The Jovian stratosphere in the ultraviolet     

Richard Wagener  John Caldwell  Tobias Owen  Therese Encrenaz  Michel Combes 《Icarus》1985,63(2):222-236

The center-of-disk reflectivity of Jupiter in the wavelength range from 1450 to 3150A?has been computed from 30 low-dispersion IUE spectra taken during solar maximum in 1978–1980. A vertically inhomogeneous radiative transfer program is used to compute model reflectivities of various stratospheric compositions for comparison. Ammonia and acetylene are well determined because they show narrow absorption bands in the ultraviolet. Above 1800A?, these two gases provide a good fit to the data, but not below. At shorter wavelengths the fit would be much improved by a small amount (5–15 ppb) of propadiene/allene (C₃H₄). Voyager IRIS spectra show that the IR bands of allene are not strong enough to be detected in such a small amount. Additional absorption around 1600A?can be reproduced best with the presence of cyclopropane (C₃H₆, <15ppb), although other absorbers (e.g., hydrocarbon molecules with more than three carbon atoms, oxygen- or nitrogen-containing molecules, or a high-attitude haze) could also explain the spectrum in this region. The data are too noisy to detect possible CO Cameron band absorption near 2000A?.  相似文献   

Eemian landscape response to climatic shifts and evidence for northerly Neanderthal occupation at a palaeolake margin in northern Germany     

Michael Hein  Brigitte Urban  David Colin Tanner  Anton Hermann Buness  Mario Tucci  Philipp Hoelzmann  Sabine Dietel  Marie Kaniecki  Jonathan Schultz  Thomas Kasper  Hans von Suchodoletz  Antje Schwalb  Marcel Weiss  Tobias Lauer 《地球表面变化过程与地形》2021,46(14):2884-2901

The prevailing view suggests that the Eemian interglacial on the European Plain was characterized by largely negligible geomorphic activity beyond the coastal areas. However, systematic geomorphological studies are sparse. Here we present a detailed reconstruction of Eemian to Early Weichselian landscape evolution in the vicinity of a small fingerlake on the northern margin of the Salzwedel Palaeolake in Lower Saxony (Germany). We apply a combination of seismics, sediment coring, pollen analysis and luminescence dating on a complex sequence of colluvial, paludal and lacustrine sediments. Results suggest two pronounced phases of geomorphic activity, directly before the onset and at the end of the Eemian period, with an intermediate period of pronounced landscape stability. The dynamic phases were largely driven by incomplete vegetation cover, but likely accentuated by fluvial incision in the neighbouring Elbe Valley. Furthermore, we discovered Neanderthal occupation at the lakeshore during Eemian pollen zone (PZ) E IV, which is chronologically in line with other known Eemian sites of central Europe. Our highly-resolved spatio-temporal data substantially contribute to the understanding of climate-induced geomorphic processes throughout and directly after the last interglacial period. It helps unraveling the landscape dynamics between the coastal areas to the north and the loess belt to the south.  相似文献   

Results from the Huygens probe on Titan     

Jean-Pierre Lebreton  Athena Coustenis  Jonathan Lunine  François Raulin  Tobias Owen  Darrell Strobel 《Astronomy and Astrophysics Review》2009,17(2):149-179

The Cassini–Huygens mission, comprising the NASA Saturn Orbiter and the ESA Huygens Probe, arrived at Saturn in late June 2004. The Huygens probe descended under parachute in Titan’s atmosphere on 14 January 2005, 3 weeks after separation from the Orbiter. We discuss here the breakthroughs that the Huygens probe, in conjunction with the Cassini spacecraft, brought to Titan science. We review the achievements ESA’s Huygens probe put forward and the context in which it operated. The findings include new localized information on several aspects of Titan science: the atmospheric structure and chemical composition; the aerosols distribution and content; the surface morphology and composition at the probe’s landing site; the winds, the electrical properties, and the implications on the origin and evolution of the satellite.  相似文献   

The formation of ultra-compact dwarf galaxies and nucleated dwarf galaxies     

Tobias Goerdt  Ben Moore  Stelios Kazantzidis  Tobias Kaufmann  rea V. Macciò  Joachim Stadel 《Monthly notices of the Royal Astronomical Society》2008,385(4):2136-2142

  相似文献   

Architecture and temporal variations of a terrestrial CO2 degassing site using electric resistivity tomography and self-potential     

Nickschick  Tobias  Flechsig  Christina  Meinel  Cornelia  Mrlina  Jan  Kämpf  Horst 《International Journal of Earth Sciences》2017,106(8):2915-2926

International Journal of Earth Sciences - The Hartoušov mofette field in NW Bohemia, Czech Republic, is characterized by strong CO2 degassing from the Lithospheric Mantle. In a test survey...  相似文献   

Effects of thermal energy storage on shallow aerobic aquifer systems: temporary increase in abundance and activity of sulfate-reducing and sulfur-oxidizing bacteria     

Tobias Lienen  Klas Lüders  Hannah Halm  Anke Westphal  Ralf Köber  Hilke Würdemann 《Environmental Earth Sciences》2017,76(6):261

Aquifer thermal energy storage may result in increases in the groundwater temperature up to 70 °C and more. This may lead to geochemical and microbiological alterations in the aquifer. To study the temperature effects on the indigenous microbial community composition, sediment column experiments at four different temperatures were carried out and the effluents were characterized geochemically and microbiologically. After an equilibrium phase at groundwater temperature of 10 °C for 136 days, one column was kept at 10 °C as a reference and the others were heated to 25, 40 and 70 °C. Genetic fingerprinting and quantitative PCR revealed a change in the bacterial community composition and abundance due to the temperature increase. While at 25 °C only slight changes in geochemical composition and gene copy numbers for bacteria were observed, increasing concentrations of total organic carbon in the 40 °C column were followed by a strong increase in bacterial abundance. Thermophilic bacteria became dominant at 70 °C. Temporary sulfate reduction took place at 40 and 70 °C and this correlated with an increased abundance of sulfate-reducing bacteria (SRB). Furthermore, a coexistence of SRB and sulfur-oxidizing bacteria (SOB) at all temperatures indicated an interaction of these physiological groups in the sediments. The results show that increased temperatures led to significant shifts in the microbial community composition due to the altered availability of electron donors and acceptors. The interplay of SRB and SOB in sedimentary biofilms facilitated closed sulfur cycling and diminished harmful sulfur species.  相似文献   

Sulfur isotope fractionation during the May 2003 eruption of Anatahan volcano, Mariana Islands: Implications for sulfur sources and plume processes     

J. Maarten de Moor  Tobias P. Fischer  Erik H. Hauri  Viorel Atudorei 《Geochimica et cosmochimica acta》2010,74(18):5382-5397

Sulfur isotope compositions of pumice and adsorbed volatiles on ash from the first historical eruption of Anatahan volcano (Mariana arc) are presented in order to constrain the sources of sulfur erupted during the period 10-21 May, 2003. The isotopic composition of S extracted from erupted pumice has a narrow range, from δ³⁴S_V-CDT +2.6‰ to +3.2‰, while the composition of sulfur adsorbed onto ash has a larger range (+2.8‰ to +5.3‰). Fractionation modeling for closed and open system scenarios suggests that degassing of SO₂ raised the δ³⁴S_V-CDT value of S dissolved in the melt from an initial composition of between +1.6‰ and +2.6‰ for closed-system degassing, or between −0.5‰ and +1.5‰ for open-system degassing, however closed-system degassing is the preferred model. The calculated values for the initial composition of the magma represent a MORB-like (δ³⁴S_V-CDT ∼ 0‰) mantle source with limited contamination by subducted seawater sulfate (δ³⁴S_V-CDT +21‰). Modeling also suggests that the δ³⁴S_V-CDT value of SO₂ gas in closed-system equilibrium with the degassed magma was between +0.9‰ and +2.5‰. The δ³⁴S_V-CDT value of sulfate adsorbed onto ash in the eruption plume (+2.8‰ to +5.1‰) is consistent with sulfate formation by oxidation of magmatic SO₂ in the eruption column. The sulfur isotope composition of sulfate adsorbed to ash changes from lower δ³⁴S values for ash erupted early in the eruption to higher δ³⁴S values for ash erupted later in the eruption. We interpret the temporal/stratigraphic change in sulfate isotopic composition to primarily reflect a change in the isotopic composition of magmatic SO₂ released from the progressively degassing magma and is attributed to the expulsion of an accumulated gas phase at the beginning of the eruption. More efficient oxidation of magmatic SO₂ gas to sulfate in the early water-rich eruption plume probably contributed to the change in S isotope compositions observed in the ash leachates.  相似文献   

Transtensional fault-termination basins: an important basin type illustrated by the Pliocene San Jose Island basin and related basins in the southern Gulf of California, Mexico     

Paul J. Umhoefer  Tobias Schwennicke†  Maya T. Del Margo  Gabriela Ruiz-Geraldo†  James C. Ingle Jr.  ‡  William McIntosh§ 《Basin Research》2007,19(2):297-322

Transtensional basins are sparsely described in the literature compared with other basin types. The oblique‐divergent plate boundary in the southern Gulf of California has many transtensional basins: we have studied those on San Jose island and two other transtensional basins in the region. One major type of transtensional basin common in the southern Gulf of California region is a fault‐termination basin formed where normal faults splay off of strike‐slip faults. These basins suggest a model for transtensional fault‐termination basins that includes traits that show a hybrid nature between classic rift and strike‐slip (pull‐apart) basins. The traits include combinations of oblique, strike‐slip and normal faults with common steps and bends, buttress unconformities between the fault steps and beyond the ends of faults, a common facies pattern of terrestrial strata changing upward and away from the faults into marine strata, small fault blocks within the basin that result in complex lateral facies relations, common Gilbert deltas, dramatic termination of the margin of the basin by means of fault reorganization and boundary faults dying and an overall short basin history (few million years). Similar transtensional fault‐termination basins are present in Death Valley and other parts of the Eastern California shear zone of the western United States, northern Aegean Sea and along ancient strike‐slip faults.  相似文献   

Process-based interpretation of tracer tests in carbonate aquifers   总被引：6，自引：0，他引：6  

Birk S  Geyer T  Liedl R  Sauter M 《Ground water》2005,43(3):381-388

A tracer test in a carbonate aquifer is analyzed using the method of moments and two analytical advection-dispersion models (ADMs) as well as a numerical model. The numerical model is a coupled continuum-pipe flow and transport model that accounts for two different flow components in karstified carbonate aquifers, i.e., rapid and often turbulent conduit flow and Darcian flow in the fissured porous rock. All techniques employed provide reasonable fits to the tracer breakthrough curve (TBC) measured at a spring. The resulting parameter estimates are compared to investigate how each conceptual model of flow and transport processes that forms the basis of the analyses affects the interpretation of the tracer test. Numerical modeling results suggest that the method of moments and the analytical ADMs tend to overestimate the conduit volume because part of the water discharged at the spring is wrongly attributed to the conduit system if flow in the fissured porous rock is ignored. In addition, numerical modeling suggests that mixing of the two flow components accounts for part of the dispersion apparent in the measured TBC, while the remaining part can be attributed to Taylor dispersion. These processes, however, cannot reasonably explain the tail of the TBC. Instead, retention in immobile-fluid regions as included in a nonequilibrium ADM provides a possible explanation.  相似文献   

Volatile inventories on Mars     

Tobias Owen 《Icarus》1976,28(2):171-177

Predictions for the total inventory of outgassed volatiles on Mars can be developed by studying volatiles in meteorites, terrestial rocks, and the atmospheres of Venus, the Moon, and the Earth. Two models are presented following the basic assumption that the devolatilization of Mars has been analogous to that of the Earth. The recent discovery of a high abundance of argon in the Martian atmosphere appears to indicate that Mars has outgassed as completely as the Earth, but present uncertainties and lacunae in the essential data set permit several other interpretations.  相似文献