¹Daniele Fulvio,¹Leonardo Fuks,¹Maron Yaima,¹Cires Perez,¹Tahir Tommaso,¹Del Rosso
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114532]
¹Department of Physics, Pontifícia Universidade Católica do Rio de Janeiro, Rua Marques de São Vicente, 22451- 900 Rio de Janeiro, Brazil
Copyright Elsevier

The term “space weathering” refers to processes that include changes in the physical, chemical, mineralogical, and spectral properties of the surface of asteroids, comets, and some planets and their satellites, such as the bombardment by micrometeorites, solar wind ions, and cosmic rays. In this study, we focus on micrometeorite impacts, which may be the primary contributor to the annual mass flow of material that reaches the surface of such bodies. Studying the processes and effects associated with micrometeorite impacts is fundamental for understanding the evolution of the solar system and its components. From an experimental point of view, it is typically assumed that micrometeorite impacts may be simulated by ns -pulsed lasers and, indeed, many experimental studies have been performed based on such assumption. These studies have the common main goal to understand how micrometeorite impacts may change the physical -chemical and spectral properties of the bombarded surfaces. However, here we perform the first experimental study dedicated to the morphological characterization of the impact craters created by ns -pulsed laser ablation, in order to determine how well ns -pulsed lasers simulate the crater morphology of natural micrometeorite impacts. For this purpose, the laser ablation technique was applied to three different silicates: feldspar, quartz, and jadeite. For each of these minerals, two ablation scenarios have been considered: in air and in water. The craters formed by ns -pulsed laser ablation were characterized, from the morphological point of view, using a profilometer. Using this data we estimated the depth:diameter ratio of each crater. The comparison with literature data shows that the simple craters formed by ns -pulsed laser ablation closely resemble craters formed by natural micrometeorite impacts. In other words, from a morphological point of view, ns -pulsed laser ablation is appropriate for the simulation of micrometeorite impacts. We additionally verified that the value of the depth:diameter ratio does not depend, within errors, on the total number of laser pulses or the repetition frequency, at least within the ranges covered in these experiments: i) between 1 and 1200 laser pulses and ii) between 1 and 10 Hz.

¹Shaunna M. Morrison,¹Robert M. Hazen
American Mineralogist 106, 730–761 Link to Article [http://www.minsocam.org/msa/ammin/toc/2021/Abstracts/AM106P0730.pdf]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, D.C. 20015, U.S.A
Copyright: The Mineralogical Society of America

The fourth installment of the evolutionary system of mineralogy considers two stages of planetesimal mineralogy that occurred early in the history of the solar nebula, commencing by 4.566 Ga and lasting for at least 5 million years: (1) primary igneous minerals derived from planetesimal melting and differentiation into core, mantle, and basaltic components and (2) impact mineralization resulting in shock-induced deformation, brecciation, melting, and high-pressure phase transformations.
We tabulate 90 igneous differentiated asteroidal minerals, including the earliest known occurrences
of minerals with Ba, Cl, Cu, F, and V as essential elements, as well as the first appearances of numerous
phosphates, quartz, zircon, and amphibole group minerals. We also record 40 minerals formed through
high-pressure impact alteration, commencing with the period of asteroid accretion and differentiation.
These stages of mineral evolution thus mark the first time that high pressures, both static and dynamic,
played a significant role in mineral paragenesis.

¹S.Anbazhagan et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114511]

¹Centre for Geoinformatics and Planetary Studies, Periyar University, Salem 636 011, Tamil Nadu, India
Copyright Elsevier

Lunar Regolith Simulants are imperative materials required for In-Situ Resource Utilization (ISRU), simulating physical and chemical properties of the lunar terrain, testing landers and mobility of rovers, and calibration of payloads and sensors. The available simulants do not represent all the lunar terrain environments and are insufficient to conduct the above experiments. The Indian Space Research Organization (ISRO) took up necessary steps to launch the Chandrayaan-2 mission after successfully completing the Chandrayaan-1 mission. The Chandrayaan-2 mission included an orbiter, a lander and a rover. ISRO’s UR Rao Satellite Centre (URSC) has decided to have a dedicated Lunar Terrain Testing Facility (LTTF) at Bengaluru. URSC has planned for a bulk quantity of lunar soil simulant similar to Lunar highland composition. The task was assigned to the Centre for Geoinformatics and Planetary Studies, Department of Geology at Periyar University in southern India. The bulk quantity of Lunar soil stimulant was produced from the anorthosite rocks collected from the Sittampundi Anorthosite Complex (SAC) exposed in the southern part of India. We report the merit of the source area, geological setting, chemistry, mineral phase, soil characteristics, and grain size distribution of simulant material. The anorthosite rocks collected from SAC have a higher abundance of calcic plagioclase, and the proportion of major oxides is mostly equivalent to lunar highland anorthosite. ISRO’s lunar soil simulant LSS-ISAC-1 has similarity with the Lunar highland regolith in the majority and has fidelity to represent the highland terrain. The testing facility, LTTF, was used for testing the soft landing of the lander and mobility of the rover of the Chandrayaan-2 mission.

¹Eugene G. Grosch,²Janice L. Bishop,³Christian Mielke,⁴Alessandro Maturilli,⁴Jörn Helbert
American Mineralogist 106, 672–684 Link to Article [http://www.minsocam.org/MSA/AmMin/TOC/2021/Abstracts/AM106P0672.pdf]
¹Geology Department, Rhodes University, Grahamstown/Makhanda 6140, South Africa 2
²Carl Sagan Center, SETI Institute and NASA-Ames Research Center, Mountain View, California 94043, U.S.A. 3
³GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam 4
⁴Institute for Planetary Research, DLR, Rutherfordstrasse 2, 12489, Berlin-Adlershof, Germany
Copyright: The Mineralogical Society of America

Characterization of terrestrial analog sites is critical for detection and determination of clay mineralogy in remote sensing studies of Mars aimed at geological, hydrological, and potentially biological
investigations. In this study, we investigate a suite of hydrothermally altered early Archean rocks from
the Barberton greenstone belt (BGB) of South Africa as potential petrological, mineralogical, and
spectral analogs to hydrothermally altered metabasalts and mafic-ultramafic intrusions in the martian
subsurface and impact craters. We present the first spectral imaging measurements on exceptionally
well-preserved early Archean mafic-ultramafic rocks from the BGB, with the aim of studying their
clay mineralogy and spectral signatures. Multiple spectral analyses were conducted on different
sample textures (rock powders, crushed rocks, and rock slabs) appropriate for Mars rover and remote
sensing exploration. Visible/near-infrared (VNIR) and mid-IR reflectance spectra were acquired on
particulate samples, while VNIR spectral imaging data were collected on rock slabs. Mid-IR emission
spectra were measured for the rock slabs and grains. Spectral features are compared from these different spectral techniques to identify the minerals present in the samples and compare macroscale vs.
microscale detections. The measured spectra reveal absorption bands that correspond to clay mineralogy of the serpentine and chlorite mineral groups, consistent with petrographic observations, as well
as magnetite, olivine, quartz, feldspar, and Al-phyllosilicate. The spectral data acquired in this study
expand the reference spectra data set for remote sensing studies. The implications of this study are that
rocks from early Archean greenstone belts, such as those of the BGB, serve as potential clay-bearing
petrological analogs for hydrothermal environments on Mars.

¹L.Mandon,^2,3P.Beck,¹C.Quantin-Nataf,¹E.Dehouck,⁴A.Pommerol,⁴Z.Yoldi,⁴R.Cerubini,¹L.Pan,¹M.Martinot,⁵V.Sautter
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114517]
¹Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, F-69622 Villeurbanne, France
²Université Grenoble-Alpes, CNRS, IPAG, UMR, 5274 Grenoble, France
³Institut Universitaire de France, France
⁴Space Research & Planetary Sciences Division, Physikalisches Institut, Universität Bern, Bern, Switzerland
⁵Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, 75005 Paris, France
Copyright Elsevier

In the next decade, two rovers will characterize in situ the mineralogy of rocks on Mars, using for the first time near-infrared reflectance spectrometers: SuperCam onboard the Mars 2020 rover and MicrOmega onboard the ExoMars rover, although this technique is predominantly used in orbit for mineralogical investigations. Until successful completion of sample-return missions from Mars, Martian meteorites are currently the only samples of the red planet available for study in terrestrial laboratories and comparison with in situ data. However, the current spectral database available for these samples does not represent their diversity and consists primarily of spectra acquired on finely crushed samples, albeit grain size is known to greatly affect spectral features. Here, we measured the reflected light of a broad Martian meteorite suite as a means to catalogue and characterize their spectra between 0.4 and 3 μm. These measurements are achieved using a point spectrometer acquiring data comparable to SuperCam, and an imaging spectrometer producing hyperspectral cubes similarly to MicrOmega. Our results indicate that point spectrometry is sufficient to discriminate the different Martian meteorites families, to identify their primary petrology based on band parameters, and to detect their low content in alteration minerals. However, significant spectral mixing occurs in the point measurements, even at spot sizes down to a few millimeters, and imaging spectroscopy is needed to correctly identify the various mineral phases in the meteorites. Additional bidirectional spectral measurements on a consolidated and powdered shergottite confirm their non-Lambertian behavior, with backward and suspected forward scattering peaks. With changing observation geometry, the main absorption strengths show variations up to ~10–15%. The variation of reflectance levels is reduced for the rock surface compared to the powder. All the spectra presented are provided in the supplementary data for further comparison with in situ and orbital measurements.

¹Lingzhi Sun,¹Paul G. Lucey,¹G. Jeff Taylor
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2020JE006445]
¹Hawai‘i Institute of Geophysics and Planetology, Dept. of Earth Sciences, University of Hawai‘i at Manoa, 1680 East‐West Rd., Honolulu, Hi, 96822 USA
Published by arrangement with >John Wiley & Sons

Although lunar soils contain rock and mineral components from the breakdown of a mixture of rock types, a classification based on the abundances of the major silicate minerals plagioclase, olivine, low‐Ca pyroxene (LCP) and high‐Ca pyroxene can be used to evaluate the major compositional classes that are represented within a given soil. We studied the compositional classes for Apollo 15, 16 and 17 soil samples based on the mineral modal abundances derived by X‐ray diffraction (XRD). Using the XRD results as a ground truth, we determined the compositional classes of the Apollo 15, 16 and 17 sampling stations using mineral maps from the Kaguya Multiband Imager (MI), then mapped areas having compositional classes similar to the sampling stations on regional and global scales. Global distribution of compositional classes was also mapped using MI mineral maps, and the major compositional classes of lunar nonmare surfaces are noritic anorthosite (40 %), anorthositic norite (24 %), and anorthosite (23 %). Our maps show that the lunar highlands and the South Pole‐Aitken (SPA) basin are enriched with noritic materials, indicating the widespread occurrence of LCP‐rich and olivine‐poor assemblages. In contrast to the SPA basin and the highlands, the basin rings of Serenitatis, Crisium, Humorum, Nectaris, Orientale and Hertzsprung exhibit higher olivine/pyroxene ratios (>2), and we interpret this signature as reflecting a contribution from olivine‐rich upper mantle components.

¹Paul Frossard,²Zhiguo Guo,²Mary Spencer,¹Maud Boyet,^2,3Audrey Bouvier
Earth and Planetary Science Letters 566, 116968 Link to Article [https://doi.org/10.1016/j.epsl.2021.116968]
¹Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France
²Department of Earth Sciences, University of Western Ontario, N6A 5B7 London, Ontario, Canada
³Bayerisches Geoinstitut, Universität Bayreuth, 95447 Bayreuth, Germany
Copyright Elsevier

Heterogeneity in isotopic compositions within the protoplanetary disc has been demonstrated for a number of elements measured in extra-terrestrial materials, mostly based on chondrite meteorite analyses. However, precise 182Hf-182W and 26Al-26Mg ages of iron meteorites, achondrites, and chondrules show that chondrites accreted later than achondrites and therefore do not strictly represent the early (<2 Ma) solar system composition. Here we present the Nd mass-independent stable isotopic compositions of a suite of diverse achondrites to better constrain the Nd isotope evolution of the early solar system. Carbonaceous (C) achondrites are indistinguishable from their chondritic counterpart. However, early formed planetesimals as sampled by silicate-rich non-carbonaceous (NC) achondrite meteorites have higher 145Nd/144Nd and 148Nd/144Nd ratios (3.9 < Nd < 11.0 and 9.1 < Nd < 17.9 in part per million deviation, or Nd) compared to NC chondrites (2.7 < Nd < 3.3 and 2.2 < Nd < 8.1). Moreover, the three terrestrial planets for which we have samples available (Earth, Mars, and the Moon) as well as the silicate inclusions from the non-magmatic IIE iron meteorite Miles present a systematic deficit in Nd and Nd compared to early-formed NC achondrites. Unlike chondrites, the Nd anomalies in achondrites are not correlated to the heliocentric distance of accretion of their respective parent bodies as inferred from redox conditions. Chronological constraints on planetesimal accretion suggest that Nd (and other elements such as Mo and Zr) nucleosynthetic compositions of the inner part of the protoplanetary disc significantly changed around 1.5 Ma after Solar System formation due to thermal processing of dust in the protoplanetary disc. This relatively late event coincides with the beginning of chondrule formation or at least their preservation. Terrestrial planets formed subsequently by a complex accretion regime during several million years. Therefore, two scenarios are envisioned considering the reported Nd isotope composition of early planetesimals: 1) Terrestrial planets accreted mostly chondritic material similar in composition to enstatite chondrites, or 2) early planetesimals constitute substantial parts of terrestrial planets building blocks mixed with highly thermally processed material enriched in s-process, still unsampled by meteorites.

¹Hisayoshi Yurimoto,²Alan E. Rubin,³Shoichi Itoh,⁴John T. Wasson
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13652]
¹Isotope Imaging Laboratory (IIL), Natural History Sciences, Hokkaido University, Sapporo, 001–0021 Japan
²Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095–1567 USA
³Department of Earth and Planetary Sciences, Kyoto University, Kyoto, 606–8502 Japan
⁴Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, 90095–1567 USA
Published by arrangement with John Wiley & Sons

We studied a unique super‐refractory inclusion with a core‐mantle structure from CO3.0 Yamato 81020 by secondary ion mass spectrometry, electron microprobe, and scanning electron microscope techniques. The core consists largely of hibonite and nonstoichiometric Al‐rich spinel indicating formation as a liquid at an exceptionally high temperature (>1900 °C). The mantle consists almost entirely of melilite with gehlenitic compositions (ranging from Åk2 to Åk25). The oxygen‐ and magnesium‐isotopic compositions of the core and mantle are very different; typically, Δ17O (≡δ17O − 0.52 δ18O) ~–26‰ and ƒMg (mass fractionation of Mg isotopes) ~10‰/amu in the core and Δ17O ~–7‰ and ƒMg ~1‰/amu in most of the mantle. The chemical and O, Mg‐isotopic data indicate that the core and mantle formed in separate events, and that the melilite now in the core was formed during the mantle‐melting event, probably filling preexisting voids and surficial cavities. Analyses of core and mantle phases plot along a single 26Al‐26Mg isochron with initial (26Al/27Al)0 corresponding to 4.8 ± 1.0 (±2σ) × 10–5, suggesting a similar formation age to normal CAIs in chondrites.

¹Stella Rombeck,¹Christian Vollmer,²Julia Roszjar,³Adam R. Sarafian,¹Stephan Klemme
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13651]
¹Institut für Mineralogie, Westfälische Wilhelms‐Universität Münster, Corrensstrasse 24, 48149 Münster, Germany
²Department of Mineralogy and Petrography, Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria
³Corning Incorporated, Science and Technology Division, 21 Lynn Morse Rd., Painted Post, New York, 14870 USA
Published by arrangement with John Wiley & Sons

Some basaltic eucrites and basaltic lithologies in howardites derived from the asteroid 4 Vesta exhibit unusual secondary veinlet textures consisting mostly of fayalitic olivine and Fe‐enrichments within pyroxenes. Recent studies discussed the formation of these Fe‐rich phases either by interaction with a vapor and/or liquid phase (metasomatism), or by a high‐temperature melting process. We therefore performed a series of heating and hydrothermal experiments with liquids of different compositions on natural pyroxene crystals (augite and orthopyroxene) to evaluate these contrasting hypotheses. The results of the heating experiments show that incongruent melting of pyroxenes at about 1070 °C causes textures that are very similar to those observed in the meteorites. We conclude that a part of the natural secondary veins might be explained by heating processes at similar temperatures. The hydrothermal experiments with aqueous liquids of different Fe‐enriched compositions clearly indicate ion exchange reactions resulting in partial Fe‐enrichments of the pyroxene. Interestingly, these Fe‐enrichments occurred independent of the Fe content of the liquid, which can be explained by an internal origin of Fe from the pyroxenes. In one hydrothermal experiment of augite with Fe‐oxalate solution, deposition of fayalitic olivine was observed. From our experimental observations, we conclude that aqueous liquids are plausible candidates for explaining the deposition of Fe‐enrichments and fayalitic olivine inside the fractures of pyroxene. However, we cannot rule out a high‐temperature melting process slightly above the peritectic point of pyroxene to explain a fraction of observed secondary Fe‐enrichments.

¹Stefan Farsang,²Ian A. Franchi,^,Xuchao Zhao,³Timothy D. Raub,⁴Simon A.T. Redfern,^2,5Monica M. Grady
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13647]
¹Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ UK
²School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
³School of Earth & Environmental Sciences, University of St Andrews, Irvine Building, St Andrews, KY16 9AL UK
⁴Asian School of the Environment, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798 Singapore
⁵Department of Earth Sciences, Natural History Museum, Cromwell Rd, London, SW7 5BD UK
Published by arrangement with John Wiley & Sons

The paragenesis of carbonates in the Cold Bokkeveld CM chondrite is determined from a detailed petrographic, chemical, spectroscopic, and isotopic study of nine associations of carbonates (aragonite, calcite, and dolomite) with other secondary minerals that occur within the meteorite. Our study reveals the existence of carbonates displaying petrographic features that are distinct from those of type 1 and type 2 carbonates commonly observed in CM2 meteorites. These include carbonates interstitial to octahedral magnetite crystals, for which a new designation of “type 1c” is suggested. The O isotopic values of dolomite (δ¹⁸O ranging from +21.1 to +25.8‰ and Δ¹⁷O from −4.9 to −4.0‰) are similar to those measured in dolomites from other CM chondrites. The presence of complex carbonates with a CaCO₃ core and Mg‐enriched rim implies several generations of fluids and/or their evolving composition on the CM parent body(ies). Petrographic characteristics indicate at least six stages of potentially overlapping carbonate and phyllosilicate formation events. We show that type 1 and type 2 calcite have distinct Raman spectral characteristics. Type 1 calcite is characterized by very broad peaks, whereas type 2 calcite displays narrow peaks similar to those of typical abiotic terrestrial calcite, suggesting high crystallinity. A carbonate Raman spectrum showing features characteristic of both aragonite and calcite likely documents an aragonite‐calcite phase transition. Raman spectroscopy also reveals the presence of organic matter in the majority of carbonates. This indicates that organic carbon was mobilized by aqueous fluids for extended periods.