¹Kaori Jogo,²Motoo Ito, ³Tomoki Nakamura, ²Sachio Kobayashi, ⁴Jong Ik Lee
Earth, Planets and Space 70, 37 Link to Article [https://doi.org/10.1186/s40623-018-0809-5]
¹Division of Earth-System Polar Research Institute, Incheon South Korea
²Kochi Institute for Core Sample Research, JAMSTEC Nankoku Japan
³Division of Earth and Planetary Materials Science Tohoku University Sendai Japan
⁴Unit of Antarctic K-route Expeditio nKorea Polar Research Institute Incheon South Korea

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¹S. A. Prevec,¹S. H. Büttner
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13076]
¹Department of Geology, Rhodes University, Grahamstown, South Africa
Published by arrangement with John Wiley & Sons

The offset dykes of the Sudbury Igneous Complex comprise two distinct main magmatic facies, a high‐temperature inclusion‐free quartz diorite (QD), and a subsequently intruded lower temperature, mineralized, and inclusion‐rich quartz diorite (MIQD). The MIQD facies was emplaced after QD dykes had solidified. Key controlling factors of the two injection phases were (1) the development of a coherent roof, which confined the melt sheet; and (2) the periodic increase of melt and fluid pressure within the melt sheet. For the injection of QD melt, the melt pressure exceeded the normal stress acting on fracture surfaces. For the later refracturing of QD dykes and the injection of MIQD melt, the melt pressure increased further, exceeding the tensile strength of, and the normal stress acting on, QD dykes. We associate the melt pressure increase required for both injection episodes with degassing and devolatilization of cooling melt close to the roof. Within the hydraulically connected melt column, the related pressure increase was transmitted to the base of the melt sheet where QD and MIQD melt was extracted into dykes. Residual core to rim thermal gradients in the QD dykes produced tensile strength gradients, accounting for the typically central location of MIQD dykes within QD dykes.

¹Ronald T. Daly, ¹Peter H. Schultz
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13081]
¹Department of Earth, Environmental and Planetary Sciences, Brown University, , Providence, Rhode Island, USA
Published by arrangement with John Wiley & Sons

Impact angle plays a significant role in determining the fate of the projectile. In this study, we use a suite of hypervelocity impact experiments to reveal how impact angle affects the preservation, distribution, and physical state of projectile residues in impact craters. Diverse types of projectiles, including amorphous silicates, crystalline silicates, and aluminum, in two sizes (6.35 and 12.7 mm), were launched into blocks of copper or 6061 aluminum at speeds between 1.9 and 5.7 km s−1. Crater interiors preserve projectile residues in all cases, including conditions relevant to the asteroid belt. These residues consist of projectile fragments or projectile‐rich glasses, depending on impact conditions. During oblique impacts at 30° and 45°, the uprange crater wall preserves crystalline fragments of the projectile. The fragments of water‐rich projectiles such as antigorite remain hydrated. Several factors contribute to enhanced preservation on the uprange wall, including a weaker shock uprange, uprange acceleration as the shock reflects off the back of the projectile, and rapid quenching of melts along the projectile–target interface. These findings have two broader implications. First, the results suggest a new collection strategy for flyby sample return missions. Second, these results predict that the M‐type asteroid Psyche should bear exogenic, impactor‐derived debris.

¹Yasuhito Sekine,²Kenya Kodama,³Takamichi Kobayashi,²Seiji Obata,¹Yu Chang,⁴Nanako O. Ogawa,⁴Yoshinori Takano,⁴Naohiko Ohkouchi,²Koichiro Saiki,⁵Toshimori Sekine
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13075]
¹Department of Earth and Planetary Science, The University of Tokyo, , Bunkyo, Tokyo, Japan
²Department of Complexity Science and Engineering, The University of Tokyo, Kashiwa, Chiba, Japan
³National Institute for Materials Science, Tsukuba, Ibaraki, Japan
⁴Department of Biogeochemistry, JAMSTEC, Yokosuka, Kanagawa, Japan
⁵Center for High Pressure Science and Technology Advanced Research, , Shanghai, China
Published by arrangement with John Wiley & Sons

The present study systematically investigates shock‐induced alteration of organic simulants of planetary bodies (OSPBs) as a function of peak shock pressure and temperature by impact experiments. Our results show that the composition and structure of OSPBs are unchanged upon impacts at peak pressures ≤~5 GPa and temperatures ≤~350 °C. On the other hand, these are dramatically changed upon impacts at >7–8 GPa and > ~400 °C, through loss of hydrogen‐related bonds and concurrent carbonization, regardless of the initial compositions of OSPBs. Compared with previous results on static heating of organic matter, we suggest that shock‐induced alteration cannot be distinguished from static heating only by Raman and infrared spectroscopy. Our experimental results would provide a proxy indicator for assessing degree of shock‐induced alteration of organic matter contained in carbonaceous chondrites. We suggest that a remote‐sensing signature of the 3.3–3.6 μm absorption due to hydrogen‐related bonds on the surface of small bodies would be a promising indicator for the presence of less‐thermally‐altered (i.e., <350 °C) organic matter there, which will be a target for landing to collect primordial samples in sample‐return spacecraft missions, such as Hayabusa2 and OSIRIS‐REx.

^1,2Xiaojia Zeng, ¹Shijie Li, ³Ingo Leya, ¹Shijie Wang, ³Thomas Smith, ¹Yang Li, ⁴Peng Wang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13073]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²University of Chinese Academy of Sciences, Beijing, China
³Physics Institute, University of Bern, , Bern, Switzerland
⁴Division of Mines and Geology, Sixth Geological Brigade, Hami, China
Published by arrangement with John Wiley & Sons

The Kumtag 016 strewn field was found in the eastern part of the Kumtag desert, Xinjiang Province, China. In this study, 24 recovered meteorites have been characterized by a suite of different analytical techniques to investigate their petrography, mineralogy, bulk trace elements, noble gas isotopic composition, density, and porosity. We attribute to the strewn field 22 L5 chondrites with shock stage S4 and weathering grade W2–W3. Two different meteorites, Kumtag 021, an L4 chondrite and Kumtag 032, an L6 chondrite, were recognized within the strewn field area. Moreover, Kumtag 003, an H5 chondrite, was previously found in the same area. We infer that the Kumtag 016 strewn field most likely consists of at least four distinct meteorite falls. The effects of terrestrial weathering on the studied meteorites involve sulfide/metal alteration, chemical changes (Sr, Ba, Pb, and U enrichments and depletion in Cr, Co, Ni, and Cs abundances), and physical modifications (decrease of grain density and porosity). Measurements of the light noble gases indicate that the analyzed Kumtag L5 samples contain solar wind‐implanted noble gases with a 20Ne/22Ne ratio of ~12.345. The cosmic‐ray exposure (CRE) ages of the L5 chondrites are in a narrow range (3.6 ± 1.4 Ma to 5.2 ± 0.4 Ma). For L4 chondrite Kumtag 021 and L6 chondrite Kumtag 032, the CRE ages are 5.9 ± 0.4 Ma and 4.7 ± 0.8 Ma, respectively.

¹Christopher T. Adcock, ¹Arya Udry, ¹Elisabeth M. Hausrath, ¹Oliver Tschauner
American Mineralogist 103, 502-516 Link to Article [DOI: https://doi.org/10.2138/am-2018-6193]
¹Department of Geoscience, University of Nevada, 4505 Maryland Parkway, Las Vegas, Nevada 89154-4010, U.S.A.
Copyright: The Mineralogical Society of America

The availability of terrestrial sites that are martian analogs allows researchers to investigate Mars using knowledge gained on Earth. Among the terrestrial analog sites for Mars is Craters of the Moon National Monument (COTM) in Idaho, U.S.A. Craters of the Moon National Monument is home to over 60 basalt lava flows, many of which have been dated from 2050 to 18 340 years before present (y.b.p.). Following previous authors, we examined the chemistry and petrogenesis of COTM basalts compared to basaltic martian rocks, martian meteorites, and meteorite clasts, and then examined the results of chemical weathering of the basaltic flows. Results of our comparative chemical analysis suggest COTM basalts are generally more evolved than the martian materials, with a few notable exceptions. Several COTM flow basalts, including rocks of the >18 000 year old Kimama flow, have high FeO, TiO2, and P2O5 contents similar to the Wishstone and Watchtower class rocks analyzed at Gusev Crater, Mars, by the Mars Exploration Rover Spirit. The youngest basalts of COTM, such as those of the Minidoka (3890 y.b.p.) and Blue Dragon (2050 y.b.p.) flows have similarities in SiO2, alkali contents, and mineralogical norms with select clasts in meteorite Northwest Africa (NWA) 7034. These similarities over a range of flow ages therefore suggest that COTM basalts have the potential to shed important light on specific igneous processes occurring on Mars.

Many of the basaltic rocks measured by rovers on Mars are thought to have experienced chemical weathering during aqueous interactions; however, few basalt weathering rates exist for terrestrial Mars-relevant field environments to help interpret these processes. COTM, which has important similarities to some martian rocks discussed above, also represents a basalt flow chronosequence, and therefore allows for the investigation of basalt weathering as a function of time. We measured the depth of developed porosity in a suite of basalt flows ranging from 2050 to 18 340 y.b.p., and compared field weathering relationships at COTM to weathering rinds developed on the Gusev Crater martian rocks Humphrey, Champagne, Mazatzal, and Wooly Patch. Our results indicate that depths of incipient weathering in COTM rocks increase with time at a rate of 2.32 × 10−2 to 3.04 × 10−2 μm/yr, which is comparable to other terrestrial advance rates. Interestingly, this rate also indicates that chemical weathering strongly outpaces physical weathering even in this arid to semi arid environment. Weathering primarily of the matrix glass indicates that glass may be functioning as the profile-controlling mineral, which may have implications for chemical weathering in glass-rich rocks on Mars. Weathering rates of glass and other minerals can also help constrain the conditions (pH, temperature) of alteration on Mars. Of the altered martian rocks we compared to COTM (Humphrey, Champagne, Mazatzal, and Wooly Patch), altered surfaces of Mazatzal rock at Gusev Crater show the most similarities to weathered surfaces at COTM. Comparisons of chemical weathering in COTM basalts with altered surfaces of rocks in Gusev Crater, Mars, indicate Gusev Crater martian rocks have undergone significantly more aqueous alteration than that experienced by basaltic flows at COTM.

^1,3Elena S.Amador, ²Joshua L.Bandfield, ³Nancy H.Thomas
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.03.021]
¹University of Washington, Department of Earth and Space Sciences and Astrobiology, Seattle, WA
²Space Science Institute, Boulder, CO
³California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA
Copyright Elsevier

Sites associated with serpentinization processes, both on Earth and throughout the Solar System, are becoming increasingly compelling for the study of habitability and astrobiology. The co-occurrence of serpentine, Mg-carbonate, and talc/saponite on Mars is most like terrestrial sites where this mineral suite is produced in low-temperature serpentinizing environments, and where on Earth these reactions support biological activity. This study aims to understand the global distribution of minerals associated with serpentinization. We performed a comprehensive analysis of the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral dataset using factor analysis and target transformation methods to efficiently parse through the large quantity of data. These methods allow for the rapid analysis of thousands of images and provide a quantitative means to determine the significant spectral constituents of an image. These methods were used to produce a global distribution map of CRISM images with a significant likelihood of containing the spectral types of interest. Previous detections of serpentine using traditional CRISM analysis techniques were typically corroborated and additional detections were identified in isolated locations across the martian southern highlands. Most serpentine across Mars is associated with another Fe/Mg-phyllosilicate phase like talc and/or saponite. Except for in the Nili Fossae region, serpentine shows no clear relationship with ultramafic bedrock or with the other mineral phases investigated (Mg-carbonate and talc/saponite). Most serpentine detections were found in isolated exposures, associated with crater ejecta, knobby terrain, or as part of discontinuous layers in crater or valley walls. Nili Fossae shows more pervasive and extensive detections of a serpentine + phyllosilicate endmember than previously recognized, particularly in the eastern portion of Nili Fossae where the highest concentration of olivine-rich basalts is located. These findings imply that large, regional-scale near surface serpentinizing systems were likely rare on Mars. However, low-concentration serpentine detections across the southern highlands do suggest more pervasive serpentinization early in Mars history, when the planet was more geologically active.

¹J. L’Haridon et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.01.028]
¹Laboratoire de Planétologie et de Géodynamique, Université de Nantes, Nantes, France
Copyright Elsevier

ChemCam has observed a wide range of diagenetic features along the Curiosity rover traverse including pervasive Ca-sulfate veins. Observations by multiple instruments on Curiosity indicate that these veins are hydrated, formed during diagenetic fluid event(s). In this study, we delve into the chemical variability in these Ca-sulfate bearing veins and have identified two subsets in the Murray formation with enrichments in Fe and Fe+Mg. These chemical trends do not reflect a sampling mixture with the surrounding host rock but likely indicates the presence of authigenic phases formed during the emplacement of these veins. Based on passive reflectance spectral analysis and correlation with other elements, Fe3+ oxides and/or sulfates are proposed to account for the Fe-rich observations in the vicinity of the Naukluft Plateau whereas the Fe+Mg trend is also observed in adjacent dark-toned features with elevated Mn and P near the Old Soaker outcrop. The specific localization of these observations in the Gale stratigraphy implies changing pH and redox conditions in the groundwater at the time of formation of these veins, from oxidizing and likely more acidic near the Naukluft Plateau to more reducing conditions in the upper part of the Murray formation.

¹Thomas B.McCord, ²Francesca Zambon
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.03.004]
¹The Bear Fight Institute, 22 Fiddler’s Road, Winthrop WA 98862
²Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy
Copyright Elsevier

Ceres’ surface composition is of special interest because it is a window into the interior state and the past evolution of this dwarf planet. Disk-integrated telescopic spectral observations indicated that Ceres’ surface is hydroxylated, similar to but not exactly the same as some of the carbonaceous chondrite classes of meteorites. Furthermore, Ceres’ bulk density is low, suggesting significant water content. The Dawn mission in orbit around Ceres provided a new and much larger set of observations on the mineralogy, molecular and elemental composition, and their distributions in association with surface features and geology. The set of articles contained in this special issue is the first treatment of the entire surface composition of Ceres using the complete High Altitude Mapping Orbit (HAMO) Dawn Ceres data set and the calibrations from all the Dawn instruments. Most articles here treat the different geologic quadrangles of Ceres within the context of the entire body. There also are articles that treat global or technical topics. As a whole, these articles provide a current and comprehensive view of Ceres’ surface composition. Ceres’ surface composition shows a fairly uniform and widespread distribution of NH4- and Mg-phyllosilicates and carbonates, mixed with a dark component and with some exposures of salts and water-ice on Ceres’ surface, all indicative of the presence of aqueous alteration processes that involved the entire dwarf planet. There is also likely some contamination by low velocity infall, as seen on Vesta, but it is more difficult to distinguish this infall from native Ceres material, unlike for the Vesta case. This article introduces and provides the context for the following papers, presents a summary of the various findings, and integrates them into some general conclusions.

¹A.Longobardo et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2018.02.022]
¹INAF-IAPS, via Fosso del Cavaliere 100, Rome I-00133, Italy
Copyright Elsevier

Spectral parameters of Ceres measured by the Dawn/VIR imaging spectrometer are studied as a function of illumination angles, by applying a semi-empirical method based on a statistical analysis of the VIR dataset acquired up to September 2016. The study also focuses on the photometry of the Occator faculae, i.e. the brightest spots of the Ceres surface, showing an albedo up to eight times the Ceres average. The considered semi-empirical approach takes into account the small extension (and hence small dataset) of this region and lays the groundwork to apply scattering models even on such a limited area.

The behavior of Ceres visible and infrared reflectance with phase angle is similar to other asteroids belonging to its same spectral class, i.e. C-type. The depth of the bands at 2.7 µm (phyllosilicates), 3.1 µm (ammonium), 3.4 µm (magnesium carbonates) and the infrared spectral slope linearly increase with phase angle, showing analogies with other asteroids and occurrence of phase reddening. The different behavior of the 3.9 µm band depth (also due to Mg carbonates), independent of illumination angles, could indicate that other carriers contribute to the 3.4 µm band and play a more important role in photometry outside the carbonate deposits.

The phase function of the Occator faculae is much steeper than expected from its high albedo. Mixture of bright and dark material and larger roughness can be at the basis of this result. The phyllosilicate bands show a steeper increase with phase angle with respect to the Ceres average, due to the lower presence of dark materials, and/or again larger roughness. The absence of trends with phase angles of the two carbonate bands and of the spectral slope suggests that carbonates do not produce phase reddening.