The season finale of Saturday Night Live offered us a nip of Mojo, the first album from Tom Petty and the Heartbreakers since 2002. Now, a lot can happen to a rock band in eight years: The musicians can lose all their hair, or, even worse, try to recapture youth by updating their image and sound. But not Petty. Arguably the most down-to-earth star in rock, he appeared as casually cool as ever in that recent television appearance. The Heartbreakers — very nearly the same lineup from 1976 — were loose-limbed and playful, tearing through a heavy rumbler called "I Should Have Known It" and a catchy blues tune about Thomas Jefferson's love affair with his mixed-race slave.