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51.
Erika?Kaufmann Günter?Kargl Norbert?I.?K?mleEmail author Manfred?Steller Johann?Hasiba Florian?Tatschl Stefan?Ulamec Jens?Biele Marc?Engelhardt Jens?Romstedt 《Earth, Moon, and Planets》2009,105(1):11-29
One possibility to explore the subsurface layers of icy bodies is to use a probe with a “hot tip", which is able to penetrate
ice layers by melting. Such probes have been built and used in the past for the exploration of terrestrial polar ice sheets
and may also become useful tools to explore other icy layers in the Solar System. Examples for such layers are the polar areas
of Mars or the icy crust of Jupiter’s moon Europa. However, while on Earth a heated probe launched into an ice sheet always
causes melting with subsequent refreezing, the behaviour of such a probe in a low pressure environment is quite different.
We report on the results of some experiments with a simple “melting probe" prototype with two different kinds of hot tips
in a vacuum environment. For one of the tips the probe moved into two types of ice samples: (i) compact water ice and (ii)
porous water ice with a snow (firn) like texture. It was also found that the penetration behaviour was basically different
for the two sample types even when the same kind of tip was used. While in the porous sample the ice was only subliming, the
phase changes occurring during the interaction of the tip with the compact ice are much more complex. Here alternating phases
of melting and sublimation occur. The absence of the liquid phase has severe consequences on the performance of a “melting
probe" under vacuum conditions: In this environment we find a high thermal resistance between the probe surface and the underlying
ice. Therefore, only a low percentage of the heat that is generated in the tip is used to melt or sublime the ice, the bulk
of the power is transferred towards the rear end of the probe. This is particularly a problem in the initial phases of an
ice penetration experiment, when the probe has not yet penetrated the ice over its whole length. In the compact ice sample,
phases could be observed, where a high enough gas pressure had built up locally underneath the probe, so that melting becomes
possible. Only during these melting periods the thermal contact between the probe and the ice is good and in consequence the
melting probe works effectively. 相似文献
52.
Jean-Pierre Raulin Pedro Correia de Matos David Rubens Hadano Antonio C. V. Saraiva Emilia Correia Pierre Kaufmann 《Earth, Moon, and Planets》2009,104(1-4):247-261
In this paper we present the South America VLF NETwork (SAVNET), a new observing facility at very low frequencies. It has been recently installed at different locations spread over Latin America, in Brazil, Peru and Argentina. It consists of a network of seven Very Low Frequency (VLF) receivers with the main scientific objective of monitoring the solar activity on short (minutes to hours) and long (years) time scales. Other objectives include a better understanding of the spatial structure of the South Atlantic Magnetic Anomaly, the study of atmospheric phenomena and the search for genuine seismic-electromagnetic effects. After discussing the scientific goals, the details of the installation are presented as well as the first results recently obtained. 相似文献
53.
T. Mark Harrison Julien Célérier Joerg Hermann 《Geochimica et cosmochimica acta》2009,73(4):1039-1051
Hydrothermal treatment of closely sized muscovite aggregates in a piston-cylinder apparatus induced 40Ar∗ loss that is revealed in 40Ar/39Ar step heating spectra. Age spectra and Arrhenius data, however, differ from that expected from a single diffusion length scale. A numerical model of episodic loss assuming the presence of multiple diffusion domains yields excellent fits between synthetic and actual degassing spectra. We used this model to isolate 40Ar∗ loss from the grains that remained intact during hydrothermal treatment at 10 kbar permitting calculation of diffusion coefficients in the temperature range 730-600 °C. Diffusion data generated in this manner yield an activation energy (E) of 63 ± 7 kcal/mol and frequency factor (Do) of 2.3 cm2/s. Experiments at 20 kbar yield diffusivities lower by about an order of magnitude and correspond to an activation volume of ∼14 cm3/mol. Together, these parameters predict substantially greater retentivity of Ar in muscovite than previously assumed and correspond to a closure temperature (Tc) of 425 °C for a 100 μm radius grain cooling at 10 °C/Ma at 10 kbar (Tc = 405 °C at 5 kbar. Age and log (r/ro) spectra for the run products show strong correlations indicating that muscovites can retain Ar diffusion boundaries and mechanisms that define their natural retentivity during vacuum step heating. This may permit the application of high resolution, continuous 40Ar/39Ar thermochronology to low grade, regionally metamorphosed terranes. 相似文献
54.
The Viséan (Carboniferous) sedimentary succession of the basinal Kulm facies (Rhenish Mountains) was investigated in detail in order to achieve a high‐resolution stratigraphic subdivision and correlation. Additionally, the ranges of fossil index taxa (ammonoids), fossil marker beds, volcaniclastic horizons and sedimentary features (e.g. colour changes) were integrated in the correlation. As a result, a comprehensive database was compiled, which contains 190 stratigraphic events of the Viséan interval of this area. Several sections are almost completely composed of shales, which are regarded to represent a slow but constant basinal background sedimentation of the Kulm facies. The thickness of lithological homogeneous sections thus indicates an approximately linear record of time and the average thicknesses of biozones and positions of stratigraphic events can easily be calculated from the compiled database. The result is an approximately time‐linear biostratigraphic scale for the Viséan Stage of the Kulm Basin. Given a numerical length of the Viséan Stage of ca. 19 Ma, 190 stratigraphic events give a mean resolution of 100 000 years. This is unique in Palaeozoic stratigraphy. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
55.
The recently discovered water vapor plumes on Saturn's moon Enceladus, the polar caps of planet Mars and the possible ice volcanism on the Jovian satellites call for suitable techniques to explore deep ice layers of the solar system bodies. This paper presents a novel approach to deliver scientific probes into deeper layers of planetary ice. Several existing locomotion concepts and techniques for such probes are presented. After studying the mathematical framework of the melting locomotion process, melting tests with different head forms were done to evaluate the influence of the head's geometry on the melting process. This work led to a novel concept of a thermal drill head, using heat and mechanical drill in combination to penetrate the ice. We compare the performance of such a hybrid concept versus the melting penetration alone by a mathematical model and tests in ice with a prototype of the melting drill head. 相似文献
56.
Natural Hazards - Natural hazards, occurring all over the world, may become a disaster when humans and nature interact. In Brazil, landslides triggered by heavy rainfall are the most common... 相似文献
57.
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59.
Hermann Habicht 《International Journal of Earth Sciences》1951,39(1):303-304
Ohne Zusammenfassung 相似文献
60.
Hermann Scholtz 《International Journal of Earth Sciences》1953,41(1):103-110
Ohne Zusammenfassung 相似文献