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11.
Philip A. Helmke Douglas P. Blanchard Larry A. Haskin Karen Telander Charles Weiss Jeffrey W. Jacobs 《Earth, Moon, and Planets》1973,8(1-2):129-148
The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na2O, K2O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow. At least two and possible three parent magmas can be identified from the samples of the quartz normative group on the basis of their concentration ratios of Sm to Eu. Within each group, the compositions of the samples appear to be related by crystallization of olivine or pyroxene. Significant variations of the ratio of concentration of Sm to Eu cannot be produced without plagioclase-liquid equilibrium. The source material of mare basalt may be depleted in Eu. Alternatively, the magmas may have assimilated a small volume of material similar to KREEP.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973. 相似文献
12.
Herbert Weiss Kathe Bertine Minoru Koide Edward D. Goldberg 《Geochimica et cosmochimica acta》1975,39(1):1-10
Chemical analyses on water from dated strata of a south Greenland permanent ice sheet revealed that there is a larger amount of sulfate in samples accumulated during the past decade than in those 60 or more years older. This increase is attributed to combustion of fossil fuel. With the exception of mercury, cadmium and possibly copper, the heavy metal distributions in the glacial waters are similar to those in atmospheric dusts. Previously reported higher mercury values in recently deposited strata were not confirmed. 相似文献
13.
A. Quirrenbach J. Larkin M. Barczys T. Gasaway C. Iserlohe A. Krabbe M. McElwain I. Song J. Weiss S. Wright 《New Astronomy Reviews》2006,49(10-12):639
OSIRIS (OH-Suppressing Infra-Red Integral-field Spectrograph) is a new facility instrument for the Keck Observatory. After seeing first light in February 2005, OSIRIS is currently undergoing commissioning. OSIRIS provides the capability of performing three-dimensional spectroscopy in the near-infrared z, J, H, and K bands at the resolution limit of the Keck II telescope, which is equipped with adaptive optics and a laser guide star. The science case for OSIRIS is summarized, and the instrument and associated data reduction software are described. 相似文献
14.
Stratigraphic sections are often sampled at well-defined discrete points. Because of the incompleteness of the fossil record, a particular species may not be observed even when it is extant at a sampling point. We introduce a model and Bayesian analysis for estimating the true time of disappearance of a lineage from a section in the face of the possibility that failure to find the species beyond its observed stratigraphic range may represent false negatives. We incorporate proper prior information, including an estimated longevity of the species and the probability that it will be observed if extant. Our analysis produces a posterior density for the true extinction time of the species. Summaries of this probability distribution provide a point estimate of the extinction time, a standard deviation for the uncertainty in the estimate, and confidence intervals for the time of extinction. We apply our model to stratigraphic ranges of benthic foraminifera collected from the early Late Cretaceous (Cenomanian and Turonian) from Eastbourne, England. 相似文献
15.
David Parry Rubincam Nelson R. Weiss 《Celestial Mechanics and Dynamical Astronomy》1986,38(3):233-296
The long-period perturbations in the orbit of Lageos satellite due to the earth's albedo have been found using a new analytical formalism. The earth is assumed to be a sphere whose surface diffusely reflects sunlight according to Lambert's law. Specular reflection is not considered. The formalism is based on spherical harmonics; it produces equations which hold regardless of whether the terminator is seen by the satellite or not. Specializing in the case of a realistic zonal albedo shows that Lageos' orbital semimajor axis changes periodically by only about a centimeter and the eccentricity by two parts in 105. The longitude of the node increases secularly by about 6×10–4 arc sec yr–1. The effect considered here can explain neither the secular decay of 1.1 mm day–1 in the semimajor axis nor the observed along-track variations in acceleration of order 2×10–12 ms–2. 相似文献
16.
ABSTRACT Distribution patterns of benthic foraminiferal faunas from ODP Leg 170 Sites 1041 and 1042 show that the Costa Rican convergent margin subsided from coastal to abyssal depth from Middle Miocene to Present. This favours the model of a margin undergoing active subduction erosion. We propose that subduction erosion leads to the removal of material from the base of the forearc wedge and, as a consequence, to progressive subsidence of the forearc. A mean subsidence rate is estimated to be approximately 0.4 mm yr−1 . 相似文献
17.
Martina M. Halmer 《地学学报》2005,17(6):500-502
Earth's ozone layer is only a very small part of the atmosphere, but its intact abundance is most important to the vitality of human beings. Observations have shown that especially after the plinian eruption of Pinatubo volcano in 1991 the ozone layer showed a dramatic depletion. Could a similar hypothetic eruption in the future cause an equal effective destruction of ozone while considering the increasing reduction of man-made halogens in the stratosphere after the Montreal protocol in 1987? 相似文献
18.
As part of our study of the larger-scale remanent magnetic field of the Moon, we have examined the effects of cratering in
an otherwise spherically symmetrical shell magnetized by a concentric dipolar magnetic fieldH
o to an intensity of magnetizationc
H
o, wherec is a constant. In our initial model, we assume that the material excavated from the craters is distributed with random orientation
and thus does not contribute to the remanent dipole momentM
g
. We further assume that the mare fill does not contribute significantly toM
g
. We choose the magnetizing dipole momentM
o and the constantc such that the magnitude of the productcH
o ≃ 3 × 10−4Г at the outer surface of the shell in the equatorial plane of the dipole. This value of the intensity of remanent magnetization
was chosen to be within the range 10−7−10−3Г’; the intensities of thermo-remanent magnetization exhibited by Apollo samples. Finally, we use the locations and diameters
of the 10 largest craters on the Moon and the depth-to-diameter ratios of Pike’s formulation to model approximately the excavation
of the magnetized shell.
The remanent dipole momentM
g
was calculated for each of three orthogonal orientations of the magnetizing dipoleM
o. The three magnitudes ofM
g
fall in the range 4 × 1018−1 × 1019Г cm3 which is close to the upper limit of 1019Г cm3 estimated forM
g
from the field measurements obtained with the Apollo subsatellites. Further, the distribution of the craters is such as to
produce a significant transverse component ofM
g
with acute angles between the spin axis andM
g
in the range 51°–77°. 相似文献
19.
20.
Yveline Lebreton Josefina Montalbán Jørgen Christensen-Dalsgaard Ian W. Roxburgh Achim Weiss 《Astrophysics and Space Science》2008,316(1-4):187-213
We compare stellar models produced by different stellar evolution codes for the CoRoT/ESTA project, comparing their global quantities, their physical structure, and their oscillation properties. We discuss the differences between models and identify the underlying reasons for these differences. The stellar models are representative of potential CoRoT targets. Overall we find very good agreement between the five different codes, but with some significant deviations. We find noticeable discrepancies (though still at the per cent level) that result from the handling of the equation of state, of the opacities and of the convective boundaries. The results of our work will be helpful in interpreting future asteroseismology results from CoRoT. 相似文献