CLASSIFICATION OF TWENTY-SIX CHONDRITES FROM ROOSEVELT COUNTY,NEW MEXICO     

Paul P. Sipiera  Mary J. Becker  Yosuke Kawachi 《Meteoritics & planetary science》1987,22(2):151-155

Twenty-six of the fifty-seven stone meteorites listed in Huss (1979) from Roosevelt County, New Mexico, have been classified in the present study. Microprobe analyses indicate 15 H type, 9 L type and 2 LL type chondrites. Based on compositional, textural, and locational comparisons, as many as 10 chondrites may be paired to three distinct falls.  相似文献   

Calibration of the radiometric asteroid scale using occultation diameters     

R.Hamilton Brown  David Morrison  C.M. Telesco  William E. Brunk 《Icarus》1982,52(1):188-195

We report a new approach to the calibration of the radiometric asteroid scale using the recent accurate occultation measurements of the diameters of 2 Pallas and 3 Juno, and the Voyager diameter of J4 Callisto, and new infrared photometry of these objects obtained with the NASA 3-m Infrared Telescope Facility. This calibration is internally consistent to better than 5% and probably has an absolute accuracy of ±5%. A revision of the TRIAD radiometric diameters downward is required to bring them into agreement with the new calibration.  相似文献   

Ground-Water Contamination and Well Construction in Southeast Nebraska     

Mary E. Exner  Roy F. Spalding 《Ground water》1985,23(1):26-34

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Temperature of Comet IRAS-Araki-Alcock (1983d)     

Robert Hamilton Brown  Dale P. Cruikshank  David Griep 《Icarus》1985,62(2):273-281

Infrared (1.5–20 μm) observations of the nuclear condensation of Comet IRAS-Araki-Alcock (1983d) during the interval 5–8 May 1983 (UT) show that the distribution of 3.5- to 20-μm radiation was blackbody in character with no evidence of 10-μm emission from silicate grains in the coma of the comet. The observed color temperature of the nuclear condensation of the comet was 319 ± 5°K on 7 May and 307 ± 5°K on 8 May. Low-resolution spectrophotometry on 5 May in the 1.5- to 2.6-μm region shows no obvious emission or absorption features, but thermal radiation of approximately the same color temperature as the 3.5- to 20-μm radiation was present along with reflected sunlight. Scans of the nuclear region of the comet indicate that most of the thermal radiation observed at 11.6 and 20.0 μm came from an ≤120-km-diameter, unresolved area centered on the nuclear region. Absolute flux measurements suggest that projected areas (unit emissivity) of 70 and 40 km² were responsible for the thermal radiation from the nuclear condensation on 7 and 8 May, respectively. This large change in total surface area suggests that the amount of dust in the nuclear region of Comet 1983d was highly variable and is consistent with the observation by M.A. Feierberg, F.C. Witteborn, J.R. Johnson, and H. Campins (1984, Icarus, 60, 449–454) of an outburst on 11 May 1983.  相似文献   

Effect of compaction on the acquisition of a detrital remanent magnetization in fine-grained sediments     

R. A. Blow  N. Hamilton 《Geophysical Journal International》1978,52(1):13-23

Summary. Measurements of the detrital remanent magnetization (DRM) of redeposited deep-sea sediment of the silty clay grade are described. Variations in the magnitude of an observed remanence inclination error are related to conditions of sediment accumulation, contrasted here as grain-by-grain settling from a dilute dispersion or by settling from a concentrated slurry. For these artificial redepositions post-depositional compaction is shown to be a major factor in shallowing the observed inclination from the ambient field inclination. The term compactive DRM is tentatively assigned to describe such behaviour.  相似文献   

Numerical simulation of fracture flow with a mixed-hybrid FEM stochastic discrete fracture network model     

Jiří Maryška  Otto Severýn  Martin Vohralík 《Computational Geosciences》2005,8(3):217-234

We introduce a discrete fracture network model of stationary Darcy flow in fractured rocks. We approximate the fractures by a network of planar circle disks, which is generated on the basis of statistical data obtained from field measurements. We then discretize this network into a mesh consisting of triangular elements placed in three-dimensional space. We use geometrical approximations in fracture planes, which allow for a significant simplification of the final triangular meshes. We consider two-dimensional Darcy flow in each fracture. In order to accurately simulate the channeling effect, we assign to each triangle an aperture defining its hydraulic permeability. For the discretization we use the lowest order Raviart-Thomas mixed finite element method. This method gives quite an accurate velocity field, which is computed directly and which satisfies the mass balance on each triangular element. We demonstrate the use of this method on a model problem with a known analytical solution and describe the generation and triangulation of the fracture network and the computation of fracture flow for a particular real situation.  相似文献   

Erratum/     

by Mary P. Anderson 《Ground water》2005,43(2):162-162

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Expanding the Environmental Information Exchange Network     

Mary E. Greene 《Ground Water Monitoring & Remediation》2005,25(4):44-46

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Kinetic model of olivine dissolution and extent of aqueous alteration on mars     

Julie D. Stopar  G. Jeffrey Taylor  Victoria E. Hamilton  Lauren Browning 《Geochimica et cosmochimica acta》2006,70(24):6136-6152

If water was ever present on Mars, as suggested by geomorphological features, then much of the surface and subsurface may have experienced chemical weathering. Among those materials most readily altered is olivine, which has been identified on the Martian surface with IR spectroscopy and Mossbauer techniques and occurs in Martian meteorites. We use geochemical models of olivine dissolution kinetics to constrain the residence time of olivine on the surface of Mars in the presence of liquid water. From these models, we have calculated maximum dissolution rates and minimum residence times for olivine as a function of temperature, pH, Fe-composition, and particle size. In general, the most favorable conditions for olivine dissolution are fayalite-rich compositions, small particle sizes, high temperatures, and acidic solutions that are far from equilibrium. The least favorable conditions for olivine dissolution are forsterite-rich compositions, large particle sizes, ultra-low temperatures, and a neutral pH solution near equilibrium. By using kinetic models of olivine dissolution to bound dissolution rates and residence times, we can make inferences about the temporal extent of aqueous alteration on the surface of Mars. Under favorable conditions (pH 2, 5 °C, and far from equilibrium) a relatively large 0.1 cm (radius) particle of Fo₆₅ composition can completely dissolve in 370 years. Particles may last 10²–10⁴ times longer under less favorable conditions. However, residence times of a few million years or less are small compared to the age of most of the Martian surface. The survival of olivine on the surface of Mars, especially in older terrains, implies that contact with aqueous solutions has been limited and wet periods on Mars have been short-lived.  相似文献   

Just say NO to equifinality   总被引：1，自引：0，他引：1  

Stuart Hamilton 《水文研究》2007,21(14):1979-1980

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