Something about the ocean floor has always resisted our imagination. We’ve mapped more of Mars than we have of the deep Atlantic, which means that in December of 2000, when a research team scanned an underwater mountain range west of the Mid-Atlantic Ridge and spotted something unexpected rising from the dark, they were not prepared for what they’d found. Nothing in the scientific record looked anything like it.
What they encountered, 2,300 feet below the surface, was a lost city underwater: a vast field of ghostly white towers, some barely toadstool-sized and others soaring nearly 200 feet tall, venting hydrogen and methane into the black water around them. The structures weren’t built by anyone. They grew, through a chemical reaction between seawater and the ancient rock of the Earth’s mantle, over a period scientists now estimate at more than 120,000 years. The field had been down there, in the dark, doing its thing, since long before our species learned to bury its dead.
More than two decades of research later, the Lost City Hydrothermal Field remains the only place like it that remotely operated vehicles have ever found. Its spires don’t just hold geological records. Scientists believe they may hold the answer to the oldest question there is: how life on this planet got started in the first place.
A City Built by Chemistry, Not Civilization
The research team aboard the RV Atlantis, operated by the Woods Hole Oceanographic Institution, made that initial discovery using sonar and remotely operated cameras. ScienceAlert has documented the site’s core characteristics extensively whose coverage of the 2024 Science paper brought renewed attention to the field.
The Lost City Hydrothermal Field sits on the Atlantis Massif, at the intersection of the Mid-Atlantic Ridge and the Atlantis Transform Fault in the Atlantic Ocean. The Atlantis Massif is a seafloor mountain approximately the size of Mount Rainier. It’s a dramatic address for one of Earth’s most unusual features, but the location matters – the geology of that particular intersection is what makes the whole phenomenon possible.
Unlike typical hydrothermal vents, which are powered by volcanic heat, the Lost City relies on chemical energy from the Earth’s mantle. The process driving it is called serpentinization, which sounds like something out of mythology but is, at its core, a reaction between seawater and a type of mantle rock called olivine. The hydrogen formed by that reaction is a powerful source of energy that may have fueled the formation of the first building blocks of life on Earth.
The towers range in height from tiny stacks the size of toadstools to a grand monolith standing 60 meters, nearly 200 feet, tall. The tallest of the Lost City’s formations has been named Poseidon, after the Greek god of the sea. Nearby, researchers from the University of Washington have described a cliffside area where fluid “weeps” out to form delicate, finger-like carbonate growths. Under the lights of a remotely operated vehicle, their creamy carbonate walls and columns appear ghostly blue.
The site is estimated to be older than 120,000 years based on radiocarbon dating of the oldest chimney deposits in the field. That figure is significantly younger than the Atlantis Massif itself, which may be as old as two million years, meaning the mountain that hosts the Lost City has been there since before our genus existed, and the city built itself on top of that mountain while modern humans were still learning to make tools from bone.
The Kind of Life That Rewrites the Rules
What makes the Lost City extraordinary is not just the scale of the structures. It’s what lives inside them.
The most intriguing aspect of the Lost City is its ability to support microbial life in the absence of sunlight and oxygen. At the site, microorganisms survive by consuming methane and hydrogen, chemicals produced by reactions between seawater and mantle rock. The chimneys essentially act as slow-burning chemical engines, and an entire community of organisms has organized its existence around them. Methanosarcinales-like archaea form thick biofilms inside the vents, subsisting on hydrogen and methane; bacteria related to the Bacillota also live inside the vents.
But it’s not only microbes. Chimneys spewing gases as hot as 104°F are home to an abundance of snails and crustaceans. Larger animals such as crabs, shrimp, sea urchins, and eels are rare, but still present. Life in the Lost City doesn’t follow the logic we grew up with – the logic that puts the sun at the center of every food chain. Here, the energy source is deep in the rock, and everything else adjusts accordingly.
This matters enormously for how scientists think about the origin of life. The hydrocarbons produced by the Lost City’s vents were not formed from atmospheric carbon dioxide or sunlight, but by chemical reactions on the deep seafloor. Because hydrocarbons are the building blocks of life, this leaves open the possibility that life originated in a habitat just like this one. Not in a warm pond or a lightning strike, as older theories suggested, but in an alkaline crack in the ocean floor, fed by rock and chemistry and unimaginable pressure.
Not Like the Black Smokers
It helps to understand what the Lost City is not, because the contrast is the whole story.
The Lost City differs significantly from black smokers, another type of underwater volcanic vent often discussed as a possible origin point for life. While black smokers rely on heat from magma and produce mostly iron and sulfur-rich minerals, the Lost City’s vents generate up to 100 times more hydrogen and methane, and its calcite structures are far larger, suggesting they’ve remained active for a much longer stretch of time.
Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City, making it older than all known black smoker vents by at least two orders of magnitude. Two orders of magnitude. That’s not a small difference – that’s the difference between a photograph and a geological era. The black smokers are new. The Lost City is ancient, and its age is part of why scientists find it so compelling as a candidate for the place where life itself began.
What 2024 Dug Up
The scientific momentum around the Lost City accelerated significantly in the last two years. The drilling happened in 2023, and the first major scientific results were published in the journal Science on August 8, 2024, in a paper titled “A long section of serpentinized depleted mantle peridotite.” The core – about two-thirds ultramafic mantle rock and one-third gabbroic intrusions – recorded more melting in its history than expected and showed hydrothermal fluid-rock reaction running through its entire depth, with alteration patterns matching the chemistry of the Lost City fluids venting nearby.
The mantle, it turned out, was not lightly serpentinized – it was serpentinized to perhaps 80 to 90 percent through a layer at least 1.2 kilometers thick. For researchers trying to understand what the chemical conditions of early Earth might have looked like, the rocks in that core are as close to a time capsule as geology can offer. The 2024 recovery was a record-breaking 1,268-meter-long core sample. It’s hoped the core could provide crucial evidence on how life emerged on Earth billions of years ago under conditions preserved in the minerals.
The implications run beyond Earth. NASA’s Europa Clipper, launched in October 2024, carries instruments designed to probe exactly that ocean-rock chemistry, looking for the same serpentinization signatures on Jupiter’s moon Europa that exist inside the Lost City today. The conditions at the bottom of the Atlantic, in other words, are now being used as a template for what life-supporting environments might look like on other worlds. The microbes thriving inside those carbonate chimneys may be the closest analogue we have to whatever is happening beneath the ice of Europa right now.
Read More: The Most Isolated Inhabited Island on the Planet Can Only Be Accessed via a Six-Day Ship Voyage
The Threat That’s Already Here
The Lost City sits in international waters, which sounds like it should confer some kind of protection. It does not. In 2018, Poland was granted mining rights in the area surrounding the vent field by the International Seabed Authority. The hydrothermal chimneys themselves don’t contain valuable metals, but that’s almost beside the point. Nearby mining activity could stir up sediment plumes capable of smothering the fragile environment.
Marine geologist Deborah Kelley, who led multiple expeditions to the site, has warned that just disturbing the surrounding seafloor could be enough to irreparably harm the vents and the organisms they host. The ecosystem’s complexity – 120,000 years of biological and chemical development – could unravel faster than we could document what we’d lost.
Because of its unique natural beauty and scientific significance, the Lost City hydrothermal field is under consideration for special protection by the UNESCO World Heritage Centre and the International Union for Conservation of Nature. The Convention on Biological Diversity has designated the Lost City as an Ecologically or Biologically Significant Marine Area, recognizing its importance for biodiversity and scientific research. Scientists and conservationists have urged UNESCO to designate Lost City a World Heritage Site, but no formal protections are in place as of 2025.
That gap – between what scientists know the Lost City is worth and what international law currently does to protect it – is the thing that keeps the researchers who study it up at night. The field has survived for 120 millennia. It may not survive the next decade of policy delays.
What This Place Might Tell Us
There’s a tendency to frame discoveries like this in terms of what they could mean for humanity’s future – a potential source of insight for astrobiology, a new model for understanding pre-biotic chemistry. Those things are real. But the Lost City is also remarkable on its own terms, as a place.
In 2018, microbiologist William Brazelton told The Smithsonian that “this is an example of a type of ecosystem that could be active on Enceladus or Europa right this second,” referring to the moons of Saturn and Jupiter. That framing – an ecosystem active right now on other worlds – is one of the stranger ideas in contemporary science to actually be taken seriously by serious scientists. The Lost City isn’t just old. It’s a working model of something that may be happening across the solar system at this very moment.
There are several arguments to be made that the transition from geologically produced organic molecules to biologically produced organic molecules occurred at alkaline, serpentinite-hosted hydrothermal vents similar to those at the Lost City. Knowing the conditions that lead to the production of organic compounds through non-biological chemistry is critical to understanding the conditions in which life arose.
A Find We Can’t Afford to Lose
The word “discovery” tends to imply something finished – a moment that already happened, filed away and accounted for. The Lost City is the opposite. Every expedition brings back something that reshapes what the previous expedition thought it understood. The 2024 core sample alone changed how researchers think about the depth and extent of the serpentinization happening under the Atlantis Massif. The field is not a static artifact. It’s an ongoing process that has been running for longer than our species has existed.
What makes the situation urgent is precisely that: there’s still so much to learn, and the window to learn it may be closing. Mining exploration rights already ring the field. Formal international protections haven’t materialized yet. The scientific community is clear about what’s at stake – not just for understanding how life began on this planet, but for what we might recognize as life when we eventually look for it elsewhere.
Some questions are so large that humans have spent their entire recorded history circling them without ever getting close. The Lost City is, right now, the closest we have ever gotten to understanding where the first living thing on Earth came from. What happens to it next is a decision that will have to be made by people who are alive today. That’s either a sobering thought or a motivating one, depending on how you’re inclined to hold that weight. What it cannot be is someone else’s problem to solve later, because later is already closer than the policy calendars suggest.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.