Spatially resolved organic analysis of the allende meteorite

The distribution of polycyclic aromatic hydrocarbons(PAHs) in the Allende meteorite has been probed with two-step laser desorption/laser multiphoton ionization mass spectrometry. This method allows direct in situ analysis with a spatial resolution of 1 square millimeter or better of selected organic molecules. Spectra from freshly fractured interior surfaces of the meteorite show that PAH concentrations are locally high compared to the average concentrations found by wet chemical analysis of pulverized samples. The data suggest that the PAHs are primarily associated with the fine-grained matrix, where the organic polymer occurs. In addition, highly substituted PAH skeletons were observed. Interiors of individual chondrules were devoid of PAHs at our detection limit(about 0.05 parts per million).     

Radionuclide composition of the allende meteorite from nondestructive gamma-ray spectrometric analysis

The concentrations of beryllium-7, sodium-22, aluminum-26, potassium-40, scandium-46, vanadium-48, chromium-51, manganese-54, cobalt-57, cobalt-60, and thorium-232 (thallium-208) have been measured in the Allende meteorite by nondestructive gamma-ray spectrometry. The high cobalt-60 content of the meteorite is indicative of a preatmospheric body with a minimum effective radius of 50 centimeters and a weight of 1650 kilograms; the aluminum-26 activity indicates a minimum exposure age of 3 million years.     

686例鼻咽癌的CT分析

目的：通过分析鼻咽癌的ＣＴ表现，提高对鼻咽癌放疗前后的认为。方法：对６８６例病理证实的鼻咽癌，全部做鼻咽部ＣＴ横断扫描，并详细分析所得资料。结果：鼻咽癌放疗前后的ＣＴ表现，主要有鼻咽癌以及周围软组织改变、淋巴结肿大、颅底骨质增生硬化、颅内直接侵犯、颅内转移、副鼻窦及乳突炎症。结论：ＣＴ检查可以较好地显示鼻咽癌放疗前后的表现，辅助放疗的定位及定量，也有利于病例的追踪。     

Melting relations of the aliende meteorite

The proportions of major oxides in the Allende carbonaceous chondrite after partial reduction are remarkably similar to those in possible mantle material of the earth. When heated, the Allende meteorite generates a sulfide melt (47 percent iron, 25 percent nickel, and 24 percent sulfur by weight), a ferrobasaltic melt, and olivine with or without pyroxene, over a wide pressure range (5 to 25 kilobars). The silicate melt contains more sodium and less titanium than lunar ferrobasalts. An aggregate of the Allende chondrite rich in calcium and aluminum produces silica-undersaturated, calcium-rich melt and spinel over a wide pressure and temperature range. From these studies, it is suggested that the earth's core contains significant amounts of both nickel and sulfur and that a 3 : 2 mixture of Allende bulk sample and calcium- and aluminum-rich aggregates is closer in major element abundances than either of these components to the average composition of the moon.     

Olivine-garnet transformation in a meteorite

Garnet has been identified for the first time as a meteorite mineral in the Coorara chondrite from Western Australia. It replaces olivine grains in a 1-millimeter veinlet traversing the body of the meteorite. The associated olivine has abnormally low birefringence, which suggests a highly shocked condition. Microprobe analyses do not distinguish the garnet from the associated olivine, which has the composition (Mg(.75)Fe(.25))(2) SiO(4); the garnet may have the composition Mg(3)Fe(2)Si(3)O(12) but be unresolvable from the accompanying olivine, or alternatively is nonstoichiometric. Transformation of olivine to garnet under high pressure could have significant implications for the phase composition of the Earth's mantle.     

Pyroxene-garnet transformation in coorara meteorite

Majorite is a new garnet in a veinlet of the Coorara meteorite. Its chemical composition is compatible with derivation mostly from original pyroxene, not from olivine as originally reported. Silicon is partly in sixfold coordination. Ringwoodite, a spinel of olivine composition, occurs as purple grains set in a matrix of fine-grained garnet. The similar mineralogy and texture of the Coorara and Tenham meteorites suggest a common parent body.     

Denver meteorite: a new fall

A meteorite, a single stone weighing 230 grams, was discovered in the roof of a warehouse on 17 July 1967; evidently it fell during the preceding week. The warehouse is on the northeast edge of Denver, Colorado; coordinates, 39 degrees 46'57'N, 104 degrees 55'50'W. This is the first recovered fresh fall in the United States since the Bells (Texas) meteorite of 9 September 1961. The composition and structure are those of an olivine-hypersthene chondrite.     

Aromatic hydrocarbons in the murchison meteorite

Polynuclear aromatic hydrocarbons in the Murchison meteorite have been identified by the combined techniques of gas chromatography and mass spectrometry. The distribution of the aromatic compounds suggests that they are the products of a high-temperature synthesis.     

Amphibole: first occurrence in a meteorite

This is the first report of an amphibole mineral found in any meteorite. The amphibole richterite (soda tremolite), Na(2)Ca(Mg, Fe)(5)Si(8)O(22)(OH, F)(2), occurs as a primary (preterrestrial) mineral enclosed within graphite nodules in the iron meteorite from Wichita County, Texas.     

Discovery of ancient silicate stardust in a meteorite

We have discovered nine presolar silicate grains from the carbonaceous chondrite Acfer 094. Their anomalous oxygen isotopic compositions indicate formation in the atmospheres of evolved stars. Two grains are identified as pyroxene, two as olivine, one as a glass with embedded metal and sulfides (GEMS), and one as an Al-rich silicate. One grain is enriched in 26Mg, which is attributed to the radioactive decay of 26Al and provides information about mixing processes in the parent star. This discovery opens new means for studying stellar processes and conditions in various solar system environments.     

The frequency of meteorite falls on the Earth

Photographic observations from a network of 60 cameras in western Canada are used to derive the influx rate of meteorites on the earth's surface, the first time instrumental data have been used for this purpose. Forty-three observed events are believed to have dropped between 0.1 and 12 kilograms of meteorites each. The flux values are corrected for a minor latitude effect and agree with earlier estimates near 10 kilograms but vary more slowly with mass. Eight events per year drop at least 1 kilogram of meteorites in an area of 10(6) square kilometers.     

Netschaevo: a new class of chondritic meteorite

The ratios of refractory elements to silicon and of zinc to silicon indicate that the silicate portion of the Netscha?vo meteorite is an ordinary chondrite. The scarcity of chondrules, the large dimensions (about 100 micrometers) of plagioclase grains, and the low indium content (0.09 nanogram per gram) indicate that Netscha?vo belongs to petrologic type 6. On a diagram of reduced iron versus oxidized iron, Netscha?vo lies along an extrapolation of the LL-L-H ordinary chondrite fractionation trend. The abundances of siderophile elements (nickel, germanium, iridium, and gold) are about 1.6 to 2.0 times greater than in H-group chondrites, and siderophile/nickel ratios are, with one exception, those expected from LL-L-H trends. This evidence indicates that Netscha?vo is an extremely iron-rich member of the ordinary chondrite sequence, and that plausible models to account for the ordinary chondrite sequence must produce materials having iron/silicon ratios 25 percent greater than those in CI carbonaceous chondrites. The existence of Netscha?vo emphasizes that the chondritic meteorites in terrestrial collections are a biased and incomplete selection of primitive solar system materials.     

Exsolution in ferromagnesian olivine of the divnoe meteorite

Ferromagnesian olivine, one of the most common minerals in the solar system, has been widely regarded as a continuous solid solution, although several thermodynamic analyses have suggested the possibility of a miscibility gap at low temperatures. Natural ferromagnesian olivine from the Divnoe meteorite contains compositionally different exsolution lamellae, providing direct evidence for the existence of a miscibility gap in iron-magnesium olivine solid solutions.     

Farmington meteorite: cristobalite xenoliths and blackening

The Farmington chondrite contains two small xenoliths of granular cristobalite, each surrounded by a thin reaction rim of diopsidic clinopyroxene. Similarities between the blackened structure and drusy cavities, characteristic of this meteorite, and those of an experimentally heat-treated chondrite suggest that Farmington was reheated rather than shocked, but neither the exact stage in the history of this stone at which reaction rims developed around the xenoliths nor the source of the calcium necessary to form rim diopside have been established with certainty.     

The organic content of the Tagish Lake meteorite

The Tagish Lake meteorite fell last year on a frozen lake in Canada and may provide the most pristine material of its kind. Analyses have now shown this carbonaceous chondrite to contain a suite of soluble organic compounds (approximately 100 parts per million) that includes mono- and dicarboxylic acids, dicarboximides, pyridine carboxylic acids, a sulfonic acid, and both aliphatic and aromatic hydrocarbons. The insoluble carbon exhibits exclusive aromatic character, deuterium enrichment, and fullerenes containing "planetary" helium and argon. The findings provide insight into an outcome of early solar chemical evolution that differs from any seen so far in meteorites.     

Amino acids indigenous to the murray meteorite

Analysis of the Murray meteorite, a type II carbonaceous chondrite, has led to the identification of 17 amino acids. For seven of the amino acids nearly equal amounts of the D and L isomers are present, and 11 of the amino acids are not found in protein. These results suggest that these amino acids, like the amino acids of the Murchison meteorite, are extraterrestrial in origin.     

Dislocations in a campo del cielo meteorite

Thin-film transmission electron microscopy showed that a Campo del Cielo meteorite has an immobile dislocation network of high density. The network is not related to attendant precipitates.