Here the process by which our Solar System came into being is outlined. The Sumerian text describes how our Sun and its messenger Mercury were first joined by a planet called Tiamat. It goes on to describe how a pair of planets Venus and Mars coalesced between the Sun and Tiamat followed by two pairs beyond - Jupiter and Saturn and Uranus and Neptune. These later two were unknown to astronomers until 1781 and 1846 respectively. As these celestial bodies pulled and tugged gravitationally between one another, some of them sprouted satellites or moons. Tiamat sprouted eleven satellites. One of them was so big it began to assume the aspects of a planet.
Into that unstable Solar System there appeared another invader (planet) from outer space - a planet not born of the same system. Millennia before modern astronomy knew of pulsars and exploding stars, Sumerian cosmology already knew of these concepts. And so, Enuma elish related, one such cast off planet, reaching the outskirts of our system, began to be drawn into its midst.
As this intruder passed by the outer planets, it caused changes that account for enigmas such as the cause for Uranus' tilt on its side, or the retrograde orbit of Triton, or what pulled Pluto from its place as a satellite to a planet with an odd orbit. The more the invader was pulled into our Solar System's center, the more is was forced into a collision course with Tiamat. This eventually resulted in a "Celestial battle". In the series of collisions, with the invader's satellites repeatedly smashing into Tiamat, the olden planet split in two. One half of it was smashed to bits and became the Asteroid Belt between Mars and Jupiter along with various comets. The other half was thrust into a new orbit to become the planet we know as Earth. In the process this "new" planet retained Tiamat's largest satellite as what we know as the Moon. The invader itself was captured in the Sun's gravity well permanently to become the Solar System's twelfth member (Sun, moon, and 10 planets). The Sumerians called it Niburu - "Planet of the Crossing". The Babylonians renamed it to Marduk in honor of their national god. It was during this epic celestial battle that the "seed of life" brought by Niburu was passed to Earth.
You obviously have never read the Epic of creation.