Reaching the discontinuity by drilling remains an important scientific objective. Soviet scientists at the Kola Superdeep Borehole pursued the goal from 1970 until 1992. They reached a depth of , the world's deepest hole, before abandoning the project. One proposal considers a rock-melting radionuclide-powered capsule with a heavy tungsten needle that can propel itself down to the Moho discontinuity and explore Earth's interior near it and in the upper mantle. The Japanese project Chikyu Hakken ("Earth Discovery") also aims to explore in this general area with the drilling ship, "Chikyū", built for the Integrated Ocean Drilling Program (IODP).