SP-345 Evolution of the Solar
System
FIGURE 21.12.3.- Simplified diagram of
the effect of transplanetary condensation on the chemical composition
of the planets. The primary emplacement of plasma controlled by the
critical velocity produced the A, B, C, and D clouds. The
A and
B clouds
were enriched in He and H. The C cloud composition was
enriched in C, 0, N, and Ne, while the D cloud contained an
excess of heavy elements. Part of the D cloud condensation
took place outside the solar magnetic field and resulted in particles
and embryos in almost parabolic orbits, passing through the
interplanetary clouds. Due m ablation of these bodies in the
massive A and B clouds, and chemical interaction with the hydrogen in
the latter, substantial amounts of transplanetary D-type material
were deposited in the inner part of the solar system (and in the
corresponding regions of the satellite systems). The distribution
after transplanetary falldown and H-He diffusion indicates the
possible redistribution of heavy elements into the A- and B-cloud regions and the
diffusion of H and He to the C region, where light
gases could be partially accreted by giant planetary embryos. The
observed density distribution among the planets (see fig. 20.7.1a)
reflects the compositions of the respective clouds. The terrestrial
planets, forming in the A
and B clouds, have higher
densities than the giant planets which formed in the C cloud. Pluto and
Triton have higher densities indicative of the composition of the
D cloud
in which they accreted.
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