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  • 1
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    Martian water ice clouds: A view from Mars Global Surveyor Thermal Emission Spectrometer (2011)
    Wiley
    Details
    Publication Date: 2011-04-13
    Description: We have used the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) data to map water ice clouds in the Martian atmosphere in the latitude range –60 to +60 over a period of three Martian years. We have used the same method we have previously used on Viking Infrared Thermal Mapper data in order to allow direct comparison of the cloud behavior in the Viking and MGS eras and confirmed the validity of this method by comparing it to MGS TES standard retrievals. We note that the large-scale behavior of water ice clouds is remarkably consistent, both between the Viking and the MGS eras as well as between years observed by MGS. We also compare our results to water ice absorption-only optical depths derived from TES data and show that correlation is best for type 2 water ice clouds.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Textures of the soils and rocks at Gusev Crater from Spirit's Microscopic Imager (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-08-07
    Description: The Microscopic Imager on the Spirit rover analyzed the textures of the soil and rocks at Gusev crater on Mars at a resolution of 100 micrometers. Weakly bound agglomerates of dust are present in the soil near the Columbia Memorial Station. Some of the brushed or abraded rock surfaces show igneous textures and evidence for alteration rinds, coatings, and veins consistent with secondary mineralization. The rock textures are consistent with a volcanic origin and subsequent alteration and/or weathering by impact events, wind, and possibly water.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Herkenhoff, K E -- Squyres, S W -- Arvidson, R -- Bass, D S -- Bell, J F 3rd -- Bertelsen, P -- Cabrol, N A -- Gaddis, L -- Hayes, A G -- Hviid, S F -- Johnson, J R -- Kinch, K M -- Madsen, M B -- Maki, J N -- McLennan, S M -- McSween, H Y -- Rice, J W Jr -- Sims, M -- Smith, P H -- Soderblom, L A -- Spanovich, N -- Sullivan, R -- Wang, A -- New York, N.Y. -- Science. 2004 Aug 6;305(5685):824-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉U.S. Geological Survey Astrogeology Team, Flagstaff, AZ 86001, USA. kherkenhoff@usgs.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15297663" target="_blank"〉PubMed〈/a〉
    Keywords: Extraterrestrial Environment ; Geologic Sediments ; *Mars ; Volcanic Eruptions ; Water ; Wind
    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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  • 3
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    Evidence from Opportunity's Microscopic Imager for water on Meridiani Planum (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-12-04
    Description: The Microscopic Imager on the Opportunity rover analyzed textures of soils and rocks at Meridiani Planum at a scale of 31 micrometers per pixel. The uppermost millimeter of some soils is weakly cemented, whereas other soils show little evidence of cohesion. Rock outcrops are laminated on a millimeter scale; image mosaics of cross-stratification suggest that some sediments were deposited by flowing water. Vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis. Microscopic images support the hypothesis that hematite-rich spherules observed in outcrops and soils also formed diagenetically as concretions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Herkenhoff, K E -- Squyres, S W -- Arvidson, R -- Bass, D S -- Bell, J F 3rd -- Bertelsen, P -- Ehlmann, B L -- Farrand, W -- Gaddis, L -- Greeley, R -- Grotzinger, J -- Hayes, A G -- Hviid, S F -- Johnson, J R -- Jolliff, B -- Kinch, K M -- Knoll, A H -- Madsen, M B -- Maki, J N -- McLennan, S M -- McSween, H Y -- Ming, D W -- Rice, J W Jr -- Richter, L -- Sims, M -- Smith, P H -- Soderblom, L A -- Spanovich, N -- Sullivan, R -- Thompson, S -- Wdowiak, T -- Weitz, C -- Whelley, P -- New York, N.Y. -- Science. 2004 Dec 3;306(5702):1727-30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉U.S. Geological Survey Astrogeology Team, Flagstaff, AZ 86001, USA. kherkenhoff@usgs.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15576607" target="_blank"〉PubMed〈/a〉
    Keywords: Extraterrestrial Environment ; Ferric Compounds ; Geologic Sediments ; *Mars ; Minerals ; Silicates ; Spacecraft ; *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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  • 4
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    Benthic protists: the under-charted majority (2016)
    Oxford University Press
    Details
    Publication Date: 2016-06-26
    Description: Marine protist diversity inventories have largely focused on planktonic environments, while benthic protists have received relatively little attention. We therefore hypothesize that current diversity surveys have only skimmed the surface of protist diversity in marine sediments, which may harbor greater diversity than planktonic environments. We tested this by analyzing sequences of the hypervariable V4 18S rRNA from benthic and planktonic protist communities sampled in European coastal regions. Despite a similar number of OTUs in both realms, richness estimations indicated that we recovered at least 70% of the diversity in planktonic protist communities, but only 33% in benthic communities. There was also little overlap of OTUs between planktonic and benthic communities, as well as between separate benthic communities. We argue that these patterns reflect the heterogeneity and diversity of benthic habitats. A comparison of all OTUs against the Protist Ribosomal Reference database showed that a higher proportion of benthic than planktonic protist diversity is missing from public databases; similar results were obtained by comparing all OTUs against environmental references from NCBI's Short Read Archive. We suggest that the benthic realm may therefore be the world's largest reservoir of marine protist diversity, with most taxa at present undescribed.
    Print ISSN: 0168-6496
    Electronic ISSN: 1574-6941
    Topics: Biology
    Published by Oxford University Press
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  • 5
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    The Protist Ribosomal Reference database (PR2): a catalog of unicellular eukaryote Small Sub-Unit rRNA sequences with curated taxonomy (2012)
    Oxford University Press
    Details
    Publication Date: 2012-12-20
    Description: The interrogation of genetic markers in environmental meta-barcoding studies is currently seriously hindered by the lack of taxonomically curated reference data sets for the targeted genes. The Protist Ribosomal Reference database (PR 2 , http://ssu-rrna.org/ ) provides a unique access to eukaryotic small sub-unit (SSU) ribosomal RNA and DNA sequences, with curated taxonomy. The database mainly consists of nuclear-encoded protistan sequences. However, metazoans, land plants, macrosporic fungi and eukaryotic organelles (mitochondrion, plastid and others) are also included because they are useful for the analysis of high-troughput sequencing data sets. Introns and putative chimeric sequences have been also carefully checked. Taxonomic assignation of sequences consists of eight unique taxonomic fields. In total, 136 866 sequences are nuclear encoded, 45 708 (36 501 mitochondrial and 9657 chloroplastic) are from organelles, the remaining being putative chimeric sequences. The website allows the users to download sequences from the entire and partial databases (including representative sequences after clustering at a given level of similarity). Different web tools also allow searches by sequence similarity. The presence of both rRNA and rDNA sequences, taking into account introns (crucial for eukaryotic sequences), a normalized eight terms ranked-taxonomy and updates of new GenBank releases were made possible by a long-term collaboration between experts in taxonomy and computer scientists.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 6
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    Molecular analysis shows that soil fungi from ancient semi-natural woodland exist in sites converted to non-native conifer plantations (2014)
    Oxford University Press
    In: Forestry
    Details
    Publication Date: 2014-10-11
    Description: The restoration of microbial communities may be central to the re-establishment of plant–soil interactions and renovation of function in degraded woodland systems. However, there is currently little knowledge of the extent to which the soil microbial communities associated with past vegetation persist in such systems. This study used fungal-specific internal transcribed spacer (ITS) ribosomal DNA environmental clone libraries to compare fungal communities in four ancient semi-natural woodland sites in the UK with adjacent non-native conifer plantations, and with adjacent grassland. In total, we recovered 190 distinct ITS sequence types (ITS types), of which the greatest diversity occurred in ancient semi-natural woodland. Although ancient semi-natural woodland and adjacent conifer plantations shared 27 ITS types, none were shared between woodland and grassland sites. A total of 16 ectomycorrhizal genera were subsequently identified using BLASTn searches, of which nine were recovered from both woodland types and none were shared between woodland and grassland sites. Only eight of these genera had previously been identified from sporophores during 50 years of surveying carried out at the same woodland sites. We conclude that fungal communities associated with ancient semi-natural woodland also exist on sites converted to non-native conifer plantations. In consequence, attempts to restore native, semi-natural woodland may have an increased chance of success when focussed on restoration of plantations, rather than the creation of new woodland on ex-agricultural land.
    Print ISSN: 0015-752X
    Electronic ISSN: 1464-3626
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 7
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    Martian water ice clouds: A view from Mars Global Surveyor Thermal Emission Spectrometer (2011)
    American Geophysical Union
    Details
    Publication Date: 2011-04-13
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 8
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    Martian North Polar Water-Ice Clouds During the Viking Era (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Viking Orbiters determined that the surface of Mars' northern residual cap consists of water ice. Observed atmospheric water vapor abundances in the equatorial regions have been related to seasonal exchange between reservoirs such as the polar caps, the regolith and between different phases in the atmosphere. Kahn modeled the physical characteristics of ice hazes seen in Viking Orbiter imaging limb data, hypothesizing that ice hazes provide a method for scavenging water vapor from the atmosphere and accumulating it into ice particles. Given that Jakosky found that these particles had sizes such that fallout times were of order one Martian sol, these water-ice hazes provided a method for returning more water to the regolith than that provided by adsorption alone. These hazes could also explain the rapid hemispheric decrease in atmospheric water in late northern summer as well as the increase during the following early spring. A similar comparison of water vapor abundance versus polar cap brightness has been done for the north polar region. They have shown that water vapor decreases steadily between L(sub s) = 100-150 deg while polar cap albedo increases during the same time frame. As a result, they suggested that late summer water-ice deposition onto the ice cap may be the cause of the cap brightening. This deposition could be due to adsorption directly onto the cap surface or to snowfall. Thus, an examination of north polar waterice clouds could lend insight into the fate of the water vapor during this time period. Additional information is contained in the original extended abstract.
    Keywords: Lunar and Planetary Science and Exploration
    Type: International Conference on Mars Polar Science and Exploration; 166-167; LPI-Contrib-1057
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  • 9
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    The Contribution of Water Ice Clouds to the Water Cycle in the North Polar Region of Mars: Preliminary Analysis (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: While it has long been known that Mars' north residual polar cap and the Martian regolith are significant sources of atmospheric water vapor, the amount of water vapor observed in the northern spring season by the Viking Mars Atmospheric Water Detector instrument (MAWD) cannot be attributed to cap and regolith sources alone. Kahn suggested that ice hazes may be the mechanism by which additional water is supplied to the Martian atmosphere. Additionally, a significant decrease in atmospheric water vapor was observed in the late northern summer that could not be correlated with the return of the cold seasonal C02 ice. While the detection of water ice clouds on Mars indicate that water exists in Mars' atmosphere in several different phases, the extent to which water ice clouds play a role in moving water through the Martian atmosphere remains uncertain. Work by Bass et. al. suggested that the time dependence of water ice cap seasonal variability and the increase in atmospheric water vapor depended on the polar cap center reaching 200K, the night time saturation temperature. Additionally, they demonstrated that a decrease in atmospheric water vapor may be attributed to deposition of water ice onto the surface of the polar cap; temperatures were still too warm at this time in the summer for the deposition of carbon dioxide. However, whether water ice clouds contribute significantly to this variability is unknown. Additional information is contained in original extended abstract.
    Keywords: Lunar and Planetary Science and Exploration
    Type: International Conference on Mars Polar Science and Exploration; 6-7; LPI-Contrib-1057
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  • 10
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    Albedo Variations on the Martian Northern Polar Cap as Seen by MGS (2003)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The Viking Orbiters determined that the surface of Mars northern residual cap is water ice. Many researchers have related observed atmospheric water vapor abundances to seasonal exchange between reservoirs such as the polar caps, but the extent to which the exchange between the surface and the atmosphere remains uncertain. Early studies of the ice coverage and albedo of the northern residual Martian polar cap using Mariner 9 and Viking images reported that there were substantial internannual differences in ice deposition on the polar cap, a result that suggested a highly variable Martian climate. However, some of the data used in these studies were obtained at differing values of heliocentric solar longitude (Ls). Reevaluation of this dataset in indicated that the residual cap undergoes seasonal brightening throughout the summer, and indicated that this process repeats from year to year. In this study we continue this work with data acquired with Mars Global Surveyor s Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES) instruments. We use MOC Wide Angel (WA) red filter images
    Keywords: Lunar and Planetary Science and Exploration
    Type: Third International Conference on Mars Polar Science and Exploration; LPI-Contrib-1184
    Format: application/pdf
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