Deep Sea Drilling Project, U.S. program designed to investigate the evolution of ocean basins by core drilling of ocean sediments and underlying oceanic crust. Funded by the National Science Foundation, the project was directed by the Joint Oceanographic Institution for Deep Earth Sampling (JOIDES), a consortium of leading U.S. oceanographic institutions. Begun in 1964, a test drilling program was completed successfully in 1965; by 1968, the Glomar Challenger, displacing 10,500 tons and capable of drilling 2,500 ft (760 m) of sediment in 20,000 ft (6,100 m) of water, was leased to JOIDES. The scientific operations carried out on board consisted of continuous seismic and magnetic surveys while underway, in-hole measurements, and laboratory analysis of the cores recovered. The project verified that the present ocean basins are relatively young and confirmed aspects of seafloor spreading and plate tectonics. It also discovered thick bedded salt layers from cores taken out of the Mediterranean Sea, indicating that the sea completely dried up between 5 and 12 million years ago; that Antarctica has been covered with ice for the last 20 million years; and that the northern polar ice cap was much more extensive 5 million years ago. The Deep Sea Drilling Project drilled about 600 holes into the ocean floors over the world, about one hole per 308,880 square mi (800,000 square km). The Ocean Drilling Program (ODP), begun in 1984 and supported by a U.S.-led international consortium of 21 nations, is the successor of the Deep Sea Drilling Project. The program employs the drillship JOIDES Resolution and is managed by Joint Oceanographic Institutions (JOI). It is drilling in poorly sampled areas, including continental margins and ocean trenches. In addition, the ODP contributes to other programs, such as drilling holes in which to lower seismic instruments necessary for a global seismic network project.