Comparison of HIPWAC and Mars Express SPICAM observations of ozone on Mars 2006-2008 and variation from 1993 IRHS observations     

Kelly E. Fast  Theodor Kostiuk  Franck Lefèvre  Timothy A. Livengood  Juan D. Delgado  John Annen  Guido Sonnabend 《Icarus》2009,203(1):20-27

Ozone is a tracer of photochemistry in the atmosphere of Mars and an observable used to test predictions of photochemical models. We present a comparison of retrieved ozone abundances on Mars using ground-based infrared heterodyne measurements by NASA Goddard Space Flight Center’s Heterodyne Instrument for Planetary Wind And Composition (HIPWAC) and space-based Mars Express Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet measurements. Ozone retrievals from simultaneous measurements in February 2008 were very consistent (0.8 μm-atm), as were measurements made close in time (ranging from <1 to >8 μm-atm) during this period and during opportunities in October 2006 and February 2007. The consistency of retrievals from the two different observational techniques supports combining the measurements for testing photochemistry-coupled general circulation models and for investigating variability over the long-term between spacecraft missions. Quantitative comparison with ground-based measurements by NASA/GSFC’s Infrared Heterodyne Spectrometer (IRHS) in 1993 reveals 2-4 times more ozone at low latitudes than in 2008 at the same season, and such variability was not evident over the shorter period of the Mars Express mission. This variability may be due to cloud activity.  相似文献   

Time Analysis of the CO+ COMA OF COMET P/HALLEY BY IMAGE PROCESSING TECHNIQUES     

Voelzke  Marcos Rincon  Schlosser  Wolfgang  Schmidt-Kaler  Theodor 《Astrophysics and Space Science》1997,250(1):35-51

Photographic and photoelectric observations of comet P/Halley's ion gas coma from CO⁺ at 4250 ? were part of the Bochum Halley Monitoring Program, conducted from 1986 February 17, to April 17 at the European Southern Observatory on La Silla (Chile). In this spectral range it is possible to watch the continuous formation, motion and expansion of plasma structures. To observe the morphology of these structures 32CO⁺ photos (glass plates) from P/Halley's comet have been analysed. They have a field of view of 28°.6× 28°.6 and were obtained from 1986 March 29, to April 17 with exposure times between 20 and120 minutes. All photos were digitized with a PDS 2020 GM (Photometric Data System) microdensitometer at the Astronomisches Institut derWestf?lischen Wilhelms-Universit?t in Münster (one pixel= 25 μm × 25 μm ≈ 46′.88×46′.88). After digitization the data were reduced to relative intensities, and the part with proper calibrations were also converted to absolute intensities, expressed in terms of column densities using the image data systems MIDAS (Munich Image Data Analysis System; ESO – Image Processing Group, 1988) and IHAP (Image Handling And Processing; Middleburg, 1983). With the help of the Stellingwerf-Theta-Minimum-Method (Stellingwerf, 1978) a period of (2.22 ± 0.09) days results from analysis of structures in the plasma-coma by subtracting subsequent images. This method is also compared with the Fourier method. There may be a second cycle with a period of about 3.6 days. The idea behind subtracting subsequent images is that rotation effects are only 10% phenomena on gas distribution. Difference images are than used to suppress the static component of the gas cloud. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Temporal Behavior of Stratospheric Ammonia Abundance and Temperature Following the SL9 Impacts     

Kelly Fast  Theodor KostiukPaul Romani  Fred EspenakTilak Hewagama  Albert BetzRita Boreiko  Timothy Livengood 《Icarus》2002,156(2):485-497

Infrared emission lines of stratospheric ammonia (NH₃) were observed following the collisions of the fragments of Comet Shoemaker-Levy 9 with Jupiter in July of 1994 at the impact sites of fragments G and K. Infrared heterodyne spectra near 10.7 μm were obtained by A. Betz et al. (in Abstracts for Special Sessions on Comet Shoemaker-Levy 9, The 26th Meeting of the Division for Planetary Sciences, Washington DC, 31 Oct.-4 Nov. 1994, p. 25) using one of the Infrared Spatial Interferometer telescope systems on Mount Wilson. Lineshapes of up to three different NH₃ emission lines were measured at a resolving power of ∼10⁷ at multiple times following the impacts. We present here our radiative transfer analysis of the fully resolved spectral lineshapes of the multiple rovibrational lines. This analysis provides information on temperature structure and NH₃ abundance distributions and their temporal changes up to 18 days after impact. These results are compared to photochemical models to determine the role of photochemistry and other mechanisms in the destruction and dilution of NH₃ in the jovian stratosphere after the SL9 impacts.One day following the G impact, the inferred temperature above 0.001 mbar altitude is 283±13 K, consistent with a recent plume splashback model. Cooling of the upper stratosphere to 204 K by the fourth day and to quiescence after a week is consistent with a simple gray atmosphere radiative flux calculation and mixing with cold jovian air. During the first 4 days after impact, NH₃ was present primarily at altitudes above 1 mbar with a column density of (7.7±1.6)×10¹⁷ cm⁻² after 1 day and (3.7±0.8)×10¹⁷ cm⁻² after 4 days. (Errors represent precision.) We obtained >2.5 times more NH₃ than can be supplied by nitrogen from a large cometary fragment, suggesting a primarily jovian source for the NH₃. By 18 days postimpact, a return to quiescent upper stratospheric temperature is retrieved for the G region, with an NH₃ column density of 7.3×10¹⁷ cm⁻² or more in the lower stratosphere, possibly supplied by NH₃ upwelling across an impact-heated and turbulent tropopause, which may have been masked by initial dust and haze. Above the 1-mbar level, the maximum retrieved column density decreased to 6.5×10¹⁶ cm⁻². Comparison to photochemical models indicates that photolysis alone is not sufficient to account for the loss of NH₃ above 1 mbar by that time, even when chemical reformation of NH₃ is ignored. We speculate that the dispersion of plume material at high altitudes (above 1 mbar) is responsible for the change in the spectra observed a few days postimpact. Data on the K impact region provide qualitatively consistent results.  相似文献   

Fractal analysis of normal faults in northwestern Aegean area, Greece     

Theodor Doutsos  Ioannis Koukouvelas 《Journal of Geodynamics》1998,26(2-4)

Normal faults within the Ptolemais coal field and large seismogenic faults in the northwestern Aegean remain fractal for displacement values larger than about 1m. The kinematic parameters on reverse drag profiles such as length of rollover, footwall uplift and wavelength of footwall uplift show that all three parameters have a power law relationship, expressed by a c exponent of about 1, with the maximum displacement which take place across the fault. Footwall uplift/hanging wall subsidence ratio is about 1/2.The displacement analysis help us to propose a growth model for larger seismogenic faults in the NW Aegean, as is the ‘Hepiros fault set’ and the ‘Aliakmon fault zone’. Faults within the ‘Aliakmon fault zone’ were independently developed, at the first stages of deformation, by tip line deformation and out-of plane bifurcation, whereas later, deformation continued by segment linkage. One of these faults the ‘Sarakina fault’ was reactivated during the 1995 earthquake to produce a 25 km long surface rupture. A long term slip rate of about 0.3 mm a⁻¹ has been estimated by taking into consideration that over the past 6 Ma a maximum displacement of 1700 m across this fault has taken place.  相似文献   

Quaternary tectonics in the Gulf of Patras, western Greece     

G Ferentinos  M Brooks  T Doutsos 《Journal of Structural Geology》1985,7(6):713-717

Air gun seismic and 3.5 kHz profiling data from the Gulf of Patras, western Greece, show that it is occupied by a small asymmetric graben with several geometric similarities to the larger-scale graben in the Gulf of Corinth to the east. Major listric faulting characterizes the southern flank of the graben whilst the northern flank represents an associated rollover structure affected by antithetic and synthetic faulting. The present phase of subsidence is of Holocene age, but buried growth faults suggest earlier subsidence in the Gulf. The average rate of subsidence through the Holocene is estimated to be 10 mm/year.The Gulf of Patras graben, together with the Gulf of Corinth graben and the Megara basin, represent a continuous system of WNW-ESE trending grabens in a broad zone of intense seismicity within the Aegean domain. Individual grabens are offset and are interconnected by NE-SW trending fault systems.  相似文献   

Die Tiefenverhältnisse des Europäischen Nordmeeres     

Theodor Stocks 《Ocean Dynamics》1950,3(1-2):93-100

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Der Steingrund bei Helgoland     

Theodor Stocks 《Ocean Dynamics》1955,8(3):112-118

Zusammenfassung Der Steingrund, eine Bank in etwa 9 m Tiefe, 5–6 sm nordostwärts von Helgoland, wurde 1953 von Atair mit modernen Methoden vermessen, nachdem sich die Notwendigkeit herausgestellt hatte, die letzte vorhergehende Vermessung (1908) zu überholen. Die Form des Grundes wurde in fast der gleichen Gestalt bestätigt, und auch die geographische Lage wurde mit derjenigen von 1908 in Übereinstimmung befunden.

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The Steingrund near the Island of Heligoland

Summary The Steingrund, a bank at a depth of about 9 m, located at a distance of about 5–6 sm northeast from the Island of Heligoland was surveyed for the first time in 1908. As a verification proved to be necessary, another survey was undertaken with modern methods on board the surveying cutter Atair in 1953. According to this survey the form of the Steingrund as well as its geographical position were found to correspond almost completely with the 1908 records.

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Le Steingrund au voisinage de l'île d'Heligoland

Résumé Le Steingrund, un banc en 9 mètres de profondeur, situé à une distance de 5–6 milles marins environ au nord-est de l'île d'Heligoland fut relevé dernièrement en 1908. Comme il se montra nécessaire d'en vérifier les résultats, on effectua un autre relèvement avec des méthodes modernes à bord de la chaloupe hydrographique Atair en 1953. On trouva que la forme actuelle du Steingrund se confond prèsque complètement avec celle que l'on avait constatée en 1908 et que sa position géographique correspond également avec celle déterminée en 1908.

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Dispersal events of Triassic-Jurassic boundary faunas,and paleoenvironment of Tibetan Himalaya     

JiaRun Yin  Franz Theodor Fürsich 《中国科学D辑(英文版)》2009,52(12):1993-2000

End-Triassic ammonoid and bivalve faunas of the Germig area, Tibetan Himalaya, lived in a tropical, shallow-water environment during the Triassic-Jurassic boundary interval. High stratigraphic resolution based on ammonite-biochrons allows to tracing the place of origin of several faunal elements. The bivalves Aguilerella and Ctenostreon occurred first in the Tibetan Himalaya and migrated from there to the eastern South Pacific, exhibiting a pantropic dispersal pattern. This dispersal route is supported by the distribution pattern of the ammonites Choristoceras, Discamphiceras, Pleuroacanthites, and Psiloceras calliphyllum. A few taxa, which went extinct everywhere else by the end of the Triassic, survived in the Tibetan Himalaya into early Early Jurassic times. They include the ammonites Choristoceras and Eopsiloceras, and the bivalves Newaagia, Terquemia, Persia, Ryderia guangdongensis, and Cultriopsis angusta. This suggests that the Tibetan Himalaya may have played a refugia role in the course of the end-Triassic mass extinction.  相似文献   

Ozone abundance on Mars from infrared heterodyne spectra: I. Acquisition, retrieval, and anticorrelation with water vapor     

Kelly Fast  Theodor Kostiuk  Fred Espenak  John Annen  David Buhl  Michael F. A'Hearn  Timothy A. Livengood  Guido Sonnabend  Frank Schmülling 《Icarus》2006,181(2):419-431

Observations of ozone on Mars were made using the Goddard Space Flight Center's Infrared Heterodyne Spectrometer and Heterodyne Instrument for Planetary Wind and Composition at the NASA Infrared Telescope Facility. Ozone is an important observable tracer of martian photochemistry. Infrared heterodyne spectroscopy with spectral resolution ?¹⁰⁶ is the only technique that directly measures ozone in the martian atmosphere from the surface of the Earth. Ozone column abundances down to the martian surface were acquired in seven data sets taken between 1988 and 2003 at various orbital positions (LS=40°, 74°, 102°, 115°, 202°, 208°, 291°). Ozone abundances are compared with those retrieved using ultraviolet techniques, showing good agreement. Odd hydrogen (HO_X) chemistry predicts anticorrelation of ozone and water vapor abundances. Retrieved ozone abundances consistently show anticorrelation with corresponding water vapor abundances, providing strong confirmation of odd hydrogen activity. Deviation from strict anticorrelation between the observed total column densities of ozone and water vapor suggests that constituent vertical distribution is an additional, significant factor.  相似文献   

Ozone abundance on Mars from infrared heterodyne spectra: II. Validating photochemical models     

Kelly Fast  Theodor Kostiuk  Tilak Hewagama  Timothy A. Livengood  Sebastien Lebonnois 《Icarus》2006,183(2):396-402

Ozone is an important observable tracer of martian photochemistry, including odd hydrogen (HO_x) species important to the chemistry and stability of the martian atmosphere. Infrared heterodyne spectroscopy with spectral resolution ?¹⁰⁶ provides the only ground-based direct access to ozone absorption features in the martian atmosphere. Ozone abundances were measured with the Goddard Infrared Heterodyne Spectrometer and the Heterodyne Instrument for Planetary Wind and Composition at the NASA Infrared Telescope Facility on Mauna Kea, Hawai'i. Retrieved total ozone column abundances from various latitudes and orbital positions (LS=40°, 74°, 102°, 115°, 202°, 208°, 291°) are compared to those predicted by the first three-dimensional gas phase photochemical model of the martian atmosphere [Lefèvre, F., Lebonnois, S., Montmessin, F., Forget, F., 2004. J. Geophys. Res. 109, doi:10.1029/2004JE002268. E07004]. Observed and modeled ozone abundances show good agreement at all latitudes at perihelion orbital positions (LS=202°, 208°, 291°). Observed low-latitude ozone abundances are significantly higher than those predicted by the model at aphelion orbital positions (LS=40°, 74°, 115°). Heterogeneous loss of odd hydrogen onto water ice cloud particles would explain the discrepancy, as clouds are observed at low latitudes around aphelion on Mars.  相似文献