In 1961, the CUSS I barge drilled 183 meters into the seabed, pioneering dynamic positioning, but the Moho boundary remained elusive as funding and priorities shifted.
Project aims to reach the Moho
In 1957, a group of American researchers proposed drilling through the Earth's crust to reach the Moho, the boundary between the crust and the mantle. They chose the ocean over the continents because the oceanic crust is thinner, making the journey to the mantle shorter.Initial funding and preparation
The U.S. federal agency for science showed interest in the project and granted an initial aid of $15,000, half of the requested sum, to fund the study. Four years later, the barge CUSS I, a former naval barge modified for drilling, set out on its mission.Drilling tests and achievements
In March and April 1961, the barge conducted tests off the coast of San Diego under about 950 meters of water. It later moved to the vicinity of the island of Guadalupe, off Baja California, Mexico. The drill bit reached the seabed on March 28, 1961, under approximately 3,570 meters of water, more than ten times the height of the Eiffel Tower.Technical innovation and costs
The team drilled five holes, with the deepest reaching 183 meters below the seabed and penetrating a few meters into the basalt. A key core was retrieved on April 2, 1961. The barge remained above the hole without an anchor, using four large motors controlled by a single lever. This innovation, known as dynamic positioning, later became standard at sea.Unmet goal and project shift
The 1961 phase did not reach the Moho, as the primary goal was to prove the method worked rather than to touch the mantle. In February 1962, the project was handed over to a construction company from Houston, which had no prior drilling experience. This decision surprised many, given the complexity of the task.Rising costs and scientific disagreement
Cost estimates for the project rose from several million dollars to over $100 million. Researchers disagreed on priorities, with some advocating for shallower, more accessible holes in sediments rather than a direct jump toward the mantle. The project continued with a growing budget and a divided scientific community.Funding cut and legacy
In 1966, both the House and Senate refused further funding, and the project was officially canceled after about $57 million had been spent. This amount was nearly 38 times the cost of the 1961 phase. Despite the financial failure, the methods tested in 1961 contributed to the development of scientific ocean drilling.Continuing influence and related projects
A deep-sea sediment drilling program began in June 1966, focusing on shallower, more numerous holes. This approach helped confirm the theory of plate tectonics. Modern oil platforms and drilling ships use the dynamic positioning technology tested by the CUSS I. The Kola well, launched in 1970, was a land-based attempt to reach the mantle and is considered the terrestrial counterpart to the Mohole project.
