“Arctic Dinosaurs” (8 p.m., PBS): Close to 65 million years ago, or so the story goes,

“Arctic Dinosaurs” (8 p.m., PBS): Close to 65 million years ago, or so the story goes, really cool dinosaurs marched around the coldest parts of the planet.

Presidential Debate (9 p.m., all major networks): It’s Round 2 for Barack Obama and John McCain as the presidential candidates square off in another debate. Tom Brokaw moderates the event, which will be carried by all the major networks and news-related cable channels.

“The Real Housewives of Atlanta” (9 p.m., Bravo): Showing that not all self-involved women live on the West Coast or New York City, the reality series moves south for the season.