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  • 1
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    Mineralogy and chemistry of San Carlos high-alkali basalts: Analyses of alteration with application for Mars exploration (2017)
    Mineralogical Society of America
    Details
    Publication Date: 2017-02-02
    Description: The discovery of Fe, Mg, and Al phyllosilicates on Mars using visible and short-wave infrared (VSWIR) spectroscopy from orbit indicates aqueous alteration of basaltic rocks. Analyses at Gusev Crater by the Spirit rover and Gale Crater by the Curiosity rover have discovered alkaline basaltic rocks. In this work, multiple methods—VSWIR spectroscopy, X-ray diffraction (XRD), and chemical analyses—were used to study a suite of alkaline basalts from San Carlos, Arizona, which have been altered by water in an oxidative, semi-arid environment. As an analog for the weathering of alkaline basaltic rocks on Mars, a suite of rocks visually identified to have different degrees of alteration were characterized to understand the spectral, mineralogical, and chemical trends in alteration as sensed by multiple techniques. Samples with strong 1.9 μm H 2 O-related absorptions in VSWIR commonly exhibited absorption bands at 1.4, 2.2, and/or 2.3 μm, indicating the presence of clay minerals or silica as well as features at 0.5–0.9 μm indicative of ferric iron oxides. Primary mineralogy for all samples, as determined by point analyses with the microprobe and XRD, consisted of olivine, plagioclase, nepheline, augite, and titanomagnetite. Compositional imaging and spot analyses with the microprobe revealed distinct alteration textures and phases, suggesting weathering pathways involving the oxidation of iron in olivine and primary Fe 2+ oxides to form Fe 3+ oxides as well as the formation of aluminum phyllosilicates and magnesium phyllosilicates from feldspars and olivines, respectively, while pyroxene remained relatively unaltered. Bivariate plots of major oxides both from bulk-chemical analysis and microprobe measurements also revealed trends in alkali and silica depletion and calcium enrichment, but there was little chemical fractionation in most of the major oxides. The strength of the 1.9 μm H 2 O absorption, loss on ignition, and depletion in silica and sodium, correlated with increasing alteration. The data sets provide an analog for understanding possible weathering pathways in martian alkaline basalts and thresholds for the detection of aqueous alteration in multiple data sets.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 2
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    Petrography, relationships, and petrogenesis of the gabbroic lithologies in Northwest Africa 773 clan members Northwest Africa 773, 2727, 3160, 3170, 7007, and 10656 (2019)
    Details
    Publication Date: 2019
    Description: Abstract The Northwest Africa (NWA) 773 clan of lunar meteorite stones are coarse‐grained breccias that provide an opportunity to examine a lunar igneous system that includes inferred intrusive and extrusive lithologies, possibly related through a common liquid line of descent from a single source region. Such extensive sampling of a single very low‐Ti (VLT) magmatic system on the Moon is unprecedented among the lunar samples. This study focuses on the olivine gabbro (OG), anorthositic gabbro (AG), and ferroan gabbro (FG) lithologies variably contained in NWA 773, NWA 2727, NWA 3160, NWA 3170, NWA 7007, and NWA 10656. Mineral compositions in the three gabbros indicate the crystallization sequence OG → AG → FG. Petrologic modeling of these three lithologies, and an olivine phyric basalt that also occurs in the NWA 773 clan, however, suggests that the relationship among the lithologies is more complex. The OG and basalt can be modeled as originating from a VLT KREEP‐bearing parental melt similar to the Apollo 14 Green Glass b1 composition through mainly equilibrium crystallization. The AG and FG, however, do not fit this simple model and require either a more complex crystallization sequence involving fractional crystallization, magma chamber recharge, or perhaps heterogeneity in the source region.
    Print ISSN: 1086-9379
    Electronic ISSN: 1945-5100
    Topics: Geosciences , Physics
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  • 3
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    Opportunity Mars Rover mission: Overview and selected results from Purgatory ripple to traverses to Endeavour crater (2011)
    Wiley
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    Publication Date: 2011-02-08
    Description: Opportunity has been traversing the Meridiani plains since 25 January 2004 (sol 1), acquiring numerous observations of the atmosphere, soils, and rocks. This paper provides an overview of key discoveries between sols 511 and 2300, complementing earlier papers covering results from the initial phases of the mission. Key new results include (1) atmospheric argon measurements that demonstrate the importance of atmospheric transport to and from the winter carbon dioxide polar ice caps; (2) observations showing that aeolian ripples covering the plains were generated by easterly winds during an epoch with enhanced Hadley cell circulation; (3) the discovery and characterization of cobbles and boulders that include iron and stony-iron meteorites and Martian impact ejecta; (4) measurements of wall rock strata within Erebus and Victoria craters that provide compelling evidence of formation by aeolian sand deposition, with local reworking within ephemeral lakes; (5) determination that the stratigraphy exposed in the walls of Victoria and Endurance craters show an enrichment of chlorine and depletion of magnesium and sulfur with increasing depth. This result implies that regional-scale aqueous alteration took place before formation of these craters. Most recently, Opportunity has been traversing toward the ancient Endeavour crater. Orbital data show that clay minerals are exposed on its rim. Hydrated sulfate minerals are exposed in plains rocks adjacent to the rim, unlike the surfaces of plains outcrops observed thus far by Opportunity. With continued mechanical health, Opportunity will reach terrains on and around Endeavour's rim that will be markedly different from anything examined to date.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Stability of Mg-sulfates at −10°C and the rates of dehydration/rehydration processes under conditions relevant to Mars (2011)
    Wiley
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    Publication Date: 2011-12-21
    Description: We report the results of low temperature (−10°C) experiments on the stability fields and phase transition pathways of five hydrous Mg-sulfates. A low temperature form of MgSO4·7H2O (LT-7w) was found to have a wide stability field that extends to low relative humidity (∼13% RH at −10°C). Using information on the timing of phase transitions, we extracted information on the reaction rates of five important dehydration and rehydration processes. We found that the temperature dependencies of rate constants for dehydration processes differ from those of rehydration, which reflect differences in reaction mechanisms. By extrapolating these rate constants versus T correlations into the T range relevant to Mars, we can evaluate the possibility of occurrence of specific processes and the presence of common Mg-sulfate species present on Mars in different periods and locations. We anticipate in a moderate obliquity period, starkeyite and LH-MgSO4·H2O should be two common Mg-sulfates at the surface, another polymorph MH-MgSO4·H2O can exist at the locations where hydrothermal processes may have occurred. In polar regions or within the subsurface of other regions, meridianiite (coexisting with water ice, near 100% RH) and LT-7w (over a large RH range) are the stable phases. During a high obliquity period, meridianiite and LT-7w should exhibit widespread occurrence. The correlations of reaction rates versus temperature found in this study imply that dehydration and rehydration of hydrous Mg-sulfates would always be slower than the sublimation and crystallization of water ice, which would be supported by mission observations from Odyssey and by Mars Exploration Rovers.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Evidence for explosive silicic volcanism on the Moon from the extended distribution of thorium near the Compton-Belkovich Volcanic Complex (2014)
    Wiley
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    Publication Date: 2014-12-31
    Description: We reconstruct the abundance of thorium near the Compton-Belkovich Volcanic Complex on the Moon, using data from the Lunar Prospector Gamma Ray Spectrometer. We enhance the resolution via a pixon image reconstruction technique, and find that the thorium is distributed over a larger (40 km × 75 km) area than the (25 km × 35 km) high albedo region normally associated with Compton-Belkovich. Our reconstructions show that inside this region, the thorium concentration is 14–26 ppm. We also find additional thorium, spread up to 300 km eastward of the complex at ~2 ppm. The thorium must have been deposited during the formation of the volcanic complex, because subsequent lateral transport mechanisms, such as small impacts, are unable to move sufficient material. The morphology of the feature is consistent with pyroclastic dispersal and we conclude that the present distribution of thorium was likely created by the explosive eruption of silicic magma.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Observations of Rock Spectral Classes by the Opportunity Rover's Pancam on northern Cape York and on Matijevic Hill, Endeavour Crater, Mars (2014)
    Wiley
    Details
    Publication Date: 2014-10-17
    Description: The Opportunity rover's exploration of the portion of the rim of Endeavour crater known as Cape York included examination of the sulfate-bearing Grasberg formation and the Matijevic Hill region. Multispectral visible and near infrared (VNIR) Pancam observations were used to characterize reflectance properties of rock units. Using spectral endmember detection and classification approaches including a principal components/n-dimensional visualization, automatic sequential maximum angle convex cone method, and classification through hierarchical clustering, six main spectral classes of rock surfaces were identified: light-toned veins, Grasberg fm., the smectite-bearing Matijevic formation, the hematitic “blueberry” spherules, resistant spherules within the Matijevic fm. dubbed “newberries”, and the Shoemaker formation impact breccia. Some of these could be divided into spectral sub-classes. There were three types of veins: veins in the bench unit of Cape York, thinner veins in the Matijevic fm., and boxwork pattern-forming veins. The bench unit veins had higher 535 nm band depths than the other two vein sub-classes and a steeper 934 to 1009 nm slope. The Grasberg fm. has VNIR spectral features that are interpreted to indicate higher fractions of red hematite than in the sulfate-bearing Burns Fm. The Matijevic fm. includes both light-toned, fine-grained matrix and dark-toned veneers. The latter has a weak NIR absorption band centered near 950 nm consistent with nontronite. Observations of Rock Abrasion Tool brushed and ground newberries indicated that cuttings from the RAT grind had a longer wavelength reflectance maximum and deeper 535 nm band depth, consistent with more oxidized materials. Greater oxidation of cementing materials in the newberries is consistent with a diagenetic concretion origin.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    The petrogenesis of impact basin melt rocks in lunar meteorite Shişr 161 (2014)
    Mineralogical Society of America
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    Publication Date: 2014-08-13
    Description: This study explores the petrogenesis of Shişr 161, an immature lunar regolith breccia meteorite with low abundances of incompatible elements, a feldspathic affinity, and a significant magnesian component. Our approach was to identify all clasts 〉0.5 mm in size in a thin section, characterize their mineral and melt components, and reconstruct their bulk major and minor element compositions. Trace element concentrations in representative clasts of different textural and compositional types indicate that the clast inventory of Shişr 161 is dominated by impact melts that include slowly cooled cumulate melt rocks with mafic magnesian mineral assemblages. Minor exotic components are incompatible-element-rich melt spherules and glass fragments, and a gas-associated spheroidal precipitate. Our hypothesis for the petrologic setting of Shişr 161 is that the crystallized melt clasts originate from the upper ~1 km of the melt sheet of a 300 to 500 km diameter lunar impact basin in the Moon’s feldspathic highlands. This hypothesis is based on size requirements for cumulate impact melts and the incorporation of magnesian components that we interpret to be mantle-derived. The glassy melts likely formed during the excavation of the melt sheet assemblage, by an impact that produced a 〉15 km diameter crater. The assembly of Shişr 161 occurred in a proximal ejecta deposit of this excavation event. A later impact into this ejecta deposit then launched Shişr 161 from the Moon. Our geochemical modeling of remote sensing data combined with the petrographic and chemical characterization of Shişr 161 reveals a preferred provenance on the Moon’s surface that is close to pre-Nectarian Riemann-Fabry basin.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
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  • 8
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    Basaltic rocks analyzed by the Spirit Rover in Gusev Crater (2004)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2004-08-07
    Description: The Spirit landing site in Gusev Crater on Mars contains dark, fine-grained, vesicular rocks interpreted as lavas. Pancam and Mini-Thermal Emission Spectrometer (Mini-TES) spectra suggest that all of these rocks are similar but have variable coatings and dust mantles. Magnified images of brushed and abraded rock surfaces show alteration rinds and veins. Rock interiors contain 〈/=25% megacrysts. Chemical analyses of rocks by the Alpha Particle X-ray Spectrometer are consistent with picritic basalts, containing normative olivine, pyroxenes, plagioclase, and accessory FeTi oxides. Mossbauer, Pancam, and Mini-TES spectra confirm the presence of olivine, magnetite, and probably pyroxene. These basalts extend the known range of rock compositions composing the martian crust.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McSween, H Y -- Arvidson, R E -- Bell, J F 3rd -- Blaney, D -- Cabrol, N A -- Christensen, P R -- Clark, B C -- Crisp, J A -- Crumpler, L S -- Des Marais, D J -- Farmer, J D -- Gellert, R -- Ghosh, A -- Gorevan, S -- Graff, T -- Grant, J -- Haskin, L A -- Herkenhoff, K E -- Johnson, J R -- Jolliff, B L -- Klingelhoefer, G -- Knudson, A T -- McLennan, S -- Milam, K A -- Moersch, J E -- Morris, R V -- Rieder, R -- Ruff, S W -- De Souza, P A Jr -- Squyres, S W -- Wanke, H -- Wang, A -- Wyatt, M B -- Yen, A -- Zipfel, J -- New York, N.Y. -- Science. 2004 Aug 6;305(5685):842-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA. mcsween@utk.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15297668" target="_blank"〉PubMed〈/a〉
    Keywords: Extraterrestrial Environment ; Geologic Sediments ; Iron Compounds ; Magnesium Compounds ; *Mars ; *Minerals ; Oxides ; *Silicates ; Spectroscopy, Mossbauer ; Spectrum Analysis ; Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Two years at Meridiani Planum: results from the Opportunity Rover (2006)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2006-09-09
    Description: The Mars Exploration Rover Opportunity has spent more than 2 years exploring Meridiani Planum, traveling approximately 8 kilometers and detecting features that reveal ancient environmental conditions. These include well-developed festoon (trough) cross-lamination formed in flowing liquid water, strata with smaller and more abundant hematite-rich concretions than those seen previously, possible relict "hopper crystals" that might reflect the formation of halite, thick weathering rinds on rock surfaces, resistant fracture fills, and networks of polygonal fractures likely caused by dehydration of sulfate salts. Chemical variations with depth show that the siliciclastic fraction of outcrop rock has undergone substantial chemical alteration from a precursor basaltic composition. Observations from microscopic to orbital scales indicate that ancient Meridiani once had abundant acidic groundwater, arid and oxidizing surface conditions, and occasional liquid flow on the surface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Squyres, S W -- Knoll, A H -- Arvidson, R E -- Clark, B C -- Grotzinger, J P -- Jolliff, B L -- McLennan, S M -- Tosca, N -- Bell, J F 3rd -- Calvin, W M -- Farrand, W H -- Glotch, T D -- Golombek, M P -- Herkenhoff, K E -- Johnson, J R -- Klingelhofer, G -- McSween, H Y -- Yen, A S -- New York, N.Y. -- Science. 2006 Sep 8;313(5792):1403-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16959999" target="_blank"〉PubMed〈/a〉
    Keywords: Acids ; Extraterrestrial Environment ; Ferric Compounds ; Geologic Sediments ; *Mars ; Minerals ; Silicates ; Spacecraft ; Sulfates ; Time ; Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Ancient impact and aqueous processes at Endeavour Crater, Mars (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-05-05
    Description: The rover Opportunity has investigated the rim of Endeavour Crater, a large ancient impact crater on Mars. Basaltic breccias produced by the impact form the rim deposits, with stratigraphy similar to that observed at similar-sized craters on Earth. Highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits. Gypsum-rich veins cut sedimentary rocks adjacent to the crater rim. The gypsum was precipitated from low-temperature aqueous fluids flowing upward from the ancient materials of the rim, leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate-rich sandstones of the Meridiani region.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Squyres, S W -- Arvidson, R E -- Bell, J F 3rd -- Calef, F 3rd -- Clark, B C -- Cohen, B A -- Crumpler, L A -- de Souza, P A Jr -- Farrand, W H -- Gellert, R -- Grant, J -- Herkenhoff, K E -- Hurowitz, J A -- Johnson, J R -- Jolliff, B L -- Knoll, A H -- Li, R -- McLennan, S M -- Ming, D W -- Mittlefehldt, D W -- Parker, T J -- Paulsen, G -- Rice, M S -- Ruff, S W -- Schroder, C -- Yen, A S -- Zacny, K -- New York, N.Y. -- Science. 2012 May 4;336(6081):570-6. doi: 10.1126/science.1220476.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Cornell University, Ithaca, NY 14853, USA. squyres@astro.cornell.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22556248" target="_blank"〉PubMed〈/a〉
    Keywords: Calcium Sulfate ; Extraterrestrial Environment ; Geological Phenomena ; *Mars ; Meteoroids ; Silicates ; Spacecraft ; *Water ; Zinc
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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