New research suggests the “giant planet migration” was responsible for the massive bombardment of Earth and its moon 4.48 billion years ago. That’s when the four biggest planets – Jupiter, Saturn, Uranus and Neptune moved from their original position near the Sun to its present location in the outer solar system. As the planets traveled during their migration they stirred up debris, including comets, asteroids and planetary fragments, which was sent hurtling into the Earth and moon.