^1,2Chen, M., ²Xie, X.
¹State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China

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Reference
Chen M, Xie X (2015) Shock-produced akimotoite in the Suizhou L6 chondrite. Science China Earth Sciences (in Press)
Link to Article [DOI: 10.1007/s11430-014-5039-5]

¹M.R.M. Izawa, ²M.A. Craig, ¹D.M. Applin, ³J.A. Sanchez, ³V. Reddy, ³L. LeCorre, ¹P. Mann, ¹E.A. Cloutis
¹Hyperspectral Optical Sensing for Extraterrestrial Reconnaissance Laboratory, Dept. Geography, University of Winnipeg, 515 Portage Ave., Winnipeg, Manitoba, Canada R3B 2E9
²Dept. Earth Sciences/Centre for Planetary Science and Exploration, Western University, 1151 Richmond St., London, ON, Canada, N6A 5B7
³Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719, USA

Reflectance spectra of many asteroids and other solar system bodies are commonly reported as “featureless”. Here, we show that weak but consistently detectable absorption bands are observable in 200-2500 nm spectra of the Tagish Lake meteorite, a likely compositional and spectral analogue for low-albedo, “spectrally-featureless” asteroids. Tagish Lake presents a rare opportunity to study multiple lithologies within a single meteorite. Reflectance spectra of Tagish Lake display significant variation between different lithologies. The spectral variations are due in part to mineralogical variations between different Tagish Lake lithologies. Ultraviolet reflectance spectra (200-400 nm), few of which have been reported in the literature to date, reveal albedo and spectral ratio variations as a function of mineralogy. Similarly visible-near infrared reflectance spectra reveal variations in albedo, spectral slope, and the presence of weak absorption features that persist across different lithologies and can be attributed to various phases present in Tagish Lake. These observations demonstrate that significant spectral variability may exist between different lithologies of Tagish Lake, which may affect the interpretation of potential source body spectra. It is also important to consider the spectral variability within the meteorite before excluding compositional links between possible parent bodies in the main belt and Tagish Lake. Tagish Lake materials may also be spectral-compositional analogues for materials on the surfaces of other dark asteroids, including some that are targets of upcoming spacecraft missions. Tagish Lake has been proposed as a spectral match for ‘ultra-primitive’ D or P-type asteroids, and the variability reported here may be reflected in spatially or rotationally-resolved spectra of possible Tagish Lake parent bodies and source objects in the near-Earth asteroid population. A search for objects with spectra similar to Tagish Lake has been carried out among the Near-Earth Asteroids. We have identified three possible spectral matches, the best of which are asteroids (326732) 2003 HB6, and (17274) 2000 LC16.

Reference
Izawa MRM, Craig MA, Applin DM, Sanchez JA, Reddy V, LeCorre L, Mann P, Cloutis EA (2015) Variability, absorption features, and parent body searches in “spectrally featureless” meteorite reflectance spectra: Case study – Tagish Lake. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.013]

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¹SCHMIEDER, M., ²CHENNAOUI AOUDJEHANE, H., ^3,4BUCHNER, E., ¹TOHVER, E.
¹School of Earth and Environment, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
²Hassan II University Casablanca, Faculty of Sciences Ain Chock, GAIA Laboratory, BP 5366 Maârif 20000, Casablanca, Morocco
³HNU – Neu-Ulm University of Applied Sciences, Wileystrasse 1, 89231 Neu-Ulm, Germany
⁴Institut für Mineralogie und Kristallchemie, Universität Stuttgart, Azenbergstraße 18, 70174 Stuttgart, Germany

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Reference
Schmieder M, Chennaoui Aoudjehane H, Buchner E, Tohver E (2015) Meteorite traces on a shatter cone surface from the Agoudal impact site, Morocco. Geological Magazine (in Press)
Link to Article [DOI: 10.1017/S0016756815000047]

^1,2F. Javier Martín-Torres et al. (>10)*
¹Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), 18100 Armilla, Granada, Spain
²Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, S98192 Kiruna, Sweden
*Find the extensive, full author and affiliation list on the publishers website

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Reference
Martín-Torres FJ et al. (2015) Transient liquid water and water activity at Gale crater on Mars. Nature Geoscience (in Press)
Link to Article [doi:10.1038/ngeo2412]

^1,2Richard G. Kraus, ³Seth Root, ⁴Raymond W. Lemke, ^1,5Sarah T. Stewart, ¹Stein B. Jacobsen, ⁴Thomas R. Mattsson

¹Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA
²Shock Physics Group, Lawrence Livermore National Laboratory, PO Box 808, L-487, Livermore, California 94551-0808, USA
³Dynamic Material Properties Group, Sandia National Laboratory, PO Box 5800, Albuquerque, New Mexico 87185-1195, USA
⁴High Energy Density Physics Theory, Sandia National Laboratory, PO Box 5800, Albuquerque, New Mexico 87185-1189, USA
⁵Department of Earth and Planetary Sciences, UC Davis, One Shields Avenue, Davis, California 95616, USA

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Reference
Kraus RG, Root S, Lemke RW, Stewart ST, Jacobsen SB, Mattsson TR (2015) Impact vaporization of planetesimal cores in the late stages of planet Formation. Nature Geoscience 8, 269–272
Link to Article [doi:10.1038/ngeo2369]

¹Kimberly R. Kuhlman, ²Kumar Sridharan, ³Alexander Kvit
¹Planetary Science Institute, 1700 East Fort Lowell Blvd., Suite 106, Tucson, AZ 85719
²University of Wisconsin – Madison, Department of Engineering Physics, 1500 Engineering Drive, Madison, WI 53706
³University of Wisconsin – Madison, Materials Science Center & Department of Materials Science and Engineering, 1509 University Ave., Madison, WI 53706

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Reference
Kuhlman KR, Sridharan K, Kvit A (2015) Simulation of solar wind space weathering in orthopyroxene. Planetary and Space Science (in Press)
Link to Article [doi:10.1016/j.pss.2015.04.003]

¹Amira Elsenousy, ²Jennifer Hanley, ¹Vincent F. Chevrier
¹Arkansas Center for Space and Planetary Sciences, STON, University of Arkansas, 346 1/2 N. Arkansas Ave., Fayetteville, AR 72701, USA
²Southwest Research Institute, 1050 Walnut St, Suite 300, Boulder, CO 80302, USA

The WCL (Wet Chemistry Lab) instrument on board the Phoenix Lander identified the soluble ionic composition of the soil at the landing site. However, few studies have been conducted to understand the parent salts of these soluble ions. Here we studied the possible salt assemblages at the Phoenix landing site using two different thermodynamic models: FREZCHEM and Geochemist’s Workbench (GWB). Two precipitation pathways were used: evaporation (T<0Tusing only FREZCHEM). Through applying three different models of initial ionic concentrations (from sulfate to chlorate/perchlorate dominated), we calculated the resulting precipitated minerals. The results—through both freezing and evaporation—showed some common minerals that precipitated regardless of the ionic initial concentration. These ubiquitous minerals are magnesium chlorate hexahydrate Mg(ClO₃)₂⋅6H₂O, potassium perchlorate (KClO₄) and gypsum (CaSO₄⋅2H₂O). Other minerals evidence specific precipitation pathway. Precipitation of highly hydrated salts such as meridianiite (MgSO₄⋅11H₂O) and MgCl₂⋅12H₂O indicate freezing pathway, while precipitation of the low hydrated salts (anhydrite, kieserite and epsomite) indicate evaporation. The present hydration states of the precipitated hydrated minerals probably reflect the ongoing thermal processing and recent seasonally varying humidity conditions at the landing site, but these hydration states might not reflect the original depositional conditions. The simulations also showed the absence of Ca-perchlorate in all models, mainly because of the formation of two main salts: KClO₄ and gypsum which are major sinks for ClO⁻₄ and Ca²⁺ respectively. Finally, in consideration to the Martian life, it might survive at the very low temperatures and low water activities of the liquids formed. However, besides the big and widely recognized challenges to life posed by those extreme environmental parameters (especially low water activity), another main challenge for any form of life in such an environment is to maintain contact with the small droplets of the stable liquids in the regolith and to interact with life in other isolated droplets.

Reference
Elsenousy A, Hanley J, Chevrier VF (2015) Effect of evaporation and freezing on the salt paragenesis and habitability of brines at the Phoenix landing site. Earth and Planetary Science Letters 421, 39–46
Link to Article [doi:10.1016/j.epsl.2015.03.047]

Copyright Elsevier

¹H.W. Lin, ²Fumi Yoshida, ³Y.T. Chen, ^1,4W.H. Ip, ¹C.K. Chang
¹Institute of Astronomy, National Central University, Taoyuan 32001, Taiwan
²National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JAPAN
³Institute of Astronomy and Astrophysics, Academia Sinica, P. O. Box 23-141, Taipei 106, Taiwan
⁴Space Science Institute, Macau University of Science and Technology, Taipa, Macau

The size-dependent effects of asteroids on surface regolith and collisional lifetimes suggest that small asteroids are younger than large asteroids. In this study, we performed multicolor main-belt asteroid (MBA) survey by Subaru telescope/Suprime-Cam to search for subkilometer-sized ordinary chondrite (Q-type) like MBAs. The total survey area was 1.5 deg2 near ecliptic plane and close to the opposition. We detected 150 MBAs with 4 bands (B,V,R,IB,V,R,I) in this survey. The range of absolute magnitude of detected asteroids was between 13 and 22 magnitude, which is equivalent to the size range of kilometer to sub-kilometer diameter in MBAs.
From this observation, 75 of 150 MBAs with color uncertainty less than 0.1 were used in the spectral type analysis, and two possible Q-type asteroids were detected. This mean that the Q-type to S-type ratio in MBAs is < 0.05. Meanwhile, the Q/S ratio in near Earth asteroids (NEAs) has been estimated to be 0.5 to 2 (Binzel et al., 2004 and Dandy et al., 2003). Therefore, Q-type NEAs might be delivered from the main belt region with weathered, S-type surface into near Earth region and then obtain their Q-type, non-weathered surface after undergoing re-surfacing process there. The resurfacing mechanisms could be: 1. dispersal of surface material by tidal effect during planetary encounters (Binzel et al., 2010 and Nesvorný et al., 2010), 2. the YORP spin-up induced rotational-fission (Polishook et al., 2014) or surface re-arrangement, or 3. thermal degradation (Delbo et al., 2014).

Reference
Lin HW, , Yoshida F, Chen YT, Ip WH, Chang CK (2015) A Search for Subkilometer-sized Ordinary Chondrite Like Asteroids in the Main-Belt. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.007]

Copyright Elsevier

¹Martha Gilmore, ²Nils Mueller, ²Jörn Helbert
¹Dept. of Earth and Environmental Sciences, Wesleyan University, 265 Church St., Middletown, CT, 06459, USA
²Institute for Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany

The composition of Venus tessera terrain is unknown. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard Venus Express (VEx) collects data that yields the surface emissivity at ∼1 micron, which contains information convolving a number of surface properties, including composition. We examine the variation of emissivity in the vicinity of Alpha Regio, which is the largest exposure of tessera terrain imaged by VIRTIS. We find that the emissivity of Alpha Regio tessera is lower than adjacent plains materials and the deposits and flows of Eve corona, both of which have previously been interpreted to be basaltic. The emissivity of the bulk of Alpha is also lower than its western boundary, which is interpreted to comprise plains structurally deformed to the same degree as tessera terrain. This suggests that the lower emissivity of Alpha is independent of structural elements, macroscale roughness, or sedimentation processes, and is due to material properties like composition or grain size. The deviation of the emissivity of Alpha from that of the plains for which a bulk basaltic composition is well supported corresponds to a significant difference in rock type or surface mineral assemblage. The 1 μm emissivity of Alpha is consistent with rocks with low ferrous iron content. This includes felsic igneous rocks like granitoids that form under either water-rich or water-poor conditions. A water-rich origin would require both a hydrosphere and a plate recycling mechanism and thus be limited to the lifetime of surface water on Venus. Alternatively, granitoids could form via the differentiation of basaltic melts. The production of all tessera terrain by this mechanism would require the accumulation and preservation of felsic melts from a volume of mafic magma that exceeds what is preserved in the currently observed plains. Both mechanisms of granitoid formation would require that tessera terrain be formed prior to the emplacement of the plains, consistent with their stratigraphic position. Anorthosites also satisfy the emissivity signature and can form from copious amounts of partial melting of a mafic source. Low emissivity values are also consistent with carbonates, sulfates, phyllosilicates and their dehydration products, which may have formed via weathering of basalts under conditions of higher atmospheric PH2O. All of these hypotheses suggest the mineralogy of Alpha tessera records an extinct era of Venus history and is a key target for future exploration.

Reference
Gilmore M, Mueller N, Helbert J (2015) VIRTIS Emissivity of Alpha Regio, Venus, with Implications for Tessera Composition. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.04.008]

Copyright Elsevier

¹Wataru Fujiya, ²Naoji Sugiura, ^3,4Yves Marrocchi, ⁵Naoto Takahata, ¹Peter Hoppe, ⁵Kotaro Shirai, ⁵Yuji Sano, ²Hajime Hiyagon
¹Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany
²Department of Earth and Planetary Science, The University of Tokyo, 7-3-1- Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
³Université de Lorraine, CRPG, UMR 7358, Vandoeuvre les Nancy, F-54501, France
⁴CNRS, CRPG UMR 7358, Vandoeuvre les Nancy, F-54501, France
⁵Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8564, Japan

We have performed in situ analyses of C and O isotopic compositions, trace element concentrations, and cathodoluminescence (CL) intensities on calcite in Murchison, a weakly altered CM chondrite. We found that the trace element (Mg, Mn, and Fe) concentrations are heterogeneous within single calcite grains. Grain to grain heterogeneity is even more pronounced. The analyzed calcite grains can be separated into two distinct types with respect to their C isotopic ratios, trace element concentrations, and CL characteristics: Calcite grains with higher δ13CPDB values (∼75 ‰) have low trace element concentrations and uniformly dark CL, while grains with lower δ13C values (∼35 ‰) have higher trace element concentrations and CL zoning. In contrast to the C isotopic ratios, O isotopic ratios are similar for both types of calcites (δ18OSMOW ∼ 34 ‰).
The O isotopic ratios, trace element concentrations, and CL characteristics provide no evidence for C-isotope evolution in fluids from a single C reservoir by Rayleigh-type isotope fractionation (i.e., removal of C-bearing gaseous species). Also, it seems difficult to explain the O and C isotopic compositions of the two types of calcites by their formation at different temperatures from a single fluid. Instead, the δ13C variation suggests the presence of at least two C reservoirs with different isotopic ratios in the aqueous fluids from which the calcites precipitated. The C reservoirs with lower δ13C values are likely to be organic matter. The same holds for the C reservoirs with higher δ13C values which might have significant contributions from the 13C-enriched grains identified in meteoritic insoluble organic matter. Thermodynamic calculations show that calcite with lower Fe concentrations formed under more reduced conditions than calcite with higher Fe concentrations. If this is the case, the 13C-rich organic grains may have been destroyed and dissolved in the fluids under more reduced conditions than other organic components. The fact that the two types of calcites were found in different domains in the same thin section suggests that microenvironments with diverse physicochemical conditions such as redox states were present at scales of 100’s μm.

Reference
Fujiya W, Sugiura N, Marrocchi Y, Takahata N, Hoppe P, Shirai K, Sano Y, Hiyagon H (2015) Comprehensive study of carbon and oxygen isotopic compositions, trace element abundances, and cathodoluminescence intensities of calcite in the Murchison CM chondrite. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.04.010]

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