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¹A.A.Nemchin,²M.D.Norman,³M.L.Grange,⁴R.A.Zeigler,³M.J.Whitehouse,⁵J.R.Muhling,⁶R.Merle
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.12.013]
¹School of Earth and Planetary Sciences, Curtin University, Australia
²Research School of Earth Sciences, The Australian National University, Canberra ACT 2601, Australia
³Swedish Museum of Natural History, S-104 05 Stockholm, Sweden
⁴Astromaterials Acquisition and Curation Office, NASA Johnson Space Center, Houston Texas USA
⁵School of Earth Sciences, The University of Western Australia, 6009, Perth, Australia
⁶Department of Earth Sciences, Natural Resources and Sustainable Development, Uppsala University, Sweden
Copyright Elsevier

Glass beads formed by ejection of impact-melted lunar rocks and soils are an important component of lunar soils. These glasses range from 10’s of microns to up to a few cm in diameter and contain variable, but usually relatively low (several hundred ppb to a few ppm), quantities of U. Because Pb is a volatile element, it tends to be lost from the melts, so individual impact glasses can be dated by the U-Th-Pb isotopic systems. The presence of two additional Pb components in lunar glasses, likely linked to addition of lunar Pb to the beads during their residence on the lunar surface and from terrestrial laboratory contamination, require corrections to the data before accurate formation ages of the glasses can be determined. Here we report a U-Th-Pb isotopic and geochemical study of impact glasses from the Apollo 14 soil 14163, which documents multiple impacts into chemically diverse targets that can be linked to the main groups of rocks found on the Moon, i.e., mare basalts, highlands plagioclase-rich rocks, and KREEP (from high contents of K, REE and P) enriched rocks. The impact ages show a bimodal distribution with peaks at ∼3500-3700 Ma and <1000 Ma, similar to that obtained previously by 40Ar-39Ar dating of other suites of lunar regolith glasses. Our data suggest two predominant age peaks at ∼100 Ma and ∼500 Ma, with other statistically definable clusters of ages also possible. As Pb is relatively resistant to subsolidus diffusive loss in these glasses, the age clusters probably represent primary formation ages during impact events, although processes such as preferential preservation of young glasses and impact conditions necessary for production of regolith glasses need further quantification.

¹Jonathan A.Lewis,^1,2Rhian H.Jones
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.12.014]
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131
²Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
Copyright Elsevier

Thermal metamorphism in undisrupted ordinary chondrite (OC) parent bodies is thought to occur through the radioactive decay of 26Al, producing an onion-shell-like structure with higher peak metamorphic temperatures corresponding to increasing depth. During retrograde metamorphism, the onion-shell model predicts slower cooling rates with increasing petrologic type. However, cooling rates determined by pyroxene diffusion, metallographic, and other methods are inconsistent with onion-shell-like cooling, leading to a model of asteroid disruption and reaccretion into a rubble pile, after peak metamorphism. Potassium-feldspar exsolution in albite, in a perthite texture, has been noted in OCs and can be used as another method for determining cooling rates. We conducted a survey of K-feldspar occurrences and textures, within chondrules, in petrologic type 3.6-6 H, L, and LL OCs. Potassium-feldspar is present as a secondary feature, in primary and secondary albite, as fine-scale exsolution lamellae, 0.1-1.5 μm wide, as well as in larger patches up to 50 μm in size. Exsolution is present in all OC groups and is most common in petrologic type 4.

In the H4 chondrite Avanhandava, we estimate the cooling rate from perthite to be 3-17 °C/yr over a temperature interval of 765-670 °C. Peristerite is also present in Avanhandava for which we estimate a cooling rate of 0.2-2.4×10-3 °C/yr from 570-540 °C. In general, the relatively fast, high-temperature cooling rate determined by perthite is similar to cooling rates recovered from two-pyroxene speedometry. The peristerite cooling rate is closer to the slow, lower temperature metallographic cooling rates. Because K-feldspar exsolution is present in similar fine-scale lamellae in all OC groups, we suggest that all OC parent bodies experienced the same cooling history at high temperatures. These results are inconsistent with predictions of OC asteroid cooling from undisturbed onion-shell metamorphism but are consistent with models involving disruption after peak metamorphism followed by reassembly.

¹Conel M. O’D. Alexander
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.12.012]
¹Earth and Planets Laboratory, 5241 Broad Branch Road, NW, Washington DC 20015, USA
Copyright Elsevier

Here, two of a range of possible models are explored that assume that: (i) two of the main chondritic components (chondrules and refractory inclusions) dominated the Earth’s building blocks, (ii) that their relative abundances differed from those of known chondrites, and (iii) that the elemental compositions of all components, as well as the isotopic compositions of refractory inclusions, resembled those of the components in carbonaceous chondrites.

In terms of the elemental abundances, the chondrules can explain the moderately volatile element fractionations in the bulk silicate Earth (BSE), except for a few elements like F and In, while the refractory inclusions explain the BSE’s refractory lithophile element enrichment. Accretion of a CM- or EL-like late veneer reproduces the S, Se, Te and highly siderophile element abundances in the BSE. The accretion of CI- or CM-like material prior to the late veneer, along with small amounts of cometary and implanted solar wind material, can explain the BSE elemental and isotopic abundances of the noble gases as well as the elemental abundances of most other highly volatile elements (e.g., H, C and N) provided that variable fractions of them can be sequestered into the core or into hidden mantle reservoirs. This CI- or CM-like material provides an upper limit for the contribution to the BSE from matrix that is much less than in any chondrites. In the models, Si, O and S are the dominant light elements in the core, in that order, and their abundances are constrained to be consistent with the first principles calculations of Umemoto and Hirose (2020). The core compositions of the models are also consistent with most geochemical constraints.

Satisfying all isotopic constraints is a challenge. The BSE Os isotopes are consistent with an EL dominated late veneer, but Ru isotopic evidence is best explained by the addition of CM-like material in the late veneer. Either CI- or CM-like material, in combination with small amounts of cometary and implanted solar wind material, can reproduce the BSE Ne, Ar and Kr isotopic compositions. CM-like, but not CI-like, material can roughly reproduce the BSE’s H and C isotopic compositions, but neither material can explain the BSE N isotopic composition. The BSE composition requires that the O isotopic compositions of the refractory inclusions (initially Δ17O≤-20 ‰) in Earth’s building blocks were reset in the nebula by interaction with high Δ 17O H2O, perhaps during chondrule formation. To plot on the inner Solar System ε54Cr vs. ε 50Ti (or ε 48Ca) trend, either the average Cr content of the chondrules was roughly half of that assumed here or most of the CI/CM-like and refractory-inclusion-rich materials were accreted late.

¹Sandrine Péron,¹Sujoy Mukhopadhyay,²Mark D. Kurz,³David W. Graham
Nature 600, 462-467 Link to Article [DOI
https://doi.org/10.1038/s41586-021-04092-z%5D
¹Department of Earth and Planetary Sciences, University of California, Davis, Davis, CA, USA
²Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
³College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA

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

¹Kathie L.Thomas-Keprta,²Simon J.Clemett,⁷Everett K.Gibson,⁴Zia Rahman,⁵Neha Baskar,⁶Susan J.Wentworth,⁷Nathaniel T.Keprta,³David S.McKay
Geochimica et Cosmochimica Acta (in Press) Libnk to Article [https://doi.org/10.1016/j.gca.2021.12.010]
¹Barrios Technology, NASA Johnson Space Center, Mail Code XI3, Houston, TX 77058, USA
²ERC, Inc, NASA Johnson Space Center, Mail Code XI3, Houston, TX 77058, USAc
³NASA Johnson Space Center, Mail Code XI3, Houston, TX 77058, USA
⁴Jacobs, NASA Johnson Space Center, Mail Code XI3, Houston, TX 77058, USA
⁵Texas A&M University, College Station, TX 77843, USA
⁶HEPCO, Inc, NASA Johnson Space Center, Mail Code XI2, Houston, TX 77058, USA
⁷University of Houston Clear Lake, Houston, TX 77058, USA
Copyright Elsevier

While indigenous organic matter has been previously reported in the Mars meteorite Nakhla, little is known as to either its form or distribution. A notable feature of Nakhla is the prevalence of secondary phases associated with aqueous alteration. By analogy with the terrestrial environment, our objective was to determine whether Martian secondary minerals could also act to accumulate and preserve such organic matter. Through a multidisciplinary approach, we have characterized the nature of carbonaceous matter and spatially associated phases within the Martian meteorite Nakhla using a wide-ranging suite of analytical instrumentation including optical microscopy, laser Raman spectroscopy, focused ion beam microscopy, secondary ion mass spectrometry, and scanning and transmission electron microscopy. In freshly fractured chips of Nakhla, we found carbonaceous phases intimately associated with secondary aqueous alteration phases, both mineral and amorphous, interpreted to have formed through the low-temperature aqueous dissolution of the host basalt while on Mars. The carbonaceous matter is present both in condensed phases and in a dispersed state spatially associated with secondary alteration phases. In the former, we identified discrete refractory micron to submicron assemblages that appear macromolecular in nature and, in several cases, associated with fluorine and, in one case, significant nitrogen. Textural, chemical, mineralogical and isotopic considerations argue for a non-terrestrial origin of this carbonaceous matter. Additionally, we report the presence of the ferrous hydroxycarbonate mineral chukanovite () within some of the secondary mineral aggregates studied. Neither the intimate association of carbonaceous matter with secondary phases nor the identification of chukanovite have been previously reported in any of the Martian meteorites. In this regard, we note such microscale features within alteration phases would most likely be lost in the preparation of conventional polished thin sections and thus explain why they have not been previously reported. In lieu of sample return, the sui generis nature provided by Mars meteorites provide insight to alteration processes on Mars currently denied to robotic exploration and remote sensing. Our results show a variety of habitability-related sample attributes, formed hundreds of millions of years ago near Mars’ surface, have persisted there until very recently and may be more widespread in the surface regolith than previously thought. This may have implications in sample selection criteria for Mars sample return.

¹F.Foucher,¹N.Bost,²G.Guimbretière,^1,3A.Courtois,⁴ K.Hickman-Lewis,^1,3E.Marceau,⁵P.Martin,¹F.Westall
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114848]
¹CNRS, Centre de Biophysique Moléculaire, UPR4301, 3E avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France
²CNRS, Laboratoire de l’Atmosphère et des Cyclones, UMR8105, 15 avenue René Cassin, 97744 Saint-Denis Cedex 9, La Réunion, France
³Université d’Orléans, Château de la Source, avenue du Parc Floral, BP 6749, 45067 Orléans Cedex 2, France
⁴Department of Earth Sciences, The Natural History Museum, Cromwell Rd, South Kensington, London SW7 5BD, United Kingdom
⁵CNRS, Laboratoire de Physique et de Chimie de l’Environnement et de l’Espace, UMR73028, 3E avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France
Copyright Elsevier

Powdered rocks are commonly present at the surface of extraterrestrial bodies and are widely analysed by in situ space probes. Moreover, a number of rovers exploring the surface of Mars are equipped with drills enabling them to access unaltered material and collect samples. During drilling operations, a cone of powder made of the drilled materials forms at the surface. These powders will be particularly large during the ESA/Roscosmos ExoMars 2022 mission since the rover Rosalind Franklin will drill to 2 m depth below the Martian surface. These fines are generally observed by the rovers’ cameras after the drilling process and analysed by a limited range of instruments. In order to maximise the scientific return of planetary missions to Mars and other bodies in the solar system, we propose to use the images taken by rover cameras to identify the composition of the powdered materials. This could be particularly useful during the ExoMars 2022 mission where the CLUPI camera will take pictures during drilling and could thus document changes in the regolith composition (Josset et al., 2017). In the absence of a controlled light source, we used an image processing method called CaliPhoto that we previously developed for generic purposes. To test the ability of the method to identify volcanic rocks, more than twenty Mars-analogue samples were crushed at various grain sizes and photographed. The images were then processed via the CaliPhoto method and used to construct a database of reference images. New images were then taken under different lighting conditions, processed using the same method, and compared to the database. We show that it is possible to estimate igneous rock powder lithology with greater than 90% accuracy considering the uncertainties. Furthermore, when using images of polished and powdered samples, identification reaches 100%. We also show that the method permits precise lithological identification of samples that are not in the initial database. Finally, we demonstrate that the proposed method is extremely efficient, while at the same time very easy to implement on any in situ space probe. It could thus be used to help in identifying powdered igneous rocks during future missions to Mars or other rocky body in the solar system.

¹A.Karthi,¹S.Arivazhagan
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114844]
¹Centre for Applied Geology, The Gandhigram Rural Institute – Deemed to be University, Gandhigram, Dindigul, Tamilnadu, India
Copyright Elsevier

The lunar multiring mare basins have different ages, compositions and are associated with the diverse unit of mare deposits, providing evidence for the origin and evolution of the lunar crust. The multiring basins offer the opportunity to assess many unknown questions that may reveal the lunar geologic standpoint. The Mare Orientale basin is one of the youngest impact multiring basins on the Moon, which covers about 930 km in diameter and coordinates centered at 20⁰S 95⁰W. In the present study, the compositional, topographical, and chronological studies have been done by using Moon Mineralogy Mapper (M³) from Chandrayaan-1 orbiter and Lunar Reconnaissance Orbiter Camera-Wide Angle Camera (LROC-WAC) image from Lunar Reconnaissance Orbiter (LRO). The M³ data used to map the Optical maturity (OMAT), FeO & TiO₂ concentrations of the basin. The Standard Band Ratio (SBR) of the Orientale basin has been prepared to discriminate the different mare and highland lithologies. The 1 μm and 2 μm band depths have been mapped to demarcate the mafic minerals such as olivine and pyroxenes. The age of the Orientale basin mare units was mapped as Orientale event (3.72 Ga – Upper Imbrian), Orientale South West (3.7 Ga), Orientale West unit (3.37 Ga), Lacus Veris North unit- 1, 2, and 3 (3.1 Ga, 2.63 Ga, and 3.3 Ga), Lacus Veris East (2.9 Ga), Lacus Autumni – North (3.1 Ga), Middle (2.01 Ga), South (2.27 Ga) and Kopff crater (mare) (2.92 Ga) by using LROC-WAC data through Crater Size Frequency Distribution (CSFD) technique. Characterization of M³ reflectance spectra profiles was done to map the Orientale basin lithologies like olivine, pyroxene (low calcic and high calcic), plagioclase, ilmenite, Mg-spinel, and olivine – pyroxene mixtures that are present in the anorthositic, basaltic, noritic, and gabbroic rocks. It is revealed that the Orientale basin could have been formed either by global thermal evolution and basin mare volcanic evolution or pressure release melting and associated with secondary convection.

^1,2,3R.Martinez,¹A.Agnihotri,³E.F.da Silveira,⁴M.E.Palumbo,⁴G.Strazzulla,¹P.Boduch,¹A.Domaracka,¹H.Rothard
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114830]
¹Centre de Recherche sur les Ions, les Matériaux et la Photonique, Normandie University, ENSICAEN, UNICAEN, CEA, CNRS, CIMAP, 14000 Caen, France
²Physics Department, Universidade Federal do Amapá, Brazil
³Physics Department, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marquês de São Vicente 225, 22453-900 Rio de Janeiro, RJ, Brazil
⁴INAF-Osservatorio Astrofisico di Catania, Italy
Copyright Elsevier

Silicates are ubiquitous in space. They dominate the surfaces of the inner rocky planets (Mercury in the case of the Solar System), the Moon, and asteroids, forming the major part of the non-volatile material. The physical and chemical properties of the rocky surfaces are determined not only by their initial composition but also by the processes occurring on them. Here we discuss one of these processes; irradiation by energetic cosmic particles that induces many effects among which structural changes and sputtering, the latter contributing to the formation of exospheres. In the current work we report the results of experiments conducted on anorthite, jadeite and nepheline silicates that have been irradiated with energetic heavy ions with the aim to better understand the interaction of galactic cosmic rays, solar wind, and solar energetic particles with planetary and small body surfaces. The sputtering effects induced by energetic (MeV/u) multicharged heavy ions (e.g., ¹⁰⁵Rh and ¹⁴⁰Ba) were analyzed by the PDMS-TOF-SIMS technique (plasma desorption mass spectrometry – time-of-flight secondary ion mass spectrometry). Positive and negative secondary ionic species are identified: Na⁺, K⁺, Al⁺, Ca⁺, SiO₂⁻. Ejection of (SiO₂)_n⁻ and (AlSi)O_m⁻ cluster series are also observed. Less frequent, negative ion yields are one order of magnitude less than positive ones, or greater, which is the case for nepheline, with 0.671 ions impact⁻¹ for positive and 0.126 ions impact⁻¹ for negative ions. The results concerning ejection of ionic species show, for instance, that the Na⁺/K⁺ ratio is ~2.5, which is in very good agreement with that observed in the Hermean exosphere found to be ~2.3.

¹M. N. Rao,²L. E. Nyquist,³P. D. Asimow,^4,5D. K. Ross,^6,7S. R. Sutton,⁸T. H. See,⁴C. Y. Shih,⁴D. H. Garrison,⁹S. J. Wentworth,¹⁰J. Park
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13770]
¹SCI, Johnson Space Center, Houston, Texas, 77058 USA
²XI, NASA, Johnson Space Center, Houston, Texas, 77058 USA
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125 USA
⁴Jacobs JETS, NASA, Johnson Space Center, Houston, Texas, 77058 USA
⁵UTEP-CASSMAR, El Paso, Texas, 79968 USA
⁶Department of Geophysical Sciences, University of Chicago, Chicago, Illinois, 60439 USA
⁷CARS, Argonne National Laboratory, Argonne, Illinois, 60439 USA
⁸Barrios Technology/Jacobs JETS, NASA, Johnson Space Center, Houston, Texas, 77058 USA
⁹HEPCO, Jacobs JETS, NASA Johnson Space Center, Houston, Texas, 77058 USA
¹⁰Kingsborough Community College, Brooklyn, New York, 11235 USA
Published by arrangement with John Wiley & Sons

Large impact-melt pockets in shergottites contain both Martian regolith components and sulfide/sulfite bleb clusters that yield high sulfur concentrations locally compared to bulk shergottites. The regolith may be the source of excess sulfur in the shergottite melt pockets. To explore whether shock and release of secondary Fe-sulfates trapped in host rock voids is a plausible mechanism to generate the shergottite sulfur bleb clusters, we carried out shock recovery experiments on an analog mixture of ferric sulfate and Columbia River basalt at peak pressures of 21 and 31 GPa. The recovered products from the 31 GPa experiment show mixtures of Fe-sulfide and Fe-sulfite blebs similar to the sulfur-rich bleb clusters found in shergottite impact melts. The 21 GPa experiment did not yield such blebs. The collapse of porosity and local high-strain shear heating in the 31 GPa experiment presumably created high-temperature hotspots (~2000 °C) sufficient to reduce Fe3+ to Fe2+ and to decompose sulfate to sulfite, followed by concomitant reduction to sulfide during pressure release. Our results suggest that similar processes might have transpired during shock production of sulfur-rich bleb clusters in shergottite impact melts. It is possible that very small CO presence in our experiments could have catalyzed the reduction process. We plan to repeat the experiments without CO.