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Astronomers have long believed that the powerful gravity of Jupiter helps deflect incoming comets away from the Earth. Until recently, however, there was little hard evidence to back up this comforting belief. But using computer simulations, Dr Jonti Horner of the University of New South Wales, Australia, and Professor Barrie Jones of the Open University, have now tested the idea and found that, contrary to the textbook claims, Jupiter actually increases the risk of a cosmic impact on Earth. The simulations reveal that while the giant planet does a good job of deflecting comets that come from far beyond our Solar System, it actually drives more nearby comets and asteroids onto a collision course with the Earth, boosting the overall rate of impact.
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