New technologies used to locate sunken treasure

New York Times : As a way to raise money, strapped governments have begun looking to retrieve treasure from sunken ships. The British government recently contracted with a Florida company called Odyssey Marine Exploration to retrieve an estimated 20 tons of silver from a vessel that was sunk off the coast of Ireland during World War I. The SS Mantola, owned by the British Indian Steam Navigation Company, was attacked by a German torpedo in 1917. At today’s prices the metal it carried would be worth about $18 million.To locate sunken craft, Odyssey technicians comb the sea floor with side-scan sonar and magnetometers. Then they send down a tethered robot to capture real-time video images of any interesting anomalies. For the Mantola, they were able to identify the wreck by noting the ship’s dimensions, its layout, and a display of painted letters on the stern. Last month Odyssey discovered another wreck, of the British steamship SS Gairsoppa, off the coast of Ireland; its cargo is estimated to be worth more than $200 million. The salvage expedition for the Mantola and Gairsoppa is planned for spring 2012.