The Navy commissioned Ballard and his team to carry out a month-long expedition every year for four years, to keep Argo / Jason in good working condition.[29] It agreed to Ballard's proposal to use some of the time to search for Titanic once the Navy's objectives had been met; the search would provide an ideal opportunity to test Argo / Jason. In 1984 the Navy sent Ballard and Argo to map the wrecks of the sunken nuclear submarines USS Thresher and USS Scorpion, lost in the North Atlantic at depths of up to 9,800 ft (3,000 m).[30] The expedition found the submarines and made an important discovery. As Thresher and Scorpion sank, debris spilled out from them across a wide area of the seabed and was sorted by the currents, so that light debris drifted furthest away from the site of the sinking.