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41.
R. Schulz 《Solar System Research》2009,43(4):343-352
One of the two planetary cornerstone missions of the European Space Agency is the Rosetta mission to comet 67P/Churyumov-Gerasimenko. Rosetta is a rendezvous mission with a comet nucleus, which combines an Orbiter with a Lander. It will monitor the evolution of the comet nucleus and the coma as a function of increasing and decreasing solar flux input along the comet’s pre- and post-perihelion orbit. Different instrumentations will be used in parallel, from multi-wavelength spectrometry to in-situ measurements of coma and nucleus composition and physical properties. Rosetta will go in orbit around the nucleus of its target comet 67P/Churyumov-Gerasimenko, when it is still far from the Sun and accompany the comet along its way to perihelion and beyond. In addition the Rosetta Lander Philae will land on the nucleus surface, before the comet is too active to permit such a landing (i.e. at around r = 3 AU) and examine the surface and subsurface composition of the comet nucleus as well as its physical properties. 相似文献
42.
E. Jehin D. Bockelée-Morvan N. Dello Russo J. Manfroid D. Hutsemékers H. Kawakita H. Kobayashi R. Schulz A. Smette J. Stüwe M. Weiler C. Arpigny N. Biver A. Cochran J. Crovisier P. Magain H. Rauer H. Sana R. J. Vervack H. Weaver J.-M. Zucconi 《Earth, Moon, and Planets》2009,105(2-4):343-349
We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very Large Telescope. Such multi-wavelength and coordinated observations are a good example of what can be done to support space missions. From high resolution optical spectroscopy of the CN (0,0) 388 nm and NH2 (0,9,0) 610 nm bands using UVES at UT2 we determined 12C/13C = 90 ± 10 and 14N/15N = 150 ± 20 in CN and we derived a nuclear spin temperature of NH3 of 29 ± 1 K. These values are similar to those found in Oort-Cloud and Jupiter Family comets. From low resolution long slit spectroscopy with FORS1 at UT2 we determined the CN, C3 and C2 production rates and the parent and daughter scale lengths up to 5.2 105 km tailward. From high resolution IR spectroscopy with CRIRES at UT1 we measured simultaneously the production rates and mixing ratios of H2O, HCN, C2H2, CH4, C2H6, and CH3OH. 相似文献
43.
Breakdown of hydrous ringwoodite to pyroxene and spinelloid at high P and T and oxidizing conditions
To get deeper insight into the phase relations in the end-member system Fe2SiO4 and in the system (Fe, Mg)2SiO4 experiments were performed in a multi-anvil apparatus at 7 and 13 GPa and 1,000–1,200°C as a function of oxygen fugacity.
The oxygen fugacity was varied using the solid oxygen buffer systems Fe/FeO, quartz–fayalite–magnetite, MtW and Ni/NiO. The
run products were characterized by electron microprobe, Raman- and FTIR-spectroscopy, X-ray powder diffraction and transmission
electron microscopy. At fO2 corresponding to Ni/NiO Fe-ringwoodite transforms to ferrosilite and spinelloid according to the reaction: 9 Fe2SiO4 + O2 = 6 FeSiO3 + 5 Fe2.40Si0.60O4. Refinement of site occupancies in combination with stoichiometric Fe3+ calculations show that 32% of the total Fe is incorporated as Fe3+ according to From the Rietveld refinement we identified spl as spinelloid III (isostructural with wadsleyite) and/or spinelloid V. As
we used water in excess in the experiments the run products were also analyzed for structural water incorporation. Adding
Mg to the system increases the stability field of ringwoodite to higher oxygen fugacity and the spinel structure seems to
accept higher Fe3+ but also water concentrations that may be linked. At oxygen fugacity corresponding to MtW conditions similar phase relations
in respect to the breakdown reaction in the Fe-end-member system were observed but with a strong fractionation of Fe into
spl and Mg into coexisting cpx. Thus, through this strong fractionation it is possible to stabilize very Fe-rich wadsleyite
with considerable Fe3+ concentrations even at an intermediate Fe–Mg bulk composition: assuming constant K
D independent on composition and a bulk composition of x
Fe = 0.44 this fractionation would stabilize spl with x
Fe = 0.72. Thus, spl could be a potential Fe3+ bearing phase at P–T conditions of the transition zone but because of the oxidizing conditions and the Fe-rich bulk composition
needed one would expect it more in subduction zone environments than in the transition zone in senso stricto.
相似文献
M. Koch-MüllerEmail: |
44.
45.
Bergrat Dr. phil. Eugen Schulz 《International Journal of Earth Sciences》1913,4(2):126-136
Ohne Zusammenfassung 相似文献
46.
47.
Johannes Becherer Jacobus Hofstede Ulf Gräwe Kaveh Purkiani Elisabeth Schulz Hans Burchard 《Ocean Dynamics》2018,68(1):131-151
The impact of sea level rise (SLR) on the future morphological development of the Wadden Sea (North Sea) is investigated by means of extensive process-resolving numerical simulations. A new sediment and morphodynamic module was implemented in the well-established 3D circulation model GETM. A number of different validations are presented, ranging from an idealized 1D channel over a semi-idealized 2D Wadden Sea basin to a fully coupled realistic 40-year hindcast without morphological amplification of the Sylt-Rømøbight, a semi-enclosed subsystem of the Wadden Sea. Based on the results of the hindcast, four distinct future scenarios covering the period 2010–2100 are simulated. While these scenarios differ in the strength of SLR and wind forcing, they also account for an expected increase of tidal range over the coming century. The results of the future projections indicate a transition from a tidal-flat-dominated system toward a lagoon-like system, in which large fractions of the Sylt-Rømøbight will remain permanently covered by water. This has potentially dramatic implications for the unique ecosystem of the Wadden Sea. Although the simulations also predict an increased accumulation of sediment in the back-barrier basin, this accumulation is far too weak to compensate for the rise in mean sea level. 相似文献
48.
Transfer functions describing the coprecipitation of various trace elements (TE; As, Cd, Co, Cu, Cr, Mo, Ni, Pb, Zn), precipitating
with iron(oxihydr)oxides from an aqueous solution, were developed and implemented in the computer model ‘Seeper’. ‘Seeper’
was developed to predict the progression of the concentrations of inorganic pollutants in unsaturated soils underneath contaminated
areas and to evaluate the prospective contamination of the groundwater. Transfer functions provide a straight and simple relation
between the coprecipitation of TE and easy to obtain standard soil parameters, without excessive repercussions on the usability
and computation time of the model. Laboratory experiments were conducted to quantify coprecipitation in solutions with pH
values ranging from 5 to 12 and containing various iron and TE concentrations. For the examined TE, the transfer functions
describe the coprecipitated fraction as a function of the pH value and the concentration ratio between precipitated iron and
a TE. The transfer functions yielded a good prediction of cadmium, cobalt, copper, molybdenum, nickel, and zinc (R
2 from 0.73 to 0.83). As for arsenic, chromium, and lead the correlation was not as good albeit a significant influence of
precipitating iron on the mobility of these elements was observed and represented in the corresponding transfer functions. 相似文献
49.
Hong Kong has undergone substantial economic transformations and developed into a sophisticated business and financial center in the Asia-Pacific region,since the return of sovereignty to China as a Special Administrative Region under the One Country Two Systems (OCTS) in 1997.This paper discusses and analyzes the industrial structural changes of Hong Kong in recent decades as well as its future challenges and opportunities.The data and finding reveal that even though Hong Kong will face fierce competition from the Mainland’s cities as the rise of China,the important role as a bridge between China and the rest of the world will brace Hong Kong itself under the OCTS for developing into a service hub for business and trade in the Asia-Pacific region. 相似文献
50.
Richard P. Mied William J. Schulz Robert A. Handler Charlotte M. Snow Robert A. Fusina John H. Porter 《Continental Shelf Research》2010
The effects of local and remote wind forcing of water level heights in the Virginia Coast Reserve (VCR) are examined in order to determine the significant forces governing estuarine motions over subtidal time scales. Recent (1996–2008) data from tide and wind stations in the lagoon, a tide station to the north at Sandy Hook, NJ, and one offshore wind station at the Chesapeake Light Tower are examined. Sea surface height spectrum calculations reveal significant diurnal and semidiurnal tidal effects along with subtidal variations, but a suppressed inertial signal. Sea-surface heights (SSH) with 2–5 day periods at Wachapreague, VA are coherent with those at Sandy Hook and lag them in time, suggesting that southward-propagating continental shelf waves provide subtidal variability within the lagoon. The coherence between lagoon winds and sea surface height, as well as between winds and cross-lagoon sea height gradient, were significant at a relatively small number of frequency and wind direction combinations. The frequencies at which this wind forcing occurs are the tidal and subtidal bands present to the north, so that lagoon winds selectively augment existing SSH signals, but do not generate them. The impact of the wind direction is closely related to the geometry of the lagoon and bounding landmasses. The effect of wind stress is also constrained by geometry in affecting the cross-lagoon water height gradient. Water levels at subtidal frequencies are likely forced by a combination of local wind forcing, remote wind forcing and oceanic forcing modified by the complex topography of the lagoon, shelf, and barrier islands. 相似文献