Approximately 66 million years ago, a mass extinction event
 occurred. 80 percent of all animals were killed, including all non-
 avian dinosaurs. no one knows for sure what caused this event,
 although the leading hypothesis is that a giant meteor impacted the
 earth releasing energy 1 billion times greater than that of an atomic
 bomb. it's hypothesized that the impact created a dust cloud that
 blocked the sunlight for up to one year. how could this massive
 meteor impact have changed the climate so much as to cause this
 global mass extinction?