Uninhabited habitats on Mars     

Charles S. Cockell  Matt Balme  John C. Bridges  Alfonso Davila  Susanne P. Schwenzer 《Icarus》2012,217(1):184-193

Investigations of Mars as a potential location for life often make the assumption that where there are habitats, they will contain organisms. However, the observation of the ubiquitous distribution of life in habitable environments on the Earth does not imply the presence of life in martian habitats. Although uninhabited habitats are extremely rare on the Earth, a lack of a productive photosynthetic biosphere on Mars to generate organic carbon and oxygen, thus providing a rapidly available redox couple for energy acquisition by life and/or a lack of connectivity between habitats potentially increases the scope and abundance of uninhabited habitats for much of the geological history of the planet. Uninhabited habitats could have existed on Mars from the Noachian to the present-day in impact hydrothermal systems, megaflood systems, lacustrine environments, transient melted permafrost, gullies and local regions of volcanic activity; and there may be evidence for them in martian meteorites. Uninhabited habitats would provide control habitats to investigate the role of biology in planetary-scale geochemical processes on the Earth and they would provide new constraints on the habitability of Mars. Future robotic craft and samples returned from Mars will be able to directly show if uninhabited habitats exist or existed on Mars.  相似文献   

Do macrophytes, diatoms and non-diatom benthic algae give redundant information? Results from a case study in Poland     

Susanne C. Schneider  A.E. LawniczakJ. Picińska-Faltynowicz  K. Szoszkiewicz 《Limnologica》2012,42(3):204-211

We analyzed species composition and abundance of macrophytes, diatoms and non-diatom benthic algae, water chemistry and habitat structure of 24 river sites in Poland, in order to better understand which parameters structure macrophyte and benthic algae communities. Community patterns for macrophytes and diatoms are most closely related, while macrophytes and non-diatom benthic algae have the weakest relationship. Environmental parameters best explaining community patterns are channel substrate parameters for non-diatom benthic algae, and a combination of channel substrate and river bank characteristics for submerged macrophytes, emergent macrophytes and diatoms. Among the organism groups investigated, the diatom community pattern is best correlated to the environmental data similarity matrix. We hypothesize that the results can be explained by the shorter generation time of diatoms compared to macrophytes, and by a higher dispersal rate of diatoms compared to macrophytes and non-diatom benthic algae. This has several practical consequences for bioindication: (1) Diatoms are usually the organism group most closely following environmental parameters, for both increasing and decreasing impact. (2) Since the biotic indices developed for the Water Framework Directive are meant to primarily indicate ecological changes, not water chemistry, the nature of diatoms to closely reflect water chemistry is not necessarily advantageous. (3) The applicability of macrophyte and probably also non-diatom benthic algae indices is more locally restricted, while diatom indices are applicable to greater areas. (4) In ecosystems which are subject to changing environmental conditions, differences in biotic indices between macrophytes, diatoms and non-diatom benthic algae are to be expected. These differences could provide information relating to ecosystem stability. (5) In stable ecosystems, analyzing one of the three organism groups “diatoms”, “non-diatom benthic algae” and “macrophytes” will be sufficient to characterize the quality element “macrophytes and phytobenthos”, as required by the Water Framework Directive. However, in ecosystems subject to increasing pressure, macrophytes likely will have a tendency to indicate “too good”, while in ecosystems subject to decreasing pressure, diatoms will have a tendency to indicate “too good”.  相似文献   

Plastic ingestion by the northern fulmar (Fulmarus glacialis) in Iceland     

Kühn S  van Franeker JA 《Marine pollution bulletin》2012,64(6):1252-1254

In 2011, northern fulmars (Fulmarus glacialis) from Iceland were used to test the hypothesis that plastic debris decreases at northern latitudes in the Atlantic when moving away from major human centres of coastal and marine activities. Stomach analyses of Icelandic fulmars confirm that plastic pollution levels in the North Atlantic tend to decrease towards higher latitudes. Levels of pollution thus appear to link to regions of intense human coastal and marine activities, suggesting substantial current inputs in those areas.  相似文献   

Sources and fate of nutrients in a subtropical reservoir   总被引：1，自引：0，他引：1  

Michele?A.?BurfordEmail author  Susanne?A.?Green  Andrew?J.?Cook  Suzanne?A.?Johnson  Jason?G.?Kerr  Katherine?R.?O’Brien 《Aquatic Sciences - Research Across Boundaries》2012,74(1):179-190

This study examined the sources and fate of nutrient inputs from two principal tributaries to the eutrophic subtropical Wivenhoe reservoir: an unregulated river and a dammed river with regular releases, during a period of declining reservoir water levels. Nutrient budgets were constructed over a period of 6 years, and combined with short-term data on nutrient concentrations and forms, and δ¹⁵N stable isotope data. Our study found that over a 6 year period, there was net retention of phosphorus (P) in the reservoir, with 60% of inputs retained. Most of the P input load came from the unregulated river, with an agricultural catchment, during periods of high flow. During one event half of the total TP load from the unregulated river in the study period was delivered in only 12 days. Much of the P was dissolved inorganic P (DIP) and was derived from high P concentrations in soils and sediments. This highlights the importance of appropriate catchment management practices to reduce P losses from terrestrial systems because retention of P in reservoir sediments reduces the availability of this nutrient for agricultural production. In contrast, there was negligible retention of nitrogen (N). The unregulated river was an important source of N derived from N fixation in the river and adjacent soils, while the source from the dammed river was mostly reprocessed N. The high retention of P relative to N is consistent with relatively higher accumulation of P in sediments.  相似文献   

Wave observation in the marginal ice zone with the TerraSAR-X satellite   总被引：1，自引：1，他引：0  

Claus Gebhardt  Jean-Raymond Bidlot  Johannes Gemmrich  Susanne Lehner  Andrey Pleskachevsky  Wolfgang Rosenthal 《Ocean Dynamics》2016,66(6-7):839-852

This article investigates the penetration of ocean waves into the marginal ice zone (MIZ), observed by satellite, and likewise provides a basis for the future cross-validation of respective models. To this end, synthetic aperture radar images from the TerraSAR-X satellite (TS-X) and numerical simulations of the European Centre for Medium-Range Weather Forecasts (ECMWF) are used. The focus is an event of swell waves, developed during a storm passage in the Atlantic, penetrating deeply into the MIZ off the coast of Eastern Greenland in February 2013. The TS-X scene which is the basis for this investigation extends from the ice-free open ocean to solid ice. The variation of the peak wavelength is analysed and potential sources of variability are discussed. We find an increase in wavelength which is consistent with the spatial dispersion of deep water waves, even within the ice-covered region.  相似文献   

Composition,Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions   总被引：2，自引：0，他引：2  

Kelly K. Bradbury  Colter R. Davis  John W. Shervais  Susanne U. Janecke  James P. Evans 《Pure and Applied Geophysics》2015,172(5):1053-1078

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Sea Surface Salinity Observations from Space with the SMOS Satellite: A New Means to Monitor the Marine Branch of the Water Cycle     

Nicolas Reul  Severine Fournier  Jaqueline Boutin  Olga Hernandez  Christophe Maes  Bertrand Chapron  Gaël Alory  Yves Quilfen  Joseph Tenerelli  Simmon Morisset  Yann Kerr  Susanne Mecklenburg  Steven Delwart 《Surveys in Geophysics》2014,35(3):681-722

While it is well known that the ocean is one of the most important component of the climate system, with a heat capacity 1,100 times greater than the atmosphere, the ocean is also the primary reservoir for freshwater transport to the atmosphere and largest component of the global water cycle. Two new satellite sensors, the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius SAC-D missions, are now providing the first space-borne measurements of the sea surface salinity (SSS). In this paper, we present examples demonstrating how SMOS-derived SSS data are being used to better characterize key land–ocean and atmosphere–ocean interaction processes that occur within the marine hydrological cycle. In particular, SMOS with its ocean mapping capability provides observations across the world’s largest tropical ocean fresh pool regions, and we discuss from intraseasonal to interannual precipitation impacts as well as large-scale river runoff from the Amazon–Orinoco and Congo rivers and its offshore advection. Synergistic multi-satellite analyses of these new surface salinity data sets combined with sea surface temperature, dynamical height and currents from altimetry, surface wind, ocean color, rainfall estimates, and in situ observations are shown to yield new freshwater budget insight. Finally, SSS observations from the SMOS and Aquarius/SAC-D sensors are combined to examine the response of the upper ocean to tropical cyclone passage including the potential role that a freshwater-induced upper ocean barrier layer may play in modulating surface cooling and enthalpy flux in tropical cyclone track regions.  相似文献   

Effects of Roll Vortices on Turbulent Fluxes in the Hurricane Boundary Layer   总被引：1，自引：0，他引：1  

Jun A. Zhang  Kristina B. Katsaros  Peter G. Black  Susanne Lehner  Jeffrey R. French  William M. Drennan 《Boundary-Layer Meteorology》2008,128(2):173-189

Boundary-layer secondary circulations or ‘roll vortices’ can have a significant influence on the turbulent exchange of momentum, sensible heat and moisture throughout the hurricane boundary layer. In this study, analyses of data from a WP-3D aircraft of the National Oceanic and Atmospheric Administration (NOAA) are presented. As part of the Coupled Boundary Layer Air-Sea Transfer (CBLAST)-hurricane experiment sponsored through the Office of Naval Research and NOAA’s annual hurricane research program, flights were conducted to investigate energy exchange across the air–sea interface. We present the first in-situ aircraft-based observations of rolls in the hurricane boundary layer and investigate their influence on energy and momentum exchange. The rolls detected in Hurricane Isidore (year 2002) have a characteristic wavelength of about 900 m, in good agreement with analyses of data from a synthetic aperture radar image captured by the Canadian Space Agency’s RADARSAT satellite in the same storm. Our analyses of the airborne data suggest that roll vortices may be a significant factor modulating the air–sea momentum exchange.  相似文献   

Impact of sill emplacement on sandstones in the Northern Atlantic region     

Susanne Schmid 《Journal of Geochemical Exploration》2009

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Quartz Reference Materials for Oxygen Isotope Analysis by SIMS          下载免费PDF全文

Susanne Seitz  Lukas P. Baumgartner  Anne‐Sophie Bouvier  Benita Putlitz  Torsten Vennemann 《Geostandards and Geoanalytical Research》2017,41(1):69-75

Two quartz samples of igneous origin, UNIL‐Q1 (Torres del Paine Intrusion, Chile) and BGI‐Q1 (Shandong province, China), were calibrated for their oxygen isotope composition for SIMS measurements. UNIL‐Q1 and BGI‐Q1 were evaluated for homogeneity using SIMS. Their reference δ¹⁸O values were determined by CO₂ laser fluorination. The average δ¹⁸O value found for UNIL‐Q1 is 9.8 ± 0.06‰ and that for BGI‐Q1 is 7.7 ± 0.11‰ (1s). The intermediate measurement precision of SIMS oxygen isotope measurements was 0.32–0.41‰ (2s; UNIL‐Q1) and 0.40–0.48‰ (2s; BGI‐Q1), respectively. While less homogeneous in its oxygen isotope composition, BGI‐Q1 is also suitable for SIMS trace element measurements.  相似文献