Deep-Sea Geology

Scientists Discover the Hidden Plumbing of the Lost City Hydrothermal Field

More than 700 meters beneath the Atlantic Ocean, the Lost City hydrothermal field has puzzled scientists for decades. Now, a record-breaking drill core has revealed the deep geological plumbing that feeds its otherworldly white chimneys — and the discovery has implications for the origin of life on Earth and beyond.

During IODP Expedition 399 in 2023, scientists aboard the JOIDES Resolution drilled Hole U1601C to a depth of 1,268 meters (4,160 feet) below the seafloor — the longest mantle core ever recovered — just 800 meters north of the Lost City vents.
Analysis of the core revealed that up to 80% of the deepest samples came from superheated water that had risen from beneath the mantle rock, providing the first direct evidence that the Lost City's hydrothermal system is fed by deep, high-temperature fluid circulation through mantle peridotites.
The findings confirm that serpentinization — the chemical reaction between seawater and mantle rock — can sustain hydrothermal activity for tens of thousands of years, creating conditions that may mirror the environment where life first emerged on Earth.

The Lost City Hydrothermal Field, discovered in 2000, is unlike the black smokers found at mid-ocean ridges. Its iconic white carbonate chimneys rise up to 60 meters tall and emit alkaline fluids rich in hydrogen and methane — a chemical cocktail produced when seawater reacts with mantle rock in a process called serpentinization. But until now, scientists could only speculate about the depth and scale of the hidden plumbing system driving these reactions.

The drill core, composed primarily of peridotite (a rock from Earth's mantle) with layers of gabbro, revealed fractures and alteration zones that serve as conduits for seawater to reach deep, hot rock. Temperature measurements and chemical analysis of fluid inclusions confirmed that water circulates to depths far greater than previously assumed, reaching temperatures high enough to drive the serpentinization reactions that sustain the vent field. The deeper the drill went, the more of the sampled water came from subterranean sources — up to 80% at the deepest levels.

Beyond explaining the longevity of the Lost City, the discovery has profound implications for astrobiology. Similar serpentinization reactions may occur on icy moons like Enceladus and Europa, where liquid water contacts rocky interiors. If hydrothermal systems like Lost City can persist for tens of millennia powered by chemical reactions alone, then the subsurface oceans of these moons may contain the same ingredients — hydrogen, methane, and warm alkaline water — that on Earth provided the energy for life's first sparks.