^1,2,3Zélia Dionnet et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13807]
¹Institut d’Astrophysique Spatiale, CNRS, Université Paris-Saclay, Orsay, 91405 France
²Dip. Di Scienze Applicate, Università di Napoli Parthenope, Centro Direzionale di Napoli, Isola C4, Naples, 80143 Italy
³Istituto di Astrofisica e Planetologia Spaziali—INAF, Rome, Italy
Published by arrangement with John Wiley & Sons

In this paper, we report the results of a campaign of measurements on four fragments of the CM Aguas Zarcas (AZ) meteorite, combining X-ray computed tomography analysis and Fourier-transform infrared (FT-IR) spectroscopy. We estimated a petrologic type for our sampled CM lithology using the two independent techniques, and obtained a type CM2.5, in agreement with previous estimations. By comparing the Si-O 10-µm signature of the AZ average FT-IR spectra with other well-studied CMs, we place AZ in the context of aqueous alteration of CM parent bodies. Morphological characterization reveals that AZ has heterogeneous distribution of pores and a global porosity of 4.5 ± 0.5 vol%. We show that chondrules have a porosity of 6.3 ± 1 vol%. This larger porosity could be inherited due to various processes such as temperature variation during the chondrule formation and shocks or dissolution during aqueous alteration. Finally, we observed a correlation between 3D distributions of organic matter and mineral at micrometric scales, revealing a link between the abundance of organic matter and the presence of hydrated minerals. This supports the idea that aqueous alteration in AZ’s parent body played a major role in the evolution of the organic matter.

¹C.M.Lisse,^2.3J.K.Steckloff
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114995]
¹Space Exploration Sector, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD, USA 20723
²Planetary Science Institute, Tucson, AZ 85719, USA
³Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, TX 78712, USA
Copyright Elsevier

In 2010 Jewitt and Li published a paper examining the behavior of “comet-asteroid transition object” 3200 Phaethon, arguing it was asteroid-like in its behavior throughout most of its orbit, but that near its perihelion, at a distance of only 0.165 AU from the sun, its dayside temperatures would be hot enough to vaporize rock (>1000 K, Hanus et al., 2016). Thus it would act like a “rock comet” as gases produced from evaporating rock were released from the body, in a manner similar to the more familiar sublimation of water ice into vacuum seen for comets coming within ~3 AU of the Sun. In this Note we predict that the same thermal effects that would create “rock comet” behavior with Qgas ~ 1022 mol/s at perihelion would also help bluen the surface via preferential thermal alteration and sublimative removal of surface Fe and refractory organics, known reddening and darkening agents. These predictions are testable by surveying other objects on Phaethon-like small perihelion orbits, and by in situ measurements from the upcoming DESTINY+ mission to Phaethon by JAXA.

¹Amanda C. Stadermann,²Bradley L. Jolliff,²Michael J. Krawczynski,¹Christopher W. Hamilton,¹Jessica J. Barnes
Meteoritics & Planetary Sciences (in Press) Link to Article [https://doi.org/10.1111/maps.13795]
¹Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd, Tucson, Arizona, 85721 USA
²Department of Earth and Planetary Sciences & McDonnell Center for Space Sciences, Washington University in St. Louis, 1 Brookings Dr, St. Louis, Missouri, 63130 USA
Published by arrangement with John Wiley & Sons

Sample 12032,366-18 is a 41.2 mg basaltic rock fragment collected during the Apollo 12 mission to the Moon. It is enriched in incompatible trace elements (e.g., 7 ppm Th), but does not have a bulk composition that would be considered a KREEP (enriched in potassium, rare earth elements, and phosphorous) basalt. The sample is of particular interest because it may be representative of some of the mare basalts within Oceanus Procellarum that are inferred to be Th-rich, based on remote sensing data. The major mineral assemblage of 12032,366-18 is pyroxene, plagioclase, olivine, and ilmenite, and the bulk composition has 4.2 wt% TiO2, 11.7 wt% Al2O3, and 0.25 wt% K2O. The sample contains regions of late-stage crystallized minerals and glass (collectively termed mesostasis), including K-feldspar, apatite, rare earth (RE) merrillite, ilmenite, troilite, silica, and relatively sodic plagioclase adjacent to ferroan pyroxene. The mesostasis also occurs in several areas that are highly enriched in silica and intergrown with K-feldspar and very fine-grained, high-mean-atomic-number phases. We explore the petrology of this sample, including the origin of the Si-K-rich mesostasis to assess whether the mesostasis had formed by silicate liquid immiscibility (SLI). We used experiments to determine if the bulk composition of 12032,366-18 is representative of a bulk liquid composition, how the residual liquid evolves, and to investigate the partitioning of elements between phases as the melt evolves. Experiments support that the mesostasis formed by SLI after crystallization of minerals closely matches the major-mineral assemblage of 12032,366-18. Experiments bracket the onset of SLI and merrillite saturation between 1024 and 1002 °C. Some high field strength elements, such as Zr and P, partition preferentially into the Fe-rich liquid. From the experiments, we infer that the bulk composition of 12032,366-18 represents the magma from which it crystallized. Based on the Th-rich and KREEP-bearing chemistry of this sample, along with experimental evidence showing that the sample is representative of a bulk liquid composition and not a cumulate, we conclude that basalt fragment 12032,366-18 was delivered to the Apollo 12 landing site as ejecta from a distant impact and could represent an Oceanus Procellarum basalt. Missions to Oceanus Procellarum, such as Chang’E 5, have the potential to confirm whether some of those basalts are indeed enriched in Th and other incompatible trace elements as indicated by remote sensing.

¹Jie-Jun Jing,²Yanhao Lin,³Jurrien S.Knibbe,¹Wim van Westrenen
Earth and Planetary Science Letters 584, 117491 Link to Article [https://doi.org/10.1016/j.epsl.2022.117491]
¹Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
²Center for High Pressure Science and Technology Advanced Research, Beijing, 100094, People’s Republic of China
³Royal Observatory of Belgium, Ringlaan 3, 1180 Ukkel, Belgium
Copyright Elsevier

High-pressure, high-temperature experiments have been conducted at deep lunar mantle conditions to constrain the garnet stability field. Using the Taylor Whole Moon composition, garnet is found to be stable at pressures above 3 GPa and temperatures below 1700 °C, yielding a smaller stability field than previously suggested on the basis of thermodynamic calculations. Experimental data are used to model equilibrium crystallization in a ‘two-stage’ model of lunar magma ocean (LMO) crystallization starting from a fully molten Moon. In the first stage, isothermal (1600 °C) equilibrium crystallization of the LMO would produce garnet-bearing lherzolite cumulates (containing up to ∼20 wt.% garnet) in the lowermost lunar mantle. Garnet in the deep lunar mantle would significantly decrease the Al2O3 content of the residual LMO and impact HREE/MREE fractionation. Numerical modeling of the second stage (residual LMO fractional crystallization) shows a delay in plagioclase saturation compared to models of single-stage fractional crystallization of a whole-Moon LMO of the Taylor Whole Moon composition, thinning the anorthositic crust from 95 km to 75 km. To reach the upper limit of current estimates of the average lunar crustal thickness (∼45 km), the two-stage scenario needs to be accompanied by a total of 10% liquid trapped in cumulates and 70% efficiency of plagioclase flotation. We also conduct trace element evolution modeling and reproduce a REE pattern identical to high K, REE, and P (KREEP) compositions after 99.8% solidification, when starting with a CI chondritic REE abundance. The density of a garnet-bearing deep lunar mantle is significantly higher than the density of olivine/orthopyroxene mixtures without garnet. The present-day lowest mantle in the Moon could therefore be characterized by chemical interactions between the earliest (garnet-bearing) and latest (ilmenite-bearing) products of LMO crystallization.

¹Vasilije V.Dobrosavljevic,²Dongzhou Zhang,¹Wolfgang Sturhahn,³Jiyong Zhao,³Thomas S.Toellner,⁴Stella Chariton,⁴Vitali B.Prakapenka,¹Olivia S.Pardo,¹Jennifer M.Jackson
Earth and Planetary Science Letters 584, 117358 Link to Article [https://doi.org/10.1016/j.epsl.2021.117358]
¹Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI, USA
³Advanced Photon Source, Argonne National Laboratory, Chicago, IL, USA
⁴Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL, USA
Copyright Elsevier

Many studies have suggested silicon as a candidate light element for the cores of Earth and Mercury. However, the effect of silicon on the melting temperatures of core materials and thermal profiles of cores is poorly understood, due to disagreements among melt detection techniques, uncertainties in sample pressure evolution during heating, and sparsity of studies investigating the combined effects of nickel and silicon on the phase diagram of iron. In this study we develop a multi-technique approach for measuring the high-pressure melting and solid phase relations of iron alloys and apply it to Fe0.8Ni0.1Si0.1 (Fe-11wt%Ni-5.3wt%Si), a composition compatible with recent estimates for the cores of Earth and Mercury. This approach combines results (20-83 GPa) from two atomic-level techniques: synchrotron Mössbauer spectroscopy (SMS) and synchrotron x-ray diffraction (XRD). Melting is independently detected by the loss of the Mössbauer signal, produced exclusively by solid-bound iron nuclei, and the onset of a liquid diffuse x-ray scattering signal. The use of a burst heating and background updating method for quantifying changes in the reference background during heating facilitates the determination of liquid diffuse signal onsets and leads to strong reproducibility and excellent agreement in melting temperatures determined separately by the two techniques. XRD measurements additionally constrain the hcp-fcc phase boundary and in-situ pressure evolution of the samples during heating. We apply our updated thermal pressure model to published SMS melting data on fcc-Fe and fcc-Fe0.9Ni0.1 to precisely evaluate the effect of silicon on melting temperatures. We find that the addition of 10 mol% Si to Fe0.9Ni0.1 reduces melting temperatures by ∼250 K at low pressures (<60 GPa) and flattens the hcp-fcc phase boundary. Extrapolating our results, we constrain the location of the hcp-fcc-liquid quasi-triple point at 147±14 GPa and 3140±90 K, which implies a melting temperature reduction of 500 K compared with Fe0.9Ni0.1. The results demonstrate the advantages of combining complementary experimental techniques in investigations of melting under extreme conditions.

¹Yoann Quesnel,²Natalia S. Bezaeva,³Dilyara M. Kuzina,¹Pierre Rochette,¹Jérôme Gattacceca,¹Minoru Uehara,²Dmitry D. Badyukov,³Bulat M. Nasyrtdinov,^4,5,6Dmitry A. Chareev,⁷Cedric Champollion
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13806]
¹Aix-Marseille Université, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
²V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19 Kosygin str, 119991 Moscow, Russia
³Institute of Geology and Petroleum Technologies, Kazan Federal University, 4/5 Kremlyovskaya Str, 420008 Kazan, Russia
⁴Institute Experimental Mineralogy, Russian Academy of Science, 4 Academician Osipyan Str, 142432 Chernogolovka, Moscow Region, Russia
⁵Institute of Physics and Technology, Ural Federal University, 19 Mira Str, 620002 Ekaterinburg, Russia
⁶National University of Science and Technology “MISiS”, 4 Leninsky Prospekt, 119049 Moscow, Russia
⁷Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France
Published by arrangement with John Wiley & Sons

With no significant topographic expression and limited bedrock exposure, the ~10 km diameter Karla impact structure (Tatarstan, Russia) is poorly known. The age of the impact is also poorly constrained stratigraphically to between 4 and 60 Ma, even if an upper Miocene age is more likely. Targeted gravity and magnetic field surveys were conducted over Karla to explore its size and structure in 2019. Bouguer gravity anomaly data reveal a central positive (+2 mGal) peak ~2 km in diameter surrounded by a concentric negative (−1 mGal) anomaly extending to ~3 km radius; a more irregular, outward-decreasing (+1 to −1 mGal) positive anomaly extends to 6–8 km radius. A complex impact structure with diameter of 8–10 km is consistent with the Bouguer anomalies. Magnetic field data show 1 to several km-wavelength anomalies with amplitude variation from +150 to −150 nT and little concentric structure, although the impact feature broadly corresponds to a magnetic low with a weak central high. A 2-D numerical model of the structure was built using these potential-field data and petrophysical properties measured on collected samples. It confirms a central uplift composed of Paleozoic sediments and Archean crystalline basement up to 1 km of depth. A 500 m deep collapsed disruption cavity filled by breccia and lacustrine deposits accounts for the Bouguer negative ring. The reversely polarized and weak central magnetic anomalies are controlled by the geometry of the crystalline basement associated with the deformation during the central uplift.

¹N.G.Rudraswami,²M.D.Suttle,³Y.Marrocchi,⁴S.Taylor,³J.Villeneuve
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.03.015]
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
²School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
³CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre-les-Nancy, F-54501, France
⁴Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, New Hampshire 03755–1290, USA
Copyright Elsevier

We report high-precision secondary ion mass spectrometer triple oxygen isotope systematics (95 individual analyses) from 37 micrometeorites (MMs) collected from South Pole Water Well (SPWW), Antarctica. The study population focuses on unmelted coarse-grained (Cg) MMs (n=23) with both multiple (n=14) and single-mineral (n=9) varieties investigated. We also analysed relict minerals in porphyritic cosmic spherules (n=13) and the relict matrix in a single scoriaceous fine-grained (Fg) MM. The target minerals investigated are primarily olivine (Fo ∼43–99%) and spinel. Textural, chemical and isotopic data confirm that both olivine and spinel grains have retained their pre-atmospheric O-isotope compositions, allowing inferences to be drawn about their formation and parent body affinities. We separate the study population into three groups: spinel-free particles (consisting of the CgMMs and PO cosmic spherules), spinel-bearing MMs and the single FgMM.

Olivine grains in spinel-free MMs vary between δ17O: –12.6‰ and +3.5‰, δ18O: –9.6‰ and +7.5‰, and Δ17O: –9.5‰ and +1.3‰ and define a slope-1 profile in δ18O–δ17O isotope space. They are most likely fragmented chondrules, with both type I and type II varieties represented. Their observed Mg#-Δ17O distribution is best explained by a mixture of CM chondrules and either CR chondrules, Tagish Lake chondrules or WILD2 cometary silicates. One of these chondrule-like MMs has an isotopically heterogeneous composition, characterised by a single olivine grain with a markedly 16O-rich composition (Δ17O: –16.3‰), suggesting it is a relict silicate fragment of AOA material that was incorporated into the chondrule precursor.

We analysed 11 spinel grains in five spinel-bearing MMs. In all instances spinels are nearly pure MgAl2O4 with isotopically light (16O-rich) compositions (ranging from δ17O: –34.4‰ to –0.9‰, δ18O: –30.8‰ to +11.0‰, and Δ17O: –18.3‰ to –4.4‰). They are therefore 16O-poor relative to spinel found in unaltered CAIs, indicating a different origin. Grains with high Cr2O3 contents (>0.5 wt%) are interpreted originating from Al-rich chondrule precursors, while low Cr2O3 spinels (<0.5 wt%) are interpreted as CAI-derived material affected by parent body aqueous alteration. Finally, we report a single FgMM with a 16O-poor composition (Δ17O > 0‰ and δ18O > +15.0‰). This particle adds to our growing inventory of water-rich C-type asteroid samples united by their formation history which is characterised by accretion of abundant heavy water.

Our work strongly supports findings from earlier in-situ O-isotope studies, concluding that small MMs overwhelmingly sample material from CC parent bodies and that CgMMs largely sample chondrules and, to a lesser extent, CAI material. The analysis of CgMMs therefore provides insights into the primitive O-isotope reservoirs that were present in the early solar system and how they interacted.

¹Marina Martínez,¹Adrian J.Brearley
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.03.019]
¹Department of Earth & Planetary Sciences, MSC03-2040, 1University of New Mexico, Albuquerque, NM 87131, USA
Copyright Elsevier

Queen Alexandra Range (QUE) 99177 is one of the least altered CR carbonaceous chondrite known, with mineralogical and isotopic characteristics that indicate a high level of pristinity. In this study, we have examined the so-called smooth rims that surround many type I chondrules in QUE 99177, using SEM, EPMA, and FIB-TEM techniques. We have characterized their constituent phases to unravel the precursor material(s) of smooth rims, assess their formation mechanisms, and constrain the conditions of the altering fluid. Smooth rims are the most common type of rims around type I chondrules and exclusively occur around chondrules with Silica-rich Igneous Rims (SIRs). Smooth rims consist of an Fe-rich, hydrous silicate material that is Si- and Fe-rich, with minor Mg, Al, Ca, and Mn, and gives low analytical totals measured by EPMA. TEM observations reveal that the Fe-rich silicate phase is an amorphous gel that contains unaltered crystalline phases and igneous glass. Crystalline phases consist of igneous, unaltered, zoned pyroxenes with compositions consistent with pyroxenes in SIRs, as well as albite and chromite. The amorphous gel preserves previous crystal outlines with morphologies consistent with silica (cristobalite) grains in SIRs and has a composition identical to pseudomorphic silica replacements in SIRs. Based on these observations, we conclude that smooth rims derive from low-temperature aqueous alteration of silica in SIRs by an Fe-rich fluid. We suggest that the Fe was derived by leaching of amorphous silicates in the matrix, which reacted rapidly with melted water ice, although alteration of Fe,Ni metal blebs in SIRs could potentially be an additional source of Fe. Silica underwent dissolution and replacement whereas feldspar and glass remained unaltered because (1) the fluid was slightly alkaline, (2) cristobalite has a reaction rate much higher than quartz and feldspar, and (3) the alteration was very limited and fast, indicating that it was due solely to melting of accreted water ice and there was no introduction of additional fluid from external sources.

¹Steven W.Ruff,²Victoria E.Hamilton,³A. Deanne Rogers,⁴Christopher S.Edwards,⁵Briony H.N.Horgan
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.114974]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
²Southwest Research Institute, Boulder, CO, USA
³Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
⁴Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ, USA
⁵Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA
Copyright Elsevier

Exposures of bedrock rich in olivine and carbonate link Gusev crater and the Nili Fossae region (NFR), both of which have the highest abundance of olivine yet identified on Mars. They are recognized as possible explosive volcanic tephra deposits, but the nature of their eruption and emplacement is poorly constrained, limiting understanding of what may be a widespread volcanic process on early Mars. The compositional and morphologic similarities of these widely separated olivine and carbonate-rich rocks have not been investigated previously. We examined orbital and in situ thermal infrared spectra and find notably similar compositions between the two locations, with olivine ranging from ~Fo53 to Fo75 and carbonates composed of multiple Mg and Fe-rich phases, although with minimal magnesite in the NFR. A range of morphologic and textural features occur in the deposits of explosive volcanism on Earth that can be used to constrain the origin of those on Mars. We observed features of the olivine-rich bedrock in both locations that resemble those of welded ignimbrite deposits on Earth that formed from pyroclastic density currents in cataclysmic explosive volcanic eruptions. If correct, an ignimbrite interpretation for the olivine-rich bedrock in the NFR and Gusev crater may apply to other occurrences on Mars and indicate a style of volcanism more common in its early history.

¹E.B.Rampe,²B.H.N.Horgan,³R.J.Smith,²N.A.Scudder,⁴E.R.Bamber,⁵A.M.Rutledge,⁶R.Christoffersen
Earth and Planetary Science Letters 584, 117471 Link to Article [https://doi.org/10.1016/j.epsl.2022.117471]
¹Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX 77058, USA
²Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA
³Department of Geosciences, SUNY Stony Brook, Stony Brook, NY 11794, USA
⁴Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78712, USA
⁵Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, AZ 86001, USA
⁶Jacobs, NASA Johnson Space Center, Mail Code XI3, Houston, TX 77058, USA
Copyright Elsevier

Geomorphic and mineralogical data from the martian surface indicate liquid water was abundant on the martian surface and near subsurface ∼3.5 to 4 Gyr ago, but whether early Mars had a warm and wet climate or whether it was cold and icy with punctuated periods of warmth is still unknown. Mineral assemblages of sedimentary rocks on Mars help determine past aqueous conditions and sediment sources. Here, we report on the primary and secondary mineral and amorphous assemblage of glacial flour from Collier Glacier valley on the northern flank of North Sister in Oregon, U.S.A. to identify mineralogical characteristics of mafic sediments altered under cold, wet conditions. Collier glacial flour is dominated by primary igneous minerals (plagioclase is dominant, with lesser amounts of pyroxene and olivine) and comprises 10-40 wt.% X-ray amorphous materials. Crystalline secondary phases (e.g., phyllosilicates, zeolite) are not significant contributors to the authigenic alteration assemblage. High-resolution transmission electron microscopic observations of the <2 μm size fraction of the flour demonstrate that the X-ray amorphous materials are both primary (i.e., volcanic glass) and secondary in nature. The secondary X-ray amorphous materials are enriched in Si, Al, and Fe, and we observe incipient phyllosilicate formation associated with primary and secondary amorphous materials. Our results indicate chemical weathering on a cold and icy early Mars would have produced X-ray amorphous materials, but not crystalline secondary phases. We suggest that the abundant X-ray amorphous materials recognized from orbit and in situ on Mars could have formed under cold and periodically wet conditions similar to those on North Sister today. Furthermore, the lack of volumetrically significant phyllosilicate formation in Collier Glacier flour indicates phyllosilicates on Mars did not form in a cold and wet climate.