Epic Drilling Mission Sets New Record With 4,160-Foot Mantle Core

The rock beneath the Atlantic Ocean holds many secrets that can help scientists understand our planet and how life came to exist on it. That’s why a team of researchers is undertaking a difficult task: digging a hole more than three-quarters of a mile deep and extracting a record-breaking rock core from the Earth’s mantle.

Scientists often remove core samples—cylindrical samples of material deep in the earth—to examine the composition of different layers. That data can serve as a window into the planet’s past, providing information on climate and environmental change, or the formation of the Earth itself. Deep-sea drilling comes with unique challenges, so researchers have been forced to dig up rocks from the ocean floor. Analyzing the composition of these rocks can reveal valuable information, but these rocks can be altered by sea pressure and exposure to salt water.

The expedition takes place between April and June 2023 in an area of ​​the North Atlantic known as the Atlantis Massif, an underwater mountain 14,000 meters (4,267 feet) above sea level. The site was chosen because tectonic activity in the area pushes rocks that normally sink to the bottom of the ocean floor, making it easier to restore them. That still required deep drilling to find a 4,160-foot-long (1,268-meter) core near a continuous layer of peridotite, a type of igneous rock.

This extreme depth is much greater than previous attempts to drill into seabed rocks. According to the study, co-authored by C. Johan Lissenberg from Cardiff University, the scientists were able to recover 71% of the drilled material, with almost complete recovery of long sections of harzburgite embedded in the serpentine section (that is, a rock that has been slightly altered by water) .

As noted in the paper, published in the journal Science, researchers analyzed the mineral composition within the rock and found evidence to support the theory that rocks born deep in the mantle rose to the surface. In that theory, the pressure melts the rocks and then they are pushed up, mixed with magma in the crust before they erupt into the ocean floor.

The researchers also found an intrusion of a crystalline rock called gabbro, which is formed by the slow cooling of magma. They believe that gabbro plays a major role in controlling the minerals and gases found in the deep ocean, which some scientists believe is an ideal home for the formation of ancient life. Learning more about vents can lead to new ideas about how life on Earth began, and how it might form on other planets.

In the study, the researchers agreed that much analysis of what they did needs to be done. “The complete rock record obtained during Expedition 399 offers a wealth of opportunities to make important advances in our understanding of the upper ocean crust,” they said.

In an accompanying article, Utrecht University professor Eric Hellebrand said “the depth far exceeds what was recorded in previous drilling efforts and creates opportunities to see the structural and mineralogical features of the mantle and how it interacts with the hydro- and biospheres.”

He also expressed that he hopes that this excavation trip can increase the level of research on how the Earth was formed.

“Decades of ocean sampling have painted a poor picture of the mantle,” he wrote. However, each new excavation campaign reveals amazing insights into the structure of the ocean’s crust. More ambitious drilling projects will reveal key pieces for understanding the biogeochemical effects of the ocean mantle. “