¹D.Ray, ¹S.Gosh, ²T.K.Goswami, ³M.J.Jobin
Geoscience Frontiers 8, 413-423 Link to Article [https://doi.org/10.1016/j.gsf.2016.02.005]
¹PLANEX, Physical Research Laboratory, Ahmedabad 380 009, India
²Department of Applied Geology, Dibrugarh University, Assam, India
³Department of Applied Geology, Pondicherry University, India

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^1,2,3Makiko K. Haba, ^2,4Akira Yamaguchi, ¹Hiroyuki Kagi, ^1,5Keisuke Nagao, ^6,7Hiroshi Hidaka
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2017.07.028]
¹Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
³Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Tokyo 152-8551, Japan
⁴Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo 190-8518, Japan
⁵Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 21990, South Korea
⁶Department of Earth and Planetary Systems Science, Hiroshima University, Higashi Hiroshima, Hiroshima 739-8526, Japan
⁷Department of Earth and Planetary Sciences, Nagoya University, Nagoya 464-8601, Japan
Copyright Elsevier

Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2 formed during a high-temperature reheating event, which is probably related to the metal-silicate mixing event. The weighted average 207Pb-206Pb age obtained by SIMS from both zircons is 4521 ± 26 Ma (2σ). This age is younger than that of a primary magmatic zircon from Vaca Muerta (4563 ± 15 Ma) and probably corresponds to the timing of the metal-silicate mixing event or a later impact event.

¹Danna Qasim, ¹Logan Vlasak, ¹Aaron Pital, ¹Thomas Beckman, ¹Nsamba Mutanda, ¹Heather Abbott-Lyon
The Journal of Physical Chemistry 121, 13645-13654 Link to Article [DOI: 10.1021/acs.jpcc.7b01312]
¹Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, Georgia 30144, United States

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¹Mona Weyrauch, ¹Martin Oeser, ¹Annika Brüske, ¹Stefan Weyer
Journal of Analytical Atomic Spectrometry 32, 1312-1319 Link to Article [DOI:10.1039/C7JA00147A]
¹Institut für Mineralogie, Leibniz Universität Hannover, Callinstraße 3, Germany

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¹Takehiko Arai,²Tomoki Nakamura,³Satoshi Tanaka,⁴Hirohide Demura,⁴Yoshiko Ogawa,⁵Naoya Sakatani,⁶Yamato Horikawa,⁷Hiroki Senshu,⁸Tetsuya Fukuhara,³Tatsuaki Okada
Space Science Reviews 208, 239-254 Link to Article [https://doi.org/10.1007/s11214-017-0353-9]
¹Center for Global Environmental Research, Satellite Observation Center National Institute for Environmental Studies (NIES)Tsukuba Japan
²Department of Earth Science Tohoku University Sendai Japan
³Institute of Space and Astronautical Science Japan Aerospace Exploration Agency (JAXA)Sagamihara Japan
⁴Research Center for Advanced Information Science and Technology The University of Aizu Aizu-Wakamatsu Japan
⁵Department of Physics, School of Science and Technology Meiji University Kawasaki Japan
⁶Department of Space and Astronautical Science, School of Physical Sciences Graduate University for Advanced Studies Sagamihara Japan
⁷Planetary Exploration Research Center Chiba Institute of Technology Narashino Japan
⁸College of Science Rikkyo University Nishi-Ikebukuro Japan

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^1,2Márta Polgári et al. (>10)*
Journal of Environmental Radioactivity 173, 58-69 Link to Article [doi.org/10.1016/j.jenvrad.2016.11.005]
¹Research Center for Astronomy and Geosciences, Geobiomineralization and Astrobiological Research Group, Institute for Geology and Geochemistry, Hungarian Academy of Sciences, 1112, Budapest, Budaörsi út. 45, Hungary
²Eszterházy Károly University, Dept. of Physical Geography and Geoinformatics, Leányka str. 6, 3300, Eger, Hungary
*Find the extensive, full author and affiliation list on the publishers website

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¹Leticia Gomez-Nubla, ¹Julene Aramendia, ¹Silvia Fdez-Ortiz de Vallejuelo, ²Ainhoa Alonso-Olazabal, ¹Kepa Castro, ²Maria Cruz Zuluaga, ²Luis Ángel Ortega,³Xabier Murelaga, ¹Juan Manuel Madariaga
Analytical and Bioanalytical Chemistry 409, 3597-3610 Link to Article [doi:10.1007/s00216-017-0299-5]
¹Department of Analytical Chemistry, Faculty of Science and Technology University of the Basque Country UPV/EHU Bilbao Spain
²Department of Mineralogy and Petrology, Faculty of Science and Technology University of the Basque Country UPV/EHU Bilbao Spain
³Departament of Stratigraphy and Palaeontology, Faculty of Science and Technolog yUniversity of the Basque Country UPV/EHU Bilbao Spain

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^1,2Mehmet Yesiltas, ^3,4Julia Sedlmair, ¹Robert E. Peale, ⁵Carol J. Hirschmugl
Applied Spectroscopy 711198-1208 Link to Article [DOI: https://doi.org/10.1177/0003702816671072]
¹Department of Physics, University of Central Florida, Orlando, Florida, USA
²Department of Geosciences, Stony Brook University, Stony Brook, New York, USA
³Forest Products Laboratory, US Department of Agriculture Forest Service, Madison, Wisconsin, USA
⁴Bruker AXS, Madison, Wisconsin, USA
⁵Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA

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¹Rahul Das Gupta, ¹Anupam Banerjee, ^2,3Steven Goderis, ²Philippe Claeys, ³Frank Vanhaecke, ¹Ramananda Chakrabarti
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2017.07.022]
¹Centre for Earth Sciences, Indian Institute of Science, Bangalore, India, 560012
²Vrije Universiteit Brussel, Analytical-, Environmental- & Geo-Chemistry, Pleinlaan 2 – 1050 Brussels -, Belgium
³Ghent University, Department of Analytical Chemistry, Campus Sterre, Krijgslaan, 281 – S12, 9000 Ghent, Belgium
Copyright Elsevier

he ∼1.88 km diameter Lonar impact crater formed ∼570 ka ago and is an almost circular depression hosted entirely in the Poladpur suite of the ∼65 Ma old basalts of the Deccan Traps. To understand the effects of impact cratering on basaltic targets, commonly found on the surfaces of inner Solar System planetary bodies, major and trace element concentrations as well as Nd and Sr isotopic compositions were determined on a suite of selected samples composed of: basalts, a red bole sample, which is a product of basalt alteration, impact breccia, and impact glasses, either in the form of spherules (< 1 mm in diameter) or non-spherical impact glasses (> 1 mm and < 1 cm). This data includes the first highly siderophile element concentrations for Lonar spherules. The chemical index of alteration (CIA) values (36.4-42.7) for the basalts and impact breccia are low while the red bole sample shows a high CIA value (55.6 in the acid-leached sample), consistent with its origin by aqueous alteration of the basalts. The Lonar spherules are classified into two main groups based on their CIA values. Most spherules show low CIA values (Group 1: 34.7-40.5) overlapping with the basalts and impact breccia, while seven spherules show significantly higher CIA values (Group 2: > 43.0). The Group 1 spherules are further subdivided into Groups 1a and 1b, with Group 1a spherules showing higher Ni and mostly higher Cr compared to the Group 1b spherules. Iridium and Cr concentrations of the spherules are consistent with the admixture of 1-8 wt% of a chondritic impactor to the basaltic target rocks. The impactor contribution is most prominent in the Group 1a and Group 2 spherules, which show higher Ni/Co, Ni/Cr and Cr/Co ratios compared to the target basalts. In contrast, the Group 1b spherules show major and trace element compositions that overlap with those of the impact breccia and are characterised by high EFTh (Enrichment Factor for Th defined as the Nb-normalized concentration of Th relative to that of the average basalt) as well as fractionated La/Sm(N), and higher large ion lithophile element (LILE) concentrations compared to the basalts. The relatively more radiogenic Sr and less radiogenic Nd isotopic composition of the impact breccia and non-spherical impact glasses compared to the target basalts are consistent with melting and mixing of the Precambrian basement beneath the Deccan basalt with up to 15 wt% contribution of the basement to these samples. Variations in the moderately siderophile element (MSE) concentration ratios of the impact breccia as well as all spherules are best explained by contributions from three components – a chondritic impactor, the basaltic target rocks at Lonar and the basement underlying the Deccan basalts. The large variations in concentrations of volatile elements like Zn and Cu and correlated variations of EFCu-EFZn, EFPb-EFZn, EFK-EFZn and EFNa-EFZn, particularly in the Group 1a spherules, are best explained by evaporation-condensation effects during impact. While most spherules, irrespective of their general major and trace element composition, show a loss in volatile elements (e.g., Zn and Cu) relative to the target basalts, some spherules, mainly of Group 1, display enrichments in these elements that are interpreted to reflect the unique preservation of volatile-rich vapor condensates resulting from geochemical fractionation in a vertical direction within the vapor cloud.

¹Alastair W. Tait, ¹Siobhan A. Wilson, ¹Andrew G. Tomkins, ²Emma J. Gagen, ³Stewart J. Fallon, ²Gordon Southam
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2017.07.025]
¹School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC 3800, Australia
²School of Earth Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia
³Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
Copyright Elsevier

Unambiguous identification of biosignatures on Mars requires access to well-characterized, long-lasting geochemical standards at the planet’s surface that can be modified by theoretical martian life. Ordinary chondrites, which are ancient meteorites that commonly fall to the surface of Mars and Earth, have well-characterized, narrow ranges in trace element and isotope geochemistry compared to martian rocks. Given that their mineralogy is more attractive to known chemolithotrophic life than the basaltic rocks that dominate the martian surface, exogenic rocks (e.g., chondritic meteorites) may be good places to look for signs of prior life endemic to Mars. In this study, we show that ordinary chondrites, collected from the arid Australian Nullarbor Plain, are commonly colonized and inhabited by terrestrial microorganisms that are endemic to this Mars analogue site. These terrestrial endolithic and chasmolithic microbial contaminants are commonly found in close association with hygroscopic veins of gypsum and Mg-calcite, which have formed within cracks penetrating deep into the meteorites. Terrestrial bacteria are observed within corrosion cavities, where troilite (FeS) oxidation has produced jarosite [KFe3(SO4)2(OH)6]. Where terrestrial microorganisms have colonized primary silicate minerals and secondary calcite, these mineral surfaces are heavily etched. Our results show that inhabitation of meteorites by terrestrial microorganisms in arid environments relies upon humidity and pH regulation by minerals. Furthermore, microbial colonization affects the weathering of meteorites and production of sulfate, carbonate, Fe-oxide and smectite minerals that can preserve chemical and isotopic biosignatures for thousands to millions of years on Earth. Meteorites are thus habitable by terrestrial microorganisms, even under highly desiccating environmental conditions of relevance to Mars. They may therefore be useful as chemical and isotopic “standards” that preserve evidence of life, thereby providing the possibility of universal context for recognition of microbial biosignatures on Earth, Mars and throughout the solar system.