Researchers have successfully extracted the deepest rock sample ever from the Earth’s mantle, drilling 0.7 miles beneath the sea floor at an underwater mountain on the Mid-Atlantic Ridge. This location, rich with hydrothermal vents, represents a crucial area where the oceanic crust is being formed and spread apart.
Previous attempts to drill into mantle rocks exposed on the deep sea floor have achieved a depth of only 659 feet.
Gordon Southam, a geomicrobiologist from the University of Queensland and co-author of the study, notes that the previous depth was insufficient for detecting heat-loving bacteria. However, the new samples could offer valuable new insights.
“Each time the drillers extracted a new segment of deep core, our microbiology team gathered samples to culture bacteria and explore the boundaries of life within this deep-sea environment,” Southam explained. “Our primary objective is to enhance our understanding of life’s origins and to assess the potential for extraterrestrial life.”
Additional insights into mantle dynamics can be obtained from analyzing rock core samples. The new mantle sample allows researchers to understand the melting processes of various mantle components and their ascent to the Earth’s surface.
Researchers have discovered that the melts followed a steep, diagonal trajectory towards the surface, rather than moving in a vertical direction.
In 2023, scientists from the International Ocean Discovery Program embarked on a research expedition aboard a vessel, where they conducted drilling operations in the Atlantic Massif region of the Mid-Atlantic Ridge.
At this location, the ocean floor is undergoing a separation, causing mantle rocks to ascend to the surface. Drilling operations were conducted near the ‘Lost City,’ an area known for its hydrothermal vents that emit methane and hydrogen into the ocean.
Numerous microorganisms rely on these molecules for their survival, which in turn supports small invertebrates such as snails and tubeworms. The presence of life around hydrothermal vents is particularly fascinating, as these vents are unique on Earth in that they use inorganic compounds from the planet itself, rather than sunlight, as the primary energy source for sustaining life.
The team successfully retrieved substantial, intact mantle fragments measuring up to 16.4 feet. Typically, mantle rock is quite delicate and often breaks into small pieces that can obstruct drill bits. However, this time, they experienced a stroke of luck, and the drilling process proceeded smoothly without any issues.
During the two-month drilling project, microbiologists worked tirelessly, using sledgehammers nearly around the clock. They successfully extracted over 70% of the core from a 0.7-mile section.
William Brazelton, a microbiologist at the University of Utah and co-author of the study, stated, “The nearly continuous recovery to a depth of [0.7 miles] offers a valuable chance to explore how microbial diversity, abundance, and activity vary with depth and temperature, including temperatures nearing the limits for life.”
The study was published in the journal Science.
