Asteroid impact avoidance comprises a number of methods by which near-Earth objects could be diverted, preventing potentially catastrophic impact events. A sufficiently large impact would cause massive tsunamis or (by placing large quantities of dust into the stratosphere, blocking sunlight) 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 Cretaceousâ€“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 (such as Shoemaker-Levy 9) have drawn attention to such a threat, and advances in technology have opened up new options to prevent them.