Dinosaurs ruled the earth for many millions of years, but only after a mass extinction took out most of their rivals. Just how that happened remains a mystery — sounds like a case for paleoclimatologist Celina Suarez! This encore episode, Suarez walks us through her scientific detective work, with a little help from her trusty sidekick, Scientist in Residence Regina G. Barber. Have a science fact you can't stop thinking about? Email us at shortwave@npr.org! We'd love to hear from you.