Fe and O isotope composition of meteorite fusion crusts: Possible natural analogues to chondrule formation?          下载免费PDF全文

Dominik C. Hezel  Graeme M. Poole  Jack Hoyes  Barry J. Coles  Catherine Unsworth  Nina Albrecht  Caroline Smith  Mark Rehkämper  Andreas Pack  Matthew Genge  Sara S. Russell 《Meteoritics & planetary science》2015,50(2):229-242

Meteorite fusion crust formation is a brief event in a high‐temperature (2000–12,000 K) and high‐pressure (2–5 MPa) regime. We studied fusion crusts and bulk samples of 10 ordinary chondrite falls and 10 ordinary chondrite finds. The fusion crusts show a typical layering and most contain vesicles. All fusion crusts are enriched in heavy Fe isotopes, with δ⁵⁶Fe values up to +0.35‰ relative to the solar system mean. On average, the δ⁵⁶Fe of fusion crusts from finds is +0.23‰, which is 0.08‰ higher than the average from falls (+0.15‰). Higher δ⁵⁶Fe in fusion crusts of finds correlate with bulk chondrite enrichments in mobile elements such as Ba and Sr. The δ⁵⁶Fe signature of meteorite fusion crusts was produced by two processes (1) evaporation during atmospheric entry and (2) terrestrial weathering. Fusion crusts have either the same or higher δ¹⁸O (0.9–1.5‰) than their host chondrites, and the same is true for Δ¹⁷O. The differences in bulk chondrite and fusion crust oxygen isotope composition are explained by exchange of oxygen between the molten surface of the meteorites with the atmosphere and weathering. Meteorite fusion crust formation is qualitatively similar to conditions of chondrule formation. Therefore, fusion crusts may, at least to some extent, serve as a natural analogue to chondrule formation processes. Meteorite fusion crust and chondrules exhibit a similar extent of Fe isotope fractionation, supporting the idea that the Fe isotope signature of chondrules was established in a high‐pressure environment that prevented large isotope fractionations. The exchange of O between a chondrule melt and an ¹⁶O‐poor nebula as the cause for the observed nonmass dependent O isotope compositions in chondrules is supported by the same process, although to a much lower extent, in meteorite fusion crusts.  相似文献   

Objective verifications and false alarm analyses of western North Pacific tropical cyclone event forecasts by the ECMWF 32-day ensemble   总被引：1，自引：0，他引：1  

Hsiao-Chung Tsai  Russell L. Elsberry  Mary S. Jordan  Frédéric Vitart 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(4):409-420

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Regional adjustment of emission strengths via four dimensional data assimilation     

Sun-Kyoung Park  Armistead G. Russell 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(3):361-374

The Four-Dimensional Data Assimilation was performed to evaluate source emission strengths over the United States. The USEPA Models-3 system (CMAQ/MM5/SMOKE) and ridge regression are used as the forward and inverse models, respectively. The continental US is divided into six regions, and data assimilation is performed for each region in July 2001 and January 2002. In addition, two separate scaling factors are calculated for weekdays and weekends. Results show that base emissions for CO and SO₂ sources are relatively accurate. Base emissions for PEC source are overestimated 100%, but those for POA source are underestimated up to 70% when compared with the adjusted emissions. Emissions for NH₃, NO _x , and PMFINE sources are relatively accurate in July 2001, but those in January 2002 are around 100% higher than the adjusted emissions. Base VOC emissions in July 2001 are similar to the adjusted emissions but those in January 2002 are underestimated up to 70% when compared with the adjusted emissions. Though the emission adjustment itself improves the overall air quality model performance, a better improvement is expected with the modification of speciation profiles and temporal allocations in the Models-3 system, as well.  相似文献   

The effect of sideband ratio on line intensity for Herschel/HIFI     

Ronan Higgins  David Teyssier  Colin Borys  Jonathan Braine  Claudia Comito  Bertrand Delforge  Frank Helmich  Michael Olberg  Volker Ossenkopf  John Pearson  Russell Shipman 《Experimental Astronomy》2014,37(2):433-452

The Heterodyne Instrument for the Far Infrared (HIFI) on board the Herschel Space Observatory is composed of a set of fourteen double sideband mixers. We discuss the general problem of the sideband ratio (SBR) determination and the impact of an imbalanced sideband ratio on the line calibration in double sideband heterodyne receivers. The HIFI SBR is determined from a combination of data taken during pre-launch gas cell tests and in-flight. The results and some of the calibration artefacts discovered in the gas cell test data are presented here along with some examples of how these effects appear in science data taken in orbit.  相似文献   

Fabric analysis of Allende matrix using EBSD     

Lauren E. Watt  Phil A. Bland  Dave J. Prior  Sara S. Russell 《Meteoritics & planetary science》2006,41(7):989-1001

Abstract— Fabric analysis of the interstitial matrix material in primitive meteorites offers a novel window on asteroid formation and evolution. Electron backscatter diffraction (EBSD) has allowed fabrics in these fine‐grained materials to be visualized in detail for the first time. Our data reveal that Allende, a CV3 chondrite, possesses a uniform, planar, short‐axis alignment fabric that is pervasive on a broad scale and is probably the result of deformational shortening related to impact or gravitational compaction. Interference between this matrix fabric and the larger, more rigid components, such as dark inclusions (DIs) and calcium‐aluminium‐rich inclusions (CAIs), has lead to the development of locally oriented and intensified matrix fabrics. In addition, DIs possess fabrics that are conformable with the broader matrix fabric. These results suggest that DIs were in situ prior to the deformational shortening event responsible for these fabrics, thus providing an argument against dark inclusions being fragments from another lithified part of the asteroid (Kojima and Tomeoka 1996; Fruland et al. 1978). Moreover, both DIs and Allende matrix are highly porous (?25%) (Corrigan et al. 1997). Mobilizing a highly porous DI during impact‐induced brecciation without imposing a fabric and incorporating it into a highly porous matrix without significantly compacting these materials is improbable. We favor a model that involves Allende DIs, CAIs, and matrix accreting together and experiencing the same deformation events.  相似文献   

Galaxy groups in the 2dF Galaxy Redshift Survey: the number density of groups     

V. R. Eke  Carlton M. Baugh  Shaun Cole  Carlos S. Frenk  Julio F. Navarro † 《Monthly notices of the Royal Astronomical Society》2006,370(3):1147-1158

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A coleopteran fauna from the middle Würm (Weichselian) of Switzerland and its bearing on palaeobiogeography,palaeoeclimate and palaeoecology     

Monika Jost‐Stauffer  G. Russell Coope  Christian Schlüchter 《第四纪科学杂志》2001,16(3):257-268

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Substructure analysis of selected low-richness 2dFGRS clusters of galaxies     

William S. Burgett  Michael M. Vick  David S. Davis  Matthew Colless  Roberto De Propris  Ivan Baldry  Carlton Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Chris Collins  Warrick Couch  Nicholas Cross  Gavin Dalton  Simon Driver  George Efstathiou  Richard Ellis  Carlos S. Frenk  Karl Glazebrook  Edward Hawkins  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Will Percival  Bruce Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,352(2):605-654

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The jet-powered optical nebula of Cygnus X–1     

D. M. Russell  R. P. Fender  E. Gallo †  C. R. Kaiser 《Monthly notices of the Royal Astronomical Society》2007,376(3):1341-1349

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A deep AAOmega survey of low-luminosity galaxies in the Shapley supercluster: stellar population trends     

Russell J. Smith  John R. Lucey  Michael J. Hudson 《Monthly notices of the Royal Astronomical Society》2007,381(3):1035-1052

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