Origins of satellites

Abstract

Satellites are an inevitable consequence of most plausible planetary accumulation processes. They can arise from gaseous or particulate circumplanetary disks, continuously fed during accretion of the planet or infrequently created by large impacts. They can also arise from capture, aided by gas drag. Fission (in the Darwinian sense) is highly unlikely. The relative importance of these processes depends primarily on: (a) the disposition and dynamics of the gas phase; and (b) the mass spectrum of the planetesimals which feed a growing planet. It is not possible to assess these factors with great confidence at present because of considerable uncertainty concerning the mode(s) of planetary formation. This review seeks, therefore, to assess critically the alternatives within the context of current ideas of the early solar system, guided by both cosmochemical and dynamical constraints, but unencumbered by prejudices concerning planetary growth. Topics discussed include the dynamics of both gaseous and particulate disks, the role of large impacts in creating satellite source material, the role of capture, and the thermodynamics of satellite accretion. Possible explanations for each of the satellite systems are offered.

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