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191.
Mehmet Yesiltas Yoko Kebukawa Robert E. Peale Eric Mattson Carol J. Hirschmugl Peter Jenniskens 《Meteoritics & planetary science》2014,49(11):2027-2037
Synchrotron‐based Fourier transform infrared spectroscopy and Raman spectroscopy are applied with submicrometer spatial resolution to multiple grains of Sutter's Mill meteorite, a regolith breccia with CM1 and CM2 lithologies. The Raman and infrared active functional groups reveal the nature and distribution of organic and mineral components and confirm that SM12 reached higher metamorphism temperatures than SM2. The spatial distributions of carbonates and organic matter are negatively correlated. The spatial distributions of aliphatic organic matter and OH relative to the distributions of silicates in SM2 differ from those in SM12, supporting a hypothesis that the parent body of Sutter's Mill is a combination of multiple bodies with different origins. The high aliphatic CH2/CH3 ratios determined from band intensities for SM2 and SM12 grains are similar to those of IDPs and less altered carbonaceous chondrites, and they are significantly higher than those in other CM chondrites and diffuse ISM objects. 相似文献
192.
Jemma Davidson Alexander N. Krot Kazuhide Nagashima Eric Hellebrand Dante S. Lauretta 《Meteoritics & planetary science》2014,49(8):1456-1474
We report in situ O isotope and chemical compositions of magnetite and olivine in chondrules of the carbonaceous chondrites Watson‐002 (anomalous CK3) and Asuka (A)‐881595 (ungrouped C3). Magnetite in Watson‐002 occurs as inclusion‐free subhedral grains and rounded inclusion‐bearing porous grains replacing Fe,Ni‐metal. In A‐881595, magnetite is almost entirely inclusion‐free and coexists with Ni‐rich sulfide and less abundant Ni‐poor metal. Oxygen isotope compositions of chondrule olivine in both meteorites plot along carbonaceous chondrite anhydrous mineral (CCAM) line with a slope of approximately 1 and show a range of Δ17O values (from approximately ?3 to ?6‰). One chondrule from each sample was found to contain O isotopically heterogeneous olivine, probably relict grains. Oxygen isotope compositions of magnetite in A‐881595 plot along a mass‐dependent fractionation line with a slope of 0.5 and show a range of Δ17O values from ?2.4‰ to ?1.1‰. Oxygen isotope compositions of magnetite in Watson‐002 cluster near the CCAM line and a Δ17O value of ?4.0‰ to ?2.9‰. These observations indicate that magnetite and chondrule olivine are in O isotope disequilibrium, and, therefore, not cogenetic. We infer that magnetite in CK chondrites formed by the oxidation of pre‐existing metal grains by an aqueous fluid during parent body alteration, in agreement with previous studies. The differences in Δ17O values of magnetite between Watson‐002 and A‐881595 can be attributed to their different thermal histories: the former experienced a higher degree of thermal metamorphism that led to the O isotope exchange between magnetite and adjacent silicates. 相似文献
193.
Louis M. Barbier Robert Smith Scott Murphy Eric R. Christian Rodger Farley John F. Krizmanic John W. Mitchell Robert E. Streitmatter Eugene C. Loh Stephen Stochaj 《Astroparticle Physics》2005,22(5-6):439-449
We have designed and built an instrument to measure and monitor the “nightglow” of the Earth’s atmosphere in the near ultraviolet (NUV). In this paper we describe the design of this instrument, called NIGHTGLOW. NIGHTGLOW is designed to be flown from a high altitude research balloon, and circumnavigate the globe. NIGHTGLOW is a NASA, University of Utah, and New Mexico State University project. A test flight took place from Palestine, Texas on July 5, 2000, lasting about 8 h. The instrument performed well and landed safely in Stiles, Texas with little damage. The resulting measurements of the NUV nightglow are compared with previous measurements from sounding rockets and balloons. 相似文献
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Theoretical calculations of extrusive volcanic degassing on Venus yield atmospheric pressure-related rock density profiles consistent with the formation of magma neutral buoyancy zones and magma reservoirs at different depths as a function of altitude (Head and Wilson, J. geophys. Res. 97, 3877, 1992). Global analysis of radiating dike swarms interpreted to originate at magma reservoirs show that their distribution matches these predictions across approximately 90% of the planet's surface; only those highland regions whose elevations exceed 6053 km appear anomalous. The distribution of the large volcano population (extrusive reservoir products) (Keddie and Head, Planet. Space Sci. 42, 455, 1994) has yielded similar results. Comparison between the dike swarm (intrusive) and large volcano (extrusive) populations suggests that neutral buoyancy plays an important role in governing volcanic processes near the venusian surface and that the depth to the level of neutral buoyancy increases systematically at altitudes above 6051 km. 相似文献
197.
Abstract— 20–25 mg whole rock samples of the nakhlites Lafayette and Nakhla have been analyzed via the 40Ar‐39Ar technique, in part to verify their formation ages, but primarily, in an attempt to determine the timing of aqueous alteration in these martian meteorites. As in previous studies, plateaus in apparent age are observed at about 1300 Ma (1322 ± 10 for Lafayette, 1332 ± 10 and 1323 ± 11 for Nakhla), presumably corresponding to crystallization ages. The plateaus are not entirely flat, perhaps reflecting the effects of recoil during creation of 39Ar in the nuclear irradiation. The first 5–20% of the K‐derived Ar released from all three samples give apparent ages <1300 Ma. Coupled with the fact that chronometric isotopic studies of nakhlites typically show some disturbance, we believe the low temperature pattern represents more recent (than 1300 Ma) formation of martian aqueous alteration products such as iddingsite. No low temperature plateaus are observed. This is consistent with petrographic evidence for multiple formation events, although the lack of low temperature plateaus is far from conclusive. On the other hand, if there was a single time of alteration, we believe that it will be difficult, if not impossible, to determine it using the K‐Ar system. 相似文献
198.
We calculate the profile and polarization of the Lα line in the solar corona. Coronal temperature variation, solar wind and other non-thermal motions have been taken into account. Because of the relatively low atomic weight of hydrogen the profile of the Lα line is a sensitive indicator of the coronal temperature. The line polarization contains relatively little information except for strong magnetic fields (> 70 G). 相似文献
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This paper examines the issue of modeling dynamic aspects of shopping trip-making behavior using time series data and presents the results of an empirical analysis based on a two-week travel diary survey of households in Hamilton, Ontario. It is concluded that logit models incorporating time dependent variables perform significantly better in terms of both calibrated goodness-of-fit and predictive capabilities than do models which assume no time dependency between choices. 相似文献