This notion of a sequential origin, from outermost planet to innermost, influenced subsequent debate about the nature of life on our neighboring worlds. In particular, it implied that Mars was more evolved than the Earth, so that if intelligent Martians existed they were likely be more advanced than ourselves (see life on Mars), whereas Venus, being a younger world, might support only primordial forms of life. The nebular hypothesis also implied, in sharp contrast with its great rival, the catastrophic hypothesis, that planets, and possibly life, around other stars might be common.
In updated form, the nebular hypothesis has become the consensus model of planetary origin (see planetary systems, formation).
Related category PLANETS AND MOONS
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