Results 171 to 180 of about 8,432 (197)

Radioactive Heating of Porous Comet Nuclei

Icarus, 1995
Abstract Radioactive heating is the main energy source of comets residing in the distant parts of the Solar System. It should determine whether liquid water could have existed in comets and whether comets, presumably formed of amorphous ice, could have retained the ice, at least partly, in this pristine form.
D. Prialnik, M. Podolak
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Thermal evolution of comet nuclei

Advances in Space Research, 1999
Abstract The properties of cometary surfaces which influence the thermal behavior of the nucleus such as the albedo, the emissivity and the surface temperature are critically reviewed. It is shown that these properties are less firmly established than generally believed. A brief presentation is given of the state of the art in comet modelling.
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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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Sublimation Mechanisms of Comet Nuclei

Earth, Moon, and Planets, 2000
In this paper the sublimation mechanisms of parent molecules from nuclei will be reviewed from the point of view of theoretical models, and the results of models will be compared with the results of the extensive observation campaign of C/1995 O1 Hale–Bopp. The simple model of a mixture of ices in which each gas sublimates independently from the others
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Probing the internal structure of the nuclei of comets

Planetary and Space Science, 2009
There is no direct evidence about the internal structure of cometary nuclei, which are mostly hidden by their gas and dust comae, and have not yet been orbited by any spacecraft. Their densities are low, typically of about 400 kg m−3 for 9P/Tempel 1 (that was impacted by the Deep Impact probe) and 67P/Churyumov–Gerasimenko (that is the target of the ...
Levasseur-Regourd, Anny Chantal, Hadamcik, Edith, Desvoivres, E., Lasue, Jérémie   +3 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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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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COLLISIONS OF COMET NUCLEI WITH METEOROID SWARIES AND THEIR CONSEQUENCES

THE BULLETIN OF THE TAJIK NATIONAL UNIVERSITY. SERIES OF ECONOMIC AND SOCIAL SCIENCES, 2023
The article considers the collisions of nuclei of selected comets with known meteor showers. It was revealed that as a result of the collision, the nuclei of comets showed significant activity of the nucleus. For some comets, the sublimation velocity increased and as a result, dust jets were observed.
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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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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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