Contributions of the Society for Research on Meteorites最新文献

The Great-Circle Distribution of the Tektites* 玻璃陨石的大圆分布*

Contributions of the Society for Research on Meteorites Pub Date : 1900-01-01 DOI: 10.1111/J.1945-5100.1938.TB00182.X

L. L. Paz

引用次数: 6

A Photomicrograph Showing Intensity Maxima in a Meteor Trail 显示流星轨迹强度最大值的显微照片

Contributions of the Society for Research on Meteorites Pub Date : 1900-01-01 DOI: 10.1111/J.1945-5100.1939.TB00206.X

W. W. Zimmerman, C. R. Hammond

引用次数: 0

The Piñon, New Mexico, Siderite Piñon，新墨西哥州，Siderite

Contributions of the Society for Research on Meteorites Pub Date : 1900-01-01 DOI: 10.1111/J.1945-5100.1939.TB00216.X

H. H. Nininger

引用次数: 1

Photographs of the Widmanstätten Structure of the Goose Lake, California, Siderite Widmanstätten鹅湖结构的照片，加利福尼亚，菱铁矿

Contributions of the Society for Research on Meteorites Pub Date : 1900-01-01 DOI: 10.1111/J.1945-5100.1939.TB00240.X

F. C. Leonard

引用次数: 0

The Metallurgical Interpretation of the Structures found in Meteoritic Irons 陨铁结构的冶金学解释

Contributions of the Society for Research on Meteorites Pub Date : 1900-01-01 DOI: 10.1111/J.1945-5100.1939.TB00242.X

G. Derge

{"title":"The Metallurgical Interpretation of the Structures found in Meteoritic Irons","authors":"G. Derge","doi":"10.1111/J.1945-5100.1939.TB00242.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1939.TB00242.X","url":null,"abstract":"Two crystallographic mechanisms have been established for the transformation from the high-temperature, face-centered cubic lattice of γ-iron to the low-temperature, body-centered cubic lattice of α-iron. Published researches on meteorites were not adequate to establish which of these two mechanisms operated in the formation of the coarse Widmanstatten patterns found in meteorites. It was felt that a study of these patterns in meteoritic irons would contribute to the understanding of these mechanisms. \u0000 \u0000 \u0000 \u0000An investigation of the macro-and micro-crystalline perfection of an Amalia Farm [= Bethany, Great Namaqualand], South Africa, and a Canyon Diablo, Arizona, meteorite established that the latter was far better suited for an X-ray study of the orientation relationships in the structure. In the course of the research it was established that one of the mechanisms operated at high transformation temperatures, while the other operated at much lower temperatures. The orientations in the Canyon Diablo sample corresponded to those predicted by the high-temperature mechanism. This, and other metallurgical evidence, is in accord with the theory that the Widmanstatten patterns in meteorites are formed by extremely slow cooling from high temperatures. \u0000 \u0000 \u0000 \u0000Recent advances in physical metallurgy have developed very useful correlations between rates of solid reactions and the resultant structures (coarseness of pattern) and between speed and temperature of plastic deformation and the type of deformation which occurs (slip, twinning, and cleavage). The application of this knowledge, in conjunction with adequate experiments on alloys of meteoritic composition, would undoubtedly lead to definite knowledge concerning the origin and the history of meteorites.","PeriodicalId":407308,"journal":{"name":"Contributions of the Society for Research on Meteorites","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"118030276","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Determination of the Age of Iron and Stony Meteorites from their Radioactivity 用放射性测定铁陨石和石质陨石的年龄

Contributions of the Society for Research on Meteorites Pub Date : 1900-01-01 DOI: 10.1111/J.1945-5100.1938.TB00181.X

R. D. Evans

{"title":"The Determination of the Age of Iron and Stony Meteorites from their Radioactivity","authors":"R. D. Evans","doi":"10.1111/J.1945-5100.1938.TB00181.X","DOIUrl":"https://doi.org/10.1111/J.1945-5100.1938.TB00181.X","url":null,"abstract":"Observed meteor and meteorite velocities (Opik, Boothroyd) indicate that a small fraction, perhaps in the neighborhood of 15 percent, of all meteorites striking the earth are of extra-solar origin. Helium-radium age measurements (Paneth, Urry, & Koeck) on 23 iron meteorites, none of which was of known heliocentric velocity, disclose a uniform distribution of last-solidification ages with no ages clearly greater than the age of the earth. Thus, either the specimens are all from the solar system, as Paneth proposed, or the galactic system is of the same age as the earth. Two critical experiments are in progress, based on the following evidence. The abundance-ratio of the C, O, Si, Cl, Fe, Co, and Ni isotopes in meteorites has been studied by various workers, and is found to be the same as in the terrestrial elements. Moreover, the ratio of the two independent isotopes of uranium, 92U235 and 92U238, is the same in all terrestrial specimens, regardless of the geologic age of the mineral in which they are found. It is therefore taken as a reasonable premise, but regarded as a working assumption only, that the original isotopic ratio of any element is a constant of nature and is independent of its place of origin in the galactic system. Measurements of the actinouranium vs. uranium I activity-ratio, and of the specific activity of potassium, are in progress on stony meteorites selected for their known heliocentric velocities. Some of these are of extra-solar origin while others are solar-system meteorites. The final results of the analyses give the difference between the age of the atoms in the meteorites and the same type of atoms in the earth. The method is independent of all influence from varying chemical and physical conditions during the history of the meteorite, as it deals entirely with isotopic ratios. The study of both the AcU, UI ratio and the K40, K41 ratio provides an independent check on the basic assumption of the method. The apparatus, technique, and mathematical background for these experiments are fully described. The announcement of the numerical results of these analyses is deferred until all the observations and control runs have been repeated many times, in order to assure their complete reliability.","PeriodicalId":407308,"journal":{"name":"Contributions of the Society for Research on Meteorites","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120792614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0