1,091 research outputs found
Near-encounter geometry generation
Generation of near encounter spacecraft-target planet celestial geometry using two body trajectory computerized simulatio
A test of the hypothesis that impact-induced fractures are preferred sites for later tectonic activity
Impact cratering has been an important process in the solar system. The cratering event is generally accompanied by faulting in adjacent terrain. Impact-induced faults are nearly ubiquitous over large areas on the terrestrial planets. The suggestion is made that these fault systems, particularly those associated with the largest impact features are preferred sites for later deformation in response to lithospheric stresses generated by other processes. The evidence is a perceived clustering of orientations of tectonic features either radial or concentric to the crater or basin in question. An opportunity exists to test this suggestion more directly on Earth. The terrestrial continents contain more than 100 known or probable impact craters, with associated geological structures mapped to varying levels of detail. Prime facie evidence for reactivation of crater-induced faults would be the occurrence of earthquakes on these faults in response to the intraplate stress field. Either an alignment of epicenters with mapped fault traces or fault plane solutions indicating slip on a plane approximately coincident with that inferred for a crater-induced fault would be sufficient to demonstrate such an association
An investigation of stable waves along a velocity shear boundary in a two-layer sea with a geostrophic flow regime
The physical characteristics of a certain class of stable perturbations in an idealized oceanic current regime are investigated theoretically and compared with some observed featur es of the Gulf Stream. The mathematical model envisages an idealized two-layer fluid with a deep lower layer that remains essentially in static balance. T he upper layer, when in equilibrium, is characterized by a region of uniform geostrophically balanced current (hence of nonuniform thickness); adjoining this is a second region of uniform thickness that is at rest...
The origin of the grooves on Phobos
Various theories for the long, linear depressions on the surface of Phobos are reviewed. Imagery from Viking Orbiters is used to map the surface distribution of the grooves, study their morphology, and date them by means of the density of superimposed impact craters. Data is presented which tends to support the hypothesis that the deep-seated fracturing was caused by a large, nearly catastrophic cratering event. It is suggested that the grooves were produced during the creation of the Stickney crater, rather than as the result of tidal stresses induced by Mars or by drag forces during the hypothetical capture of the satellite by Mars
Phobos: Photometry and origin of dark markings on crater floors
High resolution photographs of Phobos taken during close flybys of Viking Orbiter 1 reveal many dark patches on the floors of several craters. The apparently dark material is only prominent at large phase angles. Analysis of the photometric properties indicates that the dark patches represent areas of unusually rough textures whose reflectance near zero phase is similar to that of the mean surface (approximately 6 percent in the visible), but whose phase curve is much steeper. The contrast of such areas is less than 10 percent zero phase but approaches 100 percent near phase angles of 90 degrees. It is proposed that these intricately textured deposits represent patches of vesticular impact melt
Reply to the comment by Jacobs and Thorpe
Reply to a comment on "Infinite-Cluster geometry in central-force networks",
PRL 78 (1997), 1480. A discussion about the order of the rigidity percolation
transition.Comment: 1 page revTe
Self-Attracting Walk on Lattices
We have studied a model of self-attracting walk proposed by Sapozhnikov using
Monte Carlo method. The mean square displacement
and the mean number of visited sites are calculated for
one-, two- and three-dimensional lattice. In one dimension, the walk shows
diffusive behaviour with . However, in two and three dimension, we
observed a non-universal behaviour, i.e., the exponent varies
continuously with the strength of the attracting interaction.Comment: 6 pages, latex, 6 postscript figures, Submitted J.Phys.
Mariner Mars 1971 optical navigation demonstration
The feasibility of using a combination of spacecraft-based optical data and earth-based Doppler data to perform near-real-time approach navigation was demonstrated by the Mariner Mars 71 Project. The important findings, conclusions, and recommendations are documented. A summary along with publications and papers giving additional details on the objectives of the demonstration are provided. Instrument calibration and performance as well as navigation and science results are reported
Does Religiosity Affect Stock Investors’ Herding Behaviour? Global Evidence
We investigate if religiosity promotes herding among stock market investors. In a global sample of 21 markets over the period 2006–2018, increasing religiosity fosters herding only when the absolute religiosity level is relatively high. At low levels, an increase in religiosity has the opposite effect, promoting anti-herding. Our finding that changes in religiosity, depending on its level (high versus low), exert opposing effects on herding helps to understand contradictory findings in prior literature. Religiosity further induces more herding when economic freedom is low and the state is either impotent or corrupt, and promotes anti-herding when institutional quality is high
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