Researchers Drill Deepest Rock Samples from Earth’s Mantle with a Drill Penetrating 1.2km into the Mid-Atlantic Ridge.
The core samples were extracted during the International Ocean Discovery Program 2023. Researchers aboard the JOIDES Resolution drilled into the Atlantic Mountain range at the Mid-Atlantic Ridge, where the ocean floor is spreading and mantle rock is pushing up to the surface. The drilling site is located near the “Lost City”, a hydrothermal vent field filled with tower-like and honeycomb structures that release methane and hydrogen into the seawater. Many microorganisms thrive on these molecules, supporting small invertebrate populations such as sea slugs and tube worms.
Mantle rock observed under a petrographic microscope. (Photo: Johan Lissenberg).
The mantle rock is quite fragile and prone to breaking apart, which can clog the drill bit, but the research team was fortunate to collect samples successfully. They began pulling intact sections up to 5 meters long from the borehole. In total, they obtained more than 7% of the 1.2km long core, far exceeding expectations, according to William Brazelton, a microbiologist at the University of Utah. The research team had to hammer the rock nearly 24 hours a day during the two-month drilling project.
In this rich hydrothermal vent area, the interaction between mantle rock and seawater generates crucial chemicals for life. Previous efforts to drill into mantle rock only reached a depth of 201 meters, which was insufficient to search for biological organisms such as thermophilic bacteria, according to Gordon Southam, a geomicrobiologist at the University of Queensland in Australia and co-author of the study describing the core samples published in the journal Science on August 8.
“Each time the drill retrieves another deep core sample, the microbiology team collects samples to culture bacteria to determine the limits of life in the deep subsurface marine ecosystem,” Southam stated. “Our ultimate goal is to enhance understanding of the origins of life and clarify the potential for life beyond Earth.”
The rock core may also answer many questions about the movement of the mantle, according to Johan Lissenberg, a geochemist at Cardiff University in the UK and the lead author of the study. From rock samples ejected by underwater volcanoes, researchers noted that the mantle consists of a diverse array of rock components, stemming from the recycling of tectonic plates within the Earth.
With the new mantle samples, Lissenberg and colleagues can examine the diversity of the rock materials, subsequently reconstructing the processes through which different sections of the mantle melt and how they shift toward the surface. So far, the research team has found that instead of moving vertically, they are moving diagonally toward the surface.