In a one-of-a-kind expedition, scientists have drilled deeper into the Earth’s mantle than ever before, extracting a record-breaking sample that could reshape our understanding of both geology and the origins of life.
The rock core, retrieved from a staggering depth of 1,268 meters (4,160 feet) below the seabed, was collected from the Mid-Atlantic Ridge, a tectonic boundary where the Eurasian Plate meets the North American Plate.
“It’s an incredible haul, as previous drilling into this particular type of rock — ocean peridotite — had only reached a maximum depth of 201 meters,” Professor Gordon Southam of the University of Queensland said in a statement.
“These samples will help improve our understanding of the links between the Earth’s geology, water chemistry, gases and microbiology.
Journey to the Earth’s Mantle
The successful extraction was conducted by an international team of geologists aboard the drilling vessel JOIDES Resolution. The site of the drilling, the Atlantis Massif near the Mid-Atlantic Ridge, offered a rare opportunity to access the Earth’s mantle.
The mantle is a semi-solid layer of rock that extends thousands of kilometers below the Earth’s crust. Usually, it lies buried beneath about 25 miles (40 km) of rocky crust. However, at this location, the crust is significantly thinner, allowing the mantle material to seep closer to the surface.
The research team originally planned to drill to the previous record-holding depth. However, they found the work progressing so efficiently that they continued drilling far beyond their initial goal. In the end, they surpassed the best previous efforts more than sixfold.
Understanding the structure of Earth
The extracted core samples, largely composed of a mantle rock called peridotite, have provided new insights into the complex interactions between the Earth’s interior and its surface. The peridotite was found to be “serpentinized,” meaning it had interacted with seawater, giving it a texture resembling snake skin.
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Moreover, the samples contained other types of rock that weren’t supposed to be there. This finding suggests that the boundary between the Earth’s crust and mantle may be more fluid and less defined than previously thought.
Another important discovery is the extensive carbonation 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 within the Earth’s crust.
“We are researching the role microbiology has in the transformation of carbon dioxide into stable carbonate minerals, and how we can reduce greenhouse gas concentrations in the atmosphere,” Professor Southam said.
Life in the Mantle
Beyond its geological significance, the core is also a potential treasure trove for understanding life in extreme environments. So, the research team led by Professor Southam collected samples of microorganisms living within the rock. These microorganisms, which thrive in the harsh conditions of the deep subsurface, rely on chemical reactions between olivine (a mineral found in the mantle) and seawater to produce hydrogen, a vital energy source for life in such extreme environments.
“Every time the drillers recovered another section of the deep core, we collected samples to culture bacteria,” Professor Southam said.
“We will use these samples to investigate the limits of life in this deep subsurface marine ecosystem, improving 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 utilize hydrogen in extreme conditions.
As the researchers continue to analyze the rock core using advanced techniques such as electron microscopy and X-ray fluorescence, the implications of their findings are expected to ripple across multiple scientific disciplines. The Atlantis Massif remains a critical site for understanding the formation of the oceanic lithosphere and the processes that occur at the boundary between Earth’s crust and mantle.
What they find next could have implications for future explorations of Mars and other celestial bodies where water-rock interactions may have played a role in shaping their surfaces and potential habitability.
The findings appeared in the journal Science.
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