Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Asteroid mitigation strategies are "planetary defense" methods by which near-Earth objects could be diverted, preventing potentially catastrophic impact events. A sufficiently large impact would cause massive tsunamis or an impact winter, or both. A collision between the Earth and a ~10 km object 65 million years ago is believed to have produced the Chicxulub Crater and the Cretaceous–Paleogene extinction event. While the chances of such an event are no greater now than at any other time in history, there is a very high chance that one will happen eventually. Recent astronomical events have drawn attention to such a threat, and advances in technology have opened up new options to prevent them.