“Mars once was wet and fertile. It's now bone dry. Something bad happened on Mars. I want to know what happened on Mars so that we may prevent it from happening here on Earth.”

American astrophysicist and science communicator of the late 20th and early 21st centuries, he bridges complex cosmic concepts for broad audiences. His work on the Cosmos television series and public lectures makes astronomy accessible, while his writings and media appearances champion evidence-based reasoning and critical thinking.