What Causes Mass Extinctions?

"In 2005, University of California-Berkeley researchers Robert Rohde and Richard Muller revealed that massive die-offs occur on Earth with startling regularity — about once every 62 million years. But scientists have struggled since to pinpoint a cause for the consistently recurring extinctions uncovered in the fossil record. Now, a team of University of Kansas professors has found the likely reason by looking to the heavens...

University of Kansas