The U.S. Coast Guard in Boston says a search and rescue mission is underway for a missing submarine that was exploring the wreckage of the Titanic. The sub belongs to a company called OceanGate Expeditions, which says it is "mobilizing all options to bring the crew back safely." The Titanic sits more than 12,000 feet below the ocean's surface in the North Atlantic. CBS News foreign correspondent Imtiaz Tyab has the latest.
