A groundbreaking excursion, in which the Atlantic Ocean was drilled, has given scientists their best insight into how the earth could look under its crust.

researchers have removed an almost uninterrupted 1,268 -meter -long sample of green, marble -like rock from a region in which the earth's mantle - the thick, inner layer, which is more than 80% of the planet - has been pressed by the sea floor. The samples described on August 8 in science offer unprecedented insights into processes that lead to the formation of the crust

"We had this story in our head" what such rocks should look like, but it is completely different when "you can see it on a table there," says Natsue Abe, petrologist at the Japan Agency for Marine-Earth Science and Technology in Yokohama.

The achievements of the expedition are a "fantastic milestone," says Rosalind Coggon, marine geologist at the University of Southampton, UK. "Ocean drilling offer the only access to samples from the deep inside of the earth, which are crucial to understand the origin and development of our planet."

Scientists in Hard Hats and Face Masks Examine Core Samles in A Lab On Board Joid Resolution Research Vessel

The oceanic earth coat - the type of crust that can be found mainly below the oceans of the earth, instead of under their continents - consists mainly of dense, volcanic rock called basalt. It is much thinner and younger than the continental crust, because the rocks are continuously recycled by the movements of the tectonic plates.

basalt arises when magma presses up the middle ocean back through undersees. The magma itself comes from a process that is known as partial melting in the coat - which mostly consists of translucent, green, magnesium -rich minerals. While the material rises in the coat, the pressure falls over it, which means that some of these minerals melt and form microscopic films made of magma between rock -crystals.

Usually only magma penetrates the sea floor. But in some places it also manages to the surface, where it comes into contact with sea water in a reaction called serpentineization. This changes the structure of the rock - gives it a marble -like appearance - and releases different substances, including hydrogen.

easy to drill

in May 2023 Joides Resolution visited a place where this has happened: a Unterwasserberg called Atlantis massif, which is located west of the Central Ocean back of the Atlantic. The 143 meter long ship is equipped with a 62 meter high crane for underwater drilling.

The researchers on board decided to Lost City to drill, a place on the south side of the massif. The region is shaped by hydrothermal sources in which microbial extremophiles use the outer hydrogen.

"We had only planned to drill 200 meters, because that was the deepest place where people had ever managed to drill in coat rock," says Johan Lissenberg, a petrologist at Cardiff University, Great Britain. But drilling was surprisingly simple and three times faster than usual, and long, uninterrupted rock cylinders called Kerne were attributed. "So we just decided to continue," says Lissenberg. The team only stopped when the expedition ended in accordance with its schedule.

The researchers have now published their first results. "What we report is literally what you can do on the ship. A team of 30 scientists who breed over the kernels for two months and document it in centimeters how they come up."

Deep-Sea Drilling: Diagram Showing How Researchers On a Ship Drilled into Rock That Originated In The Earth's Mant.

When the scientists examined the structure of the rock in detail, they found "weird characteristics", a characteristic signature of the prevailing theory, how Magma separates from the coat in order to become part of the crust, says Lissenberg. The coat rock was also interspersed with other types of rock in the cores, which indicates that the coat crust limit is not as sharp as seismographic data normally suggest, says Jessica Warren, geochemist at the University of Delaware in Newark. These results together "are crucial for how we understand the creation of tectonic plates in the oceans," she says.

uncertain future

The excursion crowned a worthy four decades long career for the yoid resolution , which the US National Science Foundation (NSF) had rented by a private company. But the NSF has announced that it can no longer do the $ 72 million a year that the ship's operation costs after the fulfillment of its iODP obligations and that the program is discontinued. This leaves some scientists, especially those in early career levels, uncertain about the future of the field, says Aled Evans, marine geologist at the University of Southampton.

A remaining "big challenge" for geoscientists is to drill through the basaltic layer and across the border between crust and coat-which is referred to as Mohorovičić disinuity or "Moho". This would enable them to access virgin coat rock that did not react with sea water. "We haven't drilled in the real coat yet," says Abe. The surprisingly smooth drilling to Lost City indicates these future attempts that could be carried out by the research ship Japan's chikyū . "Mantel rocks are the most common part of our entire planet," says Evans. "The rehearsals of them would be of fundamental importance for understanding what our planet is made of."