Doldrums Fracture Zone Expedition Uncovers Dual Vent Fields

7 July 2026

The Autonomous Underwater Vehicle (AUV) The Childlike Empress, cruising alongside Research Vessel Falkor (too), before diving thousands of meters below the ocean’s surface on a mapping mission. The science team used shipboard sonar to map the region, followed by The Childlike Empress AUV to generate high-resolution maps and collect environmental data in the target area. These maps allowed scientists to pinpoint precise coordinates for SuBastian deployment, leading to the discovery of two new active hydrothermal vent fields in record time. (Image credit: Alex Ingle, Schmidt Ocean Institute)

Scientists on a 35-day research expedition onboard Schmidt Ocean Institute's RV Falkor (too) discovered two new hydrothermal vent fields in a region of the middle of the Atlantic Ocean known as the Doldrums Megatransform and Fracture Zone, which lies just north of the equator about 800 miles off the northeast coast of Brazil. This large, tectonically active system cuts across the world's longest mountain chain, the Mid-Atlantic Ridge. While many hydrothermal vents have been found along the ridge, these are the first known vent fields to be discovered in and around the Doldrums system.

Initial observations suggest both vent fields are hybrid, heat-producing “plumbing” systems combining typical volcanic venting with serpentinization, a chemical reaction that occurs when rocks from the Earth’s mantle are exposed to seawater. Only a small number of mixed vent fields with both volcanic and serpentinization-related characteristics have been discovered worldwide. The Lost City hydrothermal vent field on the Mid-Atlantic Ridge is a well-known example of hydrothermal circulation driven by serpentinization.

Two new hydrothermal vent fields have been discovered in one of the least explored areas of the Atlantic Ocean, the Doldrums Megatransform and Fracture Zone. This large, tectonically active system cuts across the Mid-Atlantic Ridge, which forms the world’s longest mountain chain. These types of vent fields are rare because of their hybrid “plumbing” systems, featuring typical volcanic venting alongside serpentinization, a chemical reaction that occurs when rocks from the Earth’s mantle are exposed to seawater. (Image credit: Schmidt Ocean Institute)

“This discovery shows why exploration still matters,” said the expedition’s Chief Scientist, Dr. Aaron Micallef, a senior scientist at MBARI (Monterey Bay Aquarium Research Institute). “Even in the Atlantic Ocean, where plate boundaries have been studied for decades, there are still places where the first close look can reveal something entirely new. This expedition showed that even in one of the most remote corners of the ocean, our planet remains alive, dynamic, and full of surprises.”

ROV SuBastian pilots collect a geologic sample from a hydrothermal vent chimney nearly 3,890 meters (2.4 miles) deep. Scientists discovered two new hydrothermal vent fields in one of the least explored areas of the Atlantic Ocean, the Doldrums Megatransform and Fracture Zone. This large, tectonically active system cuts across the Mid-Atlantic Ridge, which forms the world’s longest mountain chain. These types of vent fields are rare because of their hybrid “plumbing” systems, featuring typical volcanic venting alongside serpentinization, a chemical reaction that occurs when rocks from the Earth’s mantle are exposed to seawater. (Image credit: Schmidt Ocean Institute)

One vent field was extensive, comprising 23 hydrothermal vents, 13 of which had active black smoker chimneys. It is 99,000 square meters in size—about 24 acres, or 14 FIFA-standard football fields. At this site, the team sampled superheated fluids reaching 280 degrees Celsius (536 degrees Fahrenheit) and observed anemones, crabs, and thousands of blind Rimicaris shrimp. These animals rely on chemosynthetic bacteria that use chemicals in the vent fluids as an energy source. The second vent field, much smaller and weaker, was discovered on the expedition’s last dive with the remotely operated vehicle (ROV) SuBastian and was 170 km (105 miles) from the first vent field.

The expedition is the first time that Schmidt Ocean Institute’s new autonomous underwater vehicle (AUV), The Childlike Empress, has been used for scientific missions, demonstrating its effectiveness for quickly locating interesting seafloor features.

Chief Scientist Aaron Micallef (Monterey Bay Aquarium Research Institute) studies a rock from a massive sulfide deposit. While hydrothermal vents are individual features, with brief lifespans of thousands of years, these massive sulfide deposits are formed on a much larger scale and over far greater timescales: they are highly significant, rare to find, and of great interest to the science team. (Image credit: Alex Ingle, Schmidt Ocean Institute)

During the expedition, scientists from the Brazilian Geological Survey shared observations of a water data anomaly collected in the region in 2013, which helped the team refine their search area. The team used RV Falkor (too)‘s shipboard sonar to map the region, then The Childlike Empress to generate high-resolution maps that allowed them to pinpoint the first vent field’s exact coordinates and deploy ROV SuBastian, leading to the visual confirmation of active hydrothermal vents in record time.

The science team was surprised to observe evidence of hydrothermal fluid circulation along faults, fractures, and scarps during all ROV dives undertaken across the Doldrums system. The discovery suggests that transform systems play a more significant role than previously recognized in drawing seawater into the oceanic crust and releasing it back into the ocean, and that hydrothermal venting may be more widespread in these regions than previously thought, Micallef said.

In the Computer Electronics Lab on R/V Falkor (too), Principal Investigator David Caress (Monterey Bay Aquarium Research Institute) runs through mapping mission plans with the autonomous underwater vehicle (AUV) team. The science team used shipboard sonar to map the region, followed by The Childlike Empress AUV to generate high-resolution maps and collect environmental data in the target area. These maps allowed scientists to pinpoint precise coordinates for ROV SuBastian deployment, leading to the discovery of two new active hydrothermal vent fields in record time. (Image credit: Alex Ingle, Schmidt Ocean Institute)

The expedition was also rich with deep-sea animal encounters. On one of the dives, the team observed two elusive bigfin squids (Magnapinna sp.), the deepest-dwelling squid known for its thread-like tentacles that can measure up to 8 meters (26 feet) in length. They also captured the first footage of a particular species of barreleye fish (Winteria telescopa), a deep-sea animal famous for its translucent head and tubular eyeballs.

“We arrived searching for vents, faults, and seamounts. We leave with something even more valuable: a deeper understanding of ecosystems in one of the least explored regions of the Atlantic Ocean,” said Dr. Paula Zapata Ramirez, assistant professor at the Universidad Pontificia Bolivariana. “Every sample, every image, and every discovery brings us one step closer to understanding the hidden parts of our planet.”

Dr. Olivia Soares Pereira (Monterey Bay Aquarium Research Institute) carefully removes biological samples from the tip of a hydrothermal vent chimney recovered from a newly discovered site. The science team uses the Remotely Operated Vehicle (ROV) SuBastian to gather geologic, biological, and water samples, as well as sensor readings and push cores at depth, for analysis in the ship’s labs. (Image credit: Alex Ingle, Schmidt Ocean Institute)

“Mapping almost 147 kilometers squared at 1-meter resolution during our first AUV The Childlike Empress science mission with this team of experts rapidly uncovered hidden wonders of the deep sea,” said Schmidt Ocean Institute Executive Director Dr. Jyotika Virmani. “Serpentinization is a process in which seawater reacts with minerals in rocks, producing heat and chemical energy that allow life to thrive in the deep ocean without sunlight, so a better understanding of these systems could provide clues for finding life on other planets.”