Meteors and meteorites

Calculations Black body temperature Radiodating Chemical networks on comets Temperatures of meteors and meteorites on entry Estimate of the age of a rock from the radioisotopes Extension of the idea of networks in the interstellar medium to molecular processing on the surface of comets... 

Wetherill G. W. and Revelle D. O. (1982) Relationships between comets, large meteors, and meteorites. In Comets (ed. L. L. Wikening). University of Arizona Press, Tucson, pp. 297-319. 

Metal fatigue Metal production Metallurgy Metamorphic grade Metamorphic rock Metamorphism Metamorphosis Meteorology Meteors and meteorites Methyl group Metric system Mice... 

See also Catastrophism Cosmology Evolution, evidence of Evolutionary mechanisms Meteors and meteorites. 

See also Astronomy Catastrophism Gravity and gravitation Meteors and meteorites Planetary geology Planetary nebulae. 

Concepts Solar nebula The collapsing giant molecular cloud that leads to the formation of a star, specifically our Sun with its associated debris in the form of meteorites, meteors and comets... 

Stable isotope analysis of Earth, Moon, and meteorite samples provides important information concerning the origin of the solar system. 8lsO values of terrestrial and lunar materials support the old idea that earth and moon are closely related. On the other hand three isotope plots for oxygen fractionation in certain meteoric inclusions are anomalous. They show unexpected isotope fractionations which are approximately mass independent. This observation, difficult to understand and initially thought to have important cosmological implications, has been resolved in a series of careful experimental and theoretical studies of isotope fractionation in unimolecular kinetic processes. This important geochemical problem is treated in some detail in Chapter 14. 

The meteoric rise in computer power (and meteoritic decline in hardware prices) has opened exciting avenues for computer modeling in all branches of science. Today, computer models are used in three main areas of catalysis research modeling of reaction pathways and catalytic cycles, modeling of process kinetics and reaction performance, and computing structure/activity relationships on various levels. The models cover a wide range of approaches and system types. 

Rietmeijer, F.J.M. Interrelationships among meteoric metals, meteors, interplanetary dust, micrometeorites, and meteorites. Meteoritics Planet. Sci. 2000, 35. 1025-1041. 

Current evidence indicates that all major bodies in our solar system originated about the same time, approximately 4.6 Ga ago. The oldest rocks taken from the surface of the Moon and meteorites found on Earth are about 4.5 Ga old. The Moon, Mercury, Venus, and Mars have cratered surfaces that appear to be the result of the same type of meteoric activity that produced craters on Earth. The early atmosphere on Earth was probably similar to those found today on nearby planets on which life did not evolve. Hence, we can use information about those planets to help us infer the nature of the conditions on Earth under which life presumably evolved. 

Stishovite. Stishovite was first prepared (68) ia the laboratory ia 1961 at 1200—1400°C and pressures >16 GPa (158,000 atm). It was subsequentiy discovered, along with natural coesite, ia the Ari2ona meteor crater. It has been suggested that these minerals are geological iadicators of meteorite impact stmctures. Stishovite (p = 4.35 g/cm ) is the densest known phase of silica. The stmcture, space group P42/nmn is similar to that of... 

Meteorites are of two kinds stony meteorites that are rock-like in character, and metallic meteorites that consist of metallic elements. The kinds of substances in the stony meteorites are very much like the substances in the crust of the earth, if we allow for the fact that the meteors could not bring gases or liquids with them. We feel that the other type, the metallic meteors, give valuable clues about the nature of the earth s central core. Experts have long believed that these meteorites are fragments from exploded planets that, perhaps, resembled the earth. 

Clayton DD (1999) Radiogenic iron. Meteor Planet Sci 34 A145-A160 Clayton RN (1993) Oxygen isotopes in meteorites. Ann Rev Earth Planet Sci 21 115-149 Clayton RN, Mayeda TK, Hurd JM (1974) Loss of oxygen, silicon, sulfur, and potassiimi from flie limar regolith. Proc Lunar Sci Conf 5 1801-1809... 

ON THE MONTICELUTE-LIKE MINERAL IN METEORITES, AND ON OLDHAMITE AS A METEORIC CONSTITUENT ... 

Nickel in Meteorites. Centuries before the discovery of nickel, primitive peoples shaped meteoric iron into implements and swords and appreciated the superiority of this Heaven-sent metal (125). In 1777 J. K. F. Meyer of Stettin noticed that when he added sulfuric acid to some native iron which P. S. Pallas had found in Siberia, he obtained a green solution which became blue when it was treated with ammonium hydroxide. In 1799 Joseph-Louis Proust detected nickel in meteoric iron from Peru (126). This grayish white native iron had been observed by Rubin de Celis. Since it did not rust, it was sometimes mistaken for native silver. 

Brennecka, G. A., Weyer, S., Wadhwa, M. et al. (2009) 238U/235U variations in meteor-itic materials Evidence for curium-247 in the early solar system and implications for Pb-Pb dating (abstr.). Meteoritics and Planetary Science, 44 Supplement, A40. 

Meteorio iron.—-Large masses of metallio iron have been discovered from time to time, in different parts of the globe, embedded in the soil and also lying upon the surface others of a similar kind have been known to fell from the atmosphere, and ore hence termed meteorites. These masses are generally covered over with a kind of hlack enamel, which protects tho metal from the action of tho atmosphere. The iron forms usually a sort of network round a crystallized metallic mineral of a complicated composition. These meteoric masses are sometimes so large, and the metal which they contain so pure, as to furnish the inhabitants of the ncighborhoed with ample material for knives and spearheads. When examined chemically, there seems... 

The first journal devoted entirely to meteorite research seems to have been Meteor-itika, a Russian periodical that was published irregularly since 1939. In 1944 it was followed by the Dutch De Meteoor, and in 1953 appeared Meteoritics, the journal of the (American) Meteoritical Society founded twenty years earlier. For the history of this society, see Ursula B. Marvin, The Meteoritical Society 1933 to 1993, Meteoritics 28 (1993) 261-314. 

An alternative to the terrestrial synthesis of the nucleobases is to invoke interstellar chemistry. Martins has shown, using an analysis of the isotopic abundance of 13C, that a sample of the 4.6 billion year old Murchison meteorite which fell in Australia in 1969 contains traces of uracil and a pyrimidine derivative, xanthine. Samples of soil that surrounded the meteor when it was retrieved were also analyzed. They gave completely different results for uracil, consistent with its expected terrestrial origin, and xanthine was undetectable [48], The isotopic distributions of carbon clearly ruled out terrestrial contamination as a source of the organic compounds present in the meteorite. At 0°C and neutral pH cytosine slowly decomposes to uracil and guanine decomposes to xanthine so both compounds could be the decomposition products of DNA or RNA nucleobases. They must have either travelled with the meteorite from its extraterrestrial origin or been formed from components present in the meteorite and others encountered on its journey to Earth. Either way, delivery of nucleobases to a prebiotic Earth could plausibly have been undertaken by meteors. The conditions that formed the bases need not have been those of an early Earth at all but of a far more hostile environment elsewhere in the Solar System. That environment may have been conducive to the production of individual bases but they may never have been able to form stable DNA or RNA polymers this development may have required the less extreme conditions prevalent on Earth. 

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