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Organic and inorganic constituents of carbonaceous and other selected stony meteorites
Cosmic ray produced hydrogen 3 and helium 3 in stony meteorites, estimating ratio of production
Absorption analysis for copper and zinc traces in iron and stony meteorites
Barium concentration distribution in the chondrite appear to be log-normal in shape with a median of 4.5 ppm as determined by spectrographs of 95 stony meteorites
The Al-26 content of a group of stony meteorites with low levels of He-3 (implying outgassing caused by near approach to the sun) was analyzed in a test of the possible role of cosmic radiation in determining the radionuclide concentration of meteorites. The Al-26 contents of the meteorites with He-3 losses were found to be indistinguishable from the Al-26 contents of L- and H-chondrites. It is concluded that if the He-3 outgassing occurred near the sun, the flux of particles producing Al-26 must have been nearly normal, or the diffusion process must have taken place very rapidly.
The presence of trapped solar gas in stony meteorites places their origin in the regoliths of asteroidal-type bodies. The most plausible sources are the C (carbonaceous) and S (siliceous) asteroids, in spite of the differences between the spectra of S asteroids and ordinary chondrites. This problem is a central one for the interpretation of both astronomical observations and dynamical theory.
The relationship between the production rate of Be-10 in stony meteorites and its element composition was investigated by measuring the contents of Be-10 in 21 samples from 17 meteorites with known major-element composition, and comparing the experimental Be-10 values with those obtained by the regression analysis. The Be-10 production was modeled by the equation of Stauffer (1962). The measured Be-10 contents were found to range from 16 dpm/kg in the oxygen- and magnesium-poor eucrites and the Indarch meteorite to 28 dpm/kg in the oxygen- and magnesium-rich aubrites and the mineral separates from Bruderheim. Using the regression analyses and taking in account various corrections, an equation was obtained which reproduces the measured Be-10 content with an accuracy of about 10 percent.
The Be-10 contents of 28 stony meteorites with known Ne-21 contents range from 0.97 to 23 dpm/kg and give an average Ne-21 production rate (P sub 21) of (0.28 + or - 0.02) x 10 to the -8th cu cm STP/g-My for shielding conditions corresponding to Ne-22/Ne-21 = 1.114 in an H-chondrite. This P sub 21 (Be) agrees with others' P sub 21 based on Na-22, Kr-81, and Mn-53, but not an Al-26. Temporal variations in the cosmic ray flux do not explain the disagreement satisfactorily; major errors in the radionuclide half-lives are not indicated. The discrepancy seems rooted in the data selection and the difficulties of making accurate corrections for shielding, chemical composition and other sources of variability.
Absolute production rates of He 3 and Ne 21 in average chondrites, determining radiation ages of stony meteorites aged less than two million years
The complete neutron-flux results and production rates for Cl-36, Ni-59, and Co-60 in stony meteorites of various radii and composition are presented. The relative neutron source strengths and neutron production-versus-depth profiles were determined by using calculated H-3 production rates. The absolute source strengths were normalized to that determined for the moon by Woolum et al. (1975). The energy spectrum of the source neutrons and the neutron transport calculations, which employed the ANISN computer code, were similar to those used for the moon by Lingenfelter et al. (1972). The production rates of the three radionuclides were determined as a function of depth in various spherical meteoroids from the calculated equilibrium neutron-flux distributions and from energy-dependent neutron-capture cross sections. Rates for producing these radionuclides by spallation reactions were also calculated.
Approximately 10 g of meteorite samples were analyzed. The results show that the average age of the investigated stony meteorites is 5200 yr. The set of finds used for the investigation was a more or less random selection of specimens from collections. The age value found may, therefore, well represent the average terrestrial age of finds of ordinary chondrites in the western U.S. Attention is drawn to the fact that the specimens examined were all from a part of the world with a fairly low rainfall.
Foreign inclusions in stony meteorites. II - Rare gases and oxygen isotopes in a carbonaceous chondritic xenolith in the Plainview gas-rich chondrite
Newly discovered fluid inclusions in thin sections of Bjurbole chondrules, shergottite EETA79001, lunar meteorite ALHA81005, and Apollo 16 glasses possess physical properties similar to those of fluid inclusions found in thin sections of five stony meteorites recently described by Warner et al. (1983). The distribution and physical properties of these new fluid inclusions indicate they may be artifacts of thin section preparation; it is suggested that saw coolant was sucked into vacuum vesicles in glasses and minerals through submicroscopic fractures produced during sawing. The similarities between these fluid inclusions and fluid inclusions previously described by Warner et al. (1983) indicate that many of the fluid inclusions reported earlier may be artifacts. Consequently, the origin of any fluid inclusions observed in thin sections of extraterrestrial materials must be interpreted with caution. The most probable true extraterrestrial fluid inclusions are those that have been observed in grains prepared without exposure to liquids of any kind.
Discussion of the distribution of the transition elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) among the individual minerals of stony meteorites, and comparison with data on comparable lunar and terrestrial minerals. As an example of meteorite distribution patterns, data on the Modoc meteorite are presented. For the lunar rocks, microprobe data are used, along with published information from other investigators. For comparison with terrestrial igneous rocks, Skaergaard intrusion rocks are used. They present some striking analogies in mineralogy and petrology with the lunar igneous rocks and are thus peculiarly suitable for this cross comparison.
To assess the threat posed by an asteroid entering Earth's atmosphere, one must predict if, when, and how it fragments during entry. A comprehensive understanding of the Asteroid material properties is needed to achieve this objective. At present, the meteorite material found on Earth are the only objects from an entering asteroid that can be used as representative material and be tested inside a laboratory setting. Therefore, unit cell models are developed to determine the effective material properties of stony meteorites and in turn deduce the properties of asteroids. The unit cell is representative volume that accounts for diverse minerals, porosity, and matrix composition inside a meteorite. The various classes under investigation includes H-class, L-class, and LL-class chondrites. The effective mechanical properties such as Young's Modulus and Poisson's Ratio of the unit cell are calculated by performing several hundreds of Monte-Carlo simulations. Terrestrial analogs such as Basalt and Gabbro are being used to validate the unit cell methodology.
To assess the threat posed by an asteroid entering Earths atmosphere, one must predict if, when, and how it fragments during entry. A comprehensive understanding of the Asteroid material properties is needed to achieve this objective. At present, the meteorite material found on earth are the only objects from an entering asteroid that can be used as representative material and be tested inside a laboratory setting. Therefore, unit cell models are developed to determine the effective material properties of stony meteorites and in turn deduce the properties of asteroids. The unit cell is representative volume that accounts for diverse minerals porosity, and matrix composition inside a meteorite. The various classes under investigation includes H-class, L-class, and LL-class chondrites. The effective mechanical properties such as Young's Modulus and Poisson's Ratio of the unit cell are calculated by performing several hundreds of Monte-Carlo simulations. Terrestrial analogs such as Basalt and Gabbro are being used to validate the unit cell methodology.
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