August 10, 2011 7:58 am Killer Comet Headed for Earth? Bob Redell talks to the Bay Area scientists that are tracking a comet that could be headed straight for Earth. US & World Videos 2:42 Forecast: Warm day, Saturday rain 3:05 Downtown First Thursdays offers new hope to struggling SF merchants 1:02 Crews knock down 2-alarm structure fire in SF's Nob Hill 1:11 24-hour online fundraiser underway for Peninsula nonprofits 1:43 Kari's forecast: Warm day, Saturday rain