Movement of the solar system's giant outer planets created a massive meteor storm that rocked the inner solar system 3.9 billion years ago, researchers say. The migrations of the giant planet created what astronomers call the Late Heavy Bombardment, the biggest meteor storm in our solar system's history. Scientists have long suspected the bombardment was triggered as Jupiter and Saturn moved closer in towards the Sun while Neptune and Uranus moved further out from where they formed, with the resulting gravitational effects flinging large numbers of meteors towards the inner solar system where they collided with the inner planet including the Earth and with our moon. It would have also pushed asteroids and comets into the orbits they have today, the researchers said. The study by researchers including lead author Simone Marchi from the Southwest Research Institute, in Boulder, Colo., based on analysis of moon rocks and two classes of meteoroids, was published in the journal Nature Geoscience. Simon O'Toole from the Australian Astronomical Observatory, who was not involved in the study, said it was compelling support for the theory of planetary migration in our solar system. "[The study] provides us with a good foundation stone for a better understanding of the early solar system and how it got to look the way it does now," he told the Australian Broadcasting Corp.