¹L. Fimiani et al. (>10)*
¹Physik Department, Technische Universitat Munchen, D-85748 Garching, Germany
*Find the extensive, full author and affiliation list on the publishers website

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Reference
Fimani F et al. (2016) Interstellar Fe60 on the Surface of the Moon
Physical Review Letters 116, 151104
Link to Article [DOI:http://dx.doi.org/10.1103/PhysRevLett.116.151104]

¹Hannah H. Kaplan, ¹Ralph E. Milliken, ²David Fernández-Remolar, ³Ricardo Amils, ¹Kevin Robertson, ⁴Andrew H. Knoll
¹Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, 02912 USA
²British Geological Survey, Nicker Hill, Keyworth, NG12 5GG, UK
³Centro de Astrobiologia (INTA-CSIC), Ctra Ajalvir km 4, Torrejon de Ardoz, 28850, Spain
⁴Department of Organismic and Evolutionary Biology, Harvard University, Çambridge, MA, USA

Outcrops of hydrated minerals are widespread across the surface of Mars, with clay minerals and sulfates being commonly identified phases. Orbitally-based reflectance spectra are often used to classify these hydrated components in terms of a single mineralogy, although most surfaces likely contain multiple minerals that have the potential to record local geochemical conditions and processes. Reflectance spectra for previously identified deposits in Ius and Melas Chasma within the Valles Marineris, Mars, exhibit an enigmatic feature with two distinct absorptions between 2.2 – 2.3 µm. This spectral ‘doublet’ feature is proposed to result from a mixture of hydrated minerals, although the identity of the minerals has remained ambiguous. Here we demonstrate that similar spectral doublet features are observed in airborne, field, and laboratory reflectance spectra of rock and sediment samples from Rio Tinto, Spain. Combined visible-near infrared reflectance spectra and X-ray diffraction measurements of these samples reveals that the doublet feature arises from a mixture of Al-phyllosilicate (illite or muscovite) and jarosite. Analyses of orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) shows that the martian spectral equivalents are also consistent with mixtures of Al-phyllosilicates and jarosite, where the Al-phyllosilicate may also include kaolinite and/or halloysite. A case study for a region within Ius Chasma demonstrates that the relative proportions of the Al-phyllosilicate(s) and jarosite vary within one stratigraphic unit as well as between stratigraphic units. The former observation suggests that the jarosite may be a diagenetic (authigenic) product and thus indicative of local pH and redox conditions, whereas the latter observation may be consistent with variations in sediment flux and/or fluid chemistry during sediment deposition.

Reference
Kaplan HH, Milliken RE, Fernández-Remolar D, Amils R, Robertson K, Knoll AH (2016)
Orbital Evidence for Clay and Acidic Sulfate Assemblages on Mars Based on Mineralogical Analogs from Rio Tinto, Spain. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2016.03.019]
Copyright Elsevier

¹Hannah H. Kaplan, ¹Ralph E. Milliken, ²David Fernández-Remolar, ³Ricardo Amils, ¹Kevin Robertson, ⁴Andrew H. Knoll
¹Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, 02912 USA
²British Geological Survey, Nicker Hill, Keyworth, NG12 5GG, UK
³Centro de Astrobiologia (INTA-CSIC), Ctra Ajalvir km 4, Torrejon de Ardoz, 28850, Spain
⁴Department of Organismic and Evolutionary Biology, Harvard University, Çambridge, MA, USA

Outcrops of hydrated minerals are widespread across the surface of Mars, with clay minerals and sulfates being commonly identified phases. Orbitally-based reflectance spectra are often used to classify these hydrated components in terms of a single mineralogy, although most surfaces likely contain multiple minerals that have the potential to record local geochemical conditions and processes. Reflectance spectra for previously identified deposits in Ius and Melas Chasma within the Valles Marineris, Mars, exhibit an enigmatic feature with two distinct absorptions between 2.2 – 2.3 µm. This spectral ‘doublet’ feature is proposed to result from a mixture of hydrated minerals, although the identity of the minerals has remained ambiguous. Here we demonstrate that similar spectral doublet features are observed in airborne, field, and laboratory reflectance spectra of rock and sediment samples from Rio Tinto, Spain. Combined visible-near infrared reflectance spectra and X-ray diffraction measurements of these samples reveals that the doublet feature arises from a mixture of Al-phyllosilicate (illite or muscovite) and jarosite. Analyses of orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) shows that the martian spectral equivalents are also consistent with mixtures of Al-phyllosilicates and jarosite, where the Al-phyllosilicate may also include kaolinite and/or halloysite. A case study for a region within Ius Chasma demonstrates that the relative proportions of the Al-phyllosilicate(s) and jarosite vary within one stratigraphic unit as well as between stratigraphic units. The former observation suggests that the jarosite may be a diagenetic (authigenic) product and thus indicative of local pH and redox conditions, whereas the latter observation may be consistent with variations in sediment flux and/or fluid chemistry during sediment deposition.

Reference
Kaplan HH, Milliken RE, Fernández-Remolar D, Amils R, Robertson K, Knoll AH (2016)
Orbital Evidence for Clay and Acidic Sulfate Assemblages on Mars Based on Mineralogical Analogs from Rio Tinto, Spain. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2016.03.019]
Copyright Elsevier

¹Catherine M. Weitz,²Janice L. Bishop
¹Planetary Science Institute, Tucson, AZ
²SETI Institute, Mountain View, CA

We investigate the morphology, mineralogy, and stratigraphy of light-toned layered deposits within a trough of Coprates Catena, centered at -15°N, 300°E. One of the deposits in the eastern portion of the trough contains numerous hydrated minerals, including: Al-phyllosilicates, Fe/Mg-phyllosilicates, hydrated silica, hydrated sulfates, jarosite and acid alteration products characterized by a spectral doublet between 2.2-2.3 µm, and weakly hydrated materials. The Al-phyllosilicates are observed both stratigraphically above and below the Fe/Mg-phyllosilicate unit, which is a rare and perhaps unique association on Mars. Most of the western light-toned layered deposit underlies a terraced fan. This deposit contains hydrated materials, including Al-phyllosilicates and Fe/Mg-phyllosilicates. Dip measurements indicate both the eastern and western deposits dip towards the center of the trough, indicating they post-date formation of the trough and are consequently Late Hesperian or younger in age. Volcanic ash, most likely erupted during formation of the pit crater in the eastern portion of the trough, seems to best explain our observations for several of the units. Valleys sourced from water along the plateau may have flowed into the trough and altered the sediments, with changing aqueous chemistries over time resulting in the diverse range of mineralogies now observed in the eastern light-toned deposit. Our results reveal a complex sedimentary and aqueous history within the Coprates Catena trough, indicating that localized habitable conditions were possible relatively late in martian history at a time when colder, drier conditions likely dominated the majority of the planet.

Reference
Weitz CM, Bishop JL (2016) Stratigraphy and Formation of Clays, Sulfates, and Hydrated Silica within a Depression in Coprates Catena, Mars. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2015JE004954]
Published by arrangement with John Wiley & Sons

¹James J. Wray et al. (>10)*
¹School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
*Find the extensive, full author and affiliation list on the publishers website

Carbonates are key minerals for understanding ancient Martian environments because they are indicators of potentially habitable, neutral-to-alkaline water and may be an important reservoir for paleo-atmospheric CO₂. Previous remote sensing studies have identified mostly Mg-rich carbonates, both in Martian dust and in a Late Noachian rock unit circumferential to the Isidis basin. Here we report evidence for older Fe- and/or Ca-rich carbonates exposed from the subsurface by impact craters and troughs. These carbonates are found in and around the Huygens basin northwest of Hellas, in western Noachis Terra between Argyre basin and Valles Marineris, and in other isolated locations spread widely across the planet. In all cases they co-occur with or near phyllosilicates, and in Huygens basin specifically they occupy layered rocks exhumed from ~5 km depth. We discuss factors that might explain their observed regional distribution, arguments for why carbonates may be even more widespread in Noachian materials than presently appreciated, and what could be gained by targeting these carbonates for further study with future orbital or landed missions to Mars.

Reference
Wray JJ et al. (2016) Orbital evidence for more widespread carbonate-bearing rocks on Mars. Journal of Geophysical Research, Planets (in Press)
Link to Article [DOI: 10.1002/2015JE004972]
Published by arrangement with John Wiley & Sons

¹Danilo Di Genova, ¹Kai-Uwe Hess, ²Magdgdalena Oryaëlle Chevrel, ¹Donald B. Dingwell
¹Department Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Theresienstrasse 41/III, 80333 München, Germany
²Departamento de Vulcanología, Instituto de Geofísica, Universidad Nacional Autónoma de México, 04510, México D.F., Mexico

To develop Raman spectroscopy as a quantitative tool in both geosciences and planetary sciences the effect of iron oxidation state (Fe3+/Fetot) on the Raman spectra of basaltic and pantelleritic glasses has been investigated. We have used remelted pantellerite from Pantelleria Island and synthetic iron-rich basaltic glasses [from Chevrel et al. (2014)].
The Raman spectra of pantelleritic glasses reveal dramatic changes in the high wavelength region of the spectrum (800–1200 cm–1) as iron oxidation state changes. In particular the 970 cm–1 band intensity increases with increasing oxidation state of the glass (Fe3+/Fetot ratio from 0.24 to 0.83). In contrast, Raman spectra of the basaltic glasses do not show the same oxidation state sensitivity (Fe3+/Fetot ratio from 0.15 to 0.79). A shift, however, of the 950 cm–1 band to high wavenumber with decreasing iron oxidation state can be observed.
We present here two empirical parameterizations (for silica- and alkali-rich pantelleritic glasses and for iron-rich basaltic glasses) to enable estimation of the iron oxidation state of both anhydrous and hydrous silicate glasses (up to 2.4 wt% H2O). The validation of the models derived from these parameterizations have been obtained using the independent characterization of these melt samples plus a series of external samples via wet chemistry.
The “pantelleritic” model can be applied within SiO2, FeO, and alkali content ranges of ~69–75, ~7–9, and ~8–11 wt%, respectively. The “basaltic” model is valid within SiO2, FeO, and alkali content ranges of ~42–54, ~10–22, and ~3–6 wt%, respectively.
The results of this study contribute to the expansion of the compositionally dependent database previously presented by Di Genova et al. (2015) for Raman spectra of complex silicate glasses. The applications of these models range from microanalysis of silicate glasses (e.g., melt inclusions) to handheld in situ terrestrial field investigations and studies under extreme conditions such as extraterrestrial (i.e., Mars), volcanic, and submarine environments.

Reference
Di Genova D, Hess K-U, Chevrel MO, Dingwell DB (2016) Models for the estimation of Fe3+/Fetot ratio in terrestrial and extraterrestrial alkali- and iron-rich silicate glasses using Raman spectroscopy. American Mineralogist 101, 943–952
Link to Article [DOI: http://dx.doi.org/10.2138/am-2016-5534CCBYNCND]
Copyright: The Mineralogical Society of America

¹James J. Papike, ²Steven B. Simon, ¹Paul V. Burger,¹ Aaron S. Bell, ¹Charles K. Shearer, ³James M. Karner
¹Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A.
²Department of Geophysical Sciences, The University of Chicago, Chicago, Illinois 60637, U.S.A.
³Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University, Cleveland, Ohio 44106, U.S.A.

Pyroxene is arguably the most powerful, single-phase geochemical and petrologic recorder of Solar System processes, from nebular condensation through planetary evolution, over a wide range of temperatures, pressures, and fO2. It is an important mineral phase in the crusts and mantles of evolved planets, in undifferentiated and differentiated asteroids, and in refractory inclusions—the earliest Solar System materials. Here, we review the valence state partitioning behavior of Cr (Cr2+, Cr3+), Ti (Ti3+, Ti4+), and V (V2+, V3+, V4+, V5+) among crystallographic sites in pyroxene over a range of fO2 from approximately fayalite-magnetite-quartz (FMQ) to ~7 log units below iron-wüstite (IW-7), and decipher how pyroxene can be used as a recorder of conditions of planetary and nebular environments and planetary parentage. The most important crystallographic site in pyroxene with respect to its influence on mineral/melt partitioning is M2; its Ca content has a huge effect on partitioning behavior, because the large Ca cation expands the structure. As a result, distribution coefficients (Ds) for Cr and V increase with increasing Ca content from orthopyroxene to pigeonite to augite. In addition, it is noted that V3+ is favored over V4+ in olivine and pyroxene. In pyroxene in refractory inclusions, Ti3+ is favored over Ti4+ and incorporation of Ti is facilitated by the high availability of Al for coupled substitution. The most important results from analysis of pyroxene in martian meteorites (e.g., QUE 94201) are the oxygen fugacity estimates of IW+0.2 and IW+0.9 derived from partitioning and valence data for Cr and V, respectively, obtained from experiments using appropriate temperatures and melt compositions. In angrites, changes in V valence state may translate to changes in fO2, from IW-0.7 during early pyroxene crystallization, to IW+0.5 during later episodes of pyroxene crystallization. In addition to fO2, the partitioning behavior of Cr, V, and Ti between pyroxene and melt is also dependent upon availability of other cations, especially Al, for charge-balancing coupled substitutions.

Reference
Papike JJ, Simon SB, Burger PV, Bell AS, Shearer CK, Karner JM (2016) Chromium, vanadium, and titanium valence systematics in Solar System pyroxene as a recorder of oxygen fugacity, planetary provenance, and processes
American Mineralogist 101, 907-918.
Link to Article [doi:10.2138/am-2016-5507]
Copyright: The Mineralogical Society of America

¹Joshua L. Bandfield, ²Elena S. Amador
¹Space Science Institute
²Earth and Space Sciences, University of Washington, Seattle

Thermal Emission Imaging System (THEMIS) and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral datasets were used to identify high bulk SiO2 and hydrated compositions throughout the Nilosyrtis Mensae region. Four isolated locations were identified across the region showing short wavelength silicate absorptions within the 8–12 μm spectral region, indicating surfaces dominated by high Si phases. Much more extensive exposures of hydrated compositions are present throughout the region, indicated by a spectral absorption near 1.9 μm in CRISM data. Although limited in spatial coverage, detailed spectral observations indicate that the hydrated materials contain Fe/Mg-smectites and hydrated silica along with minor exposures of Mg-carbonates and an unidentified hydrated phase. The high SiO2 and hydrated materials are present in layered sediments near the base of topographic scarps at the hemispheric dichotomy boundary, typically near or within low albedo sand deposits. The source of the high SiO2 and hydrated materials appears to be from groundwater discharge from Nili Fossae and Syrtis Major to the south, where there is evidence for extensive aqueous alteration of the subsurface. Although discontinuous, the exposures of high SiO2 and hydrated materials span a wide area and are present in a similar geomorphological context to previously identified deposits in western Hellas Basin. These regional deposits may reflect aqueous conditions and alteration within the adjacent crust of the martian highlands.

Reference
Bandfield JL, Amador ES (2016) Extensive aqueous deposits at the base of the dichotomy boundary in Nilosyrtis Mensae, Mars. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2016.04.002]
Copyright Elsevier

¹Christopher M. Wright, ^1,2Tho Do Duy, ¹Warrick Lawson
¹School of Physical, Environmental and Mathematical Sciences, UNSW Canberra, PO Box 7916, Canberra BC 2610, Australia
²Department of Physics, International University – Vietnam National University HCM, Block 6, Linh Trung, Thu Duc, Ho Chi Minh City, Viet Nam

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Reference
Wright CM, Duy TD, Lawson W (2016) Absorption at 11 μm in the interstellar medium and embedded sources: evidence for crystalline silicates. Monthly Notices of the Royal Astronomical Society 457, 1593-1625.
Link to Article [doi:10.1093/mnras/stw041]

^1,2F. C. Pignatale, ²Kurt Liffman, ²Sarah T. Maddison, ³Geoffrey Brooks
¹Université de Lyon, Lyon, F-69003, France; Université Lyon 1, Observatoire de Lyon, 9 avenue Charles André, Saint-Genis Laval, F-69230, France CNRS, UMR 5574, Centre de Recherche Astrophysique de Lyon; Ecole Normale Supérieure de Lyon, F-69007, France
²Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia
³FSET, Swinburne University of Technology, Hawthorn, VIC 3122, Australia

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

Reference
Pignatale FC, Liffman K, Maddison ST, Brooks G (2016) 2D condensation model for the inner Solar Nebula: an enstatite-rich environment. Monthly Notices of the Royal Astronomical Society 457, 1359-1370
Link to Article [doi:10.1093/mnras/stv3003]