In a unique expedition, scientists have drilled deeper into the Earth’s mantle than ever before, collecting a record-breaking sample that could fundamentally change our understanding of geology and the origins of life.

The rock core, recovered from an astonishing depth of 1,268 meters (4,160 feet) below the seafloor, came from the Mid-Atlantic Ridge, a tectonic boundary where the Eurasian Plate meets the North American Plate.

“This is an incredible yield, given that previous drilling in this particular rock type – ocean peridotite – had only reached a maximum depth of 201 metres,” said Professor Gordon Southam of the University of Queensland in a statement.

“These samples will help improve our understanding of the relationships between Earth’s geology, water chemistry, gases and microbiology.

Journey into the Earth’s mantle

The successful production was carried out by an international team of geologists on board the drilling vessel. JOIDES ResolutionThe drilling site, the Atlantis Massif near the Mid-Atlantic Ridge, offered a rare opportunity to gain access to the Earth’s mantle.

The Earth’s mantle is a semi-solid layer of rock that extends thousands of kilometers beneath the Earth’s crust. It normally lies beneath a crust of rock about 40 km thick. At this point, however, the crust is significantly thinner, allowing the mantle material to seep closer to the surface.

The research team had originally planned to drill to the previous record depth, but operations went so smoothly that they continued drilling well beyond their original target, ultimately exceeding their best previous attempts by more than six times.

Understanding the structure of the Earth

The core samples taken, which consist mostly of a mantle rock called peridotite, have provided new insights into the complex interactions between the Earth’s interior and its surface. The peridotite turned out to be “serpentinized”, meaning it had reacted with seawater to give it a texture reminiscent of snakeskin.

In addition, the samples contained other types of rock that should not be there. This finding suggests that the boundary between the Earth’s crust and mantle may be more fluid and less pronounced than previously thought.

Another important discovery is the extensive carbonization of the serpentinized peridotite. This indicates significant carbon sequestration in these deep Earth environments. This discovery has implications for understanding the global carbon cycle and the potential for storing carbon deep in the Earth’s crust.

“We are investigating the role of microbiology in converting carbon dioxide into stable carbonate minerals and how we can reduce greenhouse gas concentrations in the atmosphere,” said Professor Southam.

Life in the Earth’s mantle

Beyond its geological significance, the core is also a potential treasure trove for understanding life in extreme environments. The research team led by Professor Southam therefore collected samples of microorganisms that live in the rock. These microorganisms, which thrive in the harsh conditions of the deep underground, rely on chemical reactions between olivine (a mineral found in the Earth’s mantle) and seawater to produce hydrogen, a vital energy source for life in such extreme environments.

“Each time the drills recovered another section of the deep core, we collected samples to grow bacteria,” said Professor Southam.

“We will use these samples to explore the limits of life in this deep marine ecosystem, improve our understanding of its origins, and help define the potential for life beyond Earth.”

The team is particularly interested in the role of nickel, an essential element in the enzyme hydrogenase, which enables ancient bacteria to use hydrogen under extreme conditions.

As researchers continue to analyze the rock core using modern techniques such as electron microscopy and X-ray fluorescence, the implications of their findings are expected to have implications across multiple scientific disciplines. The Atlantis Massif remains a crucial site for understanding the formation of the oceanic lithosphere and the processes that take place at the boundary between the Earth’s crust and mantle.

Their next discoveries could have implications for future exploration of Mars and other celestial bodies where water-rock interactions may have played a role in shaping their surfaces and potential habitability.

The results were published in the journal Science.