High Quality Content by WIKIPEDIA articles! 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 (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 Cretaceous–Tertiary extinction event.