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121.
Zsolt Kővári Katalin Oláh János Bartus Klaus G. Strassmeier Michael Weber Albert Washuettl John B. Rice Szilárd Csizmadia 《Astrophysics and Space Science》2006,304(1-4):375-377
Doppler images are presented for the RS CVn-type binary ζ And. Our upgraded Doppler imaging code TempMapε takes into account the distorted geometry of the primary giant component. On the maps several low latitude spots are restored with a temperature contrast of about 1000 K. Some weak polar features are also found. Cross-correlation of the consecutive Doppler-maps suggests solar-like differential surface rotation. 相似文献
122.
Abstract— We report the first petrologic examination of all stone meteorites of Fayette County, Texas. The 10 stones represent four or five different fall events. The three recovered Bluff stones represent two falls. Bluff (a), which includes the 145.5-kg Bluff #1 stone, is classified as L5(S4), whereas Bluff (b) is classified as L4(S3) and is represented by a single stone. The studied Cedar stones are classified as H4(S3), and all four Cedar stones appear to define a strewnfield. Round Top (a), classified as L5(S3) and represented by two stones, is unrelated to either Bluff or Cedar. Round Top (b) [H4(S3); 1 stone], whose exact provenance is unknown, might be a transported fragment of the Cedar shower. 相似文献
123.
Andreas F. Voegele Christofer S. Tautermann Andreas Hallbrucker Erwin Mayer Klaus R. Liedl 《Icarus》2004,169(1):242-249
Sulfurous acid (H2SO3) has never been characterized or isolated on Earth. This is caused by the unfavorable conditions for H2SO3 within Earth's atmosphere due to the high temperatures, the high water content and the oxidizing environment. Kinetic investigations by means of transition state theory showed that the half-life of H2SO3 at 300 K is 1 day but at 100 K it is increased to 2.7 billion years. Natural conditions to form H2SO3 presumably require cryogenic SO2 or SO2/H2O mixtures and high energy proton irradiation at temperatures around 100 K. Such conditions can be found on the Jupiter moons Io and Europa. Therefore, we calculated IR-spectra of H2SO3 which we compared with Galileo's spectra of Io and Europa. From the available data we surmise that H2SO3 is present on Io and probably but to a smaller extent on Europa. 相似文献
124.
Alexander N. KROT Anders MEIBOM Michael K. WEISBERG Klaus KEIL 《Meteoritics & planetary science》2002,37(11):1451-1490
Abstract— In this paper, we review the mineralogy and chemistry of calcium‐aluminum‐rich inclusions (CAIs), chondrules, FeNi‐metal, and fine‐grained materials of the CR chondrite clan, including CR, CH, and the metal‐rich CB chondrites Queen Alexandra Range 94411, Hammadah al Hamra 237, Bencubbin, Gujba, and Weatherford. The members of the CR chondrite clan are among the most pristine early solar system materials, which largely escaped thermal processing in an asteroidal setting (Bencubbin, Weatherford, and Gujba may be exceptions) and provide important constraints on the solar nebula models. These constraints include (1) multiplicity of CAI formation; (2) formation of CAIs and chondrules in spatially separated nebular regions; (3) formation of CAIs in gaseous reservoir(s) having 16O‐rich isotopic compositions; chondrules appear to have formed in the presence of 16O‐poor nebular gas; (4) isolation of CAIs and chondrules from nebular gas at various ambient temperatures; (5) heterogeneous distribution of 26Al in the solar nebula; and (6) absence of matrix material in the regions of CAI and chondrule formation. 相似文献
125.
Ansgar GRESHAKE Alexander N. KROT Anders MEIBOM Michael K. WEISBERG Michael E. ZOLENSKY Klaus KEIL 《Meteoritics & planetary science》2002,37(2):281-293
Abstract— Fine‐grained, heavily‐hydrated lithic clasts in the metal‐rich (CB) chondrites Queen Alexandra Range (QUE) 94411 and Hammadah al Hamra 237 and CH chondrites, such as Patuxent Range (PAT) 91546 and Allan Hills (ALH) 85085, are mineralogically similar suggesting genetic relationship between these meteorites. These clasts contain no anhydrous silicates and consist of framboidal and platelet magnetite, prismatic sulfides (pentlandite and pyrrhotite), and Fe‐Mn‐Mg‐bearing Ca‐carbonates set in a phyllosilicate‐rich matrix. Two types of phyllosilicates were identified: serpentine, with basal spacing of ?0.73 nm, and saponite, with basal spacings of about 1.1–1.2 nm. Chondrules and FeNi‐metal grains in CB and CH chondrites are believed to have formed at high temperature (>1300 K) by condensation in a solar nebula region that experienced complete vaporization. The absence of aqueous alteration of chondrules and metal grains in CB and CH chondrites indicates that the clasts experienced hydration in an asteroidal setting prior to incorporation into the CH and CB parent bodies. The hydrated clasts were either incorporated during regolith gardening or accreted together with chondrules and FeNi‐metal grains after these high‐temperature components had been transported from their hot formation region to a much colder region of the solar nebula. 相似文献
126.
Analyses of Martian surface soil by Viking and Earth-based telescopes have been interpreted as indicating a regolith dominated by the weathering products of mafic or ultramafic rocks. Basaltic glass has previously been proposed as a more likely precursor than crystalline rock, given the low efficiency of surface weathering under present Martian conditions. On Earth large volumes of basaltic glass formed by quenching of magma by water. A similar interaction, between magma and ground ice, may have been a common occurrence on Mars. On the basis of this scenario palagonite, the alteration product of basaltic sideromelane glass, was studied as a possible analog to Martian soil. Samples from Iceland, Alaska, Antarctica, Hawaii, and the desert of New Mexico and Mexico were examined by optical and scanning electron microscopy, electron microprobe analysis, X-ray diffraction, spectrophotometry, and magnetic and thermogravimetric analysis. We suggest that palagonite is a good analog to the surface soil of Mars in chemical composition, particle size, spectral signature, and magnetic properties. Our model for the formation of fine-grained Martian surface soil begins with eruptions of basaltic magma through ground ice, forming deposits of glassy tuff. Individual glass shards are then altered by low-temperature hydrothermal systems to palagonitic material. Dehydration and aeolian abrasion strip the alteration rinds from the glass, and wind storms distribute the silt-sized palagonitic fragments in a planet-wide deposit. 相似文献
127.
Klaus Keil 《Meteoritics & planetary science》1989,24(4):195-208
Abstract— Enstatite meteorites are highly reduced rocks that consist of major, nearly FeO-free enstatite, variable amounts of metallic Fe, Ni and troilite, and a host of rare minerals formed under highly-reducing conditions. They are comprised of the EH and EL chondrites and the aubrites. Here I discuss some of their properties and the nature and number of their parent bodies. Conclusions: 1. EH and EL chondrites show bulk compositional differences in non-volatile major elements that were established by nebular, not planetary processes. Occurrence of abundant breccias among them but lack of clasts of EL in EH chondrites (and vice versa) suggests that EH and EL chondrites represent two separate parent bodies. 2. Aubrites were not derived from known enstatite chondrites on the same parent bodies. Aubrites represent samples from a third enstatite meteorite parent body. 3. The aubrite parent body may have experienced collisional break-up and gravitational reassembly of the debris into a rubble-pile object. 4. The aubrite source material (parent body) was probably enstatite chondrite-like in composition, but had a higher troilite/metallic Fe, Ni ratio, higher contents of titanium and diopside, and possibly less plagioclase than known enstatite chondrites. 5. Shallowater, the only non-brecciated aubrite, does not appear to have formed on the EH, EL, or aubrite parent bodies by either internal (igneous) or external (impact) melting processes. Instead, Shallowater may be a sample from yet a fourth enstatite meteorite parent body. 6. Shallowater experienced a complex three-stage cooling history, requiring an equally complex mode of origin: collisional break-up of a molten or partly molten body by impact with a solid body, followed by gravitational reassembly. 7. It is unknown why some enstatite meteorite parent bodies melted (the aubrite and Shallowater bodies), and others did not (the EH and EL bodies). If unipolar dynamo induction by a primordial T Tauri sun was the dominant heat source that heated asteroidal-sized bodies in the early Solar System, then the aubrite and Shallowater parent bodies may have melted because they were of intermediate sizes, whereas the EH and EL bodies did not melt because they were either much smaller or much larger. 相似文献
128.
R.V. Fodor Klaus Keil Martin Prinz M.-S. Ma A.V. Murali R.A. Schmitt 《Meteoritics & planetary science》1980,15(1):41-62
The Adams County, Colorado, H5 chondrite contains a lithic fragment, 1 cm in size, that is texturally and mineralogically quite different from the chondritic host. It is composed of: a groundmass of fine-grained euhedral to subhedral olivine (3–15 μm) and interstitial glass enclosing larger olivine and pyroxene grains (0.15-0.5 mm; about 15 vol %); an assemblage of enstatite grains (subfragment within) and an assemblage of olivine plus orthopyroxene (a second subfragment); and about 11 vol % grains of mixed troilite and nickel-iron metal. Analyses yielded these results: (i) olivine grains of the fragment groundmass have a compositional range (Fa12–45) and most grains contain substantial CaO and Cr2O3 (~ 0.20 and 0.30 avg. wt%, respectively); interstitial glass has ~ 55 wt% SiO2; (ii) larger olivine grains of the fragment are similarly high in CaO and Cr2O3 and also have a wide FeO/MgO range; one unusual pyroxene is an Mg-rich pigeonite; (iii) the metal is martensite in composition (11–14 wt% Ni); and (iv) major and trace element analyses by INAA indicate an H-group bulk composition for the entire 1 cm lithic fragment. On the basis of its texture and bulk and mineral compositions, the fragment is interpreted to represent unequilibrated H-group material that was partly melted by impact. The Ca- and Cr-enriched groundmass olivine and interstitial glass resulted from rapid crystallization of the chondritic melt. The Ca- and Cr-enriched larger silicate grains, including the enstatite sub-fragment and the pigeonite grain, are residual, unmelted clasts from the target material (this is supported by the presence of similar material in actual H3 chondrites). Further impact brecciation of the clast-laden melt material, and resultant impact-splashing accounts for the presence of the fragment in the H-group Adams County host and documents the coexistence of unequilibrated and equilibrated H-group material as surface regolith on one parent body. 相似文献
129.
Aurora Pun T. J. McCoy Klaus Keil Ivan E. Wilson 《Meteoritics & planetary science》1990,25(3):233-234
Abstract— Five small, weathered meteorites recovered from Roosevelt County, New Mexico, USA, are called Roosevelt County 066–070. Based on optical microscopy and electron microprobe analysis of mafic minerals, RC 066–070 are classified as L5a chondrites. RC 068 and 069 are tentatively paired. RC 066 and RC 067 are not paired with RC 068 and RC 069. RC 066, 067 and 070 do not appear to be paired with each other or with RC 001–031. 相似文献
130.