Chronology of dimict breccias and the age of South Ray crater at the Apollo 16 site   总被引：1，自引：0，他引：1  

Otto EUGSTER 《Meteoritics & planetary science》1999,34(3):385-391

Abstract— We report the noble gas isotopic abundances of five dimict breccias and one cataclastic anorthosite that were collected at the Apollo 16 landing site. Orbital and surface photographs indicate that rays from South Ray crater, an almost 1 km wide young crater in the Cayley plains, extend several kilometers from their source into the area that was sampled by the Apollo 16 mission. Previous studies have shown that South Ray crater formed 2 Ma ago and that a large number of rocks might originate from this cratering event. On the basis of cosmic-ray produced nuclei, we find that the six rocks investigated in this work yield the same lunar surface exposure age. Using literature data, we recalculate the exposure ages of additional 16 rocks with suspected South Ray crater origin and obtain an average exposure age of 2.01 ± 0.10 Ma. In particular, all nine dimict breccias (a type of rock essentially restricted to the Apollo 16 area consisting of anorthosite and breccia phases) dated until now yield an average ejection age of 2.06 ± 0.17 Ma. We conclude that they must originate from the Cayley formation or from bedrock underlying the Cayley plain. We determined the gas retention ages for the dimict breccias based on the ⁴⁰K-⁴⁰Ar and U,Th-¹³⁶Xe dating methods: rock 64425 yields a ⁴⁰K-⁴⁰Ar age of 3.96 Ga and rock 61016 a U,Th-¹³⁶Xe age of 3.97 Ga. These results, together with ³⁹Ar-⁴⁰Ar ages obtained by other workers for rocks 64535 (3.98 Ga) and 64536 (3.97 Ga), show that the dimict breccias formed 3.97 Ga ago.  相似文献   

History of lunar meteorites Queen Alexandra Range 93069, Asuka 881757, and Yamato 793169 based on noble gas isotopic abundances,radionuclide concentrations,and chemical composition     

Christoph THALMANN  Otto EUGSTER  Gregory F. HERZOG  Suizhou XUE  Jeffrey KLEIN  Urs KRHENBÜHL  Stephan VOGT 《Meteoritics & planetary science》1996,31(6):857-868

Abstract— We investigated the characteristics and history of lunar meteorites Queen Alexandra Range 93069, Yamato 793169 and Asuka 881757 based on the abundances of all stable noble gas isotopes, the concentrations of the radionuclides ¹⁰Be, ²⁶Al, ³⁶Cl, and ⁸¹Kr, and the abundances of Mg, Al, K, Ca, Fe, Cl, Sr, Y, Zr, Ba, and La. Based on the solar wind and cosmic-ray irradiations, QUE 93069 is the most mature lunar meteorite studied up to now. The ⁴⁰Ar/³⁶Ar ratio of the trapped component is 1.87 ± 0.16. This ratio corresponds to a time when the material was exposed to solar and lunar atmospheric volatiles ～400 Ma ago. On the other hand, Yamato 793169 and Asuka 881757 contain very little or no solar noble gases, which indicates that these materials resided in the top layer of the lunar regolith only briefly or not at all. For all lunar meteorites, we observe a positive correlation of the concentrations of cosmic-ray produced with trapped solar noble gases. The duration of lunar regolith residence for the lunar meteorites was calculated based on cosmic-ray produced ²¹Ne, ³⁸Ar, ⁷⁸Kr, ⁸³Kr, and ¹²⁶Xe and appropriate production rates that were derived based on the target element abundances and the shielding indicator ¹³¹Xe/¹²⁶Xe. For QUE 93069, Yamato 793169, and Asuka 881757, we obtained 1000 ± 400 Ma, 50 ± 10 Ma, and <1 Ma, respectively. Both Asuka 881757 and Yamato 793169 show losses of radiogenic ⁴He from U and Th decay and Yamato 793169 also ⁴⁰Ar loss from K-decay. For Asuka 881757, we calculate a K-Ar gas retention age of 3100 ± 600 Ma and a ²⁴⁴Pu-¹³⁶Xe fission age of 4240 ± 170 Ma. This age is one of the oldest formation ages ever observed for a lunar basalt. The exposure history of QUE 93069 after ejection from the Moon was derived from the radionuclide concentrations: ejection 0.16 ± 0.03 Ma ago, duration of Moon-Earth transit 0.15 ± 0.02 Ma and fall on Earth <0.015 Ma ago. This ejection event is distinguished temporally from those which produced the other lunar meteorites. We conclude that six to eight events are necessary to eject all the known lunar meteorites.  相似文献   

Causal thinking and support for climate change policies: International survey findings     

Ann Bostrom  Robert E. O’Connor  Gisela Böhm  Daniel Hanss  Otto Bodi  Frida Ekström  Pradipta Halder  Sven Jeschke  Birgit Mack  Mei Qu  Lynn Rosentrater  Anethe Sandve  Ingrid Sælensminde 《Global Environmental Change》2012,22(1):210-222

Few comparative international studies describe the climate change policies people are willing to support and the reasons for their support of different policies. Using survey data from 664 economics and business undergraduates in Austria, Bangladesh, Finland, Germany, Norway, and the United States, we explore how perceived risk characteristics and mental models of climate change influence support for policy alternatives. General green policies such as funding research on renewable technologies and planting trees were the overwhelmingly most popular policy alternatives. Around half the students support carbon reduction policies such as requiring higher car fuel efficiency and increasing taxes on fossil fuels. Least popular were engineering alternatives such as fertilizing the oceans and replacing fossil fuels with nuclear power. Variations among nations are generally small. Support for different policy alternatives corresponds with different causal thinking. Those who hold a pollution model of the causes of climate change, tend to blame environmental harms (e.g., air pollution from toxic chemicals), see general green policy alternatives as effective, and support general green policies. Support of carbon reduction strategies is associated with seeing carbon emissions as the cause and reducing carbon emissions as effective solutions. Support of engineering solutions increases with identifying volcanoes among causes and regarding engineering solutions as effective. Although these international students agree that climate change is a threatening problem, their causal thinking correlates with support for different mitigative policy actions, with the most popular ones not necessarily the most effective.  相似文献   

The Twannberg (Switzerland) IIG iron meteorites: Mineralogy,chemistry, and CRE ages     

Beda A. HOFMANN  Silvio LORENZETTI  Otto EUGSTER  Urs KRÄHENBÜHL  Gregory HERZOG  Feride SEREFIDDIN  Edwin GNOS  Manuel EGGIMANN  John T. WASSON 《Meteoritics & planetary science》2009,44(2):187-199

Abstract— The original mass (15915 g) of the Twannberg IIG (low Ni‐, high P) iron was found in 1984. Five additional masses (12 to 2488 g) were recovered between 2000 and 2007 in the area. The different masses show identical mineralogy consisting of kamacite single crystals with inclusions of three types of schreibersite crystals: cm‐sized skeletal (10.5% Ni), lamellar (17.2% Ni), and 1–3 × 10 μm‐sized microprismatic (23.9% Ni). Masses I and II were compared in detail and have virtually identical microstructure, hardness, chemical composition, cosmic‐ray exposure (CRE) ages, and ¹⁰Be and ²⁶Al activities. Bulk concentrations of 5.2% Ni and 2.0% P were calculated. The preatmospheric mass is estimated to have been at least 11,000 kg. The average CRE age for the different Twannberg samples is 230 ± 50 Ma. Detrital terrestrial mineral grains in the oxide rinds of the three larger masses indicate that they oxidized while they were incorporated in a glacial till deposited by the Rhône glacier during the last glaciation (Würm). The find location of mass I is located at the limit of glaciation where the meteorite may have deposited after transport by the glacier over considerable distance. All evidence indicates pairing of the six masses, which may be part of a larger shower as is indicated by the large inferred pre‐atmospheric mass.  相似文献   

A SOLAR α - ω DYNAMO STUDY AND ITS TRANSITION TO CHAOS     

Grassmugg  Maria  Hanslmeier  Arnold  Laback  Otto 《Solar physics》1997,174(1-2):437-441

In this contribution we present a nonlinear dynamo model, described by an infinite dimensional system of differential equations, whose solutions depend on the essential parameter D, the dynamo number. The solutions and the bifurcation points of the system are determined with the help of a new developed computer code. We show that, depending on D, stationary, oscillatory and chaotic solutions, which are characterized by Lyapunov exponents, result. We find that the solar dynamo may operate either in the chaotic or in the stable limit cycle domain, depending on the characteristic value of the dynamo number or the motion of the convection zone.  相似文献   

Neptune: Limb brightening within the 7300-Angstrom methane band     

Michael J. Price  Otto G. Franz 《Icarus》1980,41(3):430-438

Narrow-waveband (100 Å) photoelectric slit-scan photometry of the Neptune disk is reported. Observations were concentrated within the strong CH₄ band at λ7300 Å. For comparison, measurements were also made within a continuum waveband at λ6800 Å. Point spread function data were obtained in both colors. Qualitative estimates of the true intensity distribution over the Neptune disk were made. Within the λ6800-Å continuum band, Neptune appears as an essentially uniform disk. Within the λ7300 Å CH₄ band, the planet exhibits strong limb brightening. Our results appear to require the presence of an optically thin layer of brightly scattering aerosol particles high in the Neptune atmosphere.  相似文献   

Autobiographical sketch of Otto D.L. Strack     

Strack OD 《Ground water》2003,41(4):550-554

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Simultaneous measurements of turbulence over land and water     

Niels Otto Jensen 《Boundary-Layer Meteorology》1978,15(1):95-108

Turbulence and mean flow variables under unstable conditions are examined with special emphasis on the consequences of roughness and surface elevation change. An interpolation formula for _w ², between neutral and free convection, is shown to bring order to the data. The spectral distribution of vertical wind variance is found to be in good agreement with results over horizontal homogeneous terrain, both with respect to form and position. In particular, the length scale _m corresponding to the maximum of nS _w(n) is unchanged. Another turbulent length scale, (k/)z, is found to be substantially reduced in the disturbed zone of the internal boundary layer. To a first approximation, the flow-acceleration effect on the non-dimensional wind shear can be separated from the diabatic effect.  相似文献   

Metamorphe Mineralreaktionen in vesuvianführenden Paragenesen     

Prof. Dr. Otto Braitsch  Dr. Niranjan Deb Chatterjee 《Contributions to Mineralogy and Petrology》1963,9(4):353-373

Zusammenfassung In Fortsetzung einer früheren Arbeit (Chatterjee, 1962) werden weitere Beispiele vesuvianführender Paragenesen aus der Grünschieferfazies Bowie aus der Albit-Epidot-Hornfelsfazies beschrieben. Hieraus ergibt sich, daß die Paragenesen Vesuvian + Epidot, Vesuvian + Tremolit und Vesuvian + Chlorit für die niedrig-temperierten Mineralfazies kennzeichnend sind, und zwar unabhängig vom wirksamen Gesamtdruck. Die Bildungsmöglichkeiten des Vesuvians und seine Umbildungen bei stärkerer Metamorphose werden anhand von stöchiometrischen Reaktionsgleichungen behandelt. Die Reaktionen Bind schematisch in ACF-Diagrammen dargestellt, und die Gleichgewichtstemperaturen sind qualitativ in Abhängigkeit von der Zusammensetzung der Gasphase mit Hilfe einer vonGreenwood (1962) aufgestellten thermodynamischen Beziehung abgeleitet.

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In continuation of a former paper (Chatterjee, 1962), further data pertaining to vesuvianite-bearing mineral parageneses from the greenschist fades of the western Alps, albite-epidote-hornfels facies of eastern Harz Mountains as well as from the hornblende hornfels facies of the Oslo region are reported. It is shown that the coexistence of vesuvianite-epidote, vesuvianite-tremolite and vesuvianite-chlorite is characteristic of the lower temperature mineral facies, irrespective of the different total pressures acting during the metamorphism. Metamorphic reactions have been derived to explain the formation of vesuvianite, successive changes of the critical parageneses as well as its final disappearence within the system CaO-(Mg, Fe²⁺)O-(Al, Fe³⁺)₂O₃-SiO₂-H₂O ± CO₂. The phase transformations are illustrated on ACF diagrams as a function of temperature and mole fraction CO₂ of the gaseous phase (in an isobaric section).

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Buchbesprechungen     

Otto Jaag  Rudolf Braun 《Aquatic Sciences - Research Across Boundaries》1956,18(2):254-256

Ohne Zusammenfassung  相似文献