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Rainer Wieler - One of the best experts on this subject based on the ideXlab platform.
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the abundance and isotopic composition of cd in iron Meteorites
Meteoritics & Planetary Science, 2013Co-Authors: Thomas S Kruijer, P Sprung, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Cadmium is a highly volatile element and its abundance in Meteorites may help better understand volatility-controlled processes in the solar nebula and on meteorite parent bodies. The large thermal neutron capture cross section of 113Cd suggests that Cd isotopes might be well suited to quantify neutron fluences in extraterrestrial materials. The aims of this study were (1) to evaluate the range and magnitude of Cd concentrations in magmatic iron Meteorites, and (2) to assess the potential of Cd isotopes as a neutron dosimeter for iron Meteorites. Our new Cd concentration data determined by isotope dilution demonstrate that Cd concentrations in iron Meteorites are significantly lower than in some previous studies. In contrast to large systematic variations in the concentration of moderately volatile elements like Ga and Ge, there is neither systematic variation in Cd concentration amongst troilites, nor amongst metal phases of different iron meteorite groups. Instead, Cd is strongly depleted in all iron meteorite groups, implying that the parent bodies accreted well above the condensation temperature of Cd (i.e., ≈650 K) and thus incorporated only minimal amounts of highly volatile elements. No Cd isotope anomalies were found, whereas Pt and W isotope anomalies for the same iron meteorite samples indicate a significant fluence of epithermal and higher energetic neutrons. This observation demonstrates that owing to the high Fe concentrations in iron Meteorites, neutron capture mainly occurs at epithermal and higher energies. The combined Cd-Pt-W isotope results from this study thus demonstrate that the relative magnitude of neutron capture-induced isotope anomalies is strongly affected by the chemical composition of the irradiated material. The resulting low fluence of thermal neutrons in iron Meteorites and their very low Cd concentrations make Cd isotopes unsuitable as a neutron dosimeter for iron Meteorites.
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hf w chronometry of core formation in planetesimals inferred from weakly irradiated iron Meteorites
Geochimica et Cosmochimica Acta, 2012Co-Authors: Thomas S Kruijer, P Sprung, C Burkhardt, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Abstract The application of Hf–W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron Meteorites is severely hampered by 182 W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182 W burnout, making the Hf–W ages for iron Meteorites uncertain. Here we present noble gas and Hf–W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron Meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages ( 182 W values (parts per 10 4 deviations from the terrestrial value) are higher than those measured for most other iron Meteorites and range from −3.42 to −3.31, slightly elevated compared to the initial 182 W/ 184 W of Ca–Al-rich Inclusions (CAI; e 182 W = −3.51 ± 0.10). The new W isotopic data indicate that core formation in the parent bodies of the IIAB, IIIAB, and IVA iron Meteorites occurred ∼1–1.5 Myr after CAI formation (with an uncertainty of ∼1 Myr), consistent with earlier conclusions that the accretion and differentiation of iron meteorite parent bodies predated the accretion of most chondrite parent bodies. One ungrouped iron meteorite (Chinga) exhibits small nucleosynthetic W isotope anomalies, but after correction for these anomalies its e 182 W value agrees with those of the other samples. Another ungrouped iron (Mbosi), however, has elevated e 182 W relative to the other investigated irons, indicating metal–silicate separation ∼2–3 Myr later than in the parent bodies of the three major iron meteorite groups studied here.
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Hf–W chronometry of core formation in planetesimals inferred from weakly irradiated iron Meteorites
Geochimica et Cosmochimica Acta, 2012Co-Authors: Thomas S Kruijer, C Burkhardt, Ingo Leya, Thorsten Kleine, Peter Sprung, Rainer WielerAbstract:Abstract The application of Hf–W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron Meteorites is severely hampered by 182W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182W burnout, making the Hf–W ages for iron Meteorites uncertain. Here we present noble gas and Hf–W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron Meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages (
Thomas S Kruijer - One of the best experts on this subject based on the ideXlab platform.
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the abundance and isotopic composition of cd in iron Meteorites
Meteoritics & Planetary Science, 2013Co-Authors: Thomas S Kruijer, P Sprung, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Cadmium is a highly volatile element and its abundance in Meteorites may help better understand volatility-controlled processes in the solar nebula and on meteorite parent bodies. The large thermal neutron capture cross section of 113Cd suggests that Cd isotopes might be well suited to quantify neutron fluences in extraterrestrial materials. The aims of this study were (1) to evaluate the range and magnitude of Cd concentrations in magmatic iron Meteorites, and (2) to assess the potential of Cd isotopes as a neutron dosimeter for iron Meteorites. Our new Cd concentration data determined by isotope dilution demonstrate that Cd concentrations in iron Meteorites are significantly lower than in some previous studies. In contrast to large systematic variations in the concentration of moderately volatile elements like Ga and Ge, there is neither systematic variation in Cd concentration amongst troilites, nor amongst metal phases of different iron meteorite groups. Instead, Cd is strongly depleted in all iron meteorite groups, implying that the parent bodies accreted well above the condensation temperature of Cd (i.e., ≈650 K) and thus incorporated only minimal amounts of highly volatile elements. No Cd isotope anomalies were found, whereas Pt and W isotope anomalies for the same iron meteorite samples indicate a significant fluence of epithermal and higher energetic neutrons. This observation demonstrates that owing to the high Fe concentrations in iron Meteorites, neutron capture mainly occurs at epithermal and higher energies. The combined Cd-Pt-W isotope results from this study thus demonstrate that the relative magnitude of neutron capture-induced isotope anomalies is strongly affected by the chemical composition of the irradiated material. The resulting low fluence of thermal neutrons in iron Meteorites and their very low Cd concentrations make Cd isotopes unsuitable as a neutron dosimeter for iron Meteorites.
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hf w chronometry of core formation in planetesimals inferred from weakly irradiated iron Meteorites
Geochimica et Cosmochimica Acta, 2012Co-Authors: Thomas S Kruijer, P Sprung, C Burkhardt, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Abstract The application of Hf–W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron Meteorites is severely hampered by 182 W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182 W burnout, making the Hf–W ages for iron Meteorites uncertain. Here we present noble gas and Hf–W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron Meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages ( 182 W values (parts per 10 4 deviations from the terrestrial value) are higher than those measured for most other iron Meteorites and range from −3.42 to −3.31, slightly elevated compared to the initial 182 W/ 184 W of Ca–Al-rich Inclusions (CAI; e 182 W = −3.51 ± 0.10). The new W isotopic data indicate that core formation in the parent bodies of the IIAB, IIIAB, and IVA iron Meteorites occurred ∼1–1.5 Myr after CAI formation (with an uncertainty of ∼1 Myr), consistent with earlier conclusions that the accretion and differentiation of iron meteorite parent bodies predated the accretion of most chondrite parent bodies. One ungrouped iron meteorite (Chinga) exhibits small nucleosynthetic W isotope anomalies, but after correction for these anomalies its e 182 W value agrees with those of the other samples. Another ungrouped iron (Mbosi), however, has elevated e 182 W relative to the other investigated irons, indicating metal–silicate separation ∼2–3 Myr later than in the parent bodies of the three major iron meteorite groups studied here.
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Hf–W chronometry of core formation in planetesimals inferred from weakly irradiated iron Meteorites
Geochimica et Cosmochimica Acta, 2012Co-Authors: Thomas S Kruijer, C Burkhardt, Ingo Leya, Thorsten Kleine, Peter Sprung, Rainer WielerAbstract:Abstract The application of Hf–W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron Meteorites is severely hampered by 182W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182W burnout, making the Hf–W ages for iron Meteorites uncertain. Here we present noble gas and Hf–W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron Meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages (
Ingo Leya - One of the best experts on this subject based on the ideXlab platform.
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the abundance and isotopic composition of cd in iron Meteorites
Meteoritics & Planetary Science, 2013Co-Authors: Thomas S Kruijer, P Sprung, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Cadmium is a highly volatile element and its abundance in Meteorites may help better understand volatility-controlled processes in the solar nebula and on meteorite parent bodies. The large thermal neutron capture cross section of 113Cd suggests that Cd isotopes might be well suited to quantify neutron fluences in extraterrestrial materials. The aims of this study were (1) to evaluate the range and magnitude of Cd concentrations in magmatic iron Meteorites, and (2) to assess the potential of Cd isotopes as a neutron dosimeter for iron Meteorites. Our new Cd concentration data determined by isotope dilution demonstrate that Cd concentrations in iron Meteorites are significantly lower than in some previous studies. In contrast to large systematic variations in the concentration of moderately volatile elements like Ga and Ge, there is neither systematic variation in Cd concentration amongst troilites, nor amongst metal phases of different iron meteorite groups. Instead, Cd is strongly depleted in all iron meteorite groups, implying that the parent bodies accreted well above the condensation temperature of Cd (i.e., ≈650 K) and thus incorporated only minimal amounts of highly volatile elements. No Cd isotope anomalies were found, whereas Pt and W isotope anomalies for the same iron meteorite samples indicate a significant fluence of epithermal and higher energetic neutrons. This observation demonstrates that owing to the high Fe concentrations in iron Meteorites, neutron capture mainly occurs at epithermal and higher energies. The combined Cd-Pt-W isotope results from this study thus demonstrate that the relative magnitude of neutron capture-induced isotope anomalies is strongly affected by the chemical composition of the irradiated material. The resulting low fluence of thermal neutrons in iron Meteorites and their very low Cd concentrations make Cd isotopes unsuitable as a neutron dosimeter for iron Meteorites.
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hf w chronometry of core formation in planetesimals inferred from weakly irradiated iron Meteorites
Geochimica et Cosmochimica Acta, 2012Co-Authors: Thomas S Kruijer, P Sprung, C Burkhardt, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Abstract The application of Hf–W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron Meteorites is severely hampered by 182 W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182 W burnout, making the Hf–W ages for iron Meteorites uncertain. Here we present noble gas and Hf–W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron Meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages ( 182 W values (parts per 10 4 deviations from the terrestrial value) are higher than those measured for most other iron Meteorites and range from −3.42 to −3.31, slightly elevated compared to the initial 182 W/ 184 W of Ca–Al-rich Inclusions (CAI; e 182 W = −3.51 ± 0.10). The new W isotopic data indicate that core formation in the parent bodies of the IIAB, IIIAB, and IVA iron Meteorites occurred ∼1–1.5 Myr after CAI formation (with an uncertainty of ∼1 Myr), consistent with earlier conclusions that the accretion and differentiation of iron meteorite parent bodies predated the accretion of most chondrite parent bodies. One ungrouped iron meteorite (Chinga) exhibits small nucleosynthetic W isotope anomalies, but after correction for these anomalies its e 182 W value agrees with those of the other samples. Another ungrouped iron (Mbosi), however, has elevated e 182 W relative to the other investigated irons, indicating metal–silicate separation ∼2–3 Myr later than in the parent bodies of the three major iron meteorite groups studied here.
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Hf–W chronometry of core formation in planetesimals inferred from weakly irradiated iron Meteorites
Geochimica et Cosmochimica Acta, 2012Co-Authors: Thomas S Kruijer, C Burkhardt, Ingo Leya, Thorsten Kleine, Peter Sprung, Rainer WielerAbstract:Abstract The application of Hf–W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron Meteorites is severely hampered by 182W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182W burnout, making the Hf–W ages for iron Meteorites uncertain. Here we present noble gas and Hf–W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron Meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages (
Peter Jenniskens - One of the best experts on this subject based on the ideXlab platform.
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recovery of Meteorites using an autonomous drone and machine learning
Meteoritics & Planetary Science, 2021Co-Authors: R Citron, Peter Jenniskens, Chris Watkins, Sravanthi Sinha, Amar Shah, Chedy Raissi, Hadrien A R Devillepoix, Jim AlbersAbstract:The recovery of freshly fallen Meteorites from tracked and triangulated meteors is critical to determining their source asteroid families. However, locating meteorite fragments in strewn fields remains a challenge with very few Meteorites being recovered from the meteors triangulated in past and ongoing meteor camera networks. We examined if locating Meteorites can be automated using machine learning and an autonomous drone. Drones can be programmed to fly a grid search pattern and take systematic pictures of the ground over a large survey area. Those images can be analyzed using a machine learning classifier to identify Meteorites in the field among many other features. Here, we describe a proof-of-concept meteorite classifier that deploys off-line a combination of different convolution neural networks to recognize Meteorites from images taken by drones in the field. The system was implemented in a conceptual drone setup and tested in the suspected strewn field of a recent meteorite fall near Walker Lake, Nevada.
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the impact and recovery of asteroid 2008 tc 3
Nature, 2009Co-Authors: Peter Jenniskens, Muawia H Shaddad, Diyaa Numan, Saadia Elsir, Ayman M Kudoda, M E Zolensky, G A Robinson, Jon M Friedrich, D RumbleAbstract:On 6 October 2008, a small Earth-bound asteroid designated 2008 TC3 was discovered by the Catalina Sky Survey. Some 19 hours — and many astronomical observations — later it entered the atmosphere and disintegrated at 37 km altitude. No macroscopic fragments were expected to have survived but a dedicated search along the approach trajectory in a desert in northern Sudan has recovered 47 Meteorites, fragments of a single body named Almahata Sitta, with a total mass of 3.95 kg. The asteroid and meteorite reflectance spectra identify the asteroid as surface matter from a class 'F' asteroid, material so fragile that it was not previously represented in meteorite collections. To have recovered Meteorites from a known class of asteroids is a coup on a par with a successful spacecraft sample-return mission — without the rocket science. On 6 October 2008, a small asteroid designated 2008 TC3 hit the Earth in northern Sudan. Jenniskens et al. searched along the approach trajectory and luckily found 47 bits of a meteorite named Almahata Sitta. Analysis reveals it to be a porous achondrite and a polymict ureilite, and so the asteroid was F-class (dark carbon-rich anomalous ureilites). In the absence of a firm link between individual Meteorites and their asteroidal parent bodies, asteroids are typically characterized only by their light reflection properties, and grouped accordingly into classes1,2,3. On 6 October 2008, a small asteroid was discovered with a flat reflectance spectrum in the 554–995 nm wavelength range, and designated 2008 TC3 (refs 4–6). It subsequently hit the Earth. Because it exploded at 37 km altitude, no macroscopic fragments were expected to survive. Here we report that a dedicated search along the approach trajectory recovered 47 Meteorites, fragments of a single body named Almahata Sitta, with a total mass of 3.95 kg. Analysis of one of these Meteorites shows it to be an achondrite, a polymict ureilite, anomalous in its class: ultra-fine-grained and porous, with large carbonaceous grains. The combined asteroid and meteorite reflectance spectra identify the asteroid as F class3, now firmly linked to dark carbon-rich anomalous ureilites, a material so fragile it was not previously represented in meteorite collections.
Tatjana Kleine - One of the best experts on this subject based on the ideXlab platform.
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the abundance and isotopic composition of cd in iron Meteorites
Meteoritics & Planetary Science, 2013Co-Authors: Thomas S Kruijer, P Sprung, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Cadmium is a highly volatile element and its abundance in Meteorites may help better understand volatility-controlled processes in the solar nebula and on meteorite parent bodies. The large thermal neutron capture cross section of 113Cd suggests that Cd isotopes might be well suited to quantify neutron fluences in extraterrestrial materials. The aims of this study were (1) to evaluate the range and magnitude of Cd concentrations in magmatic iron Meteorites, and (2) to assess the potential of Cd isotopes as a neutron dosimeter for iron Meteorites. Our new Cd concentration data determined by isotope dilution demonstrate that Cd concentrations in iron Meteorites are significantly lower than in some previous studies. In contrast to large systematic variations in the concentration of moderately volatile elements like Ga and Ge, there is neither systematic variation in Cd concentration amongst troilites, nor amongst metal phases of different iron meteorite groups. Instead, Cd is strongly depleted in all iron meteorite groups, implying that the parent bodies accreted well above the condensation temperature of Cd (i.e., ≈650 K) and thus incorporated only minimal amounts of highly volatile elements. No Cd isotope anomalies were found, whereas Pt and W isotope anomalies for the same iron meteorite samples indicate a significant fluence of epithermal and higher energetic neutrons. This observation demonstrates that owing to the high Fe concentrations in iron Meteorites, neutron capture mainly occurs at epithermal and higher energies. The combined Cd-Pt-W isotope results from this study thus demonstrate that the relative magnitude of neutron capture-induced isotope anomalies is strongly affected by the chemical composition of the irradiated material. The resulting low fluence of thermal neutrons in iron Meteorites and their very low Cd concentrations make Cd isotopes unsuitable as a neutron dosimeter for iron Meteorites.
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hf w chronometry of core formation in planetesimals inferred from weakly irradiated iron Meteorites
Geochimica et Cosmochimica Acta, 2012Co-Authors: Thomas S Kruijer, P Sprung, C Burkhardt, Tatjana Kleine, Ingo Leya, Rainer WielerAbstract:Abstract The application of Hf–W chronometry to determine the timescales of core formation in the parent bodies of magmatic iron Meteorites is severely hampered by 182 W burnout during cosmic ray exposure of the parent meteoroids. Currently, no direct method exists to correct for the effects of 182 W burnout, making the Hf–W ages for iron Meteorites uncertain. Here we present noble gas and Hf–W isotope systematics of iron meteorite samples whose W isotopic compositions remained essentially unaffected by cosmic ray interactions. Most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron Meteorites and, for iron meteorite standards, have very low noble gas and radionuclide based cosmic ray exposure ages ( 182 W values (parts per 10 4 deviations from the terrestrial value) are higher than those measured for most other iron Meteorites and range from −3.42 to −3.31, slightly elevated compared to the initial 182 W/ 184 W of Ca–Al-rich Inclusions (CAI; e 182 W = −3.51 ± 0.10). The new W isotopic data indicate that core formation in the parent bodies of the IIAB, IIIAB, and IVA iron Meteorites occurred ∼1–1.5 Myr after CAI formation (with an uncertainty of ∼1 Myr), consistent with earlier conclusions that the accretion and differentiation of iron meteorite parent bodies predated the accretion of most chondrite parent bodies. One ungrouped iron meteorite (Chinga) exhibits small nucleosynthetic W isotope anomalies, but after correction for these anomalies its e 182 W value agrees with those of the other samples. Another ungrouped iron (Mbosi), however, has elevated e 182 W relative to the other investigated irons, indicating metal–silicate separation ∼2–3 Myr later than in the parent bodies of the three major iron meteorite groups studied here.
