The search for the missing submersible that was exploring the wreckage of the Titanic has entered a critical stage. The point at which the U.S. Coast Guard had estimated the vessel’s oxygen could run out — 96-hours after its departure — has passed, but Rear Adm. John Mauger said Thursday that the search-and-rescue mission would not stop. A remote vehicle exploring the search area Thursday afternoon discovered a debris field, a finding authorities are evaluating, the Coast Guard announced.
