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  • 1
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    Transport processes induced by metastable boiling water under Martian surface conditions (2016)
    Springer Nature
    Details
    Publication Date: 2016-06-02
    Description: Nature Geoscience 9, 425 (2016). doi:10.1038/ngeo2706 Authors: M. Massé, S. J. Conway, J. Gargani, M. R. Patel, K. Pasquon, A. McEwen, S. Carpy, V. Chevrier, M. R. Balme, L. Ojha, M. Vincendon, F. Poulet, F. Costard & G. Jouannic Liquid water may exist on the Martian surface today, albeit transiently and in a metastable state under the low atmospheric surface pressure. However, the identification of liquid water on Mars from observed morphological changes is hampered by our limited understanding of how metastable liquids interact with sediments. Here, we present lab experiments in which a block of ice melts and seeps into underlying sediment, and the resulting downslope fluid propagation and sediment transport are tracked. In experiments at Martian surface pressure, we find that pure water boils as it percolates into the sediment, inducing grain saltation and leading to wholesale slope destabilization: a hybrid flow mechanism involving both wet and dry processes. For metastable brines, which are more stable under Martian conditions than pure water, saltation intensity and geomorphological impact are reduced; however, we observed channel formation in some briny flow experiments that may be analogous to morphologies observed on Mars. In contrast, under terrestrial-like experimental conditions, there is little morphological impact of seeping water or brine, which are both stable. We propose that the hybrid flow mechanism operating in our experiments under Martian surface pressure could explain observed Martian surface changes that were originally interpreted as the products of either dry or wet processes.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 2
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    History of the clay-rich unit at Mawrth Vallis, Mars: High resolution mapping of a candidate landing site (2015)
    Wiley
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    Publication Date: 2015-10-21
    Description: The Mawrth Vallis region is covered by some of the largest phyllosilicate-rich outcrops on Mars, making it a unique window into the past history of Mars in terms of water alteration, potential habitability and the search for past life. A landing ellipse had been proposed for the Curiosity rover. This area has been extensively observed by HiRISE and CRISM data, offering the possibility to produce geologic, structural and topographic maps at very high resolution. These observations provide an unprecedented detailed context of the rocks at Mawrth Vallis, in terms of deposition, alteration, erosion and mechanical constraints. Our analyses demonstrate the presence of a variety of alteration environments on the surface and readily accessible to a rover, the presence of flowing water at the surface postdating the formation of the clay-rich units, and evidence for probable circulation of fluids in the rocks at different depths. These rocks undergo continuous erosion, creating fresh outcrops where potential biomarkers may have been preserved. The diversity of aqueous environments over geological time coupled to excellent preservation properties make the area a very strong candidate for future robotic investigation on Mars, like the NASA Mars 2020 mission.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Global investigation of olivine on Mars: Insights into crust and mantle compositions (2013)
    Wiley
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    Publication Date: 2013-02-22
    Description: [1]  We present the distribution of olivine on Mars, derived from spectral parameters based on the 1 µm olivine absorption band. The olivine can be defined with respect to two spectral end-members: type 1 corresponds to olivine with low iron content and/or small grain size and/or small abundance, and type 2, which corresponds to olivine with higher iron content and/or larger grain size and/or larger abundance. The spatial and statistical analysis of the global olivine distribution points out five major geological settings where olivine is detected: (1) Early Hesperian olivine-bearing smooth crater floors and flat intercrater plains throughout the southern highlands; (2) olivine deposits around the three main basins Argyre, Hellas, and Isidis; (3) olivine in intercrater dunes, crater ejecta, or extended deposits in the northern plains; (4) olivine associated with outcrops and sand in the floor of Valles Marineris; and (5) olivine-bearing butte outcrops in the vicinity of Hellas. The geological context, the age, and the composition of the olivine detections associated with these five major geological settings are detailed. Their origin and the implication of their occurrence on the composition of the Martian mantle and crust, as well as on the evolution of Mars volcanism are discussed.
    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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    Dark aeolian sediments in Martian craters: Composition and sources (2011)
    Wiley
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    Publication Date: 2011-03-03
    Description: Our research focuses on the mineralogical characteristics of dark sediment deposits in Martian craters (dunes, dune fields, and sand sheets) and their local sediment sources, carried out on the basis of 70 selected localities. Morphological analyses reveal dark layers exposed in a number of crater walls, showing indications of material transport from the layers downwall to the intracrater deposits. Additional sites show dark sediment emerging from several craters floors, suggesting a dark material source beneath the crater floor. Spectral analyses of OMEGA and CRISM data showed for the first time that a direct mineralogical connection exists between the dark layers in the crater walls and the intracrater dune and sand sheet material. Based on these findings, it is shown that these layers are the local sources for the dark aeolian sediment inside the craters. Spectral analyses further indicate that all deposits are nearly of the same mafic mineralogical composition, hinting at a similar origin. We conclude that the mineralogical composition points to a volcanic origin of the material. The dark layers which we infer to be the material sources might represent layers of volcanic ash, almost globally deposited in Early Noachian times and subsequently covered by regolith. Groundwater, impact erosion, and crustal movement led to the highly fragmented situation of the dark layers today. However, burial protected the layers of dark sediment from chemical alteration caused by surficial fluvial processes. Impact erosion after the wet periods on Mars led to the exposure and mobilization of the material today.
    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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    Ancient plutonic processes on Mars inferred from the detection of possible anorthositic terrains (2013)
    Springer Nature
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    Publication Date: 2013-11-29
    Description: Nature Geoscience 6, 1008 (2013). doi:10.1038/ngeo1995 Authors: J. Carter & F. Poulet The mineralogical diversity preserved on ancient terrains of Mars provides insights into the planet’s early geological state and subsequent evolution. The martian crust is predominantly composed of mafic rocks with low silica contents, with the exception of a few localized volcanic sequences that indicate some compositional evolution towards compositions richer in silicate minerals. Anorthosite, which is dominated by the silicate mineral plagioclase, is rare in the Solar System. It is thought to require an evolved magmatic source in which lighter elements have been concentrated. Anorthosite has been observed previously only on Earth within localized continental plutons of intrusive igneous origin, and more widely on the Moon where the anorthositic highland crust is thought to derive from crystallization of a primordial magma ocean. Using near-infrared spectral data obtained by the Mars Reconnaissance Orbiter, we report the detection of iron-bearing plagioclase-rich rocks at eight sites in the southern highlands of Mars with a spectral signature consistent with ferroan anorthosites. The paucity of detections suggests a localized plutonic origin similar to terrestrial anorthosites, although a lunar-like global anorthosite crust on early Mars cannot be entirely excluded. Our detections of anorthositic compositions at several locations on the martian surface suggest that magmatic processes that produce highly evolved melts were active on ancient Mars.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 6
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    Internal brain state regulates membrane potential synchrony in barrel cortex of behaving mice (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-07-18
    Description: Internal brain states form key determinants for sensory perception, sensorimotor coordination and learning. A prominent reflection of different brain states in the mammalian central nervous system is the presence of distinct patterns of cortical synchrony, as revealed by extracellular recordings of the electroencephalogram, local field potential and action potentials. Such temporal correlations of cortical activity are thought to be fundamental mechanisms of neuronal computation. However, it is unknown how cortical synchrony is reflected in the intracellular membrane potential (V(m)) dynamics of behaving animals. Here we show, using dual whole-cell recordings from layer 2/3 primary somatosensory barrel cortex in behaving mice, that the V(m) of nearby neurons is highly correlated during quiet wakefulness. However, when the mouse is whisking, an internally generated state change reduces the V(m) correlation, resulting in a desynchronized local field potential and electroencephalogram. Action potential activity was sparse during both quiet wakefulness and active whisking. Single action potentials were driven by a large, brief and specific excitatory input that was not present in the V(m) of neighbouring cells. Action potential initiation occurs with a higher signal-to-noise ratio during active whisking than during quiet periods. Therefore, we show that an internal brain state dynamically regulates cortical membrane potential synchrony during behaviour and defines different modes of cortical processing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Poulet, James F A -- Petersen, Carl C H -- England -- Nature. 2008 Aug 14;454(7206):881-5. doi: 10.1038/nature07150. Epub 2008 Jul 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratory of Sensory Processing, Brain Mind Institute, Faculty of Life Sciences, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18633351" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Electroencephalography ; Exploratory Behavior/*physiology ; Male ; Membrane Potentials/*physiology ; Mice ; Mice, Inbred C57BL ; Neurons/*physiology ; Somatosensory Cortex/*physiology ; Wakefulness/*physiology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 7
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    Hydrated silicate minerals on Mars observed by the Mars Reconnaissance Orbiter CRISM instrument (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-07-18
    Description: Phyllosilicates, a class of hydrous mineral first definitively identified on Mars by the OMEGA (Observatoire pour la Mineralogie, L'Eau, les Glaces et l'Activitie) instrument, preserve a record of the interaction of water with rocks on Mars. Global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy (Fe/Mg and Al smectite clays). This was interpreted to indicate that phyllosilicate formation occurred during the Noachian (the earliest geological era of Mars), and that the conditions necessary for phyllosilicate formation (moderate to high pH and high water activity) were specific to surface environments during the earliest era of Mars's history. Here we report results from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of phyllosilicate-rich regions. We expand the diversity of phyllosilicate mineralogy with the identification of kaolinite, chlorite and illite or muscovite, and a new class of hydrated silicate (hydrated silica). We observe diverse Fe/Mg-OH phyllosilicates and find that smectites such as nontronite and saponite are the most common, but chlorites are also present in some locations. Stratigraphic relationships in the Nili Fossae region show olivine-rich materials overlying phyllosilicate-bearing units, indicating the cessation of aqueous alteration before emplacement of the olivine-bearing unit. Hundreds of detections of Fe/Mg phyllosilicate in rims, ejecta and central peaks of craters in the southern highland Noachian cratered terrain indicate excavation of altered crust from depth. We also find phyllosilicate in sedimentary deposits clearly laid by water. These results point to a rich diversity of Noachian environments conducive to habitability.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mustard, John F -- Murchie, S L -- Pelkey, S M -- Ehlmann, B L -- Milliken, R E -- Grant, J A -- Bibring, J-P -- Poulet, F -- Bishop, J -- Dobrea, E Noe -- Roach, L -- Seelos, F -- Arvidson, R E -- Wiseman, S -- Green, R -- Hash, C -- Humm, D -- Malaret, E -- McGovern, J A -- Seelos, K -- Clancy, T -- Clark, R -- Marais, D D -- Izenberg, N -- Knudson, A -- Langevin, Y -- Martin, T -- McGuire, P -- Morris, R -- Robinson, M -- Roush, T -- Smith, M -- Swayze, G -- Taylor, H -- Titus, T -- Wolff, M -- England -- Nature. 2008 Jul 17;454(7202):305-9. doi: 10.1038/nature07097. Epub 2008 Jul 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA. john_mustard@brown.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18633411" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Experimental hydrothermal alteration of basaltic glass with relevance to Mars (2019)
    Details
    Publication Date: 2019
    Description: Abstract Phyllosilicates, carbonates, zeolites, and sulfates on Mars give clues about the planet's past environmental conditions, but little is known about the specific conditions in which these minerals formed within the crust and at the surface. The aim of the present study was to gain increased understanding on the formation of secondary phases by hydrothermal alteration of basaltic glass. The reaction processes were studied under varying conditions (temperature, pCO2, water:rock ratio, and fluid composition) with relevance to aqueous hydrothermal alteration in fully and partly saturated Martian basalt deposits. Analyses made on reaction products using X‐ray diffraction (XRD) and scanning electron microscope (SEM) were compared with near infrared spectroscopy (NIR) to establish relative detectability and spectral signatures. This study demonstrates that comparable alteration minerals (phyllosilicates, carbonates, zeolites) form from vapor condensing on mineral surfaces in unsaturated sediments and not only in fully water‐saturated sediments. In certain environments where water vapor might be present, it can alter the basaltic bedrock to a suite of authigenic phases similar to those observed on the Martian surface. For the detection of the secondary phases, XRD and SEM‐EDS were found to be superior to NIR for detecting and characterizing zeolites. The discrepancy in detectability of zeolites between NIR and XRD/SEM‐EDS might indicate that zeolites on Mars are more abundant than previously thought.
    Print ISSN: 1086-9379
    Electronic ISSN: 1945-5100
    Topics: Geosciences , Physics
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  • 9
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    Phyllosilicate diversity and past aqueous activity revealed at Mawrth Vallis, Mars (2008)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2008-08-09
    Description: Observations by the Mars Reconnaissance Orbiter/Compact Reconnaissance Imaging Spectrometer for Mars in the Mawrth Vallis region show several phyllosilicate species, indicating a wide range of past aqueous activity. Iron/magnesium (Fe/Mg)-smectite is observed in light-toned outcrops that probably formed via aqueous alteration of basalt of the ancient cratered terrain. This unit is overlain by rocks rich in hydrated silica, montmorillonite, and kaolinite that may have formed via subsequent leaching of Fe and Mg through extended aqueous events or a change in aqueous chemistry. A spectral feature attributed to an Fe2+ phase is present in many locations in the Mawrth Vallis region at the transition from Fe/Mg-smectite to aluminum/silicon (Al/Si)-rich units. Fe2+-bearing materials in terrestrial sediments are typically associated with microorganisms or changes in pH or cations and could be explained here by hydrothermal activity. The stratigraphy of Fe/Mg-smectite overlain by a ferrous phase, hydrated silica, and then Al-phyllosilicates implies a complex aqueous history.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bishop, Janice L -- Dobrea, Eldar Z Noe -- McKeown, Nancy K -- Parente, Mario -- Ehlmann, Bethany L -- Michalski, Joseph R -- Milliken, Ralph E -- Poulet, Francois -- Swayze, Gregg A -- Mustard, John F -- Murchie, Scott L -- Bibring, Jean-Pierre -- New York, N.Y. -- Science. 2008 Aug 8;321(5890):830-3. doi: 10.1126/science.1159699.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉SETI Institute and NASA Ames Research Center, Mountain View, CA 94043, USA. jbishop@seti.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18687963" target="_blank"〉PubMed〈/a〉
    Keywords: Extraterrestrial Environment ; Iron/analysis ; Magnesium/analysis ; *Mars ; Silicates/*analysis ; 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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  • 10
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    Sulfates in the north polar region of Mars detected by OMEGA/Mars Express (2005)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2005-02-19
    Description: The Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite (OMEGA) imaging spectrometer observed the northern circumpolar regions of Mars at a resolution of a few kilometers. An extended region at 240 degrees E, 85 degrees N, with an area of 60 kilometers by 200 kilometers, exhibits absorptions at wavelengths of 1.45, 1.75, 1.94, 2.22, 2.26, and 2.48 micrometers. These signatures can be unambiguously attributed to calcium-rich sulfates, most likely gypsum. This region corresponds to the dark longitudinal dunes of Olympia Planitia. These observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Langevin, Yves -- Poulet, Francois -- Bibring, Jean-Pierre -- Gondet, Brigitte -- New York, N.Y. -- Science. 2005 Mar 11;307(5715):1584-6. Epub 2005 Feb 17.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut d'Astrophysique Spatiale (IAS), Batiment 121, 91405 Orsay Campus, France. yves.langevin@ias.u-psud.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15718428" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; *Calcium Sulfate ; Carbon Dioxide ; Extraterrestrial Environment ; Geologic Sediments ; *Mars ; Minerals ; Spacecraft ; Spectroscopy, Near-Infrared ; Spectrum Analysis ; *Sulfates ; Temperature ; 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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