Geology of solar terrestrial planets Earth, and Mars) have substantial atmospheres; all have impact craters and tectonic surface features such as rift valleys and volcanoes. The term "inner planet" should not be confused with "inferior planet", which refers to any planet that is closer to the Sun than the observer's planet is, but usually refers to Mercury and Venus. The Solar System is believed to have formed according to the nebular hypothesis, first proposed in 1755 by Immanuel Kant and independently formulated by Pierre-Simon Laplace. This theory holds that 4.6 billion years ago the Solar System formed from the gravitational collapse of a giant molecular
History of Solar System formation and evolution hypotheses of dynamics makes capture most unlikely as it requires special conditions. Swiss astronomer Louis Jacot (in 1951, 1962, 1981), like Weisacker and Ter Haar, continued the Cartesian idea of vortices but proposed a hierarchy of vortices or vortices within vortices, i.e., a lunar system vortex, a Solar System vortex, and a galactic vortex. He put forward the notion that planetary orbits are spirals, not circles or ellipses. Jacot also proposed the expansion of galaxies (stars move away from the hub), and that moons move away from their planets. He also maintained that planets were expelled, one at a time, from