For the first time, an international team of scientists has successfully recovered a significant section of rocks from the Earth's mantle, the vast layer beneath the crust that constitutes the largest portion of our planet’s interior. This unprecedented 4,160-foot (1,268-meter) segment of nearly continuous mantle rock offers valuable insights into the Earth’s geological processes, especially its more explosive features. The findings were detailed in a study published on August 8 in the journal *Science*, revealing that the recovered rocks had undergone more extensive melting than the researchers initially anticipated.
These rocks were extracted from a tectonic window—a unique area on the seabed where mantle rocks are exposed—located along the Mid-Atlantic Ridge. This underwater mountain range spans 10,000 miles from the Arctic to the southern tip of Africa, forming the longest mountain range on Earth. The Mid-Atlantic Ridge, like other mid-ocean ridges, plays a crucial geological role as it is where new ocean floor is created as tectonic plates diverge.
The core sample was obtained in Spring 2023 during Expedition 399, titled “Building Blocks of Life, Atlantis Massif,” aboard the ocean drilling vessel JOIDES Resolution. The research team hopes that these mantle rocks will shed light on the mantle’s contribution to the origin of life on Earth, the generation of volcanic activity through mantle melting, and the global cycles of key elements like hydrogen and carbon.
Led by the International Ocean Discovery Program, a global marine research initiative involving over 20 countries, the team has been analyzing the sediment cores—cylindrical samples of rock, sand, and sediment from the ocean floor—that serve as a timeline of Earth’s geological history. Since the core drilling, the team has been cataloging the mantle rocks to better understand their composition, structure, and geological context.
Johan Lissenberg, a study co-author and geologist at Cardiff University in Wales, emphasized the significance of the discovery. “Recovering these mantle rocks was a monumental achievement in Earth sciences,” Lissenberg stated. “But beyond that, their real value lies in what they can reveal about the composition and evolution of our planet.” The study delves into the mineralogy and chemical makeup of the mantle rocks, with surprising results—lower levels of pyroxene and higher concentrations of magnesium, indicating more extensive melting than initially expected. This melting occurred as the mantle ascended from deeper within the Earth toward the surface. Further analysis of this process could deepen our understanding of magma formation and the mechanisms driving volcanism.
Lissenberg also highlighted the discovery of channels through which molten material traveled through the mantle, allowing researchers to trace the path of magma from its formation to its emergence at the Earth's surface. This is crucial for understanding how the mantle melts and how this process fuels volcanic activity, particularly on the ocean floor, where most of Earth's volcanism occurs.
Additionally, the preliminary analysis of the core has provided insights into how olivine, a common mineral in mantle rocks, interacts with salty seawater. This interaction triggers chemical reactions that produce hydrogen and other molecules capable of sustaining life, which scientists believe may have been a critical process in the origin of life on Earth.
Study co-author Susan Q. Lang, a geologist at the Woods Hole Oceanographic Institution, noted the importance of these findings in understanding Earth’s early history. “The rocks we recovered resemble those that were present on early Earth more closely than the rocks that make up our continents today,” Lang explained. “By analyzing them, we gain a vital perspective on the chemical and physical conditions that existed early in Earth’s history, potentially offering a consistent source of energy and favorable conditions that could have supported the earliest life forms over extended geological periods.”