondrites were most likely formed in the early solar system when additional impact heat overlapped on the “heated” type 5–6 chondrites. Integrated with the previous cooling rates of LL6-7 chondrites, the prevailing two-stage cooling rates of LL chondrites provide compelling evidence for the fragmentation-re-accretion process in the early history of LL chondrite parent body. This early impact event also happened in other ordinary chondrite groups and some iron meteorites.

¹M.D. Cashion, ^1,2B.C. Johnson, ³R. Deienno, ³K.A. Kretke, ³K.J. Walsh, ⁴A.N. Krot
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116400]

¹Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, United States of America
²Department of Physics and Astronomy, Purdue University, West Lafayette, IN, United States of America
³Southwest Research Institute, Boulder, CO, United States of America
⁴Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI, United States of America
Copyright Elsevier

Chondrules, igneous spherules found in most meteorites, formed throughout the protoplanetary disk, but their formation is largely unexplored beyond the water snowline, in the outer disk. Combining simulations of giant planet core accretion with simulations of planetesimal collisions, we find that impact jetting can produce chondrules to distances of ~15 AU from the Sun. In our simulations, chondrule formation ceases by the time the first giant planet core exceeds isolation mass, ~10 Earth masses. The time it takes to reach this mass is sensitive to the total mass of the disk, and how the mass is distributed within planetesimals and small pebbles. Measured chondrule ages subsequently constrain the time of Jupiter’s core formation to approximately 3–4 Myr after the first solar system solids. This protracted growth indicates the separation of non‑carbonaceous and carbonaceous material reservoirs predates the formation of Jupiter’s core.

¹Ivy Ettenborough, ¹Anna Szynkiewicz
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116384]
¹Department of Earth and Planetary Sciences, University of Tennessee, 1621 Cumberland Ave., Knoxville, TN 37996, USA
Copyright Elsevier

Secondary sulfate minerals are common throughout the sedimentary deposits of Mount Sharp, located within Gale crater on Mars. However, the source of sulfate (SO42−) and past climatic conditions during their formation are not well understood. Therefore, we investigated the δ34S, δ18O, and δ2H of gypsum veins and other Mg- and Ca- sulfates forming as salt crusts and cement within the shallow sediments of the Rio Puerco watershed in central New Mexico. The δ34S values of vein gypsum and acid-soluble SO42− (cement) varied over the same range (₋33.3 to ₋12.9 ‰ and ₋34.6 to ₋12.1 ‰, respectively), which was similar to the δ34S of bedrock sulfide minerals (₋37.4 to ₋5.9 ‰). This implies that sulfide oxidation is the main source of SO42− in the Rio Puerco aqueous system. The measured δ18O values of SO42− (₋8.9 to +3.1 ‰) as well as δ18O and δ2H values of gypsum hydration water (₋8.9 to +0.6 ‰, and ₋112 to ₋82 ‰, respectively) overlapped with the isotope composition of local meteoric precipitation, suggesting that sulfide oxidation to SO42− and gypsum formation have occurred under semi-arid climate conditions. The isotope results suggest the top-down infiltration of meteoric water leads to leaching of SO42−, Mg+, and Ca2+ from bedrock sulfide weathering followed by abundant formation of Mg- and Ca-sulfates in surface deposits and gypsum veins with depth. Because of spatial and mineralogical similarities in the secondary Mg- and Ca-sulfate mineral occurrences, we hypothesize that chemical weathering of sulfide minerals could have been the main source of SO42− in the aqueous system of Gale crater.

^1,2A. Morbidelli, ³T. Kleine, ⁴F. Nimmo
Earth and Planetary Science Letters 650, 119120 Open Access Link to Article [https://doi.org/10.1016/j.epsl.2024.119120]
¹Collège de France, CNRS, PSL Univ., Sorbonne Univ., Paris, 75014, France
²Observatoire de la Côte d’Azur, Université Cote d’Azur, CNRS, Laboratoire Lagrange, Boulevard de l’Observatoire, 06304 Cedex 4 Nice, France
³Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
⁴Dept. Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz CA 95060, USA
Copyright Elsevier

The dominant accretion process leading to the formation of the terrestrial planets of the Solar System is a subject of intense scientific debate. Two radically different scenarios have been proposed. The classic scenario starts from a disk of planetesimals which, by mutual collisions, produce a set of Moon to Mars-mass planetary embryos. After the removal of gas from the disk, the embryos experience mutual giant impacts which, together with the accretion of additional planetesimals, lead to the formation of the terrestrial planets on a timescale of tens of millions of years. In the alternative, pebble accretion scenario, the terrestrial planets grow by accreting sunward-drifting mm-cm sized particles from the outer disk. The planets all form within the lifetime of the disk, with the sole exception of Earth, which undergoes a single post-disk giant impact with Theia (a fifth protoplanet formed by pebble accretion itself) to form the Moon. To distinguish between these two scenarios, we revisit all available constraints: compositional (in terms of nucleosynthetic isotope anomalies and chemical composition), dynamical and chronological. We find that the pebble accretion scenario is unable to match these constraints in a self-consistent manner, unlike the classic scenario.

¹Susmita Garai, ¹Peter Olson, ¹Zachary Sharp
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.11.021]
¹Earth and Planetary Sciences, University of New Mexico, United States
Copyright Elsevier

Pebble accretion provides new insights into Earth’s building blocks and early protoplanetary disk conditions. Here, we show that mixtures of chondritic components: metal grains, chondrules, calcium-aluminum-rich inclusions (CAIs), and amoeboid olivine aggregates (AOAs) match Earth’s major element composition (Fe, Ni, Si, Mg, Ca, Al, O) within uncertainties, whereas no combination of chondrites and iron meteorites does. Our best fits also match the ε54Cr and ε50Ti values of Earth precisely, whereas the best fits for chondrites, or components with a high proportion of E chondrules, fails to match Earth. In contrast to some previous studies, our best-fitting component mixture is predominantly carbonaceous, rather than enstatite chondrules. It also includes 16 wt% of early-formed refractory inclusions (CAIs + AOAs), which is similar to that found in some C chondrites (CO, CV, CK), but notably higher than NC chondrites. High abundances of refractory materials is lacking in NC chondrites, because they formed after the majority of refractory grains were either drawn into the Sun or incorporated into terrestrial protoplanets via pebble accretion. We show that combinations of Stokes numbers of chondritic components build 0.35–0.7 Earth masses in 2 My in the Hill regime accretion, for a typical pebble column density of 1.2 kg/m2 at 1 au. However, a larger or smaller column density leads to super-Earth or moon-mass bodies, respectively. Our calculations also demonstrate that a few My of pebble accretion with these components yields a total protoplanet mass inside 1 au exceeding the combined masses of Earth, Moon, Venus, and Mercury. Accordingly, we conclude that pebble accretion is a viable mechanism to build Earth and its major element composition from primitive chondritic components within the solar nebula lifetime.

¹Maria Schönbächler et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14279]
¹Department of Earth Sciences, Institute for Geochemistry and Petrology, ETH Zurich, Zurich, Switzerland
Published by arrangement with John Wiley & Sons

Nucleosynthetic isotope variations are powerful tracers to determine genetic relationships between meteorites and planetary bodies. They can help to link material collected by space missions to known meteorite groups. The Hayabusa 2 mission returned samples from the Cb-type asteroid (162173) Ryugu. The mineralogical, chemical, and isotopic characteristics of these samples show strong similarities to carbonaceous chondrites and in particular CI chondrites. The nucleosynthetic isotope compositions of Ryugu overlap with CI chondrites for several elements (e.g., Cr, Ti, Fe, and Zn). In contrast to these isotopes, which are of predominately supernovae origin, s-process variations in Mo isotope data are similar to those of carbonaceous chondrites, but even more s-process depleted. To further constrain the origin of this depletion and test whether this signature is also present for other s-process elements, we report Zr isotope compositions for three bulk Ryugu samples (A0106, A0106-A0107, C0108) collected from the Hayabusa 2 mission. The data are complemented with that of terrestrial rock reference materials, eucrites, and carbonaceous chondrites. The Ryugu samples are characterized by distinct 96Zr enrichment relative to Earth, indicative of a s-process depletion. Such depletion is also observed for carbonaceous chondrites and eucrites, in line with previous Zr isotope work, but it is more extreme in Ryugu, as observed for Mo isotopes. Since s-process Zr and Mo are coupled in mainstream SiC grains, these distinct s-process variations might be due to SiC grain depletion in the analyzed materials, potentially caused by incomplete sample digestion, because the Ryugu samples were dissolved on a hotplate only to avoid high blank levels for other elements (e.g., Cr). However, local depletion of SiC grains cannot be excluded. An alternative, equally possible scenario is that aqueous alteration redistributed anomalous, s-process-depleted, Zr on a local scale, for example, into Ca-phosphates or phyllosilicates.

¹David T. King Jr,^2,3Michael R. Rampino,¹Lucille W. Petruny
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14290]
¹Department of Geosciences, Auburn University, Auburn, Alabama, USA
²Department of Biology, New York University, New York, New York, USA
³Department of Environmental Studies, New York University, New York, New York, USA
Published by arrangement with John Wiley & Sons

The central uplift area of Araguainha impact structure (Brazil) includes a quartzite pebble- and cobble-bearing stratigraphic facies that have been profoundly affected by impact processes. These quartzite clasts have been studied previously for their planar deformation features (PDFs), but not with regard to their noteworthy transverse fractures. Petrographic study of transverse fractures within seven selected impact-affected cobbles from the conglomeratic fluvial facies of the target Devonian Furnas Formation (near the central uplift of Araguainha impact structure) has revealed that there is a micro-breccia within these transverse fractures, and this micro-breccia originated by comminution of the host cobble. Further, the transverse fractures in these cobbles have different styles (well-defined, poorly defined, complex, and diffuse) and are evidently post-shock, brittle deformation features. We suggest that a late compression-stage process, perhaps collapse of the central peak, may be responsible for the development of these transverse fractures.

¹Kevin Righter
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14289]
¹Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York, USA
Published by arrangement with John Wiley & Sons

ALH 84001 is an orthopyroxenite that is the oldest known Martian meteorite. Given this rock type and age, and the possible source locations, ALH 84001 represents an opportunity to learn more about basic geologic relations in the Martian highlands in the southern hemisphere. Its orthopyroxene-rich mineralogy is unique and also includes C-, S-, P-bearing minerals. ALH 84001 can provide constraints on chronology, geology and surface features, crust formation, paleomagnetism, weathering, climate, magmatism, and interior structure. When it was recognized to be of Martian origin (~1994), there were ~12 known Martian meteorite samples. That number is now >150, with only one other meteorite (NWA 7034) having clasts that are similar in age to ALH 84001. Thus, it remains a unique sample and continues to provide opportunities to understand this early period of Martian history.