Guest: David Morrison.

The age of the dinosaurs ended some 65 million years ago when a large asteroid hit the Earth. What are the chances that sometime in the future, Earth would again be a target? Today on Focus, our guest will be David Morrison, Senior Scientist at the NASA Astrobiology Institute. He says a large impact is not expected in our lifetime... but the possibility is still out there. Today he'll talk about the effort to chart large objects in space that have the potential to strike the Earth.