Comets and planets - Their interrelated origin

This report gives a concise summary of the conclusions of cosmogonic studies linking the origin of comets with the origin of the Jovian planets at the dawn of the solar system. Cometary nuclei are shown to be original planetesimals ejected from and returning to the solar system. Formation processes for comets are described in detail, emphasizing the preplanetary rings of the Jovian planets, condensation and accretion from diffuse matter, and the origin of Oort's sphere. Physical and mechanical properties of comets are discussed, including the composition of cometary gases, the size and composition of cometary nuclei, the placement of comets in Oort's sphere, and the density of nuclei in that region. Unresolved difficulties in models of planet and comet formation are considered.