¹Kashima, Aruto,²Urashima, Shu-hei,^1,2Yui, Hiroharu
Journal of Raman Spectroscopy (in Press) Open Access Link to Article [DOI 10.1002/jrs.6355]
¹Department of Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
²Water Frontier Research Center, Research Institute for Science and Technology, Tokyo University of Science, Tokyo, Japan

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^1,2,3Natsuki Hosono,⁴Shun-ichiro Karato
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2021JE006971]
¹Department of Planetology, Kobe University, Kobe, Japan
²RIKEN Center for Computational Science, Kobe, Japan
³Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
⁴Department of Earth and Planetary Sciences, Yale University, New Haven, CT, USA
Published by arrangement with John Wiley & Sons

We explore the role of various equations of state (EoS) in controlling the composition of the Moon formed by a giant impact (GI) using a density-independent SPH code. A limitation in our previous model Hosono et al. (2019), https://doi.org/10.1038/s41561-019-0354-2 is improved by replacing the EoS of the solid from Tillotson EoS to M-ANEOS, and we also explored two recently proposed EoSs by Stewart et al. (2020), https://doi.org/10.1063/12.0000946 and Wissing and Hobbs (2020a), https://doi.org/10.1051/0004-6361/201935814; Wissing and Hobbs (2020b), https://doi.org/10.1051/0004-6361/201936227. The goal is to investigate to what extent we can explain the observed composition of the Moon including the similarity in the isotopic composition and the dissimilarity in the FeO/(FeO + MgO) ratio as compared to that of Earth by the different types of EoS assuming the conventional collision conditions. We found that changing the EoS for solids from Tillotson to M-ANEOS EoS resolves the issues of latent heat, but its effect on the composition of the disk is small compared to the influence of the hard-sphere EoS of magma ocean in controlling the composition of the disk. Similarly, two recently proposed EoSs have small effects on the composition of the disk in comparison to the model where the hard-sphere EoS is used for preexisting magma ocean. We attribute this difference to a fundamental difference in thermodynamic behavior of silicate melts captured by the hard-sphere EoS and by newly proposed EoSs; in the hard-sphere model of silicate melts, configurational entropy dominates in free energy, whereas in the newly proposed model, entropy is dominated by vibrational entropy similar to entropy of solids.

¹Cyril Sturtz,¹Angela Limare,¹Marc Chaussidon,¹Édouard Kaminski
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115100]
¹Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, Paris, F-75005, France
Copyright Elsevier

Meteorites are interpreted as relics of early formed planetary bodies, and they provide information about the processes that occurred in the first few of our solar system. The ages measured for some differentiated meteorites (achondrites), indicate that planetesimals formed a differentiated silicate crust as early as after the beginning of the solar system. The composition of the recently discovered achondrite Erg Chech 002 (EC002), the oldest andesitic rock known so far, betokens partial melting of a chondritic source taking place as early as before all other known achondrites. However, thermal models of early accreted planetesimals predict massive melting of the planetesimal during core/mantle differentiation and cannot account for the preservation of a substantial amount of chondritic material. In this paper, we propose a way to interpret petrological and geochemical constraints provided by differentiated meteorites by introducing a refined thermal model of planetesimals formation and evolution. We demonstrate that continuous, protracted accretion of cold undifferentiated material upon a magma ocean over a timescale 2 times larger than the lifetime of the 26Al heat source leads to the preservation of a few km thick chondritic crust. During accretion, the heat released by radioactive decay further induces episodes of partial melting at the base of the crust, which can led to the formation of andesitic rocks such as EC002. Using the available constraints on the age of EC002 and its cooling rate, the application of our model constraints the terminal radius of its parent body between 70 and .

¹Andrew Rodriguez,¹Lindsey Hunt,²Charity Phillips-Lander,³Daniel Mason,¹Megan Elwood Madden
Icarus (in Print) Link to Article [https://doi.org/10.1016/j.icarus.2022.115111]
¹OU School of Geosciences, United States of America
²Southwest Research Institute, United States of America
³UNM School of Earth and Planetary Sciences, United States of America
Copyright Elsevier

Salts and basalt are widespread on the surface of Mars. Therefore, basalt-brine interactions may have significant effects on both the aqueous history of the planet, and near-surface alteration assemblages. Raman spectra were collected from McKinney Basalt samples that were immersed in eight near-saturated brines composed of Na-Cl-H2O, Na-SO4-H2O, Na-ClO4-H2O, Mg-Cl-H2O, Mg-SO4-H2O, and two salt mixtures (Mg-Cl-SO4-H2O and Na-ClO4-SO4-H2O), as well as ultra-pure water for up to one year. Secondary minerals were observed in the Raman specta, including iron oxides, hydrated sulfates, amorphous silica, phosphates, and carbonates. Detection of these secondary minerals demonstrates the utility of Raman spectroscopy to identify basalt-brine alteration assemblages on Mars. This work also demonstrates that major classes of alteration phases can be distinguished using Raman spectra with resolution similar to those expected from the Raman instruments aboard the Perseverance and Rosalind Franklin Mars rovers. In addition, observations of carbonate minerals within alteration assemblages suggest CO2 from the atmosphere readily reacted with ions released from the basalt during alteration in near-saturated brines.

¹Catherine M.Weitz,²Janice L.Bishop,³John A.Grant,³Sharon A.Wilson,³Rossman P.IrwinIII,⁴Arun M.Saranathan,⁴Yuki Itoh,⁴Mario Parente
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115090]
¹Planetary Science Institute, 1700 E Fort Lowell, Tucson, AZ 85719, USA
²SETI Institute, Carl Sagan Center, 339 Bernardo Ave., Mountain View, CA 94043, USA
³Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, 6th at Independence SW, Washington, DC 20560, United States of America
⁴University of Massachusetts Amherst, Dept. Electrical & Computer Engineering, 151 Holdsworth Way, Amherst, MA 01003, United States of America
Coypright Elsevier

The morphology and mineralogy of light-toned layered sedimentary deposits were investigated using multiple orbital datasets across the Ladon basin region, including within northern Ladon Valles, southern Ladon basin, and the southwestern highlands of Ladon basin. Light-toned layered deposits are particularly widespread in Ladon Valles and Ladon basin, ranging laterally for distances over 200 km, with the thickest exposure (54 m) located at the mouth of Ladon Valles. The restriction of layered sediments below a common elevation (−1850 m) in Ladon Valles and Ladon basin and their broad conformable distribution with bedding dips between 1 and 4° favor a lacustrine environment within this region during the Late Noachian to Early Hesperian. The Ladon layered deposits have spectral signatures consistent with Mg-smectites, even when the morphology of the layering varies considerably in color and brightness. These phyllosilicates were most likely eroded from the highlands upstream to the south, but the lacustrine environment may have also been favorable for in situ alteration and formation of clays. The southwestern highlands also display light-toned layered deposits within valleys and small basins. These sediments predominantly have signatures of Mg-smectites, although we also identified Fe/Mg-smectites and additional hydrated phases in some deposits. One of these altered deposits was found within a younger Holden crater secondary chain, possessing a Late Hesperian to Early Amazonian age for valleys and sediments that postdate the deposits within Ladon Valles and Ladon basin. Phyllosilicate signatures were also detected in the ejecta from two fresh craters that exposed highland materials upstream of Arda Valles, revealing that the highlands are clay-bearing and may be the most plausible source of the clay-bearing fluvial-derived sediments found within the valleys and basins downstream. Some of the highland deposits are likely coeval to similar clay-bearing sediments found to the south within Holden and Eberswalde craters, indicating late, widespread fluvial activity and deposition of allochthonous clays within the broader Margaritifer Terra region when Mars was thought to be colder and drier.

^1,2Ai-Cheng Zhang,¹Jie-Ya Li,¹Jia-Ni Chen,³Yuan-Yun Wen,⁴Yan-Jun Guo,^2,3Yang Li,⁵Naoya Sakamoto,^5,6Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.05.017]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Science and Engineering, Nanjing University, Nanjing 210023, China
²CAS Center for Excellence in Comparative Planetary, Hefei 230026, China
³Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
⁴CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China
⁵Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo 010-0021, Japan
⁶Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan
Copyright Elsevier

Impact is a fundamental process shaping the formation and evolution of planets and asteroids. It is inevitable that some materials on the surface of planets and asteroids have been impacted for many times. However, unambiguous petrological records for multiple post-formation impact events are rarely described. Here, we report that the thin shock melt veins of the shocked eucrite Northwest Africa 8647 are dominated by a fine-grained intergranular or vermicular pigeonite and anorthite assemblage, rather than compact vacancy-rich clinopyroxene. Vacancy-rich clinopyroxene in the veins instead is ubiquitous as irregularly-shaped, relict grains surrounded by intergranular or vermicular pigeonite and anorthite assemblage. The silica fragments entrained in shock melt veins contain a coesite core and a quartz rim. The occurrences of vacancy-rich clinopyroxene and coesite can be best explained by two impact events. The first impact event produced the shock melt veins and lead to the formation of vacancy-rich clinopyroxene and coesite. The second impact event heated the fine-grained melt veins and lead to the widespread partial decomposition of vacancy-rich clinopyroxene and the partial back-transformation of coesite. This paper is the first report of the decomposition reaction of shock-induced vacancy-rich clinopyroxene in extraterrestrial materials. We propose that widespread decomposition and/or back-transformation of high-pressure minerals in shocked meteorites can be considered as important records of multiple impact events.

¹Kosuke Kurosawa et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2021JE007133]
¹Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016 Japan
Published by arrangement with John Wiley & Sons

Shock metamorphism of minerals in meteorites provides insights into the ancient Solar System. Calcite is an abundant aqueous alteration mineral in carbonaceous chondrites. Return samples from the asteroids Ryugu and Bennu are expected to contain calcite-group minerals. Although shock metamorphism in silicates has been well studied, such data for aqueous alteration minerals are limited. Here, we investigated the shock effects in calcite with marble using impact experiments at the Planetary Exploration Research Center of Chiba Institute of Technology. We produced decaying compressive pulses with a smaller projectile than the target. A metal container facilitates recovery of a sample that retains its pre-impact stratigraphy. We estimated the peak pressure distributions in the samples with the iSALE shock physics code. The capability of this method to produce shocked grains that have experienced different degrees of metamorphism from a single experiment is an advantage over conventional uniaxial shock recovery experiments. The shocked samples were investigated by polarizing microscopy and X-ray diffraction analysis. We found that more than half of calcite grains exhibit undulatory extinction when peak pressure exceeds 3 GPa. This shock pressure is one order of magnitude higher than the Hugoniot elastic limit (HEL) of marble, but it is close to the HEL of a calcite crystal, suggesting that the undulatory extinction records dislocation-induced plastic deformation in the crystal. Finally, we propose a strategy to re-construct the maximum depth of calcite grains in a meteorite parent body, if shocked calcite grains are identified in chondrites and/or return samples from Ryugu and Bennu.

¹Saverio Cambioni,²Katherine de Kleer,³Michael Shepard
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2021JE007091]
¹Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
²Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
³Department of Environmental, Geographical & Geological Sciences, Bloomsburg University, Bloomsburg, PA, USA
Published by arrangement with John Wiley & Sons

Main-belt asteroid (16) Psyche is the largest M-type asteroid, a class of object classically thought to be the metal cores of differentiated planetesimals and the parent bodies of the iron meteorites. de Kleer, Cambioni, and Shepard (2021) presented new data from the Atacama Large Millimiter Array (ALMA), from which they derived a global best-fit thermal inertia and dielectric constant for Psyche, proxies for regolith particle size, porosity, and/or metal content, and observed thermal anomalies that could not be explained by surface albedo variations only. Motivated by this, here we fit a model to the same ALMA dataset that allows dielectric constant and thermal inertia to vary across the surface. We find that Psyche has a heterogeneous surface in both dielectric constant and thermal inertia but, intriguingly, we do not observe a direct correlation between these two properties over the surface. We explain the heterogeneity in dielectric constant as being due to variations in the relative abundance of metal and silicates. Furthermore, we observe that the lowlands of a large depression in Psyche’s shape have distinctly lower thermal inertia than the surrounding highlands. We propose that the latter could be explained by a thin mantle of fine regolith, fractured bedrock, and/or implanted silicate-rich materials covering an otherwise metal-rich surface. All these scenarios are indicative of a collisionally evolved world.

¹Aditi Pandey,²Monique Nguyen-Vu,¹Paul Schwab
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115096]
¹Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77843, United States of America
²Department of Biology, Texas A&M University, College Station, TX 77843, United States of America
Copyright Elsevier

Spectral data from satellite and rover missions on Mars identified significant abundances of amorphous phases in most samples analyzed, and SiO2 is the principal amorphous constituent in the Gale crater. Identifying and quantifying these short-range ordered, highly reactive phases is challenging but necessary to gain insight into the evolution of these materials. Terrestrial analogs are frequently employed to allow detailed analyses that cannot be performed on Martian samples. Historically, chemical extraction techniques have been extensively used to characterize amorphous materials in terrestrial soils, but most automated systems are complex, expensive, and limited to analyzing a single sample at one time. This study aims to develop a cost-effective apparatus that will allow latitude in choosing an extractant, process several samples simultaneously, enable rapid sampling over time without interruption and provide the resolution for quantitative differentiation of rapidly dissolving SiO2(a) phases in natural samples. Dissolution rates as a function of time were used as input for kinetic models to estimate the abundances of amorphous phases. When 2 M Na2CO3 is used as the extractant, dissolution rates differ significantly between secondary phases such as opal and primary glass phases. A stronger base, NaOH, is necessary for the complete dissolution of basaltic glass. Palagonitic tuffs from Iceland (proposed analogs of Martian soils) with >90% (w/w) amorphous composition were analyzed with 2 M Na2CO3 in the proposed apparatus, and both primary glass and secondary SiO2 appear to be present. Using the kinetic model of the dissolution, the palagonitic tuff has a composition of approximately 25% (w/w) of a rapidly reacting amorphous phase and 13% (w/w) of the slower reacting glass-like phase. The proposed high-efficiency analytical method can be applied to screen through multiple terrestrial analogs and archive dissolution kinetics of many standard amorphous minerals. Although this paper focuses on extracting SiO2 (a), the same setup can be applied to study time-based dissolution reactions using other extractants such as ammonium oxalate oxalic acid.

¹Yevgen Grynko,²Yuriy Shkuratov,¹Samer Alhaddad,¹Jens Förstner
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115099]
¹Department of Theoretical Electrical Engineering, Paderborn University, Warburger Str. 100, 33102 Paderborn, Germany
¹Institute of Astronomy of Kharkiv National University, Sumska Str. 35, 61022 Kharkiv, Ukraine
Copyright Elsevier

We model negative polarization, which is observed for planetary regoliths at backscattering, solving a full wave problem of light scattering with a numerically exact Discontinuous Galerkin Time Domain (DGTD) method. Pieces of layers with the bulk packing density of particles close to 0.5 are used. The model particles are highly absorbing and have irregular shapes and sizes larger than the wavelength of light. This represents a realistic analog of low-albedo planetary regoliths. Our simulations confirm coherent backscattering mechanism of the origin of negative polarization. We show that angular profiles of polarization are stabilized if the number of particles in a layer piece becomes larger than ten. This allows application of our approach to the negative polarization modeling for planetary regoliths.