Constraints on the formation environment of two chondrule‐like igneous particles from comet 81P/Wild 2          下载免费PDF全文

Zack Gainsforth  Anna L. Butterworth  Julien Stodolna  Andrew J. Westphal  Gary R. Huss  Kazu Nagashima  Ryan Ogliore  Donald E. Brownlee  David Joswiak  Tolek Tyliszczak  Alexandre S. Simionovici 《Meteoritics & planetary science》2015,50(5):976-1004

Using chemical and petrologic evidence and modeling, we deduce that two chondrule‐like particles named Iris and Callie, from Stardust cometary track C2052,12,74, formed in an environment very similar to that seen for type II chondrules in meteorites. Iris was heated near liquidus, equilibrated, and cooled at ≤100 °C h^‐1 and within ≈2 log units of the IW buffer with a high partial pressure of Na such as would be present with dust enrichments of ≈10³. There was no detectable metamorphic, nebular, or aqueous alteration. In previous work, Ogliore et al. (2012) reported that Iris formed late, >3 Myr after CAIs, assuming ²⁶Al was homogenously distributed, and was rich in heavy oxygen. Iris may be similar to assemblages found only in interplanetary dust particles and Stardust cometary samples called Kool particles. Callie is chemically and isotopically very similar, but not identical to Iris.  相似文献   

The SORCE Mission     

Gary Rottman 《Solar physics》2005,230(1-2):7-25

The Solar Radiation and Climate Experiment (SORCE) satellite carries four scientific instruments that measure the solar radiation at the top of the Earth's atmosphere. The mission is an important flight component of NASA's Earth Observing System (EOS), which in turn is the major observational and scientific element of the U.S. Global Change Research Program. The scientific objectives of SORCE are to make daily measurements of the total solar irradiance and of spectral solar irradiance from 120 to 2000 nm with additional measurements of the energetic X-rays. Solar radiation provides the dominant energy source for the Earth system and detailed understanding of its variation is essential for atmospheric and climate studies. SORCE was launched on January 25, 2003 and has an expected lifetime through the next solar minimum in about 2007. The spacecraft and all instruments have operated flawlessly during the first 2 years, and this paper provides an overview of the mission and discusses the contributions that SORCE is making to improve understanding of the Sun's influence on the Earth environment.  相似文献   

The Thirty Meter Telescope (TMT): An International Observatory     

Gary H. Sanders 《Journal of Astrophysics and Astronomy》2013,34(2):81-86

The Thirty Meter Telescope (TMT) will be the first truly global ground-based optical/infrared observatory. It will initiate the era of extremely large (30-meter class) telescopes with diffraction limited performance from its vantage point in the northern hemisphere on Mauna Kea, Hawaii, USA. The astronomy communities of India, Canada, China, Japan and the USA are shaping its science goals, suite of instrumentation and the system design of the TMT observatory. With large and open Nasmyth-focus platforms for generations of science instruments, TMT will have the versatility and flexibility for its envisioned 50 years of forefront astronomy. The TMT design employs the filled-aperture finely-segmented primary mirror technology pioneered with the W.M. Keck 10-meter telescopes. With TMT’s 492 segments optically phased, and by employing laser guide star assisted multi-conjugate adaptive optics, TMT will achieve the full diffraction limited performance of its 30-meter aperture, enabling unprecedented wide field imaging and multi-object spectroscopy. The TMT project is a global effort of its partners with all partners contributing to the design, technology development, construction and scientific use of the observatory. TMT will extend astronomy with extremely large telescopes to all of its global communities.  相似文献   

Editorial introduction     

Jamie Woodward  Gary Huckleberry 《Geoarchaeology》2011,26(1):1-4

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The abundance profile of CO in Neptune's atmosphere     

Brigette E. Hesman  Gary R. Davis  Glenn S. Orton 《Icarus》2007,186(2):342-353

The J = 3-2 rotational line of CO in Neptune has been measured using the heterodyne receiver B3 at the JCMT. The spectral resolution was 1.25 MHz and 25 tunings were used to cover a frequency range of almost 20 GHz. The measured line shape, encompassing both the broad absorption feature arising in the lower atmosphere and a narrow emission core from the upper stratosphere, indicates that the CO mole ratio is not uniform with altitude, with best-fit values of in the upper stratosphere and 0.6±0.4×¹⁰⁻⁶ in the lower stratosphere and troposphere. The higher stratospheric abundance indicates that a dual, internal and external, origin of CO is most likely.  相似文献   

Compositional evolution of the protoplanetary disk: Oxygen isotopes of type-II chondrules from CR2 chondrites     

Harold C. Connolly Jr.  Gary R. Huss 《Geochimica et cosmochimica acta》2010,74(8):2473-325

Chondrules are the dominant component of chondritic meteorites and attest to high-temperature transient heating events within the protoplanetary disk. They provide valuable constraint on the disk environments in which they formed and potentially the evolution of primitive planetary materials in the disk. The oxygen isotopic composition of CR2 chondrite type-II chondrules was investigated. Our data show significant variation in the isotopic compositions of the chondrules with no petrographic or geochemical means to identify what chondrule will plot where on a three-isotope diagram. Although we cannot rule out that these chondrules may have come from another chondrite-forming region, we argue in context of type-I chondrules from CR2 chondrites that CR2 type-II chondrules record changes in solid and gas composition during formation due to the vaporization of icy bodies in localized regions of the inner disk.  相似文献   

An integrated approach to shallow aquifer characterization: combining geophysics and geostatistics   总被引：1，自引：0，他引：1  

Nicholas B. Engdahl  Gary S. Weissmann  Nedra D. Bonal 《Computational Geosciences》2010,14(2):217-229

We present a method of aquifer characterization that is able to utilize multiple sources of conditioning data to build a more realistic model of heterogeneity. This modeling approach (InMod) uses geophysical data to delineate bounding surfaces within sedimentary deposits. The depositional volumes between bounding surfaces are identified automatically from the geophysical data by a region growing algorithm. Simple geometric rules are used to constrain the growth of the regions in 3-D. The nodes within the depositional volume are assigned to categorical lithologies using geostatistical realizations and a dynamic lookup routine that can be conditioned to field data. The realizations created with this method preserve geologically expected features and produces sharp juxtapositions of high and low hydraulic conductivity lithologies along bounding surfaces. The realizations created with InMod also have higher variance than models created only with geostatistics and honor the volumetric distribution of sediments measured from field data.  相似文献   

Editorial introduction: 25 years of Geoarchaeology     

Jamie Woodward  Gary Huckleberry 《Geoarchaeology》2010,25(1):1-5

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Near ultraviolet–infrared colours of red-sequence galaxies in local clusters     

Timothy D. Rawle  Russell J. Smith  John R. Lucey  Michael J. Hudson  Gary A. Wegner 《Monthly notices of the Royal Astronomical Society》2008,385(4):2097-2106

We present GALEX near-ultraviolet ( NUV ) and Two-Micron All-Sky Survey J -band photometry for red-sequence galaxies in local clusters. We define quiescent samples according to a strict emission threshold, removing galaxies with very recent star formation. We analyse the NUV – J colour–magnitude relation (CMR) and find that the intrinsic scatter is an order of magnitude larger than for the analogous optical CMR (∼0.35 rather than 0.05 mag), in agreement with previous studies. Comparing the NUV – J colours with spectroscopically derived stellar population parameters, we find a strong  (>5.5σ)  correlation with metallicity, only a marginal trend with age, and no correlation with the α/Fe ratio. We explore the origin of the large scatter and conclude that neither aperture effects nor the UV upturn phenomenon contribute significantly. We show that the scatter could be attributed to simple 'frosting' by either a young or a low-metallicity subpopulation.  相似文献   

IUGS Commission on Geoscience Edoucation, Training and Technology Transfer （COGE） http ：//www.geoed.com.au/IUGSeducation/indexcomm.html     

Gary Lewis Wesley Hill 《《幕》》2006,29(4):310-311

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