CARBON IN DARK INCLUSIONS OF THE ALLENDE METEORITE

Carbon contents of three Dark Inclusions (DI's) of the Allende meteorite, measured chemically, range from 0.56 to 1.17 weight %. When one includes the data reported by Bunch, Chang, and Ott (two DI's), the lower limit is 0.44%. The C-concentration map of a 1.6 × 1.6 mm² area straddling the boundary of a DI and matrix, or else of a DI and its dark halo, obtained with a ¹²C (d,p)¹³ C nuclear microprobe, shows that the C-content of the core of the DI is very uniform, and that the C-content of the rim is 2.9 ± 0.3 times larger. Variability of C-content of matrix and matrix-like areas of Allende appears to be the rule. DI's cannot be reworked bulk Allende, or precursor for bulk Allende without the addition, respectively removal of significant amounts of carbon. However, some Type 1 DI's might be reworked Allende matrix or precursor matter for that matrix.     

SKETCHES IN THE HISTORY OF METEORITICS 2: THE EARLY CHEMICAL AND MINERALOGICAL WORK

The chemical and mineralogical work on meteorites over the period 1800 to 1840 is reviewed. The number of elements known to be present in meteorites rose from six to 19. Chemical techniques advanced rapidly so that by 1815 the procedure was essentially that of modern wet chemical analysts: removal of the magnetic material, dissolution of the acid-soluble portion and fusion of the remainder with alkali. After Bournon's work in 1802 much mineralogical progress was made during the 1820's, notably by G. Rose. Berzelius made important contributions by his own analyses and synthesis of the work of others. By 1840 ordinary chondrites, carbonaceous chondrites, plagioclase-pyroxene achondrites, Chassigny, pallasites and octahedrites could all be distinguished     

A STUDY OF THE RELATIVE RATES OF METEORITE FALLS ON THE EARTH'S SURFACE

Meteorite camera networks have provided reliable data on typical orbits for meteorites. Using an adopted distribution of 20 orbits we determine the relative rates of meteorite falls over the surface of the earth taking account of the important effects due to the earth's gravity. The data are then used to study the expected variation in rates as a function of daylight, twilight or night conditions; time of day; season of the year; and geographic latitude. The rates of meteorite falls have a deep minimum near the area of the earth facing the earth's apex but a surprisingly broad maximum on the opposite side, facing the antapex. Twilight rates are lower than average and nighttime rates 3% higher than daytime rates. Minimum rates occur near 6^h local time and there is a broad maximum from noon to midnight. Rates are highest near the beginning of spring for either hemisphere and lowest near the beginning of autumn. The decline in rates with increasing latitude is quite moderate. The existing camera networks observe average fall rates at night which are very close to the average rate over the whole earth for the whole year.     

THE SASKATCHEWAN FIREBALL OF 1922 AND A POSSIBLE LINK WITH THE WYNYARD CHONDRITE

A brilliant smoking meteor appeared in a clear sky in bright sunlight at 11 a.m., July 24, 1922 near Wynyard, Saskatchewan, Canada. The sight and thunderous sounds were witnessed by many hundreds of people in the rural district but no craters or meteorites were found at that time. Investigation and interviews with surviving witnesses in 1981 indicated a defined area near Big Quill Lake in which a meteorite may have fallen. Field investigation led to the Wynyard meteorite which had been found by a farmer sometime in the late 1960's at 104° 11'W 51°33'N. The Wynyard meteorite is a chondrite weighing 3.5 kg. It is moderately weathered and it may or may not have been part of the 1922 fall.     

A DETERMINATION OF THE ABSOLUTE AGES OF SEVEN FRONT FACE LUNAR BASINS†

Careful examination of seven giant front face basins on the moon will show that the basins most densely covered by younger craters are the oldest. With increasing age they exhibit lower external rims, not scarp heights. The rims are progressively more subdued with age. This paper proposes that absolute ages for these basins can be obtained by calculating an effective viscosity of the moon's outer layers from 3.85 × 10⁹ y, the date of Imbrium, to the present. Similarly viscosity measures can be determined for the oldest basin. To do this we need the present and the original rim heights. The present values are observed. The original heights are calculated by extrapolating the relationship between diameter and rim height for normal Class I craters. It turns out that as long as the larger basins have proportionately higher original heights than the smaller, the absolute values are of little importance and the ages are definitive. There are many similar families of viscosity changes with age and they yield similar absolute ages. In each case equations relating viscosity changes with age were derived and for each basin there is only one age that will yield the final rim height. Ages, × 10⁹ y, of the basins are: Orientale 3.82, Imbrium 3.85, Crisium 4.00, Nectaris 4.07, Serenitatis 4.14, Humorum 4.23 and an Unnamed basin between Werner and the Altai ring 4.30.     

SOLAR ABUNDANCES OF THE ELEMENTS

The isotopic compositions of noble gases in the solar wind show high enrichments of light isotopes. When corrected for mass fractionation all five noble gases there can be resolved in terms of the two primitive noble gas components that have been identified in planetary solids. Reasons are presented for assigning the fractionation to a solar process that selectively enriches lighter nuclei at the surface of the Sun. When abundances of the elements at the Sun's surface are corrected for this fractionation, it is shown that atomic abundances for major elements in the bulk Sun are (in decreasing order): Fe, Ni, O, Si, S and Mg. Solar elements at about the 1% atomic abundance level include He, C, Ne, Ca and Cr. These results suggest that fusion of hydrogen is probably not the Sun's primary energy source.     

THE MAGNETIC INVESTIGATION OF THE SIKHOTE-ALIN IRON METEORITE SHOWER AT THE SITE OF FALL

Individual and splinter specimens of the iron meteorite shower of Sikhote-Alin and rock samples from impact craters have been studied magnetically. The results indicate that: 1) Histograms for the distribution of natural remanent magnetization J_n of individual and splinter specimens are characterized by a high correlation coefficient (0.82 ± 0.06). For the splinter specimens, a trend to an increase in number of specimens with anomalously high J_n values is observed; 2) the Earth's magnetic field did not greatly affect the magnetic properties of this iron meteorite; and 3) for rock samples taken from different craters, there was found to be a relation between the natural remanent magnetization and the energy conditions of the crater formation.     

X-RADIOGRAPHY OF SLABS OF THE ALLENDE METEORITE

X-radiographs of eight slabs of the Allende meteorite, each about 8 mm thick, reveal significant chemical and textural heterogeneities of our Allende fragment at the 100–1000 g level. They also reveal systematic arrangements of chondrules (“strings”). Our preliminary interpretation is that the observed features are probably all due to regolith processes on Allende's parent body, and that these processes included “mini” slope slides along dry, “sandy” slopes.     

FORMS OF NONTERRESTRIAL DUST ON THE EARTH

The author carried out a study of pulverised cosmic matter extracted from the soil at the fall locality of the Sikhote Alin iron meteorite shower. Three forms of dust were distinguishable: meteoritic, sharp-angled, irregular particles from the break-up of the meteorite; meteoric, spherical, magnetic particles from ablation; and micro meteorites. Meteoritic and meteoric dust was also discovered in the soil of the regions of fall of the Boguslavka and Yardymly iron meteorites. Experiments made by the author for the purpose of obtaining artificial meteoric dust from meteoritic matter of various types have shown that the meteoric dust obtained from stony meteorites is composed of spherules similar to those extracted from the soil in the areas of fall of the Sikhote Alin, Boguslavka and Yardymly iron meteorites. Cosmic dust, the particles of which are usually called micrometeorites, due to their small size, are not subjected to the influence of temperature as they pass through the Earth's atmosphere and they reach the Earth's surface unaltered. It is proposed that meteoric and cosmic dust comprises the largest part of the cosmic matter falling onto the Earth:     

THE GOSNELLS IRON — A FRAGMENT OF THE MOUNT DOOLING OCTAHEDRITE

A 1.5 kg iron found in 1960 at Gosnells, near Perth, Western Australia, belongs to Wasson's chemical group I-An3 and is structurally unusual, being best described as a heat-altered granular coarse octahedrite. It is chemically and structurally very similar to the Mount Dooling iron, found in 1909 about 400 km away, and has a fracture surface which fits the Mount Dooling mass very closely. The Gosnells fragment was probably transported by human agency, though it is not known when or by whom.     

E-CHONDRITES: SIGNIFICANCE OF THE PARTITION OF ELEMENTS BETWEEN ‘SILICATE’ AND ‘SULPHIDE’

Bulk chemical analyses of six E-chondrites (Daniel's kuil, Khairpur, Kota Kota, Saint-Sauveur, South Oman and St Mark's) are given, together with partial analyses of a further five (Blithfield, Hvittis, Indarch, Jajh deh Kot Lalu and Pillistfer). The distribution of some normally lithophile elements (Al, Ca, Cr, K, Mg, Na, P and Ti) between silicate and sulphide groups of minerals was determined using the selective attack by dry chlorine (350°C) on magnetically separated fractions. Subdivision of the E-chondrites into types I and II (Yavnel;, 1963; Anders, 1964) is accepted and it is shown using chemical data that St Mark's and Saint-Sauveur should be included in type I. Sulphides contribute an unexpectedly high proportion of several elements to the bulk: e.g. Ca (av. 88.5% type I, 66.3% type II); Ti(av. 77.1% type I, 84.8% type II) and P as phosphide (av. 44.4% type I, > 83.2% type II). The proportion of Ti contributed to the bulk composition by the sulphides in types I and II increases with increae in ‘thermal metamorphic effect’ (Easton, 1983b) within each type. There is marked variability in the relative abundances of metal, phosphide, silicate and sulphide among the members of each type in keeping with their aggregate nature. The chemical composition of the ‘silicate’ and ‘sulphide’ in type IE-chondrites differs from that in type II (e.g. CaO in the silicates, Mg in the bulk sulphides) which therefore precludes the isochemical evolution of all E-chondrites from a common parent material. Partition of Ti between silicate and sulphide groups of minerals indicates that types I and II E-chondrites originated in separate, chemically distinct bodies.     

SUMMARY OF SEVERAL RECENT CHONDRITE FINDS FROM THE TEXAS PANHANDLE

Eleven recent chondrite finds from the Texas Panhandle have been examined and classified according to mineralogical and petrological criteria: five H's, five L's, and one LL chondrite. Five are distinct from nearby finds, while three remain ambiguous and three are related to previously reported chondrites. In addition, data are provided to classify the Muleshoe, Silverton, and Vigo Park chondrites, all of which were previously undescribed in the literature.     

Photochemical kinetics uncertainties in modeling Titan's atmosphere: First consequences

Uncertainties carried by the different kinetic parameters included in photochemical models of planetary atmospheres have rarely been considered even if they are supposed to be contributing mostly to the inconsistencies between observations and computed predictions. In this paper, we report the first detailed analysis of the propagation of uncertainties carried by the reaction rate coefficients included in an up-to-date photochemical model of Titan's atmosphere. Monte Carlo calculations performed on these reaction rate coefficients have been used to introduce their uncertainties and to investigate their significance on the photochemical modeling of Titan's atmosphere. Crude approximations in the implemented physical processes have been adopted to limit the number of free parameters. This allows us to pinpoint specifically the importance of chemical processes uncertainties in Titan's photochemical models and to evaluate their chemical robustness. First implications of this preliminary study related to purely chemical rate coefficient uncertainties are discussed. They are important enough to question indeed any comparisons between theoretical models with observations as well as any potential conclusions subsequently inferred. Since the latest missions, such as Cassini–Huygens, are likely to induce an ever-increasing interest for such kind of comparing studies, our conclusions show that it is crucial to reform the way we think of, and use, current photochemical models to understand the processes occurring in the atmospheres of the outer Solar System.     

MINERALOGY,PETROLOGY AND CHEMISTRY OF THE ISNA (C3) METEORITE

A total chemical analysis of the Isna, Egypt, meteorite is similar to analyses for chondrites of type C3, Ornans sub-type; however, comparison with one group of chemical data indicates that Isna is intermediate between the C3(O)'s and C3(V)'s in terms of total Fe. On the basis of atom ratios of Fe, Ca, Al, and Ti to Si, Isna can also be placed into a chemical group which includes types C1 and C2, as well as C3(O). Thin sections show a variety of small, closely-packed chondrules, fragments, and aggregate-like masses in a poorly translucent matrix. Olivine + clinoenstatite inclusions rich in metal and troilite, and olivine-rich inclusions are abundant and show evidence of shock. Ca-Al-Ti-rich inclusions, of probable high-temperature origin, contain olivine, spinel, Ca-rich nepheline, gehlenite, diopside, augite, enstatite, and anorthite. Kamacite and taenite from various occurrences in the meteorite have rather uniform Ni and Co contents, and Ni/Co for kamacite is close to that for several C3(O)'s.     

NEW LIGHT ON THE ORIGIN OF THE HOLY BLACK STONE OF THE KA'BA

At various times the Black Stone of the Ka'ba has been considered to be lava, basalt, a meteorite and lately an agate. This paper discusses the possibility that it may consist of impactite glass, derived from the meteoritic craters of Al-Hadidah, called Wabar.     

Evidence in a glassy cosmic spherule from Antarctica for grazing incidence encounters with the Earth's atmosphere

Abstract— Cosmic dust accreted by the Earth can be extensively reprocessed during atmospheric encounters. The textures and compositions of reprocessed material provide important constraints by which the processes affecting extraterrestrial matter in the Earth's atmosphere can be better understood. Here we report results on an unusual Antarctic glassy cosmic spherule that demonstrates strong textural evidence for at least two grazing incidence encounters with the Earth's atmosphere prior to final reentry. The particle consists of a central glassy core with four peripheral glass lobes that transect a silicate particle rim. The texture of the particle confirms previous theoretical speculations that some high velocity, low incidence angle interplanetary particles experience numerous encounters with the Earth's atmosphere and also indicates that micrometeorites demonstrating multiple melting episodes should be interpreted with caution.     

THE MINERALOGY AND CHEMISTRY OF THE ALTA'AMEEM METEORITE

The Alta'ameem hypersthene chondrite is a light gray brecciated and metamorphosed meteorite composed mainly of olivine (27% Fa), orthopyroxene (24.5% Fs) and plagioclase (An¹⁰). Other minerals include troilite, kamacite, taenite, chromite, ilmenite, clinopyroxene, chalcopyrite, and apatite or merrillite. The mineralogical and chemical analyses suggest that the Alta'ameem meteorite belongs to the amphoterite group of chondrites. The chemical composition includes the following: Fe 3.39, Ni 1.13, Co 0.05, Cu 0.01, FeS 6.48, SiO₂ 39.48, TiO₂ 0.28, Al₂O₃ 2.25, FeO 16.46, MnO 0.40, MgO 25.66, CaO 1.47, Na₂O 1.05, K₂O 0.15, P₂O₅ 0.47, Cr₂O₃ 0.45; total 99.18.     

THE CRACKING HISTORY OF SERRANIA DE VARAS: AN ALTERNATIVE VIEW

Buchwald's (1975) theory of thermally induced cracking in Serrania de Varas is critically examined from the standpoint of elementary stress analysis. New metallographic observations are presented. It is suggested that thermal cracking is unlikely to have been operating in this material.     

星表系统差及其计算方法

本文对星表系统差的性质进行了讨论，并分析和评估了目前常用的星表系统差计算方法的优、缺点，从而提出了一个新的星表系统差计算方法．同时也提出了星表系统差计算精度的检验标准．最后对用不同方法计算的系统差进行了分析比较．结果表明，新方法的系统差计算精度好于目前常用的解析方法．