Late Show with David Letterman

Dave shows the woman/duck and "rabid dingo" clips yet again; Dave discusses the new theory that a meteorite may prove life on Mars, prompting Alan Kalter to go berserk with conspiracy theories; Emmylou Harris, Gillian Welch, Alison Krauss and Dan Timinski and the Soggy Bottom Boys perform a medley of songs from the film O Brother, Where Art Thou?