Terry Gross

He's the principal scientific investigator for the twin rovers, Spirit and Opportunity, on Mars. The two landed on the surface of Mars in January, and are helping astronomers to determine whether or not there was life on the planet. Squyres will talk about the many gadgets they created to work on Mars, and what it's like working on "Mars time." Squyres is also a professor of astronomy at Cornell University.

He is the creator, executive producer and head writer of the new HBO series Deadwood, a western drama set in the Black Hills of South Dakota. Milch left a teaching job at Yale University to go to Hollywood and work on the show Hill Street Blues. He also worked on NYPD Blue, for which he won two Emmys. Milch is a former heroin addict and alcoholic.

He calls his latest project a "musical novel." It's a new CD, Greendale, a 10-song cycle with his band Crazy Horse, set in a fictional California seaside town. He also shot a feature film version on Super8, which made the film festival circuit and will be in wider distribution in April.