A record-breaking mission to drill 1,270 metres beneath the Atlantic Ocean has found the first piece of the Earth's crust.
The international expedition led by the United Kingdom, involving more than 30 countries, travelled to the middle of the ocean, across the Mid-Atlantic Ridge, where tectonic plates meet and trigger volcanic activity.
It is hoped that the discovered rocks will help unravel the role that the Earth's crust, also known as the mantle, played in the origins of life on the planet.
A psychedelic cross-section of the unique rock sample shows how volcanic activity, which melts rocks and interacts with seawater, drives global cycles of essential elements such as carbon and hydrogen.
The nearly continuous piece of mantle rock was found in a “tectonic window,” a section of the seafloor where mantle rocks are exposed in the mid-Atlantic Ocean.
Expedition 399, called “Building Blocks of Life, Atlantis Massif,” was conducted in spring 2023 on the ocean drilling ship JOIDES Resolution. The results were announced this week.
Efforts to save the oceans date back to the early 1960s. This successful salvage was a record-breaking achievement led by the International Ocean Discovery Program.
Their findings, published in the journal Science, show that the rocks found have a longer melting history than expected.
Lead author Professor Johan Lissenberg, from Cardiff University's School of Earth and Environmental Sciences, said: “When we excavated the rocks last year it was a major achievement in the history of Earth science. But more importantly, their value lies in what the cores of mantle rocks can tell us about the composition and evolution of our planet.
“Our research begins by studying the composition of the mantle by documenting the mineralogy of the rocks found, as well as their chemical composition.
“Our results are different from what we expected. There is much less of the mineral pyroxene in the rocks, and the rocks have very high concentrations of magnesium, both of which are the result of much higher amounts of melting than we predicted.”
This melting occurred as the mantle rose from the deeper parts of the Earth to the surface. Results from further analysis of this process could have major implications for understanding how magma is formed and leads to volcanism, the researchers say.
The study also provides initial insights into how olivine, a common mineral in mantle rocks, reacts with seawater, triggering a series of chemical reactions that produce hydrogen and other molecules that can fuel life. Scientists believe this could have been one of the underlying processes in the origins of life on Earth.
Dr Andrew McCaig, Associate Professor in the School of Earth and Environment at the University of Leeds, who was the main proponent of Expedition 399 and one of the expedition's lead scientists, added: “Everyone involved in Expedition 399, starting with the first proposal in 2018, can be proud of the achievements documented in this paper.
“Our new deep hole will be an example for decades to come for a variety of disciplines, including melting processes in the mantle, chemical exchange between rocks and the ocean, organic geochemistry and microbiology.
“All data from the expedition will be fully available, an example of how international science should be conducted.”
The article 'A long piece of serpentinized depleted mantle peridotite' is published in Science.