The formation of iron, stone, and mixed planetesimals in the early solar system

Gravity, Particles, and Astrophysics

“…A theory of the origin of planets and satellites that is compatible with the self-similarity revealed by Wesson (1979d) has been given by Wesson and Lermann (1978b) and Wesson (1978f). These three references together represent a self-similar theory of the origin of the Solar System.…”

“…The main conclusion of Wesson and Lermann (1978b) was that the dust from which the planets and satellites formed was charged by plasma processes like the dust in interstellar space, and that under such conditions accretion in the terrestrial zone occurred in two stages: firstly, electrostatic forces caused a separation of the material into metal (i.e., mainly iron) planetesimals of up to 1()2 em size and a cloud composed of dielectric (i.e., mainly silicate) material in the form of small ( =10-5 em) grains; secondly, gravitational forces caused the metal planetesimals to clump together into bodies of the mass of planetary cores, which were later mantled by the silicate fraction. The time scale of the charged-dust accretion process would have depended on the time-evolution of the charge distribution among the original dust grains (Simons, 1976a, b), and on the fetor (e -1)/(e + 1) which regulates the difference in electrostatic accretion force for grains composed of material with different dielectric constants e (Simpson, 1978).…”

“…The time scale of the charged-dust accretion process would have depended on the time-evolution of the charge distribution among the original dust grains (Simons, 1976a, b), and on the fetor (e -1)/(e + 1) which regulates the difference in electrostatic accretion force for grains composed of material with different dielectric constants e (Simpson, 1978). A simple model (Wesson and Lermann, 1978b) leads one to expect that the iron planetesimals formed in a time of the order of 10 7 yr, clumped in a time of 10 5 -10 7 yr, and that the silicate fraction was captured in a time not exceeding 10 8 yr.…”