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101.
All of the large impact features of the middle-sized icy satellites of Saturn and Uranus that were clearly observed by the Voyager spacecraft are described. New image mosaics and stereo-and-photoclinometrically-derived digital elevation models are presented. Landforms related to large impact features, such as secondary craters and possible antipodal effects are examined and evaluated. Of the large impacts, Odysseus on Tethys appears to have had the most profound effect on its “target” satellite of any of the impact features we examined. Our modeling suggests that the Odysseus impact may have caused the prompt formation of Ithaca Chasma, a belt of tectonic troughs that roughly follow a great circle normal to the center of Odysseus, although other hypotheses remain viable. We identify probable secondary cratering from Tirawa on Rhea. We attribute a number of converging coalescing crater chains on Rhea to a putative, possibly relatively fresh, ∼350 km-diameter impact feature. We examine the antipodes of Odysseus, the putative ∼350 km-diameter Rhean impact feature, and Tirawa, and conclude that evidence from Voyager data for damage from seismic focusing is equivocal, although our modeling results indicate that such damage may have occurred. We propose a number of observations and tests for Cassini that offer the opportunity to differentiate among the various explanations and speculations reviewed and evaluated in this study. 相似文献
102.
Interception loss, I, was determined by continuous concurrent measurements of the canopy precipitation balances of a mature seed orchard tree of Pinus radiata, and a dominant tree of Eucalyptus viminalis at a mountainous high rainfall site (900 m a.s.l.) in Tallaganda State Forest of the Upper Shoalhaven Catchment. Approximate canopy storage capacity (Sc) of the pine was 54 l, and that of the eucalypt was 11·3 l. Gross pine I was 26·5 per cent and eucalypt I was 8·3 per cent of total incident rainfall over a period of 18 months, from June 1975 to December 1976. The exponential model that provided the best fit to overall data relating I to gross rainfall (Pg) was of good precision for the pine (r2 = 0·73) but rather poor precision for the eucalypt (r2 = 0·27). A consistent pattern in interception data of the two canopy types suggested that variation in I was related to change in pervasive conditions influencing rates of evaporation from wet canopies during rainfall. Multiple regression analyses confirmed that factors such as rainfall intensity and windspeed explained some of the variation in eucalypt I but little in pine I. Negative eucalypt I and corresponding low values of pine I over a wide range of Pg (up to 20 mm) suggest that capture of wind-borne precipitation (cloud, mist, or fog) had also complicated the canopy precipitation balances. 相似文献
103.
104.
105.
David E. Lange Kent Frost Paul P. Sipiera Carleton B. Moore 《Meteoritics & planetary science》1974,9(4):271-280
The Canyonlands meteorite weighing 1,520 grams was found near the confluence of the Green and Colorado Rivers, Utah, near lat 38°11′N.; long 109°53′W. It is a shocked, brecciated H6 chondrite containing large black veins which do not differ in composition from the main chondritic mass. A black fusion crust remains on part of the meteorite. 相似文献
106.
G.A. Jungclaus G.U. Yuen C.B. Moore J.G. Lawless 《Meteoritics & planetary science》1976,11(3):231-237
Alcohols, aldehydes and ketones identified in the Murchison C2 chondrite include: methanol, ethanol, 2-propanol, butyl alcohols, formaldehyde, acetaldehyde, propionaldehyde, acetone, 2-butanone, 3-pentanone and 2-pentanone. 相似文献
107.
Ronald L. Moore 《Solar physics》1982,113(1-2):121-124
108.
R. H. Nichols J. A. Nuth C. M. Hohenberg C. T. Olinger M. H. Moore 《Meteoritics & planetary science》1992,27(5):555-559
Abstract— We have measured Ne, Ar, Kr and Xe in Si2O3 “smokes” that were condensed on Al substrates, vapor-deposited with various mixtures of CH4, NH3, H2O and noble gases at 10 K and subsequently irradiated with 1 MeV protons to simulate conditions during grain mantle formation in interstellar clouds. The noble gases were analyzed using conventional stepwise heating and static noble gas mass spectrometry. Neither Ne nor Ar is retained by the samples upon warming to room temperature, but Xe is very efficiently trapped and retained. Kr is somewhat less effectively retained, typically depleted by factors of about 10–20 relative to Xe. Isotopic fractionation favoring the heavy isotopes of Xe and Kr of about 5–10‰/amu is observed. Correlations between the specific chemistry of the vapor deposition and heavy noble gas retention are most likely the result of competition by the various species for irradiation-produced trapping sites. The concentration of Xe retained by some of these smokes exceeds that observed in phase Q of meteorites and, like phase Q, they do not seem to be carriers of the light noble gases. Such artificially prepared material may, therefore, offer clues concerning the incorporation of the heavy planetary noble gases in meteoritic material and the nature of phase Q. 相似文献
109.
Christopher Packham Keith L. Thompson Almudena Zurita Johan H. Knapen Ian Smail Robert Greimel Daniel F. M. Folha Chris Benn rew Humphrey Rene Rutten David Ciardi Matthieu Bec Richard Bingham Simon Craig Kevin Dee Derek Ives Paul Jolley Peter Moore Marti Pi i Puig Simon Rees Gordon Talbot Sue Worswick 《Monthly notices of the Royal Astronomical Society》2003,345(2):395-405
110.
This study examined suspended sediment concentration (SSC) during the ablation seasons of 2000 and 2001 in Place Creek, Canada, a steep, glacier‐fed mountain stream. Comparison of stream flow in Place Creek with that in an adjacent, almost unglacierized catchment provided a rational basis for separating the ablation seasons into nival, nival–glacial, glacial and autumn recession subseasons. Distinct groupings of points in plots of electrical conductivity against discharge supported the validity of the subseasonal divisions in terms of varying hydrological conditions. Relationships between SSC and discharge (Q) varied between the two study seasons, and between subseasons. Hysteresis in the SSC–Q relationship was evident at both event and weekly time‐scales. Some suspended sediment released from pro‐glacial Place Lake (the source of Place Creek) appeared to be lost to channel storage at low flows, especially early in the ablation season, with re‐entrainment at higher flows. Multiple regression models were derived for the subseasons using predictor variables including Q, Q2, the change in Q over the previous 3 h, cumulative discharge over the ablation season, total precipitation over the previous 24 h and SSC measured at 1500 hours as an index value for each day. The models produced adjusted R2 values ranging from 0·71 to 0·91, and provided tentative insights into the differences in SSC dynamics amongst subseasons. Introduction of the index value of SSC significantly improved the model fit during the nival–glacial and glacial subseasons for both years, as it adjusts the model to the current condition of sediment supply. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献