¹Oshtrakh, M.I.,¹Maksimova, A.A.,¹Chukin, A.V., Petrova,¹E.V.,²Jenniskens, P.,³Kuzmann, E.,¹Grokhovsky, V.I.,³Homonnay, Z.,¹Semionkin, V.A.
Spectrochimica Acta – Part A: Molecular and Biomolecular Spectroscopy 219, 206-224 Link to Article [DOI: 10.1016/j.saa.2019.03.036]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
²SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043, United States
³Institute of Chemistry, Eötvös Loránd University, Pázmány sétány 1/A, Budapest, 1117, Hungary

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¹A.H.Peslier,² R.Hervig,³S.Yang,³M.Humayun,^4,5J.J.Barnes,⁶A.J.Irving,⁷A.D.Brandon
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.04.023]
¹Jacobs, NASA-Johnson Space Center, Mail Code X13, Houston TX 77058, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
³National High Magnetic Field Lab, Florida State University, Tallahassee, FL 32310, USA
⁴ARES, NASA-Johnson Space Center, Houston, TX 77058, USA
⁵Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
⁶Dept. of Earth & Space Sciences, University of Washington, Seattle, WA, USA
⁷Dept. of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, USA
Copyright Elsevier

Knowing the distribution and origin of water in terrestrial planets is crucial to understand their formation, evolution and the source of their atmospheres and surface water. The nakhlites represent a suite of minimally shocked meteorites that likely originated from lava flows from a single volcano or from a shallow intrusion or sill complex on Mars. Measuring the water contents and D/H ratios of their igneous minerals allows identification of phases that have preserved their magmatic hydrogen, and therefrom permits estimation of the water content of their mantle source. Pyroxene, olivine, melt inclusions and mesostasis of five nakhlites (NWA 998, Nakhla, Y 000593, MIL 03346 and NWA 6148) were analyzed in situ for water contents and H isotopes, and major and trace element contents. No water was detected in olivine grains except in Y 000593. The water content of pyroxenes is highly heterogeneous within individual grains and between grains within a single meteorite. Water concentrations in pyroxene (<0.1-387 ppm H2O), melt inclusions (26-4130 ppm H2O) and mesostasis (1130-7850 ppm H2O) decrease with increasing δD (from -268 to 4858 ‰) in all nakhlites. After ruling out significant influence from spallation, exchange with the martian atmosphere, shock, surface alteration, and hydrothermal processes, the H data of the pyroxenes can be explained by degassing and crystallization processes. Degassing is consistent with a decrease of water content from pyroxene interior to edge. Fractionation of H isotopes during degassing results in increases of δD during H loss from pyroxene but in decreases in δD during H2O-OH loss from a melt. Consequently, the low-water content, high-δD of most pyroxenes is best explained by degassing after the pyroxenes had crystallized. All melt and plagioclase inclusions analyzed are located in degassed pyroxenes and are also degassed. The lower δD of the mesostasis (24 ± 131 ‰) compared to that of the least-degassed pyroxenes (430 ± 172 ‰) is likely the result of melt degassing and interaction with hydrothermal fluids. Magmatic H, however, has been preserved in each nakhlite in some pyroxenes that are characterized by > 15 ppm H2O and δD < 700‰. The H composition of the least-degassed, most-Mg-rich augites can be interpreted in two ways. If Cl-bearing hydrothermal fluids were assimilated by the parent magma of nakhlites prior to pyroxene crystallization, the H composition could represent a crustal signature. If hydrothermal fluid assimilation occurred after pyroxenes start crystallizing, it could be a mantle signature. We favor the latter scenario, in which case the martian mantle sampled by the nakhlites is estimated to contain 59-184 ppm H2O and to have a δD of 430 ± 172 ‰. These water contents, similar to those of the upper part of the terrestrial mantle, represent those of a shallow depleted martian mantle reservoir. The two to four times higher δD of the martian mantle relative to that of Earth could have resulted from the two planets acquiring their water from different proportions and types of carbonaceous chondrite-like planetesimals.

^1,2Natsuki Hosono,³Shun-ichiro Karato,^2,4Junichiro Makino,^4,5Takayuki R. Saitoh
Nature Geoscience (in Press) Link to Article [https://doi.org/10.1038/s41561-019-0354-2]
¹Yokohama Institute for Earth Sciences, Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa, Japan
²RIKEN Center for Computational Science, Kobe, Hyogo, Japan
³Department of Geology and Geophysics, Yale University, New Haven, CT, USA
⁴Department of Planetology, Kobe University, Kobe, Hyogo, Japan
⁵Earth-Life Science Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan

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¹Luca Bindi,²Frank E. Brenker,³Fabrizio Nestola,²Tamara E. Koch,⁴David J. Prior,⁴Kat Lilly,⁵Alexander N. Krot,⁶Martin Bizzarro,^7,8Xiande Xie
American Mineralogist 104, 775-778 Link to Article [http://www.minsocam.org/MSA/AmMin/TOC/2019/index.html?issue_number=05]
¹Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira 4, I-50121 Firenze, Italy
²Goethe University Frankfurt, NanoGeoscience, Altenhoeferallee 1, 60438 Frankfurt, Germany
³Dipartimento di Geoscienze, Università di Padova, Via Gradenigo, 6, 35131 Padova, Italy
⁴University of Otago, Department of Geology, Dunedin 9054, New Zealand
⁵University of Hawaii at Mānoa, Hawaii Institute of Geophysics and Planetology, 1680 East-West Road, Honolulu, Hawaii 96822, U.S.A.
⁶StarPlan—Centre for Star and Planet Formation, Natural History Museum of Denmark University of Copenhagen, Øster Voldgade 5-7, DK-1350,
Copenhagen, Denmark
⁷Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
⁸Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou 510640, China
Copyright: The Mineralogical Society of America

¹Andrew S. Rivkin,²Ellen S. Howell,³Joshua P. Emery
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2018JE005833]
¹Johns Hopkins University Applied Physics Laboratory
²University of Arizona
³University of Tennessee
Published by arrangement with John Wiley & Sons

Low‐albedo, hydrated objects dominate the list of the largest asteroids. These objects have varied spectral shapes in the 3‐μm region, where diagnostic absorptions due to volatile species are found. Dawn’s visit to Ceres has extended the view shaped by ground‐based observing, and shown that world to be a complex one, potentially still experiencing geological activity.

We present 33 observations from 2.2‐4.0 μm of eight large (D > 200 km) asteroids from the C spectral complex, with spectra inconsistent with the hydrated minerals we see in meteorites. We characterize their absorption band characteristics via polynomial and Gaussian fits to test their spectral similarity to Ceres, the asteroid 24 Themis (thought to be covered in ice frost), and the asteroid 51 Nemausa (spectrally similar to the CM meteorites). We confirm most of the observations are inconsistent with what is seen in meteorites and require additional absorbers. We find clusters in band centers that correspond to Ceres‐ and Themis‐like spectra, but no hiatus in the distribution suitable for use to simply distinguish between them. We also find a range of band centers in the spectra that approaches what is seen on Comet 67P. Finally, variation is seen between observations for some objects, with the variation on 324 Bamberga consistent with hemispheric‐level difference in composition. Given the ubiquity of objects with 3‐μm spectra unlike what we see in meteorites, and the similarity of those spectra to the published spectra of Ceres and Themis, these objects appear much more to be archetypes than outliers.

^1,2Natsumi Noda,^1,2Shoko Imamura,¹Yasuhito Sekine, ²Minako Kurisu,³Keisuke Fukushi,⁴Naoki Terada,²Soichiro Uesugi,⁵Chiya Numako,²Yoshio Takahashi,⁶Jens Hartmann
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2018JE005892]
¹Earth‐Life Science Institute, Tokyo Institute of Technology
²Department of Earth and Planetary Science, University of Tokyo
³Institute of Nature and Environmental Technology, Kanazawa University
⁴Department of Geophysics, Tohoku University
⁵Graduate School of Science, Chiba University
⁶Institute for Geology, Center for Earth System Research and Sustainability, Universität Hamburg
Published by arrangement with John Wiley & Sons

The Curiosity and Opportunity rovers have found depositions of manganese (Mn) (hydr)oxides within the veins of the sedimentary rocks at Gale and Endeavour craters. Since Mn is a redox sensitive element, revealing the chemical form of the Mn (hydr)oxide provides unique information on the redox state of the near‐surface/groundwater at the time of deposition. Here, we report results of laboratory experiments that investigated scavenging patterns of trace metals (zinc, nickel, and chromium) on different Mn (hydr)oxides in order to constrain the chemical form of the Mn precipitates found on Mars. Our results show manganese dioxide (MnO2) scavenges zinc and nickel effectively but not for chromium. The agreement of this scavenging pattern with the observations strongly suggests that the Mn (hydr)oxides found on Mars are highly likely to be MnO2. To form MnO2, oxidizing aqueous environments are required (e.g., Eh > 0.5 V at pH ~ 8). The candidates of the oxidant include molecular oxygen, ozone, nitrates, and perchlorate acids; all of which are considered to be produced by photochemical processes. The presence of MnO2 veins in sediments suggests that such atmospheric high‐Eh oxidants may have been supplied to the subsurface, possibly through hydrological cycles activated by transient warming.

^1,2Agata M. Krzesińska,³Richard Wirth,^3,4Monika A. Kusiak
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13296]
¹Centre for Earth Evolution and Dynamics, Department of Geosciences, University of Oslo, Oslo, Norway
²Department of Earth Sciences, Natural History Museum, Cromwell Road, SW7 5BD London, UK
³GeoForschungsZentrum Potsdam, Section 3.5 Surface Geochemistry, D‐14473 Potsdam, Germany
⁴Institute of Geological Sciences Polish Academy of Sciences, ING PAN, Twarda 51/55, PL‐00818 Warszawa, Poland
Published by arrangement with John Wiley & Sons

Zakłodzie is an enstatite meteorite of unknown petrogenesis. Chemically, it resembles enstatite chondrites, but displays an achondrite‐like texture. Here we report on fabric and texture analyses of Zakłodzie utilizing X‐ray computed tomography and scanning electron microscopy and combine it with a nanostructural study of striated pyroxene by transmission electron microscopy. With this approach we identify mechanisms that led to formation of the texture and address the petrogenesis of the rock. Zakłodzie experienced a shock event in its early evolution while located at some depth inside a warm parent body. Shock‐related strain inverted pyroxene to the observed mixture of intercalated orthorhombic and monoclinic polymorphs. The heat that dissipated after the peak shock was added to primary, radiogenic‐derived heat and led to a prolonged thermal event. This caused local, equilibrium‐based partial melting of plagioclase and metal‐sulfide. Partial melting was followed by two‐stage cooling. The first phase of annealing (above 500 °C) allowed for crystallization of plagioclase and for textural equilibration of metal and sulfides with silicates. Below 500 °C, cooling was faster and more heterogeneous at cm scale, allowing retention of keilite and quenching of K‐rich feldspathic glass in some parts. Our study indicates that Zakłodzie is neither an impact melt rock nor a primitive achondrite, as suggested in former studies. An impact melt origin is excluded because enstatite in Zakłodzie was never completely melted and partial melting occurred during equilibrium‐based postshock conditions. Texturally, the rock represents a transition of chondrite and achondrite and was formed when early impact heat was added to internal radiogenic heat.

¹M. Szokaluk,¹R. Jagodziński,¹A. Muszyński,¹W. Szczuciński
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13290]
¹Institute of Geology, Adam Mickiewicz University in Poznań, Bogumiła Krygowskiego 12, 61‐680 Poznań, Poland
Published by arrangement with John Wiley & Sons

Confirmed small impact craters in unconsolidated deposits are rare on Earth, and only a few have been the subjects of detailed investigations. Consequently, our knowledge of indicators permitting unambiguous identification of such structures is limited. In this work, detailed geological mapping was performed in the area of the Morasko craters, of which the largest crater is of about 96 m diameter. These craters were formed in the mid‐Holocene (~5000 yr ago) in unconsolidated sediments of a glacial terminal moraine. Fragments of the impactor—an iron meteorite—have been found in the craters’ vicinity for many decades. Despite numerous studies of the meteorite, no detailed research concerning the geological structure around the craters and of the ejecta deposits has been undertaken. The new data, including evaluation of over 52 sediment cores and 260 shallow drillings, permit the identification of four main sediment types: Neogene clays, diamicton with Neogene clay clasts containing charcoal pieces, diamicton without clasts, and sand with locally preserved paleosoil and charcoal pieces. Based on sedimentological properties, the ejecta deposits are mainly identified as diamicton with Neogene clay clasts, described as lithic impact breccia, covering locally preserved pre‐impact soil. Moreover, crater sections characterized by inverse stratigraphy of sediments are identified as belonging to overturned flaps.

¹Javier Cuadros,¹Christian Mavris,²Joseph R.Michalski,³Jose Miguel Nieto,⁴Janice L.Bishop,⁵Saverio Fiore
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.04.027]
¹Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
²Department of Earth Sciences, Laboratory for Space Research, University of Hong Kong, Pokfulam Road, Hong Kong, China
³Department of Earth Sciences, University of Huelva, 21071 Huelva, Spain
⁴SETI Institute, Mountain View, CA 94043, USA
⁵Institute of Methodologies for Environmental Analysis, CNR, Department of Geoenvironmental and Earth Sciences, University of Bari, Via Orabona 4, 70125 Bari, Italy
Copyright Elsevier

Investigation of Earth analogs and their environments is crucial for the full interpretation of geologic outcrops and processes on Mars. Phyllosilicates are important indicators of aqueous processes and their characterization is a significant piece of the geologic puzzle of Mars. They are chiefly investigated with Near-Infrared (NIR) spectroscopy from orbit. While these studies have revolutionized our understanding of aqueous processes on Mars, they are challenged by the chemical and structural complexity of phyllosilicates, non-linear response to mineral abundance, low penetration of infrared radiation in the target rocks, and spectral modifications caused by rock texture. Phyllosilicate-bearing samples from four locations in the Iberian Pyrite Belt (El Villar, Calañas, Quebrantahuesos, and Tharsis) were investigated using NIR, XRD and thermogravimetry in order to document the effects of acidic alteration under multiple environments and inform orbital detections on Mars. The samples are comprised of chlorite, illite, kaolinite, alunite, jarosite, goethite and interstratified chlorite-vermiculite and kaolinite-smectite. Kaolinite dominates the spectral signature relative to other phyllosilicates from abundances as low as 7 wt%. Only alunite and jarosite display spectral intensities similar to kaolinite. NIR spectra of bulk rock and <2 μm size fractions are very similar, indicating that spectra are dominated by the smaller particles. The octahedral Al-Fe-Mg composition of illite and kaolinite determine the positions of their OH combination band (~2.21 μm), commonly used for phyllosilicate characterization. The range of wavelength variation is narrower for kaolinite-dominated spectra, 2.205–2.216 μm, but wider than the spectral resolution of the orbital probe CRISM (~0.007 μm). Thus, in favorable conditions CRISM spectra can identify variations of kaolinite octahedral composition, a valuable tool to investigate kaolinite origin. A survey of kaolinite-bearing spectra from Mars (Leighton Crater, Mawrth Vallis and Nili Fossae regions) showed that most OH combination bands are within 2.205–2.212 μm. One spectrum displayed this band at 2.215–2.219 μm, and is a good candidate for kaolinite with significant Fe/Mg-substitution.

^1,2Philip R. Heck et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13291]
¹Robert A. Pritzker Center for Meteoritics and Polar Studies, Field Museum of Natural History, 1400 S Lake Shore Dr, Chicago, Illinois, 60605 USA
²Chicago Center for Cosmochemistry & Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA
Published by arrangement with John Wiley & Sons

This document contains suggestions for best practices by authors who refer to meteorites in publications. It can also be taken as a guide for publishers in establishing guidelines for authors. The following best practices are recommended in addition to acknowledging the loaning institution or loaning individual (unless required otherwise). The main motivations are to: help ensure that research on meteorites is reproducible, prevent confusion in the literature, and enhance tracking of specimens and related data.