Results from the Greenland Search for Meteorites expedition     

Henning Haack  John Schutt  Anders Meibom  Ralph Harvey 《Meteoritics & planetary science》2007,42(10):1727-1733

Abstract— Following discoveries of blue ice areas in Greenland resembling meteorite‐bearing blue ice fields in Antarctica, a surface search of several of the most promising sites was carried out in August 2003. The ice fields are located in Kong Christian X Land, in northeastern Greenland around 74°N at elevations between 2100 and 2400 m. No meteorites were found in any of the localities that were searched. Evidence of occasional significant melting (filled crevasses and melt sheets) suggest that summer temperatures are sometimes high enough that dark rocks, like meteorites, can melt through the upper layers of ice. Small terrestrial rocks and cryogenite were found down to 50 cm below the ice surface. Meter‐sized terrestrial rocks were found on top of the ice downstream from nunataks. These rocks shade the ice below, and since they were apparently too massive to warm up during warm days, they remained at the surface as the surrounding ice ablated away. Our findings strongly suggest that Greenland is currently unlikely to harbor significant meteorite concentrations on blue ice fields.  相似文献   

Dead zones and extrasolar planetary properties   总被引：1，自引：0，他引：1  

Soko Matsumura  Ralph E. Pudritz 《Monthly notices of the Royal Astronomical Society》2006,365(2):572-584

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Estimating the modal mineralogy of eucrite and diogenite meteorites using visible–near infrared reflectance spectroscopy          下载免费PDF全文

Shuai Li  Ralph E. Milliken 《Meteoritics & planetary science》2015,50(11):1821-1850

Reliable quantitative mapping of minerals exposed on Vesta's surface is crucial for understanding the crustal composition, petrologic evolution, and surface modification of the howardite, eucrite, and diogenite (HED) parent body. However, mineral abundance estimates derived from visible–near infrared (VIS–NIR) reflectance spectra are complicated by multiple scattering, particle size, and nonlinear mixing effects. Radiative transfer models can be employed to accommodate these issues, and here we assess the utility of such models to accurately and efficiently determine modal mineralogy for a suite of eucrite and olivine‐bearing (harzburgitic) diogenite meteorites. Hapke and Shkuratov radiative transfer models were implemented to simultaneously estimate mineral abundances and particle size from VIS–NIR reflectance spectra of these samples. The models were tested and compared for laboratory‐made binary (pyroxene–plagioclase) and ternary mixtures (pyroxene–olivine–plagioclase) as well as eucrite and diogenite meteorite samples. Results for both models show that the derived mineral abundances are commonly within 5–10% of modal values and the estimated particle sizes are within the expected ranges. Results for the Hapke model suggest a lower detection limit for olivine in HEDs when compared with the Shkuratov model (5% versus 15%). Our current implementation yields lower uncertainties in mineral abundance (commonly <5%) for the Hapke model, though both models have an advantage over typically used parameters such as band depth, position, and shape in that they provide quantitative information on mineral abundance and particle size. These results indicate that both the Hapke and Shkuratov models may be applied to Dawn VIR data in a computationally efficient manner to quantify the spatial distribution of pyroxene, plagioclase, and olivine on the surface of Vesta.  相似文献   

Controlling the collimation and rotation of hydromagnetic disc winds     

Ralph E. Pudritz  Conrad S. Rogers  Rachid Ouyed 《Monthly notices of the Royal Astronomical Society》2006,365(4):1131-1148

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Thermal interactions of the Huygens probe with the Titan environment: Constraint on near-surface wind     

Ralph D. Lorenz 《Icarus》2006,182(2):559-566

The Huygens probe lost heat to its cold environment during its descent through Titan's atmosphere and after landing. Here I report measurements of the probe's thermal behavior and comparison with ground tests (1) to provide a context for other scientific investigations, such as the release of volatiles from the landing site, and (2) to place constraints on Titan environmental parameters directly, such as the thermal conductivity of the surface material and the strength of winds at the surface. Near-surface winds are constrained to be less than 0.2 m s⁻¹, and probably much less.  相似文献   

Supersonic turbulence, filamentary accretion and the rapid assembly of massive stars and discs     

Robi Banerjee  Ralph E. Pudritz  Dave W. Anderson 《Monthly notices of the Royal Astronomical Society》2006,373(3):1091-1106

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Compressional to shear wave conversion in oceanic crust     

Robert S. White  Ralph A. Stephen 《Geophysical Journal International》1980,63(2):547-565

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Copper concentrations in surface waters off the south-eastern atlantic coast,U.S.A.     

Herbert L. Windom  Ralph G. Smith 《Marine Chemistry》1979,7(2):157-163

Copper concentrations in surface waters off the southeastern United States coast range from 0.02 to 0.33 μg/kg (0.3–5.2 nmol/kg). Mean concentrations are lowest in Onslow Bay (0.07 μg/kg) and highest over the Blake Plateau (0.20 μg/kg). An explanation, compatible with the hydrography and hydrodynamics of the area, is proposed for the observed regional variations.  相似文献   

A note on the asymmetric distribution of the impacts which created the lunar mare basins     

Nils Aall Barricelli  Ralph Metcalfe 《Earth, Moon, and Planets》1975,12(2):193-199

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Crystal Structures of Clay Minerals and Their X-Ray Identification | G.W. Brindley and G. Brown (Editors), 1980. Mineralogical Society,London, 495 pp., £stg. 28.00, US$ 70.00 (incl. of postage)     

Ralph E. Grim 《Earth》1982,18(1):84-85

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