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31.
Dicarboxylic acids were searched for in three Sutter's Mill (SM) fragments (SM2 collected prerain, SM12, and SM41) and found to occur almost exclusively as linear species of 3‐ to 14‐carbon long. Between these, concentrations were low, with measured quantities typically less than 10 nmole g?1 of meteorite and a maximum of 6.8 nmole g?1 of meteorite for suberic acid in SM12. The SM acids' molecular distribution is consistent with a nonbiological origin and differs from those of CMs, such as Murchison or Murray, and of some stones of the C2‐ungrouped Tagish Lake meteorite, where they are abundant and varied. Powder X‐ray diffraction of SM12 and SM41 show them to be dominated by clays/amorphous material, with lesser amounts of Fe‐sulfides, magnetite, and calcite. Thermal gravimetric (TG) analysis shows mass losses up to 1000 °C of 11.4% (SM12) and 9.4% (SM41). These losses are low compared with other clay‐rich carbonaceous chondrites, such as Murchison (14.5%) and Orgueil (21.1%). The TG data are indicative of partially dehydrated clays, in accordance with published work on SM2, for which mineralogical studies suggest asteroidal heating to around 500 °C. In view of these compositional traits and mineralogical features, it is suggested that the dicarboxylic acids observed in the SM fragments we analyzed likely represent a combination of molecular species original to the meteorite as well as secondary products formed during parent‐body alteration processes, such as asteroidal heating. 相似文献
32.
Alex Ruzicka Jeffrey N. Grossman Laurence Garvie 《Meteoritics & planetary science》2014,49(8):E1-E101
Meteoritical Bulletin 100 contains 1943 meteorites including 8 falls (Boumdeid [2011], Huaxi, Ko?ice, Silistra, So?tmany, Sutter's Mill, Thika, Tissint), with 1575 ordinary chondrites, 139 carbonaceous chondrites, 96 HED achondrites, 25 ureilites, 18 primitive achondrites, 17 iron meteorites, 15 enstatite chondrites, 11 lunar meteorites, 10 mesosiderites, 10 ungrouped achondrites, 8 pallasites, 8 Martian meteorites, 6 Rumuruti chondrites, 3 enstatite achondrites, and 2 angrites, and with 937 from Antarctica, 592 from Africa, 230 from Asia, 95 from South America, 44 from North America, 36 from Oceania, 6 from Europe, and 1 from an unknown location. This will be the last Bulletin published in the current format. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available online at http://www.lpi.usra.edu/meteor/ 相似文献
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Richard C. Altrock Laurence J. November George W. Simon Robert W. Milkey Simon P. Worden 《Solar physics》1975,43(1):33-37
Heights of formation of lines that do not exhibit Zeeman splitting are calculated using an LTE, partial non-LTE, and full
non-LTE approach. Non-magnetic (g=0) lines are valuable for velocity investigations in quiet-Sun magnetic field regions, and a knowledge of their formation
heights is useful for obtaining three dimensional velocity profiles in these regions.
Presently at Sacramento Peak Observatory.
Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献
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Laurence A. J. GARVIE Grant BAUMGARDNER Peter R. BUSECK 《Meteoritics & planetary science》2008,43(5):899-903
Abstract— Carbonaceous nanoglobules are ubiquitous in carbonaceous chondrite (CC) meteorites. The Tagish Lake (C2) meteorite is particularly intriguing in containing an abundance of nanoglobules, with a wider range of forms and sizes than encountered in other CC meteorites. Previous studies by transmission electron microscopy (TEM) have provided a wealth of information on chemistry and structure. In this study low voltage scanning electron microscopy (SEM) was used to characterize the globule forms and external structures. The internal structure of the globules was investigated after sectioning by focused ion beam (FIB) milling. The FIB‐SEM analysis shows that the globules range from solid to hollow. Some hollow globules show a central open core, with adjoining smaller cores. The FIB with an SEM is a valuable tool for the analysis of extraterrestrial materials, even of sub‐micron‐sized “soft” carbonaceous particles. The rapid site‐specific cross‐sectioning capabilities of the FIB allow the preservation of the internal morphology of the nanoglobules, with minimal damage or alteration of the unsectioned areas. 相似文献
39.
Laurence Hopkinson Stephen Roberts Richard Herrington Jamie Wilkinson 《Contributions to Mineralogy and Petrology》1999,137(4):342-350
Silica occurs in abundance in a variety of hydrothermal samples from the Trans-Atlantic Geotraverse (TAG) hydrothermal mound,
26°N Mid-Atlantic Ridge. The water content, trace element chemistry, and mineralogy of crystalline silica from 15 different
samples have been examined by vibrational spectroscopy and probe microanalysis. The samples are from: shallow subsurface ferric
iron oxyhydroxide silica deposits (n=4), a fragment of an active white smoker chimney (n=1), anhydrite bearing hydrothermal breccias (n=2), pyrite silica breccias (n=3), and silicified wall rock breccias (n=5). Length-fast chalcedony occurs in association with variable quantities of ferric iron oxyhydroxides in hydrothermal breccias
from the mound flanks, within shallower subsurface chert samples, and within white smoker chimney walls. Samples from the
anhydrite zone contain textures which are suggestive of an origin involving replacement of anhydrite. Samples taken from TAG
1 and 5 from below the anhydrite zone contain no chalcedony. Instead they contain subhedral quartz crystals which show oscillatory
zoning in aluminium. Two types of crystalline silica namely, type A and type B quartz, are defined on the basis of the infrared
spectra in the OH region from 3200 cm−1 to 3600 cm−1. The type A quartz occurs beneath the anhydrite zone at TAG 1 and 5. We propose a model that relates specific varieties of
crystalline silica to different thermal and chemical environments within the mound interior. Length-fast chalcedony occurs
in an outer low temperature envelope across the top and sides of the mound. The common association between length-fast chalcedony
and ferric iron oxyhydroxides suggests that chalcedony crystallization is favoured where catalysis by ferric iron can occur.
The apparent suppression of fibrous silica at the expense of single quartz crystals with increasing depth is attributed to
differing growth rates and degrees of supersaturation of silica-bearing solutions with increasing temperature within the mound.
The transition from type A to type B single crystal growth is interpreted to occur at temperatures approaching ˜360 °C due
to decreasing solubility of aluminium in quartz, so that aluminium is rendered unavailable for type A valence compensation.
Received: 10 September 1998 / Accepted: 6 July 1999 相似文献
40.
Estimating external magnetic field differences at high geomagnetic latitudes from a single station 下载免费PDF全文
Providing an accurate estimate of the magnetic field on the Earth's surface at a location distant from an observatory has useful scientific and commercial applications, such as in repeat station data reduction, space weather nowcasting or aeromagnetic surveying. While the correlation of measurements between nearby magnetic observatories at low and mid‐latitudes is good, at high geomagnetic latitudes () the external field differences between observatories increase rapidly with distance, even during relatively low magnetic activity. Thus, it is of interest to describe how the differences (or errors) in external magnetic field extrapolation from a single observatory grow with distance from its location. These differences are modulated by local time, seasonal and solar cycle variations, as well as geomagnetic activity, giving a complex temporal and spatial relationship. A straightforward way to describe the differences are via confidence intervals for the extrapolated values with respect to distance. To compute the confidence intervals associated with extrapolation of the external field at varying distances from an observatory, we used 695 station‐years of overlapping minute‐mean data from 37 observatories and variometers at high latitudes from which we removed the main and crustal fields to isolate unmodelled signals. From this data set, the pairwise differences were analysed to quantify the variation during a range of time epochs and separation distances. We estimate the 68.3%, 95.4% and 99.7% confidence levels (equivalent to the 1σ, 2σ and 3σ Gaussian error bounds) from these differences for all components. We find that there is always a small non‐zero bias that we ascribe to instrumentation and local crustal field induction effects. The computed confidence intervals are typically twice as large in the north–south direction compared to the east‐west direction and smaller during the solstice months compared to the equinoxes. 相似文献