Results 151 to 160 of about 8,069 (192)

Observational Constraints on Surface Characteristics of Comet Nuclei

Earth, Moon, and Planets, 2000
Direct observations of the nuclear surfaces of comets have been difficult; however a growing number of studies are overcoming observational challenges and yielding new information on cometary surfaces. In this review, we focus on recent determinations of the albedos, reflectances, and thermal inertias of comet nuclei. There is not much diversity in the
Humberto Campins, Yanga Fernández
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Computational study of radiation chemical processing in comet nuclei

Origins of life and evolution of the biosphere, 1991
Cometary nuclei have been exposed to high levels of ionizing radiation since their formation. We present here some results of a computer model calculation of the effect of ionizing radiation on cometary material. The external (cosmic rays) and internal (embedded radionuclides) contributions in the processing of cometary nuclei are considered.
R, Navarro-González, C, Ponnamperuma, R K, Khanna   +2 more
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Origin of Comet Nuclei and Dynamics

Space Science Reviews, 2007
We present a review of the main physical features of comet nuclei, their birthplaces and the dynamical processes that allow some of them to reach the Sun’s neighborhood and become potentially detectable. Comets are thought to be the most primitive bodies of the solar system although some processing—for instance, melting water ice in their interiors and
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Meteoroid impact into short-period comet nuclei

Nature, 1981
The effects of extended meteoroid bombardment on short-period comet nuclei are examined and their possible implications for asteroid and meteorite studies are discussed. It is suggested that after devolatilization of the nucleus, the accumulated material might combine with primary cometary solids to produce environments conducive to the formation of ...
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Note on the structure of comet nuclei

Planetary and Space Science, 1999
Abstract The recent developments in cometary studies suggest rather low mean densities and weak structures for the nuclei. They appear to be accumulations of fairly discrete units loosely bound together, as deduced from the observations of Comet Shoemaker–Levy 9 during its encounter with Jupiter. The compressive strengths deduced from comet splitting
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Numerically improved thermochemical evolution models of comet nuclei

Planetary and Space Science, 1999
Abstract An improved unidimensional model of the heat transport and gas diffusion within a porous cometary nucleus is presented, in which the time-dependent gas diffusion equation is coupled with the heat diffusion equation to describe the energy transport due to sublimation and recondensation of volatiles, but is solved independently using a ...
R. Orosei, F. Capaccioni, M.T. Capria, A. Coradini, M.C.De Sanctis, C. Federico, M. Salomone, J.-P. Huot   +7 more
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Spectral Diversity among the Nuclei of Comets

Icarus, 1993
Abstract The spectral characteristics of cometary nuclei are poorly known. To help rectify this situation, we have been obtaining spectra of cometary nuclei when they are favorably located, i.e., sufficiently far from the Sun that little cometary activity remains.
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On the visibility of nuclei of dusty comets

Icarus, 1981
Abstract The problem of visibility of a cometary nucleus discussed in general terms for single scattering by dust grains. The ratio of radiatio scattered in the dust column above the surface and that reflected from the nucleus determines the visibility of features on the nuclear surface.
R. Hellmich, H.U. Keller
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MASS FLUX OF ASTEROIDAL ORIGIN METEOROIDS ON PERIODIC COMET NUCLEI

Earth, Moon, and Planets, 2004
We examine the potential contamination of cometary nuclei through impacts from asteroidal origin meteoroids. The paper uses a simple model and has the goal of determining whether asteroidal contamination is potentially significant. We assume a meteoroid power law mass distribution with index values in the range from s=1.83 to s=2.09.
R. L. Hawkes, R. A. Eaton
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On the origin of internal layers in comet nuclei

Icarus, 2018
Abstract We present an analysis of the layered structure on 67P/Churyumov–Gerasimenko’ s Hathor cliff and propose a mechanism (self-sustaining, dual-mode propagation of amorphous to crystalline ice phase-change fronts into the nucleus interior) for its origin. If this is a viable mechanism, the strata must be geologically young (∼106 y).
Michael J.S. Belton, Xiao-Duan Zou, Jian-Yang Li, Erik Asphaug   +3 more
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