¹M. Hässig et al. (>10)*
¹Southwest Research Institute, Space Science and Engineering, 6220 Culebra Rd., San Antonio, TX 78238, USA
*Find the extensive, full author and affiliation list on the publishers website

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Reference
Hässig M (2014) The capabilities of ROSINA/DFMS to measure argon isotopes at comet 67P/Churyumov-Gerasimenko. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2014.11.015]

¹Sandra Pizzarello
¹Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85018-1604, USA

HCN is ubiquitous in extraterrestrial environments and is central to current theories on the origin of early solar system organic compounds such as amino acids. These compounds, observed in carbonaceous meteorites, were likely important in the origin and/or evolution of early life. As part of our attempts to understand the origin(s) of meteoritic CN–, we have analyzed the 15N/14N isotopic composition of HCN gas released from water extracts of the Murchison meteorite and found its value to be near those of the terrestrial atmosphere. The findings, when evaluated viz-a-viz molecular abundances and isotopic data of meteoritic organic compounds, suggest that HCN formation could have occurred during the protracted water alteration processes known to have affected the mineralogy of many asteroidal bodies during their solar residence. This was an active synthetic stage, which likely involved simple gasses, organic molecules, their presolar precursors, as well as mineral catalysts and would have lead to the formation of molecules of differing isotopic composition, including some with solar values.

Reference
Pizzarello S (2014) The Nitrogen Isotopic Composition of Meteoritic HCN. Astrophysical Journal 796, L25
Link to Article [doi:10.1088/2041-8205/796/2/L25]

¹Nirmala Jain, ¹Prakash Chauhan
¹Planetary Sciences & Marine Biology Division, Biological and Planetary Sciences and Applications Group, Space Applications Centre (SAC), Indian Space Research Organization (ISRO), Ahmedabad, Gujarat, India, 380 015

Spectral reflectance data from the MRO-CRISM (Mars Reconnaissance Orbiter-Compact Reconnaissance Imaging Spectrometer for Mars) of Capri Chasma, a large canyon within Valles Marineris on Mars, have been studied. Results of this analysis reveal the presence of minerals, such as, phyllosilicates (illite, smectite (montmorillonite)) and carbonates (ankerite and manganocalcite). These minerals hint of the aqueous history of Noachian time on Mars. Phyllosilicates are products of chemical weathering of igneous rocks, whereas carbonates could have formed from local aqueous alteration of olivine and other igneous minerals. Four different locations within the Capri Chasma region were studied for spectral reflectance based mineral detection. The study area also shows the spectral signatures of iron-bearing minerals, e.g. olivine with carbonate, indicating partial weathering of parent rocks primarily rich in ferrous mineral. The present study shows that the minerals of Capri Chasma are characterized by the presence of prominent spectral absorption features at 2.31 μm, 2.33 μm, 2.22 μm, 2.48 μm and 2.52 μm wavelength regions, indicating the existence of hydrous minerals, i.e., carbonates and phyllosilicates. The occurrence of carbonates and phyllosilicates in the study area suggests the presence of alkaline environment during the period of their formation. Results of the study are important to understand the formation processes of these mineral assemblages on Mars, which may help in understanding the evolutionary history of the planet.

Reference
Jain N, Chauhan P (2014) Study of phyllosilicates and carbonates from the Capri Chasma region of Valles Marineris on Mars based on Mars Reconnaissance Orbiter-Compact Reconnaissance Imaging Spectrometer for Mars (MRO-CRISM) observations. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2014.11.018]

Copyright Elsevier

¹Lars E. Borg, ¹Amy M. Gaffney, ²Charles K. Shearer
¹Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California, USA
²Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, USA

Data obtained from Sm-Nd and Rb-Sr isotopic measurements of lunar highlands’ samples are renormalized to common standard values and then used to define ages with a common isochron regression algorithm. The reliability of these ages is evaluated using five criteria that include whether: (1) the ages are defined by multiple isotopic systems, (2) the data demonstrate limited scatter outside uncertainty, (3) initial isotopic compositions are consistent with the petrogenesis of the samples, (4) the ages are defined by an isotopic system that is resistant to disturbance by impact metamorphism, and (5) the rare-earth element abundances determined by isotope dilution of bulk of mineral fractions match those measured by in situ analyses. From this analysis, it is apparent that the oldest highlands’ rock ages are some of the least reliable, and that there is little support for crustal ages older than approximately 4.40 Ga. A model age for ur-KREEP formation calculated using the most reliable Mg-suite Sm-Nd isotopic systematics, in conjunction with Sm-Nd analyses of KREEP basalts, is 4389 ± 45 Ma. This age is a good match to the Lu-Hf model age of 4353 ± 37 Ma determined using a subset of this sample suite, the average model age of 4353 ± 25 Ma determined on mare basalts with the 146Sm-142Nd isotopic system, with a peak in Pb-Pb ages observed in lunar zircons of approximately 4340 ± 20 Ma, and the oldest terrestrial zircon age of 4374 ± 6 Ma. The preponderance of ages between 4.34 and 4.37 Ga reflect either primordial solidification of a lunar magma ocean or a widespread secondary magmatic event on the lunar nearside. The first scenario is not consistent with the oldest ages reported for lunar zircons, whereas the second scenario does not account for concordance between ages of crustal rocks and mantle reservoirs.

Reference
Borg LE, Gaffney AM, Shearer CK (2014) A review of lunar chronology revealing a preponderance of 4.34–4.37 Ga Ages. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12373]

Published by arrangement with John Wiley&Sons

¹Romain Tartèse, ^1,2Mahesh Anand, ³Katherine H. Joy, ¹Ian A. Franchi
¹Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, UK
²Department of Earth Sciences, The Natural History Museum, London, UK
³School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK

We have investigated the H and Cl systematics in apatite from four brecciated lunar meteorites. In Northwest Africa (NWA) 4472, most of the apatites contain ∼2000–6000 ppm H2O with δD between −200 and 0‰, except for one grain isolated in the matrix, which contains ∼6000 ppm H2O with δD of ∼500–900‰. This low-δD apatite contains ∼2500–7500 ppm Cl associated with δ37Cl of ∼15–20‰, while the high-δD grain contains ∼2500 ppm Cl with δ37Cl of ∼7–15‰. In NWA 773, apatites in a first group contain ∼700–2500 ppm H2O with δD values averaging around ∼0 ± 100‰, while apatites in a second group contain ∼5500–16500 ppm H2O with δD ∼250 ± 50‰. In Sayh al Uhaymir (SaU) 169 and Kalahari (Kal) 009, apatites are similar in terms of their H2O contents (∼600–3000 ppm) and δD values (−100 to 200‰). In SaU 169, apatites contain ∼6000–10,000 ppm Cl, characterized by δ37Cl of ∼5–12‰. Overall, most of the analyzed apatite grains have δD within the range reported for carbonaceous chondrites, similar to apatite analyzed in ancient (>3.9 Ga) lunar magmatic. One grain in NWA 4472 has H and Cl isotope compositions similar to apatite from mare basalts. With an age of 4.35 Ga, this grain could be a representative of the oldest known lunar volcanic activity. Finally, since numerous evolved clasts in NWA 773 formed through silicate liquid immiscibility, the apatite grains with extremely high H2O contents, reaching pure hydroxylapatite composition, could provide insights into the effects of such process on the evolution of volatiles in lunar magmas.

Reference
Tartèse R, Anand M, Joy KH, Franchi IA (2014) H and Cl isotope systematics of apatite in brecciated lunar meteorites Northwest Africa 4472, Northwest Africa 773, Sayh al Uhaymir 169, and Kalahari 009. Meteoritics&Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12398]

Published by arrangement with John Wiley&Sons

¹R. E. Merle, ^1,2A. A. Nemchin, ¹M. L. Grange, ²M. J. Whitehouse,¹R. T. Pidgeon
¹Department of Applied Geology, Curtin University, Perth, WA, Australia
²Swedish Museum of Natural History, Stockholm, Sweden

Previous age estimates of the Imbrium impact range from 3770 to 3920 Ma, with the latter being the most commonly accepted age of this basin-forming event. The occurrence of Ca-phosphates in Apollo 14 breccias, interpreted to represent ejecta formed by this impact, provides a new opportunity to date the Imbrium event as well as refining the impact history of the Moon. We present new precise U-Pb analyses of Ca-phosphates from impact breccia sample 14311 that are concordant and give a reliable weighted average age of 3938 ± 4 Ma (2σ). Comparison with previously published U-Pb data on phosphate from Apollo 14 samples indicate that all ages are statistically similar and suggest phosphates could have been formed by the same impact at 3934 Ma ± 3 Ma (2σ). However, this age is older than the 3770 to 3920 Ma range determined for other samples and also interpreted as formed during the Imbrium impact. This suggests that several impacts occurred during a 20–30 Ma period around 3900 Ma and formed breccias sampled by the Apollo missions.

Reference
Merle RE, Nemchin AA, Grange ML, Whitehouse MJ, Pidgeon RT (2014) High resolution U-Pb ages of Ca-phosphates in Apollo 14 breccias: Implications for the age of the Imbrium Impact. Meteoritics&Planetary Science (in Press)

Link to Article [DOI: 10.1111/maps.12395]

Published by arrangement with John Wiley&Sons

¹Luca Bindi et al. (>10)*
¹Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Florence, Italy

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Bindi L et al. (2014) Steinhardtite, a new body-centered-cubic allotropic form of aluminum from the Khatyrka CV3 carbonaceous chondrite. American Mineralogist 99, 2433-2436
Link to Article [doi:10.2138/am-2014-5108]

¹Kevin Righter, ²Lindsay P. Keller, ³Zia Rahman, ³Roy Christoffersen
¹NASA JSC, Mailcode KT, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
²NASA-JSC, Mailcode KR, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
³ESCG Jacobs, Houston, Texas, U.S.A.

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Reference
Righter K, Keller LP, Rahman Z, Christoffersen R (2014)Redox-driven exsolution of iron-titanium oxides in magnetite in Miller Range (MIL) 03346 nakhlite: Evidence for post crystallization oxidation in the nakhlite cumulate pile? American Mineralogist, 99,2313-2319
Link to Article [doi:10.2138/am-2014-4926]

¹Paul G. Lucey, ¹Jessica A. Norman, ^1,2Sarah T. Crites,
¹G. Jeffrey Taylor, ¹B. Ray Hawke, ^1,2Myriam Lemelin,³H. Jay Melosh
¹Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, 1680 East West Road, Honolulu, Hawaii 96822, U.S.A.
²Department of Geology and Geophysics, University of Hawaii at Manoa, 1680 East West Road, Honolulu, Hawaii 96822, U.S.A.
³Department of Earth, Atmospheric, and Planetary Sciences, Purdue University West Lafayette, Indiana 47907, U.S.A.

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Reference
Lucey PG, Norman JA, Crites ST, Taylor GJ, Hawke BR, Lemelin M, Melosh HJ (2014) A large spectral survey of small lunar craters: Implications for the composition of the lunar mantle.American Mineralogist, 99, 2251-2257
Link to Article [doi:10.2138/am-2014-4854]

¹Allan H. Treiman et al. (>10)*
¹Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
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Reference
Treiman AH et al. (2014) Ferrian saponite from the Santa Monica Mountains (California, U.S.A., Earth): Characterization as an analog for clay minerals on Mars with application to Yellowknife Bay in Gale Crater. American Mineralogist 99, 2234-2250.
Link to Article [doi: 10.2138/am-2014-4763]