Recent measurements of methyl radicals (CH3) in the upper atmospheres of Saturn and Neptune by the Infrared Space Observatory (ISO) provide new constraints o photochemical models of hydrocarbon chemistry in the outer solar system. The derived column abundances of CH3 on Saturn above 10 mbar and Neptune above the 0.2 mbar t3 -2 ß pressure level are (2.5 6.0) x 1013 cm -2 and (0.7 2.8) x 10 cm , ...

Montréal. Il a pour mission la promotion et la valorisation de la recherche. Érudit offre des services d'édition numérique de documents scientifiques depuis 1998. Note : les règles d'écriture des références bibliographiques peuvent varier selon les différents domaines du savoir. Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduct...

Among the most significant technological developments of the past 20 years are computer-based systems (CBSs), where functional, performance, and reliability requirements demand the tight integration of physical processes and information processing. Because complex component interactions exist in these systems, we must construct the software and its associated hardware such that they can evolve ...

Overview: We have performed 8 numerical simulations of the final stages of accretion of the terrestrial planets, each starting with over 5×more gravitationally interacting bodies than in any previous simulations. Given the large number of small planetesimals in our simulations, we are able to more accurately treat the effects of dynamical friction during the accretion process. Dynamical frictio...

We build on recent new evolutionary models of Jupiter and Saturn and here extend our calculations to investigate the evolution of extrasolar giant planets of mass 0.15 to 3.0 MJ. Our inhomogeneous thermal history models show that the possible phase separation of helium from liquid metallic hydrogen in the deep interiors of these planets can lead to luminosities ∼ 2 times greater than have been ...

Interior models of Jupiter and Saturn are calculated and compared in the framework of the three-layer assumption, which rely on the perception that both planets consist of three globally homogeneous regions: a dense core, a metallic hydrogen envelope, and a molecular hydrogen envelope. Within this framework, constraints on the core mass and abundance of heavy elements (i.e. elements other than ...