The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform
R. K. Herd - One of the best experts on this subject based on the ideXlab platform.
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Stony Meteorite characterization by non‐destructive measurement of magnetic properties
Meteoritics & Planetary Science, 2020Co-Authors: D. L. Smith, Richard E. Ernst, Claire Samson, R. K. HerdAbstract:Four parameters of low-field magnetic susceptibility (bulk value, frequency dependence, degree of anisotropy, and ellipsoid shape) have been determined for 321 Stony Meteorites from the National Collection of Canada. These parameters provide a basis for rapid, non-destructive, and accurate Meteorite classification as each Meteorite class tends to have a distinct range of values. Chondrites show a clear trend of increasing bulk susceptibility from LL to L to H to E within the 3.6 to 5.6 logχ (in 10^(-9) m^3/kg) range, reflecting increasing Fe-Ni metal and Fe-Ni sulfide content. Achondrite values range in log? from 2.4 to 4.7 and primitive achondrites from 4.2 to 5.7. Frequency dependence is observed, using 19,000 Hz and 825 Hz, with variations in strength among Meteorite classes and individual specimen dependence ranging from 1-25.6%. Degrees of anisotropy range from 1 to 53% with both oblate and prolate ellipsoids present. The aubrite class is marked by high degrees of anisotropy, low bulk magnetic susceptibility, and prolate fabric. Camel Donga is set apart from other eucrites, marked by higher bulk susceptibility, degree of anisotropy, and magnitude of oblate ellipsoid shape. The Shergotty, Nakhla, and Chassigny (SNC) Meteorites show subclass distinction using frequency dependence and Chassigny is set apart with a relatively strong oblate fabric. The presence of both strong oblate and prolate fabrics among and within Meteorite classes of chondritic and achondritic material points to a complex, multi-mechanism origin for anisotropy, more so than previously thought, and likely dominated by impact processes in the later stages of Stony parent bodyformation.
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Stony Meteorite characterization by non destructive measurement of magnetic properties
Meteoritics & Planetary Science, 2006Co-Authors: D. L. Smith, Richard E. Ernst, Claire Samson, R. K. HerdAbstract:Four parameters of low-field magnetic susceptibility (bulk value, frequency dependence, degree of anisotropy, and ellipsoid shape) have been determined for 321 Stony Meteorites from the National Collection of Canada. These parameters provide a basis for rapid, non-destructive, and accurate Meteorite classification as each Meteorite class tends to have a distinct range of values. Chondrites show a clear trend of increasing bulk susceptibility from LL to L to H to E within the 3.6 to 5.6 logχ (in 10^(-9) m^3/kg) range, reflecting increasing Fe-Ni metal and Fe-Ni sulfide content. Achondrite values range in log? from 2.4 to 4.7 and primitive achondrites from 4.2 to 5.7. Frequency dependence is observed, using 19,000 Hz and 825 Hz, with variations in strength among Meteorite classes and individual specimen dependence ranging from 1-25.6%. Degrees of anisotropy range from 1 to 53% with both oblate and prolate ellipsoids present. The aubrite class is marked by high degrees of anisotropy, low bulk magnetic susceptibility, and prolate fabric. Camel Donga is set apart from other eucrites, marked by higher bulk susceptibility, degree of anisotropy, and magnitude of oblate ellipsoid shape. The Shergotty, Nakhla, and Chassigny (SNC) Meteorites show subclass distinction using frequency dependence and Chassigny is set apart with a relatively strong oblate fabric. The presence of both strong oblate and prolate fabrics among and within Meteorite classes of chondritic and achondritic material points to a complex, multi-mechanism origin for anisotropy, more so than previously thought, and likely dominated by impact processes in the later stages of Stony parent bodyformation.
D T Britt - One of the best experts on this subject based on the ideXlab platform.
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Stony Meteorite thermal properties and their relationship with Meteorite chemical and physical states
Meteoritics & Planetary Science, 2012Co-Authors: C Opeil P Sj, G Consolmagno J Sj, D J Safarik, D T BrittAbstract:Abstract– In our ongoing survey of Meteorite physical properties, we have to date measured the thermal conductivity for seventeen Stony Meteorites at temperatures ranging from 5 K to 300 K. Here, we report new results for nine ordinary chondrites, one enstatite chondrite, and the basaltic achondrites Frankfort (howardite) and Los Angeles (shergottite). We find that thermal conductivity is significantly lower than would be expected from averaging the laboratory conductivities of their constituent minerals, with a dependence on temperature different from the expected conductivity of pure minerals. In addition, we find a linear relationship between the inverse of the porosity of the samples measured and their thermal conductivity, regardless of Meteorite composition or type. We conclude that thermal conductivity is controlled by the presence of shock-induced microcracks within the Meteorites, which provide a barrier to the transmission of thermal energy via phonons. In contrast to conductivity, our first measurement of heat capacity as a function of temperature (on Los Angeles) suggests that heat capacity is primarily a function of oxide composition and is not strongly affected by the physical state of the sample.
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Stony Meteorite porosities and densities a review of the data through 2001
Meteoritics & Planetary Science, 2003Co-Authors: D T Britt, G J S J ConsolmagnoAbstract:In this review, we summarize the data published up to December 2001 on the porosity and density of Stony Meteorites. These data were taken from 925 samples of 454 different Meteorites by a variety of techniques. Most Meteorites have densities on the order of 3 to 4 g/cm^3, with lower densities only for some volatile-rich carbonaceous Meteorites and higher densities for Stony irons. For the vast majority of stones, porosity data alone cannot distinguish between different Meteorite compositions. Average porosities for most Meteorite classes are around 10%, though individual samples can range as high as 30% porosity. Unbrecciated basaltic achondrites appear to be systematically less porous unless vesicles are present. The measured density of ordinary chondrites is strongly controlled by the amount of terrestrial weathering the sample has undergone with porosities steadily dropping with exposure to the terrestrial environment. A theoretical grain density based on composition can model "pre-weathered" porosities. The average model porosity for H and LL chondrites is 10%, while L chondrite model porosities average only 6%, a statistically significant difference.
Aleš Svatoš - One of the best experts on this subject based on the ideXlab platform.
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The search for fullerenes in rocks from the Ries impact crater
Meteoritics and Planetary Science, 2005Co-Authors: Ota Frank, Věra Hamplova, Jan Jehlicka, Aleš SvatošAbstract:Since their discovery, fullerenes have been reported from various\ngeological environments. One group of these findings has been related to\nbolide impacts, e.g., the Sudbury crater and the K-T and P-T boundaries.\nImpact rocks of the Ries crater, Germany, including samples of suevites,\nmetamorphosed crystalline clasts, and glass bombs, have been collected\nin the Otting, Altebbrg, and Seelbronn quarries. No fullerenes in\nconcentrations above 1 ppb have been found in analyzed samples. Laser\ndesorption time-of-flight mass spectrometry (LD-TOF-MS) confirmed the\nabsence of fullerenes in the analyzed samples. These results Support the\nconcept that the Ries impactor was a Stony Meteorite.
R Michel - One of the best experts on this subject based on the ideXlab platform.
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accelerator mass spectrometry measurements and model calculations of iron 60 production rates in Meteorites
Meteoritics & Planetary Science, 1999Co-Authors: K Knie, S Merchel, G Korschinek, T Faestermann, U Herpers, M Gloris, R MichelAbstract:Abstract-The cosmogenic radionuclide 6OFe (TIR = 1.49 Ma) was measured in two iron Meteorites as well as in the magnetic fractions of a Stony-iron and a Stony Meteorite by means of accelerator mass spectrometry (AMS). The measured 60Fe/Fe ratios range from 1.5 x 10-14 to 6.3 x 10-14 and show a significant correlation to the respective concentrations of Ni, which is the main target element. The resulting 6OFe specific activities correspond to production rates in Meteorites in the order of 1 dpmkg Ni. In addition, model calculations of depth- and size-dependent 6oFe production rates were performed. Although there are no experimental data for the production cross sections, our measurements are in surprisingly good agreement with the theoretical predictions using production cross sections that were determined by computer model calculations. INTRODUCTION In Meteorites, cosmogenic nuclides are produced in nuclear reactions induced by primary (mostly protons) and secondary (protons and neutrons) cosmic-ray particles. Cosmogenic nuclides provide much information about (complex) exposure histories and preatmospheric sizes of Meteorites. Long-lived cosmogenic radionuclides are of special interest for this purpose,
Richard E. Ernst - One of the best experts on this subject based on the ideXlab platform.
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Stony Meteorite characterization by non‐destructive measurement of magnetic properties
Meteoritics & Planetary Science, 2020Co-Authors: D. L. Smith, Richard E. Ernst, Claire Samson, R. K. HerdAbstract:Four parameters of low-field magnetic susceptibility (bulk value, frequency dependence, degree of anisotropy, and ellipsoid shape) have been determined for 321 Stony Meteorites from the National Collection of Canada. These parameters provide a basis for rapid, non-destructive, and accurate Meteorite classification as each Meteorite class tends to have a distinct range of values. Chondrites show a clear trend of increasing bulk susceptibility from LL to L to H to E within the 3.6 to 5.6 logχ (in 10^(-9) m^3/kg) range, reflecting increasing Fe-Ni metal and Fe-Ni sulfide content. Achondrite values range in log? from 2.4 to 4.7 and primitive achondrites from 4.2 to 5.7. Frequency dependence is observed, using 19,000 Hz and 825 Hz, with variations in strength among Meteorite classes and individual specimen dependence ranging from 1-25.6%. Degrees of anisotropy range from 1 to 53% with both oblate and prolate ellipsoids present. The aubrite class is marked by high degrees of anisotropy, low bulk magnetic susceptibility, and prolate fabric. Camel Donga is set apart from other eucrites, marked by higher bulk susceptibility, degree of anisotropy, and magnitude of oblate ellipsoid shape. The Shergotty, Nakhla, and Chassigny (SNC) Meteorites show subclass distinction using frequency dependence and Chassigny is set apart with a relatively strong oblate fabric. The presence of both strong oblate and prolate fabrics among and within Meteorite classes of chondritic and achondritic material points to a complex, multi-mechanism origin for anisotropy, more so than previously thought, and likely dominated by impact processes in the later stages of Stony parent bodyformation.
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Stony Meteorite characterization by non destructive measurement of magnetic properties
Meteoritics & Planetary Science, 2006Co-Authors: D. L. Smith, Richard E. Ernst, Claire Samson, R. K. HerdAbstract:Four parameters of low-field magnetic susceptibility (bulk value, frequency dependence, degree of anisotropy, and ellipsoid shape) have been determined for 321 Stony Meteorites from the National Collection of Canada. These parameters provide a basis for rapid, non-destructive, and accurate Meteorite classification as each Meteorite class tends to have a distinct range of values. Chondrites show a clear trend of increasing bulk susceptibility from LL to L to H to E within the 3.6 to 5.6 logχ (in 10^(-9) m^3/kg) range, reflecting increasing Fe-Ni metal and Fe-Ni sulfide content. Achondrite values range in log? from 2.4 to 4.7 and primitive achondrites from 4.2 to 5.7. Frequency dependence is observed, using 19,000 Hz and 825 Hz, with variations in strength among Meteorite classes and individual specimen dependence ranging from 1-25.6%. Degrees of anisotropy range from 1 to 53% with both oblate and prolate ellipsoids present. The aubrite class is marked by high degrees of anisotropy, low bulk magnetic susceptibility, and prolate fabric. Camel Donga is set apart from other eucrites, marked by higher bulk susceptibility, degree of anisotropy, and magnitude of oblate ellipsoid shape. The Shergotty, Nakhla, and Chassigny (SNC) Meteorites show subclass distinction using frequency dependence and Chassigny is set apart with a relatively strong oblate fabric. The presence of both strong oblate and prolate fabrics among and within Meteorite classes of chondritic and achondritic material points to a complex, multi-mechanism origin for anisotropy, more so than previously thought, and likely dominated by impact processes in the later stages of Stony parent bodyformation.