History of Solar System formation and evolution hypotheses is captured by the Sun and planets form from it. In this there were 6 original planets, corresponding to 6 point-masses in the filament, with planets A and B, the 2 innermost, colliding, the former at twice the mass of Neptune, and ejecting out of the Solar System, and the latter at 1/3 the mass of Uranus, and splitting into Earth and Venus. Mars and the Moon are former moons of A. Mercury is either a fragment of B or an escaped moon of A. The collision also produced the asteroid belt and the comets. T.J.J. See was an American
Retrograde and prograde motion relative to the Sun except those of Uranus. If there is a collision, material could be ejected in any direction and coalesce into either prograde or retrograde moons, which may be the case for the moons of dwarf planet Haumea, although Haumea's rotation direction is not known. Asteroids usually have a prograde orbit around the Sun. Only a few dozen asteroids in retrograde orbits are known. Some asteroids with retrograde orbits may be burnt-out comets, but some may acquire their retrograde orbit due to gravitational interactions with Jupiter. Due to their small size and their large distance from Earth it