The deep-sea drilling vessel Chikyu made a port call Thursday in Yokohama after ending its first training mission at sea since being built in July at a cost of 500 million dollars.
The project, led by Japan and the United States with the participation of China and the European Union, seeks clues on primitive organisms that were the forerunners of life and on the tectonic plates that shake the planet's foundations.
"This is like an Apollo project under the Earth," staff scientist Kan Aoike said, referring to the landmark US lunar missions.
"The idea of the project came out half a century ago but failed halfway while the real Apollo project was carried out successfully," Aoike told AFP as he sorted out samples taken in its first training voyage.
"So this is a second and serious attempt to complete another key exploration for mankind," he said. "We are so excited to witness the mantle for the first time."
The Earth is made up of a crust, a mantle, an outer core and an inner core.
The satellite-equipped vessel, which still smells fresh with paint, is equipped with a 121-meter (400-foot) drill tower that can dig 7,000 meters (23,000 feet) below the seabed, nearly three times as deep as its predecessors.
"All these (samples) give us different ideas for how the climate changed over time, the position of the continents, what kind of land plants were living on the Earth, what's the potential for oil," said Daniel Curewitz, a US scientist working on the project.
"I presume this will help predict an earthquake, which will be a breakthrough in seismology," he said. "Even if we cannot predict it, we can get data in advance of an initial crack from an earthquake."
Japan experiences 20 percent of the world's major earthquakes.
As a first drilling spot, the operator chose the seabed some 600 kilometers (370 miles) southwest of Tokyo, where many experts say an earthquake measuring eight on the Richter scale will occur sometime in the near future.
In 1944 and 1946, more than 2,000 people in total were killed in two big earthquakes and tsunami in the seabed area known as the Nankai Trough, a boundary where two plates slide past each other.
Taira said the seabed off Sumatra island in Indonesia, the scene of the massive earthquake a year ago that triggered the Indian Ocean tsunami, is also a potential drilling spot in the future.
Oceanic drilling is preferred over land drilling because the crust at the seabed is thinner and allows for deeper digs into the crust and mantle, Taira said.
Chikyu uses technology that exists for oil drilling, but is specially equipped to prevent damage from sudden bursts if it accidentally strikes oil or gas reserves.
Some 150 crew are scheduled to make the first official voyage in 2007. The ship and its drill pipes are rigged to stay stable by adjusting to the rolling motions from the drilling and waves.
© 2005 AFP