Petrology and geochemistry of lunar feldspathic meteorite Northwest Africa 11111: Insights into the lithology of the lunar farside highlands

1,2,3Xiaohui Fu,1Haijun Cao,1Jian Chen,1Xuting Hou,1,3Zongcheng Ling,4Lin Xu,4Yongliao Zou,2Chipui Tang,3,5Weibiao Hsu
Meteoritics & Planetary Science (in Press) Link to Article []
1Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai, Shandong, 264209 China
2State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau, China
3CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Nanjing, 210034 China
4State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, 100190 China
5CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Nanjing, 210034 China
Published by arrangement with John Wiley & Sons

We performed a petrological, mineralogical, and geochemical study of the lunar feldspathic meteorite Northwest Africa (NWA) 11111. This meteorite contains several types of lithic clasts, including feldspathic clasts, mafic-rich clasts, granulites, impact melt breccias, minor basaltic clasts, and highly evolved clasts cemented in a recrystallized fine grain matrix. Both mineral chemistry and geochemical characteristics indicate a lunar origin for NWA 11111. The bulk analysis suggests that NWA 11111 is a typical feldspathic lunar meteorite, which is consistent with its large population of anorthositic clasts and plagioclase fragments. A comparison of geochemical data made by lunar orbiter missions indicates that this meteorite was likely launched from the Feldspathic Highland Terrane on the lunar farside. The chemical zoning, coupled with extensive exsolution lamellae (up to 20 μm in width) occurring in pyroxene across three sections of NWA 11111, demonstrates that this meteorite contains components derived from the surface to about 10 km of lunar crust. Magnesian anorthosite clasts are commonly present in the meteorite, indicating that magnesian anorthosite probably represents an important lithology in the lunar farside crust. Basaltic clasts in NWA 11111 range from a very low-Ti to a low-Ti mare basalt, possibly representing cryptomare on the lunar farside. Although a KREEPy signature for NWA 11111 is not evident, highly evolved clasts containing various silica polymorphs and/or K-feldspar are present. They may originate from late-stage residual liquids. Lithic clasts and mineral fragments within NWA 11111 provide new insights into the diversity of lunar crust lithology and magmatic processes on the lunar farside. This meteorite also offers rocky materials from a wide vertical section of lunar crust.

An experimental study on oxygen isotope exchange reaction between CAI melt and low-pressure water vapor under simulated Solar nebular conditions

1Daiki Yamamoto,2Noriyuki Kawasaki,1,3Shogo Tachibana,3Michiru Kamibayashi,2Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-5210, Japan
2Department of Natural History Sciences, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
3UTokyo Organization for Planetary Space Science, The University of Tokyo, Hongo, Tokyo 113-0033, Japan
Copyright Elsevier

Calcium-aluminum-rich inclusions (CAIs) are known as the oldest high-temperature mineral assemblages of the Solar System. The CAIs record thermal events that occurred during the earliest epochs of the Solar System formation in the form of heterogeneous oxygen isotopic distributions between and within their constituent minerals. Here, we explored the kinetics of oxygen isotope exchange during partial melting events of CAIs by conducting oxygen isotope exchange experiments between type B CAI-like silicate melt and 18O-enriched water vapor (PH2O = 5 × 10–2 Pa) at 1420°C. We found that the oxygen isotope exchange between CAI melt and water vapor proceeds at competing rates with surface isotope exchange and self-diffusion of oxygen in the melt under the experimental conditions. The 18O concentration profiles were well fitted with the three-dimensional spherical diffusion model with a time-dependent surface concentration. We determined the self-diffusion coefficient of oxygen to be ∼1.62 × 10–11 m2 s–1, and the oxygen isotope exchange efficiency on the melt surface was found to be ∼0.28 in colliding water molecules. These kinetic parameters suggest that oxygen isotope exchange rate between cm-sized CAI melt droplets and water vapor is dominantly controlled by the supply of water molecules to the melt surface at PH2O <∼10–2 Pa and by self-diffusion of oxygen in the melt at PH2O >∼1 Pa at temperatures above the melilite liquidus (1420–1540°C). To form type B CAIs containing 16O-poor melilite by oxygen isotope exchange between CAI melt and disk water vapor, the CAIs should have been heated for at least a few days at PH2O >10–2 Pa above temperatures of the melilite liquidus in the protosolar disk. The larger timescale of oxygen isotopic equilibrium between CAI melt and H2O compared to that between H2O and CO in the gas phase suggests that the bulk oxygen isotopic compositions of ambient gas at ∼1400°C in the type B CAI-forming region is preserved in the oxygen isotopic compositions of type B CAI melilite. Based on the observed oxygen isotopic composition, we suggest that a typical type B1 CAI (TS34) from Allende was cooled at a rate of ∼0.1–0.5 K h–1 during fassaite crystallization.

Analysis of surface morphology of basaltic grains as environmental indicators for Mars

1,2,4Zs Kapui,2,3A.Kereszturi,4S.Józsa,5Cs Király,5Z.Szalai
Planetary and Space Science (in Press) Link to Article []
1Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungary
2Konkoly Thege Miklós Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Konkoly Observatory, Hungary
3European Astrobiology Institute, Strasbourg, France
4Eötvös Loránd University, Department of Petrology and Geology, Hungary
5Geographical Institute, Research Centre for Astronomy and Earth Sciences, Hungary

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Water uptake by chlorate salts under Mars-relevant conditions

1M.S.Fernanders et al. (>10)
Icarus (in Press) Link to Article []
1Cooperative Institute for Research in Environmental Sciences and Department of Chemistry, University of Colorado, Boulder, CO, USA
Copyright Elsevier

Chlorine is ubiquitous on Mars, some of it in the form of oxy-chlorine salts. Chlorine-containing salts have been found at several landing sites, including that of Phoenix and Curiosity, in the form of perchlorates and chlorides. Several intermediate states also exist, of which chlorate is the most stable. While perchlorates have received much attention in the past few years, chlorate salts are much less studied. The ratio of perchlorate to chlorate on Mars is not well-defined but may be approximately 1:1. Chlorate salts have similar properties to perchlorates: high solubility, low eutectic temperatures, and likely low deliquescence relative humidities. Laboratory studies were performed to determine the ability of sodium and magnesium chlorate salts to take up water vapor at low temperatures (296 K to 237 K). These studies were performed using a Raman microscope equipped with an environmental chamber and a single particle optical levitator equipped with a Raman spectrometer. The deliquescence of sodium chlorate (NaClO3) was found to be temperature-dependent with the average relative humidity (RH) values ranging from 68% RH at 296 K to 80% RH at 237 K. Additionally, there was a slight deviation between experimental deliquescence values for this salt and those predicted by equilibrium thermodynamics. The observed efflorescence (recrystallization) of NaClO3 occurred at lower RH values ranging from 18% RH at 264 K to 24% RH at 249 K, demonstrating the hysteresis common to salt recrystallization. Several experiments were performed below the reported eutectic temperature of NaClO3 which resulted in supercooling of the brine and depositional ice nucleation. Based on the supercooling effects observed during our experiments, a revised metastable eutectic temperature of 237 K is suggested for NaClO3 compared to the previously reported value of 252 K. Two phases of magnesium chlorate (Mg(ClO3)2) were observed and exhibited different water uptake behavior. The most common form of Mg(ClO3)2 appeared to be a hydrated, amorphous phase, Mg(ClO3)2 • X H2O(a) that continuously took up water when the RH was increased. This water uptake behavior was even observed at very low humidity values, 5.0 (±1.9)% RH, with little temperature dependence. This detectable water persisted down to RH values close to 0%, averaging 0.5 (±0.6)% RH with no visible temperature dependence. The deliquescence relative humidity (DRH) of the hexahydrate, Mg(ClO3)2 • 6 H2O, was found to range from 50.9 (± 7.5)% at 227 K to 55.8 (± 6.6)% at 224 K and was consistent with thermodynamic calculations. Under conditions measured by the Remote Environmental Monitoring Station (REMS) instrument at Gale Crater and conditions modeled in the shallow subsurface, magnesium chlorate, if present, likely interacts with water vapor during some diurnal cycles.

Measuring the atomic composition of planetary building blocks

1,2M. K. McClure,1C. Dominik,3,4M. Kama
Astronomy & Astrophysics 642, L15 Link to Article [DOI]
1Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
2Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
3Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
4Tartu Observatory, University of Tartu, Observatooriumi 1, Tõravere 61602, Estonia

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Chemical equilibrium in AGB atmospheres: successes, failures, and prospects for small molecules, clusters, and condensates

1M. Agúndez,2J. I. Martínez,2P. L. de Andres,1J. Cernicharo,2J. A. Martín-Gago
Astronomy & Astrophysics 637, A59 Link to Article [DOI]
1Instituto de Física Fundamental, CSIC, C/ Serrano 123, 28006 Madrid, Spain
2Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Spain

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Experimental constraints on the ordinary chondrite shock darkening caused by asteroid collisions

1T.Kohout et al. (>10)
Astronomy & Astrophysics 639, A146 Link to Article [DOI]
1Department of Geosciences and Geography, University of Helsinki, Finland
2Institute of Geology, The Czech Academy of Sciences, Czech Republic

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Detecting the surface composition of geological features on Europa and Ganymede using a surface dust analyzer

1William Goode,1Sascha Kempf,2,3Jürgen Schmidt
Icarus (in Press) Link to Article []
1LASP, University of Colorado, Boulder, CO, USA
2Institute of Geological Sciences, Freie Universität, Berlin, Germany
3Space Physics and Astronomy Research Unit, University of Oulu, Finland
Copyright Elsevier

Europa and Ganymede are both likely to have subsurface oceans (Carr et al., 1998; Khurana et al., 1998; Kivelson et al., 2000). Young surface features may provide an opportunity to sample material from either a subsurface ocean or bodies of liquid water near the surface (McCord et al., 1999, 2001). Detailed compositional information is of large interest for understanding the evolution, oceanic chemistry, and habitability of these moons. To develop an altitude-dependent model for the detectability of ejecta particle composition originating from surface features of a given size, we simulate detections by a dust analyzer with the capability of measuring compositional makeup on board a spacecraft performing close flybys of Europa and Ganymede (Postberg et al., 2011). We determine the origin of simulated detections of ejecta by backtracking their trajectories to the surface using velocity distributions given in the ejecta cloud model by Krivov et al. (2003). Our model is useful for designing flybys with typical closest approach altitudes, such as the ones planned for NASA’s Europa Clipper mission, where we wish to accurately identify the composition of surface features using a dust analyzer.</sup2,3<>

Warm dust surface chemistry in protoplanetary disks

1W. F. Thi,1,6S. Hocuk,2I. Kamp,3,7P. Woitke,2Ch. Rab,4S. Cazaux,1P. Caselli,5,2M. D’Angelo
Astronomy & Astrophysics 635, A16 Link to Article []
1Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, 85741 Garching, Germany
2Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands
3SUPA, School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK
4Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
5Zernike Institute for Advanced Materials, University of Groningen, PO Box 221, 9700 AE Groningen, The Netherlands
6CentERdata, Tilburg University, PO Box 90153, 5000 LE Tilburg, The Netherlands
7Centre for Exoplanet Science, University of St Andrews, St Andrews, UK

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