Berthed in China’s port city of Guangzhou is the future of scientific ocean drilling: the $470 million Meng Xiang, a brand-new, 180-meter-long ship.
Starting next year Meng Xiang—Chinese for “Dream”—will begin drilling into seafloor rock and sediment at sites throughout the world’s oceans to investigate plate tectonics, ancient marine climates, and deep-buried microbial life. It will also embark on a daring mission to pierce Earth’s crust and reach the mantle below. At a workshop last month in Guangzhou, researchers discussed the research agenda and toured the ship, which has nine dedicated science laboratories and a drilling rig that promises to delve deeper than any previous research ship. “I’m green with jealousy,” says Henry Dick, a geologist at the Woods Hole Oceanographic Institution. “This ship has the capacity to answer fundamental climate, oceanographic, microbiological, and earth science questions … for the next 50 years,” says paleoceanographer Peter Bijl of Utrecht University.
China’s new ship—and an accompanying research program expected to be open to foreign scientists—marks a handoff in ocean drilling from the United States. Japan has a formidable research ship, the Chikyu, but for decades the U.S. led the International Ocean Discovery Program (IODP) with its drilling ship the JOIDES Resolution, which retired in September. “I’m very happy that China has stepped up in providing a ship,” says James Austin, a seismic stratigrapher at the University of Texas at Austin. But, “It’s a sad day for the United States.”
Meng Xiang’s most notable feature is its capability to drill to a depth of 11,000 meters below the sea surface, compared with the JOIDES Resolution’s 8385 meters and the 10,000 meters of Chikyu. This means Meng Xiang could make history by boring into the mantle, past a boundary known as the Mohorovičić discontinuity, or the Moho. Scientists have yearned to pierce the Moho since 1961 when the first scientific oceanic drilling program was dubbed “Project Mohole.”
Croatian seismologist Andrija Mohorovičić—the boundary’s namesake—observed that seismic waves travel through Earth faster below the Moho than above it, suggesting an abrupt change in the composition of the rocks. The textbook explanation is that the Moho separates denser mantle peridotites, magnesium-rich rocks, from lighter crustal gabbros, which crystallize from magmas. Rocks brought to the surface in volcanic eruptions or recovered at midocean ridges, where the crust is thinnest, support that picture. But seawater and other geochemical processes can alter those rocks; fresh rock samples from the Moho and the mantle could confirm their compositions and shed light on the formation and evolution of Earth’s crust.
“This is a foundational step in the plate tectonic cycle; we should understand it better than we do,” says Damon Teagle, a geologist at the University of Southampton. But the original Project Mohole was terminated after several test holes. And a 2016 effort in the Indian Ocean, the SloMo Project, didn’t make it beyond a shallow phase 1 hole.
Scientists believe the Moho is shallowest near fast-spreading ridges in the Pacific Ocean, where the water is about 4000 meters deep and the Moho another 6000 meters below that. To keep such a deep hole from collapsing under high subterranean pressures, drillers will have to pump a dense slurry called drilling mud from the ship through the borehole and back. Steering the mud through 4000 meters of water requires a new circulation system that Meng Xiang engineers hope to have ready by 2030 if not earlier, says Zhen Sun, Meng Xiang’s chief scientist and a structural geologist at the Guangzhou Marine Geological Survey.
China took up the Moho challenge because the country’s scientists played little role in the discovery of plate tectonics and decided it was time “for China to make big contributions to the international community,” Yaoling Niu, a petrologist with the Laoshan Laboratory, said during his workshop presentation.
But the ship “will do more than Moho drilling,” Sun adds. China is planning a Deep Ocean Drilling Program to manage up to 30 drilling expeditions from 2025 to 2035, according to Shouting Tuo, a sedimentologist at Tongji University. International proposals will be welcomed, and all cores and data will be openly accessible to scientists worldwide, Tuo told workshop attendees.
Some investigators hope to revive projects left orphaned by the end of IODP. These include drilling into the Sunda Shelf, a vast geological formation beneath the shallow seas of Southeast Asia, to reconstruct sea level changes from 5 million years ago; looking for evidence of a 130-million-year-old ocean basin east of Taiwan that has since been swallowed by tectonic movements in the region; and probing the Mariana Trench, created by an oceanic crustal plate plunging into the mantle southeast of Japan, for tectonic, geochemical, and biological activity.
Bijl plans to submit an especially ambitious IODP proposal. He wants to drill sediment and rock cores at four sites spaced between Australia and Antarctica for clues to the origin and evolution of the Antarctic Circumpolar Current. The current, Earth’s strongest, has a large influence on Southern Hemisphere weather and also the future of Antarctic ice sheets, because it affects how warm waters reach the underside of vulnerable ice shelves that jut into the ocean. Bijl’s proposal calls for drilling in water depths up to 5000 meters in one of the harshest ocean environments on Earth. But he says the Meng Xiang, designed to withstand winds and seas during all but the fiercest typhoons, “is the ideal vessel to execute this drilling plan.”
