¹Elizabeth C. Sklute, ¹Timothy D. Glotch, ²Jennifer L. Piatek, ¹William R. Woerner, ¹Alexis A. Martone, ¹Meredith L. Kraner
¹Department of Geosciences, Stony Brook University, Stony Brook, New York 11794, U.S.A.
²Department of Physics and Earth Sciences, Central Connecticut State University, New Britain, Connecticut 06050, U.S.A.

The hydroxy sulfate jarosite [(K,Na,H3O)Fe3(SO4)2(OH)6] has both been discovered on Mars, and is associated with areas of highly acidic runoff on Earth. Because jarosite is extremely sensitive to formation conditions, it is an important target mineral for remote sensing applications. Yet at visible and near infrared (VNIR) wavelengths, where many spacecraft spectrometers collect data, the spectral abundance of a mineral in a mixture is not linearly correlated with the surface abundance of that mineral. Radiative transfer modeling can be used to extract quantitative abundance estimates if the optical constants (the real and imaginary indices of refraction, n and k) for all minerals in the mixture are known. Unfortunately, optical constants for a wide variety of minerals, including sulfates like jarosite, are not available. This is due, in part, to the inherent difficulty in obtaining such data for minerals that tend to crystallize naturally as fine-grained (~10 μm) powders, like many sulfates including jarosite. However, the optical constants of powders can be obtained by inverting the equation of radiative transfer and using it to model laboratory spectra. In this paper, we provide robust n and k data for synthetic potassium, hydronium, and sodium jarosite in the VNIR. We also explicitly describe the calculation procedures (including access to our Matlab code) so that others may obtain optical constants of additional minerals. Expansion of the optical constants library in the VNIR will facilitate the extraction of quantitative mineral abundances, leading to more in-depth evaluations of remote sensing target locations.

Reference
Sklute EC, Glotch TD, Piatek JL, Woerner WR, Martone AA, Kraner ML (2015) Optical constants of synthetic potassium, sodium, and hydronium jarosite. American Mineralogist 100, 1110-1122
Link to Article [doi: 10.2138/am-2015-4824]

Copyright: The Mineralogical Society of America

¹N.G. Rudraswami, ¹M. Shyam Prasad, ^1,2K. Nagashima, ³R.H. Jones
¹National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403004, India
²Hawaii Institute of Geophysics and Planetology, Hawai‘i at Māanoa, 1680 East-West-Road, Honolulu, HI 96822, USA
³Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA

Most olivine relict grains in cosmic spherules selected for the present study are pristine and have not been disturbed during their atmospheric entry, thereby preserving their chemical, mineralogical and isotopic compositions. In order to understand the origin of the particles, oxygen isotope compositions of relict olivine grains in twelve cosmic spherules collected from deep sea sediments of the Indian Ocean were studied using secondary ion mass spectrometry. Most of the data lie close to the CCAM (Carbonaceous Chondrite Anhydrous Mineral) line, with Δ17O ranging from –5 to 0‰. The data overlap oxygen isotopic compositions of chondrules from carbonaceous chondrites such as CV, CK, CR and CM, which suggests that chondrules from carbonaceous chondrites are the source of relict grains in cosmic spherules. Chemical compositions of olivine in cosmic spherules are also very similar to chondrule olivine from carbonaceous chondrites. Several olivine relict grains in three cosmic spherules are 16O-rich (Δ17O –21.9 to –18.7‰), similar to oxygen isotopic compositions observed in calcium aluminium rich inclusions (CAIs), amoeboid olivine aggregates (AOAs), and some porphyritic chondrules from carbonaceous chondrites. These grains appear to have recorded the initial oxygen isotopic composition of the inner solar nebula. Three olivine grains from two cosmic spherules have δ18O values > +20‰, which could be interpreted as mixing with stratospheric oxygen during atmospheric entry.

Reference
Rudraswami NG, Shyam Prasad M, Nagashima K, Jones RH (2015) Oxygen isotopic composition of relict olivine grains in cosmic spherules: Links to chondrules from carbonaceous chondrites. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.05.004]

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¹Shohei Kaneko, ^1,2Masaaki Miyahara, ^1,3Eiji Ohtani, ⁴Tomoko Arai, ⁵Naohisa Hirao,⁶Kazuhisa Sato
¹Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
²Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 739-8526, Japan
³V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Science, 630090 Novosibirsk, Russia
⁴Planetary Exploration Research Center, Chiba Institute of Technology, Chiba 275-0016, Japan
⁵Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo, Hyogo 679-5198, Japan
⁶Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan * E-mail: miyahara@hiroshima-u.ac.jp

High-pressure polymorphs recovered in terrestrial craters are evidence of meteoroid impact events on the Earth’s surface. Despite countless impact craters on the Moon, high-pressure polymorphs have not been reported to date in returned Apollo samples. On the other hand, recent studies report that the high-pressure polymorphs of silica, coesite, and stishovite occur in shocked lunar meteorites. We investigated regolith breccia 15299, which was returned by the Apollo 15 mission, using the combined techniques of focused ion beam (FIB), synchrotron X-ray diffraction (XRD), and transmission electron microscopy (TEM). The regolith breccia 15299 studied here consists of a mafic impact melt breccia with millimeter-sized, coarse-grained, low-Ti basalt clasts. The mafic melt breccia consists of fragments of minerals (olivine, pyroxene, plagioclase, silica, and ilmenite) and glass. Several quartz, tridymite, and cristobalite grains of 10–100 μm across occur in the mafic impact melt breccia. Vesicular melt veins of less than ~200 μm wide cut across the mafic melt breccia matrix and mineral fragments. Some silica grains are entrained in the melt veins. One of the silica grains entrained in the melt veins consist of stishovite [a = 4.190(1), c = 2.674(1) Å, V = 46.95 Å3, space group P42/mnm] along with tridymite and silica glass. This is the first report of high-pressure polymorphs from returned lunar samples. TEM images show that the stishovite is needle-like in habit, and up to ~400 nm in size. Considering the lithologies and shock features of 15299, it is inferred that the stishovite possibly formed by the Imbrium impact or subsequent local impact event(s) in the Procellarum KREEP Terrane (PKT) of the nearside of the Moon.

Reference
Kaneko S, Miyahara M, Ohtani E, Arai T, Hirao N, Sato K (2015) Discovery of stishovite in Apollo 15299 sample.
American Mineralogist 100, 1308-1311
Link to Article [doi: 10.2138/am-2015-5290]

Copyright: The Mineralogical Society of America

¹Larry G. Evans et al. (>10)*
¹Computer Sciences Corporation, Lanham-Seabrook, MD 20706, USA

Orbital measurements obtained by the MESSENGER Gamma-Ray Spectrometer have been analyzed to determine the surface abundance of chlorine in Mercury’s northern hemisphere. The derived Cl/Si mass ratio is 0.0057 ± 0.001, which for an assumed Si abundance of 24.6 wt% corresponds to 0.14 ± 0.03 wt% Cl. The abundance of Cl is a factor of 2.9 ± 1.3 higher in the north polar region (>80° N) than at latitudes 0°−60° N, a latitudinal variation similar to that observed for Na. Our reported Cl abundances are consistent with measured bulk concentrations of neutron-absorbing elements on Mercury, particularly those observed at high northern latitudes. The Cl/K ratio on Mercury is chondritic, indicating a limited impact history akin to that of Mars, which accreted rapidly. Hypotheses for the origin of Mercury’s high metal-to-silicate ratio must be able to reproduce Mercury’s observed elemental abundances, including Cl. Chlorine is also an important magmatic volatile, and its elevated abundance in the northern polar region of Mercury indicates that it could have played a role in the production, ascent, and eruption of flood volcanic material in this region. We have identified several candidate primary mineralogical hosts for Cl on Mercury including the halide minerals lawrencite (FeCl2), sylvite (KCl), and halite (NaCl), as well as Cl-bearing alkali sulfides. Amphiboles, micas, apatite, and aqueously-deposited halides, in contrast, may be ruled out as mineralogical hosts of Cl on Mercury.

Reference
Evans LG et al. (2015) Chlorine on the Surface of Mercury: MESSENGER Gamma-Ray Measurements and Implications for the Planet’s Formation and Evolution. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.039]

Copyright Elsevier

¹Hiroshi Naraoka et al. (>10)*
¹Department of Earth and Planetary Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan

*Find the extensive, full author and affiliation list on the publishers Website

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Reference
Naraoka H et al. (2015) ToF-SIMS analysis of carbonaceous particles in the sample catcher of the Hayabusa spacecraft. Earth, Planets and Space 67:67
Link to Article [doi:10.1186/s40623-015-0224-0]

^1,2Ladislav Nabelek, ^1,2Martin Mazanec, ^1,2Simon Kdyr, ^1,2,3Gunther Kletetschka
¹Institute of Geology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
²Faculty of Science, Charles University in Prague, Prague 2, Czech Republic
³Lawrence Berkeley National Laboratory, Berkeley, California, USA

Magnetic images of Chelyabinsk meteorite’s (fragment F1 removed from Chebarkul lake) thin section have been unraveled by a magnetic scanning system from Youngwood Science and Engineering (YSE) capable of resolving magnetic anomalies down to 10−3 mT range from about 0.3 mm distance between the probe and meteorite surface (resolution about 0.15 mm). Anomalies were produced repeatedly, each time after application of magnetic field pulse of varying amplitude and constant, normal or reversed, direction. This process resulted in both magnetizing and demagnetizing of the meteorite thin section, while keeping the magnetization vector in the plane of the thin section. Analysis of the magnetic data allows determination of coercivity of remanence (Bcr) for the magnetic sources in situ. Value of Bcr is critical for calculating magnetic forces applicable during missions to asteroids where gravity is compromised. Bcr was estimated by two methods. First method measured varying dipole magnetic field strength produced by each anomaly in the direction of magnetic pulses. Second method measured deflections of the dipole direction from the direction of magnetic pulses. Bcr of magnetic sources in Chelyabinsk meteorite ranges between 4 and 7 mT. These magnetic sources enter their saturation states when applying 40 mT external magnetic field pulse.

Reference
Nabelek L, Mazanec M, Kdyr S, Kletetschka G (2015) Magnetic, in situ, mineral characterization of Chelyabinsk meteorite thin section. Meteoritics&Planetary Sciences (in Press)
Link to Article [DOI: 10.1111/maps.12448]

Published by arrangement with John Wiley&Sons

¹Andrea Longobardo et al. (>10)*
¹INAF Istituto di Astrofisica e Planetologia Spaziali (IAPS), via Fosso del Cavaliere, 00133 Rome, Italy
*Find the extensive, full author and affiliation list on the publishers website

This work is aimed at developing and interpreting infrared albedo, pyroxene and OH band depths, and pyroxene band center maps of Vesta’s Gegania and Lucaria quadrangles, obtained from data provided by the Visible and InfraRed (VIR) mapper spectrometer on board NASA’s Dawn spacecraft.

The Gegania and Lucaria quadrangles span latitudes from 22°S to 22°N and longitudes from 0° to 144°E. The mineralogical and spectral maps identify two large-scale units on this area of Vesta, which extend eastwards and westward of about 60°E, respectively. The two regions are not associated to large-scale geological units, which have a latitudinal distribution rather than longitudinal, but are defined by different contents of carbonaceous chondrites (CC): the eastern region, poor in CCs, is brighter and OH-depleted, whereas the western one, rich in CCs, is darker and OH-enriched.

A detailed analysis of the small-scale units in these quadrangles is also performed. Almost all the units show the typical correspondence between high albedo, deep pyroxene bands, short band centers and absence of OH and vice versa. Only a few exceptions occur, such as the ejecta from the Aelia crater, where dark and bright materials are intimately mixed.
The most characteristic features of these quadrangles are the equatorial troughs and the Lucaria tholus.
The equatorial troughs consist of graben, i.e. a depression limited by two conjugate faults. The graben do not present their own spectral signatures, but spectral parameters similar to their surroundings, in agreement to their structural origin. This is observed also in graben outside the Gegania and Lucaria quadrangles. However, it is possible to observe other structural features, such as tectonic grooves, characterized by a changing composition and hence an albedo variation. This result is confirmed not only by mineralogical maps of Vesta, but also by analyzing the VIRTIS-Rosetta observations of Lutetia. The albedo change is instead a typical behavior of geomorphic grooves. Finally, ridges are characterized by a bluer color and, in some cases, shorter band centers than their surroundings, suggesting that they are composed of fresher materials.
We also performed a comparative analysis between the three tholi of Vesta, i.e. Lucaria (which gives the name to its quadrangle), Aricia (in the Marcia quadrangle) and Brumalia (Numisia quadrangle). Whereas Brumalia tholus is a young magmatic intrusion, the absence of diogenites, the low albedo, and the orientation of Aricia and Lucaria tholi suggest that they are older features, which are covered by dark materials and therefore experienced a different geological history than Brumalia.

Reference
Longobardo A et al. (2015) Mineralogical and spectral analysis of Vesta’s Gegania and Lucaria quadrangles and comparative analysis of their key Features. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.031]
Copyright Elsevier

^1,2Chen, H.Y., ^1,2Miao, B.K., ^1,2Xie, L.F., ^1,2Xia, Z.P.
¹Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin, China
²College of Earth Sciences, Guilin University of Technology, Guilin, China

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Reference
Chen HY,Miao BK,Xie LF, Xia ZP (2015) Mineralogy, petrology and evolution history of Lunar meteorite MIL05035 from Antarctica. Acta Petrologica Sinica 31, 1171-1182

Link to Article [****]

^1,2Ai-Cheng Zhang, ³Chi Ma, ⁴Naoya Sakamoto, ¹Ru-Cheng Wang,⁵Wei-Biao Hsu, ^2,4Hisayoshi Yurimoto
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, China
²Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
⁴Isotope Imaging Laboratory, Creative Research Institution Sousei, Hokkaido University, Sapporo 001-0021, Japan
⁵Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China

Titanium-rich minerals are common in Ca-Al-rich inclusions from primitive chondrites. They are important not only for testing the condensation models for a gas with a solar composition, but also for constraining the redox conditions of the early solar nebula. In this study, we report the detailed mineralogical features and its oxygen isotope compositions of a Ti-Sc-rich ultrarefractory inclusion A0031 from a CH3 chondrite Sayh al Uhaymir 290. The A0031 inclusion has a compact and layered texture with the interior consisting of panguite, Sc-rich anosovite, Ti-rich davisite, and anorthite. A few hexaferrum, perovskite, and spinel crystals are present as inclusions in these minerals. Outside of Ti-rich davisite are a layer of Al-Ti-rich diopside and two grains of enstatite. This texture strongly suggests that A0031 has a condensation origin. Panguite is its third occurrence in nature and similar in composition to the type panguite from the Allende meteorite. Sc-rich anosovite in A0031 has a chemical formula of (Ti4+,Ti3+,Mg,Sc,Al)3O5 with the pseudobrookite structure. This is the second report of Ti3O5 in nature, but is the first description of anosovite formed in the solar nebula as an ultrarefractory phase. The discovery of Sc-rich anosovite in A0031 reveals the stability of Ti3O5 in the early solar nebula and supports the prediction of previous equilibrium condensation calculations. The panguite, Sc-rich anosovite, and Ti-rich davisite in A0031 show a large variation in Ti3+/Titot. The primitive nature of A0031 implies that the variations in Ti3+/Titot among different Ti-rich minerals are primary features. We propose that the distribution of Ti3+ and Ti4+ could be controlled mainly by their various competition abilities of incorporating into these Ti-Sc-Al-rich minerals. Similarity of Ti3+/Titot value between Ti-rich davisite from A0031 and those in other carbonaceous chondrites indicates that most refractory inclusions might have formed in highly reducing nebular settings. The 16O-depleted isotope compositions of A0031 confirm the existence of diverse oxygen reservoirs for CH Ca-Al-rich inclusions in the solar nebula.

Reference
Zhang A-C, Ma C, Sakamoto N, Wang R-C, Hsu W-B, Yurimoto H (2015) Mineralogical anatomy and implications of a Ti-Sc-rich ultrarefractory inclusion from Sayh al Uhaymir 290 CH3 chondrite. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.04.052]

Copyright Elsevier

¹Jean-Philippe Combe et al. (>10)*
¹Bear Fight Institute, 22 Fiddler’s Road, P.O. Box 667, Winthrop, WA 98862, USA
*We currently do not have a copyright agreement with this publisher and cannot display the abstract here

The surface composition of the northern regions of Vesta, observed by the Dawn spacecraft, offers the possibility to test several hypotheses related to impact-related processes. We used mostly imaging spectrometry in the visible and near infrared to assess the distribution of mafic lithologies, hydrated components and albedo properties, and use the link with howardite, eucrite and diogenite meteorites (HEDs) to investigate the origin of those materials. We established that Rheasilvia ejecta reached part of the northern regions, and have a diogenitic-rich composition characteristic of the lower crust. Investigations of the antipodes of the two major impact basins (Rheasilvia and Veneneia) did not reveal any correlation between geographic location, geological features and the surface composition. The northern wall of Mamilia crater, which is one of the freshest craters above 22°N, contains relatively pure eucritic-rich, diogenitic-rich and dark, hydrated materials, which are representative of the rest of the northern regions (and most of Vesta), with the exception of an olivine-like component found in Bellicia crater by Ammannito et al. (2013, Nature Volume 504, Issue 7478, pp. 122-125). We determined that similar types of materials are found in various proportions over a large region, including Bellicia, Arruntia and Pomponia craters, and their origin does not seem to be related to Rheasilvia ejecta. These materials are hydrated, which could indicate an exogenous origin, and not as dark as expected for carbonaceous chondrites, which likely compose the majority of dark hydrated materials on Vesta. Spectral mixture analysis reveals that mixtures of pyroxenes (hypersthene, pigeonite and diopside) could offer an alternative interpretation to olivine in this area.

Reference
Combe J-P et al. (2015) Composition of the northern regions of Vesta analyzed by the Dawn Mission. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.026]

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