¹Jeremy B. Tatum
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13403]
¹Department of Physics and Astronomy, University of Victoria, PO Box 1700, STN CSC, Victoria, British Columbia, Canada, V8P 2Y2
Published by arrangement with John Wiley & Sons

A table is provided to determine the angles within the Widmanstätten pattern as a function of orientation of the slice, and methods are provided to solve the inverse problem, namely to determine the orientation of the slice from measurements of the Widmanstätten pattern.

¹M. R. Lee,¹B. E. Cohen,²A. J. King
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13405]
¹School of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lilybank Gardens, Glasgow, G12 8QQ UK
²Department of Earth Science, Natural History Museum (London), Cromwell Rd, London, SW7 5BD UK
Published by arrangement with John Wiley & Sons

Meteorite Hills (MET) 01075 is unique among the CM carbonaceous chondrites in containing the feldspathoid mineral sodalite, and hence it may provide valuable evidence for a nebular or parent body process that has not been previously recorded by this meteorite group. MET 01075 is composed of aqueously altered chondrules and calcium‐ and aluminum‐rich inclusions (CAIs) in a matrix that is predominantly made of serpentine‐ and tochilinite‐rich particles. The chondrules have been impact flattened and define a foliation petrofabric. Sodalite occurs in a 0.6 mm size CAI that also contains spinel, perovskite, and diopside together with Fe‐rich phyllosilicate and calcite. By analogy with feldspathoid‐bearing CAIs in the CV and CO carbonaceous chondrites, the sodalite is interpreted to have formed by replacement of melilite or anorthite during alkali‐halogen metasomatism in a parent body environment. While it is possible that the CAI was metasomatized in a precursor parent body, then excavated and incorporated into the MET 01075 parent body, in situ metasomatism is the favored model. The brief episode of relatively high temperature water–rock interaction was driven by radiogenic or impact heating, and most of the evidence for metasomatism was erased by subsequent lower temperature aqueous alteration. MET 01075 is very unusual in sampling a CM parent body region that underwent early alkali‐halogen metasomatism and has retained one of its products.

¹S. Marchi,¹D.D. Durda,²C.A. Polanskey,³E. Asphaug,¹W.F. Bottke,³L.T. Elkins‐Tanton,⁴L.A.J. Garvie,⁴S. Ray,¹S. Chocron,⁴D.A. Williams
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2019JE005927]
¹Southwest Research Institute, Boulder, CO, USA
²Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
³Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
⁴School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
⁵Southwest Research Institute, San Antonio, TX, USA
Published by arrangement with John Wiley & Sons

The NASA Psyche mission will visit the 226‐km diameter main belt asteroid (16) Psyche, our first opportunity to visit a metal‐rich object at close range. The unique and poorly understood nature of Psyche offers a challenge to the mission as we have little understanding of the surface morphology and composition. It is commonly accepted that the main evolutionary process for asteroid surfaces is impact cratering. While a considerable body of literature is available on collisions on rocky/icy objects, less work is available for metallic targets with compositions relevant to Psyche. Here we present a suite of impact experiments performed at the NASA Ames Vertical Gun Range facility on several types of iron meteorites and foundry‐cast ingots that have similar Fe‐Ni compositions as the iron meteorites. Our experiments were designed to better understand crater formation (e.g., size, depth), over a range of impact conditions, including target temperature and composition.

We find that the target strength, as inferred from crater sizes, ranges from 700 to 1300 MPa. Target temperature has measurable effects on strength, with cooled targets typically 10‐20% stronger. Crater morphologies are characterized by sharp, raised rims and deep cavities.

Further, we derive broad implications for Psyche’s collisional evolution, in light of available low resolution shape models. We find that the number of large craters (>50 km) is particularly diagnostic for the overall bulk strength of Psyche. If confirmed, the number of putative large craters may indicate that Psyche’s bulk strength is significantly reduced compared to that of intact iron meteorites.

¹Debra L. Buczkowski,¹Kimberly D. Seelos,¹Christina E. Viviano,¹Scott L. Murchie,¹Frank P. Seelos,²Eric Malaret,²Christopher Hash
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2019JE006043]
¹Johns Hopkins Applied Physics Laboratory, Laurel, MD
²Applied Coherent Technology, Herndon, VA
Published by arrangement with John Wiley & Sons

The formation of widespread phyllosilicate‐bearing near‐surface layers on Mars have often been attributed to pedogenesis, a process of weathering basaltic soils by continued exposure to meteoric water percolating down from the surface which can result in layers of aluminum phyllosilicates forming over layers of iron‐magnesium phyllosilicates. We present evidence of an Fe/Mg‐smectite bearing layer stratigraphically above Al‐phyllosilicates in three circular features to the south of Coprates Chasma, suggesting that some process other than, or in addition to, a single pedogenic sequence must have been involved. A review of several formation mechanisms shows that all models require multiple episodes of aqueous alteration. In addition, only by invoking groundwater alteration in conjunction with pedogenesis can we reconcile the stratigraphic pattern of altered material exposed by these features.

¹N.E.B. Zellner
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2019JE006050]
¹Department of Physics, Albion College, Albion, MI, USA
Published by arrangement with John Wiley & Sons

Lunar impact glasses, formed during impact events when the regolith was quenched during the ejecta’s ballistic flight, are small samples whose information can lead to important advances in studies of the Moon. For example, they provide evidence that constrains both the compositional evolution of the lunar crust and the timing of the lunar impact flux starting at ~4000 million years ago. They are abundant in the lunar regolith and retain geochemical information that tells us where and when they formed. Thus they provide important details about areas of the Moon both sampled and not sampled by Apollo or Luna missions or lunar meteorites. Additionally, as a result of these glasses possessing a chemical memory of formation location and age, studies of lunar impact glasses provide a foundation on which to conduct studies of impact glasses from other planetary bodies. A summary of past and current lunar impact glass investigations, using glasses from the Apollo 11, 12, 14, 15, 16, and 17 regoliths, along with plans for future work, will be presented.

¹Marc D. Norman,²Fred Jourdan,¹Simeon S.M. Hui
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE006053]
¹Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia
²Department of Applied Geology and John de Laeter Centre, School of Earth and Planetary Sciences, Curtin University, Perth, WA, Australia
Published by arrangement with John Wiley & Sons

Lunar impact glasses are quenched droplets of melt that carry geochemical records of their target compositions, formation ages, and time‐integrated exposure in the upper layers of the lunar regolith. Here we present the first study to obtain major element, trace element, and Ar isotopic data for impact glasses from the Apollo 16 regolith sample 66031. Thirty particles were analysed with 27 of them yielding useable age information. The glasses have a wide range of major and trace element compositions, similar to that observed in lunar meteorites. Half of these glasses have compositions similar to Apollo 16 soils and are considered to be “locally derived”, whereas the others represent diverse source regions and are considered to be “exotic” particles that were delivered from a considerable distance to the landing site.
Almost 40% of the samples analysed for this study have formation ages younger than 500 Ma. Duplicate particles produced in single impact events contribute minimally to the age distribution, and diurnal or transient heating of the regolith does not appear to have had a significant effect on the 40Ar/39Ar ages. Rather, the ages reflect primarily the formation of these glasses by impact melting, with the distribution modified to some degree by preservation bias. As most of these glasses are likely formed by relatively small impactors, their age distribution cannot be compared directly with the crystalline lunar melt rocks to constrain the impact mass flux through time.

^1,2Yunhua Wu,^1,3Weibiao Hsu(徐伟彪)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.113531]
¹CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Nanjing 210033, China
²University of Chinese Academy of Sciences, Beijing 100049, China
³The State Key Laboratory of Lunar and Planetary Science/Space Science Institute, Macau University of Science and Technology, Taipa, Macau
Copyright Elsevier

Unbrecciated mare basalts are rare in the lunar meteorite collection. Found in 2015, Northwest Africa (NWA) 10597 is a medium-grained low-Ti mare basalt with a subophitic texture. The meteorite consists mostly of mm-sized pyroxene and plagioclase, with minor olivine, spinel, ilmenite, phosphates, silica, and trace Zr-rich minerals, such as baddeleyite, zirconolite and tranquillityite. A portion of plagioclase and silica has been transformed to their high-pressure polymorphs due to shock metamorphism. NWA 10597 has a low TiO₂ content (2.9 wt%) but is relatively enriched in rare earth elements (REE) (La_average = 65 × CI) with an overall unfractionated pattern except for a negative Eu anomaly. Calculated REE concentrations of parent melts in equilibrium with Mg-rich pyroxene and Ca-rich plagioclase suggest no significant assimilation of REE-rich melts after the onset of pyroxene crystallization. In situ UPb analyses of baddeleyite and apatite reveal a mutually consistent age of ~3.0 Ga, which is also in excellent agreement with that of low-Ti mare basalts NWA 4734 and LaPaz Icefield (LAP) 02205 dated with other independent techniques. The concordance suggests no significant thermal disturbance in the UPb isotopic system of NWA 10597 although it was heavily shocked. NWA 10597 closely resembles NWA 4734 in terms of petrographic texture, mineral chemistry and geochronology, indicating a pairing relationship.

^1,2,3Sen Hu,^1,2,3Yangting Lin,^1,2Jianchao Zhang,^1,2Jialong Hao,^4,5Akira Yamaguchi,^1,2Ting Zhang,^1,2Wei Yang,^1,2Hitesh Changela
Earth and Planetary Science Letters (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2019.115902]
¹Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China
³College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
⁴National Institute of Polar Research, Tokyo 190-8518, Japan
⁵Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tokyo 190-8518, Japan
Copyright Elsevier

Martian meteorites of various petrogeneses retain a record of volatiles on Mars: from the hydrosphere, crustal water to the mantle. Sputtering of the martian atmosphere by solar wind after the loss of Mars’ magnetic field enriched it in deuterium, which exchanged with martian crustal water. Recent studies show that the hydrogen isotopic composition of the martian crustal water reservoir varies from 3000 to 7000‰ but requires better constraints. Melt inclusion glasses, maskelynite and fusion crust from the depleted olivine-phyric shergotite NWA 6162 were analyzed using NanoSIMS, providing a unique insight into the hydrogen isotopic and volatile elemental content of both the martian crustal water reservoir and the mantle source.

The H₂O, S, and Cl contents of the melt inclusion glasses are ∼0-3137, 14-239, and 16-967 ppm, respectively. δD values vary from −560 to 6137‰. The water content positively correlates with the δD values in both the melt inclusion glasses and maskelynite in a two end-member mixing trend. One end-member is the magmatic water with a δD value of ∼0‰, and the other end member is the martian crustal water with δD ranging from 5000 to 6000‰. NWA 6162, a depleted olivine-phyric shergottite, originated from a different mantle source to the enriched lherzolitic shergottites. However, both types of shergottites exchanged with martian crustal water with the same δD values, indicating a homogeneous martian crustal water hydrogen isotopic composition (5000-6000‰). Most melt inclusion glasses from NWA 6162 have low water content (0-234 ppm) except for two enriched locations as micron-sized bands and dendrites. The low water content in most melt inclusion glasses, the dendritic shaped water enriched areas in melt inclusions, and the martian crustal water diffusion profile recorded in maskelynite collectively suggest short-lived water-rock interactions in the NWA 6162 parent rock that was probably induced by impact. Furthermore, a great contribution (up to 98%) of surface Cl accompanying D-enriched water was recorded in the melt inclusions supported by the positive correlation between Cl and H₂O. The presence of sulfide and S-rich hot spots and low δD end-member of the magmatic water indicate that the degassing during post-entrapment crystallization and ascent of the melt inclusion is negligible. H₂O, S, and Cl contents of the martian mantle reservoir are estimated to be 0.1-3, 0.5-15, and 0.5-4 ppm respectively, after the correction of fractional crystallization of the melt inclusions and contribution from the martian surface reservoir. The martian mantle reservoir estimated from NWA 6162 was water-, S-, and Cl-poorer than the Earth’s interior.

^1,2Jangmi Han,²Lindsay P.Keller,³Ming-Chang Liu,^1,2Andrew W.Needham,³Andreas T.Hertwig,² Scott Messenger,²Justin I.Simon
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.10.042]
¹Lunar and Planetary Institute, USRA, 3600 Bay Area Boulevard, Houston, TX 77058, USA
²Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, TX 77058, USA
³Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA
Copyright Elsevier

We carried out a coordinated mineralogical and isotopic study of a Wark-Lovering (WL) rim on a Ca,Al-rich inclusion (CAI) from the reduced CV3 chondrite Vigarano. The outermost edge of the CAI mantle is mineralogically and texturally distinct compared to the underlying mantle that is composed of coarse, zoned melilite (Åk_∼10-60) grains. The mantle edge contains fine-grained gehlenite with hibonite and rare grossite that likely formed by rapid crystallization from a melt enriched in Ca and Al. These gehlenite and hibonite layers are surrounded by successive layers of spinel, zoned melilite (Åk_∼0-10), zoned diopside that grades outwards from Al,Ti-rich to Al,Ti-poor, and forsteritic olivine intergrown with diopside. These layered textures are indicative of sequential condensation of spinel, melilite, diopside, and forsterite onto hibonite. Anorthite occurs as a discontinuous layer that corrodes adjacent melilite and Al-diopside, and appears to have replaced them, probably even later than the forsterite layer formation. Based on these observations, we conclude that the WL rim formation was initiated by flash melting and extensive evaporation of the original inclusion edge, followed by subsequent gas-solid reactions under highly dynamic conditions.

All the WL rim minerals are ¹⁶O-rich (Δ¹⁷O = ∼−23‰), indicating their formation in an ¹⁶O-rich nebular reservoir. Our Al-Mg measurements of hibonite, spinel, and diopside from the WL rim, as well as spinel and Al,Ti-diopside in the core, define a single, well-correlated isochron with an inferred initial ²⁶Al/²⁷Al ratio of (4.94 ± 0.12) × 10⁻⁵. This indicates that the WL rim formed shortly after the host CAI. In contrast, the lack of ²⁶Mg excesses in the WL rim anorthite suggest its later formation or later isotopic disturbance in the solar nebula, after ²⁶Al had decayed.

^1,2Bucurica, I.A.,^1,3Radulescu, C.,⁴Poinescu, A.A.,^1,3,5Popescu, I.V.,¹Nicolescu, C.M.,¹Teodorescu, S.,³Bumbac, M.,⁶Pehoiu, G.,⁶Murarescu, O.
Romanian Journal of Physics 64, 906 Link to Article [http://www.nipne.ro/rjp/2019_64_7-8.html]
¹Valahia University of Targoviste, Institute of Multidisciplinary Research for Science and Technology, Targoviste, 130004, Romania
²University of Bucharest, Faculty of Physics, Doctoral School of Physics, Bucharest, 050107, Romania
³Valahia University of Targoviste, Faculty of Sciences and Arts, Targoviste, 130004, Romania
⁴Valahia University of Targoviste, Faculty of Materials Engineering and Mechanics, Targoviste, 130004, Romania
⁵Academy of Romanian Scientists, Bucharest, 050094, Romania
⁶Valahia University of Targoviste, Faculty of Humanities, Targoviste, 130105, Romania

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