Scientists drilled so deep into the Earth’s core, they knocked on the mantle

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Here’s what you’ll learn as you read this story:

• Scientists drill deep into the Earth’s core to understand the mantle – the largest layer of Earth’s rocky body.

• Scientists drilled the deepest core ever and recovered serpentinized peridotite, which forms when salty water interacts with mantle rock.

• Although it is the deepest mantle scientists have ever drilled, the mission did not detect the ancient mantle beyond the Mohorovician discontinuity, or Moho, boundary.

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If you want to understand the geology of our home planet, studying the mantle is a great place to start. Separating the planet’s rocky crust and molten outer core, the mantle makes up 70 percent of Earth and 84 percent of its volume. But despite its enormous influence on the planet’s geological processes, scientists have not directly sampled rocks from this extremely important geological layer.

And that’s understandable, especially when you consider that the crust is about 9 to 12 miles thick on average. Fortunately, that average includes the outliers—areas of the world where the crust is actually incredibly thin and faults expose the mantle through cracks. One such area is the Mid-Atlantic Ridge, particularly near the underwater mountain range called the Atlantis Massif.

South of this massif is an area known as the Lost City – a hydrothermal area whose vent fluids are highly alkaline and rich in hydrogen, methane and other carbon compounds. This makes this region a particularly attractive candidate for explaining how early life evolved on Earth. Additionally, it contains mantle rock that interacts with seawater in a process known as “serpentinization” that changes the rock’s structure and gives it a green, marble-like appearance.

It was here, 800 meters south of the region, in May 2023 that members of the International Ocean Discovery Program (IODP) – on board. JOIDES resolution, The 470-foot-long research vessel—chartered by the US National Science Foundation—excavated a 1,268-meter core containing abyssal peridotites, the primary rocks that make up Earth’s upper mantle. The results of the study have been made public In the journal Science.

Although this makes this particular drill core the deepest sample of the mantle, going deeper into the rock was not the goal of this record-breaking expedition.

“We only planned to drill 200 meters, because that’s the deepest man has ever drilled into mantle rock,” said Johan Lisenberg, a petrologist at Cardiff University and co-author of the study. Nature. He said that because the drilling was so easy, it progressed three times faster than usual. The team eventually drilled 1,268 meters, and only stopped because of the mission’s limited operations window.

Andrew McGeagh – study co-author and scientist at the University of Leeds – said in an article. conversation That, according to preliminary analysis of the rock, the core composition consists of a variety of peridotite called harzburgite that may have formed from partial melting of mantle rock. It also contained rocks known as gabbros, which are coarse-grained igneous rocks. Both of these rocks then reacted chemically with seawater, changing their composition.

Although this core represents an incredible opportunity to learn more about the Earth’s mantle, as well as give a deeper view into the geological substrate underlying the lost city, the mission did not fully complete the “grand challenge” of crossing the Mohorovičić discontinuity. Otherwise known as the Moho, the Mohorovician discontinuity is known as the true boundary between the crust and the older mantle.

Future missions may continue to explore this site near the Atlantis massif, but sadly, those missions will not include it. JOIDES resolution— NSF refuses to fund additional core drilling after 2024. Just as scientists are finally knocking on the door to Earth’s most ubiquitous geological layer, the future of these types of drilling missions is now uncertain.

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