¹Varun G. Paul,¹David J. Wronkiewicz, ²Melanie R. Mormile, ³Jamie S. Foster
¹Department of Geological Sciences, Missouri University of Science and Technology, Rolla, Missouri.
²Department of Biological Sciences, Missouri University of Science and Technology, Rolla, Missouri.
³Department of Microbiology and Cell Science, University of Florida, Space Life Science Lab, Merritt Island, Florida.

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

Reference
Paul VG, Wronkiewicz DJ, Mormile MR, Foster JS (2016) Mineralogy and Microbial Diversity of the Microbialites in the Hypersaline Storr’s Lake, the Bahamas. Astrobiology 16, 4 282-300
Link to Article [doi:10.1089/ast.2015.1326]

¹Jessica J. Barnes, ^1,2Romain Tartèse, ^1,3Mahesh Anand, ⁴Francis M. McCubbin, ⁵Clive R. Neal, ¹Ian A. Franchi
¹Planetary & Space Sciences, The Open University, Walton Hall, MK7 6AA, UK
²Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Muséum National d’Histoire Naturelle, Sorbonne Universités, CNRS, UPMC & IRD, 75005 Paris, France
³Earth Sciences department, Natural History Museum, London, SW7 5BD, UK
⁴NASA Johnson Space Center, Mailcode XI2, 2101 NASA Parkway, Houston, TX 77058, USA
⁵Department of Civil & Environmental Engineering & Earth Science, University of Notre Dame, IN 46556, USA

Current models for the Moon’s formation have yet to fully account for the thermal evolution of the Moon in the presence of H2O and other volatiles. Of particular importance is chlorine, since most lunar samples are characterised by unique heavy δ37Cl values, significantly deviating from those of other planetary materials, including Earth, for which δ37Cl values cluster around ∼0‰. In order to unravel the cause(s) of the Moon’s unique chlorine isotope signature, we performed a comprehensive study of high-precision in situ Cl isotope measurements of apatite from a suite of Apollo samples with a range of geochemical characteristics and petrologic types. The Cl-isotopic compositions measured in lunar apatite in the studied samples display a wide range of δ37Cl values (reaching a maximum value of +36‰), which are positively correlated with the amount of potassium (K), Rare Earth Element (REE) and phosphorous (P) (KREEP) component in each sample. Using these new data, integrated with existing H-isotope data obtained for the same samples, we are able to place these findings in the context of the canonical lunar magma ocean (LMO) model. The results are consistent with the urKREEP reservoir being characterised by a δ37Cl ∼+30‰. Such a heavy Cl isotope signature requires metal-chloride degassing from a Cl-enriched urKREEP LMO residue, a process likely to have been triggered by at least one large crust-breaching impact event that facilitated the transport and exposure of urKREEP liquid to the lunar surface.

Reference
Barnes JJ, Tartèse R, Anand M, McCubbin FM, Neal CR, Franchi IA (2016) Early degassing of lunar urKREEP by crust-breaching impact(s). Earth and Planetary Science Letters 447, 84–94
Link to Article [doi:10.1016/j.epsl.2016.04.036]
Copyright Elsevier

¹Janice L. Bishop, ²Elizabeth B. Rampe
¹SETI Institute, Carl Sagan Center, 189 Bernardo Ave., Mountain View, CA 94043, United States
²Aerodyne Industries, Jacobs-JETS at NASA JSC, Houston, TX 77058, United States

Layered outcrops in the Mawrth Vallis region of Mars contain the greatest diversity of aqueous alteration products on the planet, and these materials are used to infer past aqueous environments. Orbital investigations indicate Al/Si-rich clay-bearing units overly an Fe/Mg-smectite-rich unit. Many different secondary minerals have been identified in the upper Al/Si-rich clay units, but the presence of poorly crystalline phases has not been previously investigated. Identification of ∼10–30% allophane and imogolite in the clay-bearing units resolves previous mineralogical discrepancies between TES and CRISM of clay-bearing units on Mars. We demonstrate here that the poorly crystalline aluminosilicates allophane and imogolite comprise a significant portion of the uppermost stratum of the Al/Si-clay-rich units. These phases are unique to immature soils derived from volcanic ash in well-drained, mildly acidic environments on Earth, and we hypothesize that the deposits discovered here originate from supervolcanic activity in nearby Arabia Terra. The transition through time from smectite-bearing units to the uppermost allophane/imogolite unit in Mawrth Vallis signifies a change in climate from a warm and wet environment to one where water was sporadic and likely depleted rapidly.

Reference
Bishop JL, Rampe EB (2016) Evidence for a changing Martian climate from the mineralogy at Mawrth Vallis. Earth and Planetary Science Letters 448,42–48
Link to Article [doi:10.1016/j.epsl.2016.04.031]
Copyright Elsevier

¹Olivier Namur, ²Bernard Charlier, ¹Francois Holtz, ²Camille Cartier, ³Catherine McCammon
¹Leibniz University of Hannover, Institute of Mineralogy, 30167 Hannover, Germany
²University of Liege, Department of Geology, 4000 Liege, Belgium
³Bayerisches Geoinstitut, University of Bayreuth, 95440 Bayreuth, Germany

Chemical data from the MESSENGER spacecraft revealed that surface rocks on Mercury are unusually enriched in sulfur compared to samples from other terrestrial planets. In order to understand the speciation and distribution of sulfur on Mercury, we performed high temperature (1200–1750 °C), low- to high-pressure (1 bar to 4 GPa) experiments on compositions representative of Mercurian lavas and on the silicate composition of an enstatite chondrite. We equilibrated silicate melts with sulfide and metallic melts under highly reducing conditions (IW-1.5 to IW-9.4; IW = iron-wüstite oxygen fugacity buffer). Under these oxygen fugacity conditions, sulfur dissolves in the silicate melt as S2−S2− and forms complexes with Fe2+Fe2+, Mg2+Mg2+ and Ca2+Ca2+. The sulfur concentration in silicate melts at sulfide saturation (SCSS) increases with increasing reducing conditions (from 10 wt.% S at IW-8) and with increasing temperature. Metallic melts have a low sulfur content which decreases from 3 wt.% at IW-2 to 0 wt.% at IW-9. We developed an empirical parameterization to predict SCSS in Mercurian magmas as a function of oxygen fugacity (fO2fO2), temperature, pressure and silicate melt composition. SCSS being not strictly a redox reaction, our expression is fully valid for magmatic systems containing a metal phase. Using physical constraints of the Mercurian mantle and magmas as well as our experimental results, we suggest that basalts on Mercury were free of sulfide globules when they erupted. The high sulfur contents revealed by MESSENGER result from the high sulfur solubility in silicate melt at reducing conditions. We make the realistic assumption that the oxygen fugacity of mantle rocks was set during equilibration of the magma ocean with the core and/or that the mantle contains a minor metal phase and combine our parameterization of SCSS with chemical data from MESSENGER to constrain the oxygen fugacity of Mercury’s interior to IW-5.4±0.45.4±0.4. We also calculate that the mantle of Mercury contains 7–11 wt.% S and that the metallic core of the planet has little sulfur (

Reference
Namur O, Charlier B,Holtz F, Cartier C, McCammon C (2016) Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury. Earth and Planetary Science Letters 448,102–114.
Link to Article [doi:10.1016/j.epsl.2016.05.024]
Copyright Elsevier

¹Derek W.G. Sears
¹Bay Area Environmental Research Institute, NASA Ames Research Center, Space Science and Astrobiology Division (MS 245-3), Mountain View, California 94035, U.S.

Thermoluminescence (TL) properties of 29 CO chondrites from the Miller Range (MIL) and five chondrites from the Dominion Range (DOM) have been measured. MIL has a relatively strong natural TL signal (19.6±14.7 krad), while some of the DOM samples have a very weak natural TL signal ( The CO chondrites: Major Recent Antarctic finds, Their Thermal and Radiation History, and Describing the Metamorphic History of Members of the Class 19.6±14.7 krad), while some of the DOM samples have a very weak natural TL signal (<1 krad) whereas others resemble the MIL meteorites. We argue that MIL and some of the DOM samples had a normal perihelion (∼1.0 AU) and terrestrial age of ∼450-700 ka, while some of the DOM samples have a terrestrial age of ∼100 ka but a perihelion of ∼0.8 AU. The DOM meteorites also show considerable heterogeneity in their induced TL properties, also suggesting that the DOM fragments represent more than one fall. The induced TL data for the MIL samples studied here are consistent with them all being from a single fragmented meteorite. Small (50 mg) chips have TL properties similar to 500 mg chips, so that the smaller chips are representative, although samples taken from original masses less than ∼2 g have low natural TL suggesting that they were heated during atmospheric fall. The properties of CO chondrites are reviewed in terms of their petrologic types. Correlations between TL sensitivity, the most quantitative technique for evaluating metamorphic alteration in CO chondrites, and data for olivine composition and heterogeneity, matrix composition, inert gas content, metal composition (Ni, Co, and Cr in the kamacite), bulk carbon, C and O isotopes, graphite ordering, spectral reflectance at 0.8 μm, and textural characteristics of the amoeboid olivine and Ca-rich inclusions are examined. The petrographic types appear to be largely metamorphic in origin with perhaps a minor role for metasomatism. Contrary to recent proposals it is here argued that petrologic type definitions should (1) be specific enough to be meaningful, but broad enough to be simple in application and robust to new developments, (2) be descriptive and not interpretative, (3) should not oversimplify and obscure important class-to-class differences, and (4) take account of all the available information, while avoiding reliance on any one technique or single observation whose application is based on interpretation. With these considerations in mind the petrographic type definitions for CO chondrites are restated and the petrologic type of 3.2 assigned to both the MIL and DOM CO chondrites.

Reference
Sears WG (2106) The CO chondrites: Major Recent Antarctic finds, Their Thermal and Radiation History, and Describing the Metamorphic History of Members of the Class.
Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2016.05.033]
Copyright Elsevier

¹Mridusmita Buragohaina, ¹Amit Pathaka, ²Peter Sarreb, ³Takashi Onakac, ³Itsuki Sakonc
¹Department of Physics, Tezpur University, Tezpur 784028, India
²School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
³Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan

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

Reference
Buragohain M,Pathak A,Sarre P,Onaka T,Sakon I (2016) Mid-infrared vibrational study of deuterium-containing PAH variants. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2016.05.001]

^1,2Yuichiro Cho, ¹Seiji Sugita, ³Yayoi N. Miura, ⁴Ryuji Okazaki, ⁵Naoyoshi Iwata, ⁶Tomokatsu Morota,¹ Shingo Kameda
¹Department of Earth and Planetary Science, University of Tokyo, 7−3−1 Hongo, Bunkyo-ku, Tokyo 113−0033, Japan
²Department of Physics, Rikkyo University, 3−34−1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171−8501, Japan
³Earthquake Research Institute, University of Tokyo, 1−1−1 Yayoi, Bunkyo-ku, Tokyo 113−0032, Japan
⁴Department of Earth and Planetary Sciences, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819−0395, Japan
⁵Department of Earth and Environmental Sciences, Yamagata University, 1–4–12 Kojirakawa, Yamagata 990–8560, Japan
⁶Department of Earth and Environmental Sciences, Nagoya University, Furo, Chikusa, Nagoya, 464−8601, Japan

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

Reference
Cho Y, Sugita S, Miura YN, Okazaki R, Iwata N, Morota T, Kameda S (2016) An in-situ K-Ar isochron dating method for planetary landers using a spot-by-spot laser-ablation technique. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2016.05.004]

^1,2,3Katharine L. Robinson, ^4,5Jessica J. Barnes, ¹Kazuhide Nagashima, ¹Aurélien Thomen, ⁵Ian A. Franchi, ^1,2,3Gary R. Huss, ^4,5Mahesh Anand, ^1,2,3G. Jeffrey Taylor
¹Hawaii Institute of Geophysics and Planetology, 1680 East-West Rd. POST 602, Honolulu, HI 96822, USA
²University of Hawaii NASA Astrobiology Institute, Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, Hawaii 96822-1839, USA
³Geology and Geophysics, University of Hawaii at Manoa, 1680 East-West Rd. POST 602, Honolulu, HI 96822, USA
⁴Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
⁵Department of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK

We have measured the abundance and isotopic composition of water in apatites from several lunar rocks representing Potassium (K), Rare Earth Elements (REE), and Phosphorus (P) – KREEP – rich lithologies, including felsites, quartz monzodiorites (QMDs), a troctolite, and alkali anorthosite. The H-isotope data from apatite provide evidence for multiple reservoirs in the lunar interior. Apatite measurements from some KREEP-rich intrusive rocks display moderately elevated δD signatures, while other samples show δD signatures similar to the range known for the terrestrial upper mantle. Apatite grains in Apollo 15 quartz monzodiorites have the lowest δD values measured from the Moon so far (as low as – 749 ‰), and could potentially represent a D-depleted reservoir in the lunar interior that had not been identified until now. Apatite in all of these intrusive rocks contains < 267 ppm H2O, which is relatively low compared to apatites from the majority of studied mare basalts (200 to > 6500 ppm H2O). Complexities in partitioning of volatiles into apatite make this comparison uncertain, but measurements of residual glass in KREEP basalt fragments in breccia 15358 independently show that the KREEP basaltic magmas were low in water. The source of 15358 contained ∼ 10 ppm H2O, about an order of magnitude lower than the source of the Apollo 17 pyroclastic glass beads, suggesting potential variations in the distribution of water in the lunar interior.

Reference
Robinson KL, Barnes JJ, Nagashima K, Thomen A, Franchi IA, Huss GR, Anand M, Taylor GJ (2016) Water in evolved lunar rocks: Evidence for multiple reservoirs. Geochimica et Cosmochmica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2016.05.030]
Copyright Elsevier

¹Daniela Comelli et al. (>10*)
¹Dipartimento di Fisica, Politecnico di Milano, Milano, Italy
*Find the extensive, full author and affiliation list on the publishers website

Scholars have long discussed the introduction and spread of iron metallurgy in different civilizations. The sporadic use of iron has been reported in the Eastern Mediterranean area from the late Neolithic period to the Bronze Age. Despite the rare existence of smelted iron, it is generally assumed that early iron objects were produced from meteoritic iron. Nevertheless, the methods of working the metal, its use, and diffusion are contentious issues compromised by lack of detailed analysis. Since its discovery in 1925, the meteoritic origin of the iron dagger blade from the sarcophagus of the ancient Egyptian King Tutankhamun (14th C. BCE) has been the subject of debate and previous analyses yielded controversial results. We show that the composition of the blade (Fe plus 10.8 wt% Ni and 0.58 wt% Co), accurately determined through portable x-ray fluorescence spectrometry, strongly supports its meteoritic origin. In agreement with recent results of metallographic analysis of ancient iron artifacts from Gerzeh, our study confirms that ancient Egyptians attributed great value to meteoritic iron for the production of precious objects. Moreover, the high manufacturing quality of Tutankhamun’s dagger blade, in comparison with other simple-shaped meteoritic iron artifacts, suggests a significant mastery of ironworking in Tutankhamun’s time.

Reference
Comelli D et al. (2016) The meteoritic origin of Tutankhamun’s iron dagger blade. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12664]
Published by arrangement with John Wiley & Sons

¹Richard W. Court, ¹Jonathan Tan
¹Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College, London, UK

Ablation of micrometeoroids during atmospheric entry yields volatile gases such as water, carbon dioxide, and sulfur dioxide, capable of altering atmospheric chemistry and hence the climate and habitability of the planetary surface. While laboratory experiments have revealed the yields of these gases during laboratory simulations of ablation, the reactions responsible for the generation of these gases have remained unclear, with a typical assumption being that species simply undergo thermal decomposition without engaging in more complex chemistry. Here, pyrolysis–Fourier transform infrared spectroscopy reveals that mixtures of meteorite-relevant materials undergo secondary reactions during simulated ablation, with organic matter capable of taking part in carbothermic reduction of iron oxides and sulfates, resulting in yields of volatile gases that differ from those predicted by simple thermal decomposition. Sulfates are most susceptible to carbothermic reduction, producing greater yields of sulfur dioxide and carbon dioxide at lower temperatures than would be expected from simple thermal decomposition, even when mixed with meteoritically relevant abundances of low-reactivity Type IV kerogen. Iron oxides were less susceptible, with elevated yields of water, carbon dioxide, and carbon monoxide only occurring when mixed with high abundances of more reactive Type III kerogen. We use these insights to reinterpret previous ablation simulation experiments and to predict the reactions capable of occurring during ablation of carbonaceous micrometeoroids in atmospheres of different compositions.

Reference
Court RW, Tan J (2016) Insights into secondary reactions occurring during atmospheric ablation of micrometeoroids. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12652]
Published by arrangement with John Wiley & Sons