The U.S. Navy opened a formal inquiry on Monday into the ramming of a Japanese trawler by a nuclear submarine, trying to answer questions about an accident that killed nine people and marred America’s relationship with Japan. The navy’s Court of Inquiry could also lead to a court martial for three or more officers of the USS Greeneville who will be asked to explain how they failed to notice the 190-ft. (58-m) fishing boat before surfacing off Diamond Head near Honolulu. The fast-attack sub is equipped with state-of-the-art sonar, and published reports have said the Greeneville’s crew was aware of a ship in the vicinity before surfacing. The Greeneville was practicing emergency maneuvers on Feb.