Researchers Extract Deepest-Ever Rock Sample From Earth’s Mantle

Scientists used an ocean drilling vessel to dig the deepest hole in rock from Earth’s mantle, reaching 4,160 feet (1,268 meters) into the Atlantic Ocean. The resulting sample provides insights about the planet’s largest layer.


This cylindrical core sample, researchers stated on Thursday, is offering insight into the composition of the upper mantle and the chemical reactions that occur when this rock interacts with seawater at various temperatures. They hypothesized that such events may have contributed to the emergence of life on Earth billions of years ago.

The mantle, which accounts for more than 80% of the planet’s bulk, is a layer of silicate rock sandwiched between Earth’s outer crust and a furiously heated core. Mantle rocks are largely inaccessible, except where they are exposed on the seafloor between the slowly shifting continent-sized plates that comprise the planet’s surface.

One such location is the Atlantis Massif, an underwater mountain where mantle rock is exposed on the seafloor. It is located in the middle of the Atlantic, slightly west of the massive mid-Atlantic Ridge that separates the North American, Eurasian, and African plates.

From April to June 2023, researchers used equipment aboard the vessel JOIDES Resolution to drill into mantle rock about 2,800 feet (850 meters) beneath the ocean’s surface. The core sample they recovered contains more than 70% of the rock from the drilled hole, measuring 2,907 feet (886 meters) in length.

“The recovery is record-breaking in that earlier attempts to drill mantle rocks have been difficult, with penetration of no more than 200 meters (656 feet) and low rock recovery. In contrast, we drilled 1,268 meters and recovered huge parts of continuous mantle rocks,” said geologist Johan Lissenberg of Cardiff University in Wales, principal author of the study published in Science.

“Previously, we have been largely limited to mantle samples dredged from the seafloor,” she said.

The core sample’s diameter is approximately 2-1/2 inches (6.5 cm).

“We did have quite a bit of difficulty starting our hole,” said geologist and study co-author Andrew McCaig of the University of Leeds in England.


The researchers attached a reinforced concrete cylinder lining to the uppermost half of the hole, McCaig said, “and then drilled unexpectedly easily.”

They studied how a mineral called olivine in the core sample reacted with seawater at different temperatures.

“The reaction between seawater and mantle rocks on or near the seafloor produces hydrogen, which then generates chemicals like methane, which supports microbial life. “This is one of the hypotheses for the origin of life on Earth,” Lissenberg explained.

“Our recovery of mantle rocks enables us to study these reactions in great detail and across a range of temperatures, and link it to the observations our microbiologists make on the abundance and types of microbes present in the rocks, and the depth to which microbes occur beneath the ocean floor,” according to Lissenberg.

The drill site was adjacent to the Lost City Hydrothermal Field, a collection of hydrothermal vents on the seafloor that spew superheated water. The core sample is expected to represent the mantle rock underlying the Lost City vents.

“One suggestion for the origin of life on Earth is that it could have happened in an environment similar to Lost City,” according to McCaig.

The core sample is still undergoing analysis. The researchers produced some preliminary results about its composition and discovered a longer history of melting (molten rock) than anticipated.

“The mineral orthopyroxene in particular showed a wide range of abundance on a range of scales, from the centimeter to hundreds of meters,” Lissenberg observed. “We associate this with the passage of melt through the upper mantle. As the upper mantle rises beneath the spreading plates, it melts and migrates to the surface, feeding volcanoes.