Researchers Secure Earth's Deepest Mantle Rock Sample

WASHINGTON (Reuters) – Scientists have achieved a remarkable milestone by drilling the deepest hole ever into Earth's mantle. Using an ocean drilling vessel, they reached 4,160 feet (1,268 meters) beneath the Atlantic Ocean's floor, obtaining a significant core sample that reveals details about this crucial layer of our planet.

This core sample is providing fresh insights into the composition of the upper mantle and the chemical interactions between mantle rock and seawater at various temperatures. Researchers suggest these interactions could have been pivotal in the emergence of life on Earth billions of years ago.

The mantle accounts for over 80% of Earth's volume, situated between the outer crust and the intensely hot core. Access to mantle rocks is rare, typically only found where they are exposed due to seafloor spreading, like at the Atlantis Massif—an underwater mountain in the Atlantic Ocean, just west of the mid-Atlantic Ridge.

Between April and June 2023, scientists aboard the JOIDES Resolution vessel drilled about 2,800 feet (850 meters) below the ocean surface. They recovered a core sample that includes more than 70% of the drilled rock—2,907 feet (886 meters) long. This accomplishment far exceeds previous drilling attempts, which had only reached up to 200 meters (656 feet) with limited rock recovery.

Geologist Johan Lissenberg from Cardiff University, lead author of the study published in Science, emphasized the importance of this achievement. The team successfully retrieved large, continuous mantle rock samples, a significant improvement over earlier efforts that produced minimal results. The core sample has a diameter of approximately 2-1/2 inches (6.5 cm).

Initial drilling was challenging, but the team overcame obstacles by adding a reinforced concrete liner, which facilitated the drilling process. They examined how the mineral olivine in the core sample reacted with seawater at different temperatures. This reaction produces hydrogen, which forms compounds like methane, potentially relevant to the origins of life.

The drilling site was close to the Lost City Hydrothermal Field, known for its hydrothermal vents. The core sample is thought to reflect the mantle rock beneath these vents, providing insights into early life conditions.

Early analysis of the core sample indicated a more extensive history of melting than anticipated. Researchers observed significant variation in the mineral orthopyroxene, suggesting complex melt flow patterns through the upper mantle. This melt movement contributes to volcanic activity as it rises beneath spreading tectonic plates.

The core sample is still being studied, with ongoing research aimed at further understanding its composition and the geological processes it represents.