¹Hontsova, S.S., ²Danilenko, I.A., ²Yakovlev, G.A., ²Petrova, E.V., ¹Maksimova, E.M., ¹Nauhatsky, I.A.
AIP Conference Proceedings 2015, 020029 Link to Article [DOI: 10.1063/1.5055102]
¹Department of Theoretical Physics and Solid State, Institute of Physical – Technical, Crimean Federal University, Simferopol, 295007, Russian Federation
²Department of Physical Techniques and Devices for Quality Control, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation

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^1,2Emmal Safi, ²Stephen P.Thompson, ¹Aneurin Evans, ²Sarah J.Day, ²Claire A.Murray, ²Annabelle R.Baker, ¹Joana M.Oliveira, ¹Jacco Th.van Loon
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2018.10.034]
¹Astrophysics Group, Lennard-Jones Laboratories, Keele University, Keele, Staffordshire, ST5 5BG, UK
²Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
Copyright Elsevier

Water on the present day Martian surface is thought to exist in two thermally distinct sub-surface reservoirs: as ice in the cryosphere and as groundwater located deeper in the crust. These sub-surface environments are thought to contain saline, rather than pure, water and laboratory studies on whether or not clathrate hydrates can form in such environments are lacking. We fill this gap by performing synchrotron radiation X-ray powder diffraction to investigate the formation and evolution of clathrate hydrates in weak chloride solutions at CO₂ pressures, and over temperature ranges, that are similar to those found in the Martian regolith. We have found that clathrate hydrates can form under conditions relevant to the Martian cryosphere, despite the presence of chloride salts. We find that the dissociation temperatures for CO₂ clathrate hydrates formed in saline solutions are depressed by 10–20 K relative to those formed in pure water, depending on the nature of the salt and the CO₂ pressure. We suggest that the inhibiting effect that salts such as MgCl₂, CaCl₂ and NaCl have on clathrate hydrate formation could also be related to the salts’ effect on the formation of the low temperature phase of ice. However, despite the inhibiting effect of the salts, we conclude that the presence of clathrate hydrates should still be possible under conditions likely to exist within the Martian cryosphere.

¹Yu.Shkuratov, ¹Ye.Surkov, ²M.Ivanov, ¹V.Korokhin, ¹V.Kaydash, ³G.Videen, ⁴C.Pieters, ¹D.Stankevich
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.11.002]

^{1V.N. Karazin Kharkiv National University, 35 Sumska St, Kharkiv, 61022, Ukraine
2V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19, Kosygin st., 119991 Moscow, Russia
3Space Science Institute, 4750 Walnut St. Suite 205, Boulder CO 80301, USA
4Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
Copyright Elsevier}

We provide and test a method to obtain significant improvement of available Chandrayaan-1 M3 data. The advance is achieved using the Gaussian λ-convolution of spectra and Fourier filtration of images. The main result is imagery of the reflectance across different wavelengths as well as parameters of 1 μm and 2 μm absorption bands with unprecedented quality. This approach can be particularly useful for further investigations using M3 data, since it produces improved imagery of various lunar surface characteristics. We studied a region comprising a portion of the Aristarchus Plateau, Montes Agricola, and a small part of the mare surface in Ocean Procellarum to the north of Montes Agricola. We found that the lava flows in the area between the Aristarchus Plateau and Montes Agricola have a chemical/mineral composition different in comparison with mare areas to the northwest of the ridge Montes Agricola. We also identified distinct spectral properties of morphologically young craters located on the plateau and mare surface. A correlation diagram for positions of the minima of the 1 μm and 2 μm bands allows a cluster analysis of the region, and we map areas associated with a cluster corresponding to pyroclastic glasses. Relationships between geologic and spectral parameter maps were established.

¹Maksimova, A.A., ²Kamalov, R.V., ^1,3Chukin, A.V., ⁴Felner, I., ¹Oshtrakh, M.I.
Journal of Molecular Structure 1174, 6-11 Link to Article [DOI: 10.1016/j.molstruc.2018.06.040]
¹Department of Experimental Physics, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
²Department of Rare Metals and Nanomaterials, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
³Department of Theoretical Physics and Applied Mathematics, Institute of Physics and Technology, Ural Federal University, Ekaterinburg, 620002, Russian Federation
⁴Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel

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¹J. Gregory Shellnutt
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.11.001]
¹National Taiwan Normal University, Department of Earth Sciences, 88 Tingzhou Road Section 4, Taipei 11677, Taiwan
Copyright Elsevier

The surface rock composition measured by gamma (γ)-ray spectrometry at the Venera 8 landing site has anomalously high Th (6.5 ± 2.2 ppm) and U (2.2 ± 0.7 ppm) concentrations with respect to the material analyzed at other landing sites (Vega 1, Vega 2, Venera 9, Venera 10). A calculated bulk rock composition of Venera 8, constrained by the measured Th, U and K₂O (4.0 ± 1.2 wt%) contents, is similar to silicic to intermediate rocks (diorite/granodiorite) that are typical of terrestrial convergent margins (magnesian, calc-alkalic). In this study, major and trace elemental modeling is applied in order to determine if the calculated whole rock composition of Venera 8 can be derived from a parental magma composition similar to Venusian basalt. The modeling results indicate that polybaric fractional crystallization of a hydrous (H₂O = 0.4 wt%) and relatively oxidizing (ΔFMQ +0.7) parental composition similar to Venera 14 can yield residual silicic liquids that match the calculated Venera 8 whole rock composition. The measured Th and U concentrations can also be reproduced within the data uncertainty. Although Venus lacks modern Earth-style plate tectonics, magnesian, calc-alkalic compositions are common within Archean greenstone belts and some rift settings (Haida Gwaii). Consequently, it is possible that the Venera 8 probe encountered a fragment of crust that resembles a terrestrial greenstone belt.

¹Hiroshi NAGAOKA, ^1,2Nobuyuki HASEBE, ²Masayuki NAITO, ¹Eido SHIBAMURA, ¹Haruyoshi KUNO, ²Miho MIZONE, ³Kyeong Ja KIM
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 16, 137-142 Link to Article [https://doi.org/10.2322/tastj.16.137]
¹Research Institute for Science and Engineering, Waseda University
²Schools of Advanced Science and Engineering, Waseda University
³Korean Institute of Geoscience and Mineral Resources (KIGAM)

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¹Kohei Fukuda, ²Wataru Fujiya, ¹Hajime Hiyagon, ³Yoshiki Makino, ¹Naoji Sugiura, ¹Naoto Takahata, ³Takafumi Hirata,⁴Yuji Sano
Geochemical Journal 52, 255-262 Link to Article [https://doi.org/10.2343/geochemj.2.0510]
¹Department of Earth and Planetary Science, The University of Tokyo
²College of Science, Ibaraki University
³Geochemical Research Center, The University of Tokyo
⁴Atmosphere and Ocean Research Institute, The University of Tokyo

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¹Naotaka Tomioka
Nihon Kessho Gakkaishi 60, 2-8 Link to Article [https://doi.org/10.5940/jcrsj.60.2]
¹Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology

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¹Cindy L.Young, ²Michael J.Poston, ³James J.Wray, ²Kevin P.Hand, ²Robert W.Carlson
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.10.032]
¹NASA Langley Research Center, Hampton, VA
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
³School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA
Copyright Elsevier

We systematically measured the mid-IR spectra of different mixtures of three silicates (antigorite, lizardite, and pure silica) with varying effective porosities and amounts of darkening agent (iron oxide and carbon). These spectra have broad implications for interpretation of current and future mission data for airless bodies, as well as for testing the capabilities of new instruments. Serpentines, such as antigorite and lizardite, are common to airless surfaces, and their mid-IR spectra in the presence of darkening agents and different surface porosities would be typical for those measured by spacecraft. Silica has been measured in the plumes of Enceladus and presents exciting possibilities for other Saturn-system surfaces due to long-range transport of E-ring material. Results show that the addition of the IR-transparent salt, KBr, to simulate surface porosity affected silicate spectra in ways that were not predictable from linear mixing models. The strengthening of silicate bands with increasing pore space, even when only trace amounts of KBr were added, indicates that spectral features of porous surfaces are more detectable in the mid-IR. Combining iron oxide with the pure silicates seemed to flatten most of the silicate features, but strengthened the reststrahlen band of the silica. Incorporating carbon with the silicates weakened all silicate features, but the silica bands were more resistant to being diminished, indicating silica may be more detectable in the mid-IR than the serpentines. Finally, we show how incorporating darkening agents and porosity provides a more complete explanation of the mid-IR spectral features previously reported on worlds such as Iapetus.

Leon Kocharov¹, Silja Pohjolainen², Mike J. Reiner^3,4, Alexander Mishev⁵, Haimin Wang^6,7, Ilya Usoskin^1,5, and Rami Vainio⁸
Astrophysical Journal Letters 863, L27 Link to Article [DOI: 10.3847/2041-8213/aad86b]
¹National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
²Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan

The site of Zn production remains an elusive and challenging problem in astrophysics. A large enhancement of the [Zn/Fe] ratios of very metal-poor stars in the Galactic halo suggests the death of short-lived massive stars, i.e., core-collapse supernovae (CCSNe), as one major site for Zn production. Previous studies have claimed that some specific CCSNe can produce Zn in sufficient quantities. However, it remains unclear which models can withstand the critical test of observations. Using a Zn abundance feature similar to that of r-process elements in faint satellite galaxies, we find evidence that Zn production took place through events that are much rarer than canonical CCSNe. This finding can be unified with the implied decrease in the rate of Zn production with an increasing metallicity for Galactic halo stars, which narrows down the major site of Zn production in the early galaxy to magnetorotational SNe (MR-SNe). On the other hand, in the later phase of galactic evolution, we predict that the major Zn-production site switched from MR-SNe to thermonuclear SNe (SNe Ia). According to this scenario, an accumulation of the contributions from two types of SNe eventually led to the solar isotope composition of Zn, which mainly owes ^66,68Zn to MR-SNe and ⁶⁴Zn to SNe Ia triggered by He-detonation. The requirement of Zn production in SNe Ia sheds a new light on the debate concerning the scenario for SN Ia progenitors, suggesting that a He-detonation model might be one major channel for SNe Ia.