‘Lost City’ Deep under the Ocean

 Scientists uncover a ‘Lost City’ deep beneath the ocean, it is unlike anything we've ever seen before 

Beneath the vast Atlantic, hidden in total darkness, an ancient city rises from the seafloor. But this is no human ruin, it’s an alien-like world of towering carbonate spires, strange life forms and eerie venting chimneys which have been active for at least 120,000 years. Known as the Lost City Hydrothermal Field, this underwater landscape is unlike anything else ever discovered on Earth. But its greatest mystery? Close to the summit of an underwater mountain west of the Mid-Atlantic Ridge, a jagged landscape of towers rises from the gloom. Scientists believe it may hold clues to how life first began, and even hint at where we might find it elsewhere in the universe. Could this strange deep-sea wonder be the key to unlocking life beyond our planet? Their creamy carbonate walls and columns appear ghostly blue in the light of a remotely operated vehicle sent to explore. They range in height from tiny stacks the size of toadstools to a grand monolith standing 60 m (nearly 200 ft) tall. This is the Lost City. In the crushing darkness 700 m (2,300 ft) beneath the Atlantic Ocean, an astonishing world lies hidden, a labyrinth of towering structures, glowing ghostly blue in the light of remotely operated vehicles. This is the Lost City Hydrothermal Field, a place so unique that nothing else like it has ever been found on Earth. First discovered in 2000, this vast network of towering carbonate formations rises from the seafloor like an ancient fortress lost to time. Discovered by scientists in 2000, the Lost City Hydrothermal Field is the longest-lived venting environment known in the ocean. Nothing else like it has ever been found.

For at least 120,000 years and maybe longer, the up thrusting mantle in this part of the world has reacted with seawater to puff hydrogen, methane, and other dissolved gases out into the ocean. In the cracks and crevices of the field's vents, hydrocarbons feed novel microbial communities even without the presence of oxygen. The monolithic spires, formed by mineral-rich fluids seeping from the Earth’s crust, range in size from small mushroom-like stacks to Poseidon, the tallest of them all, standing nearly 60 m (200 ft) high. Unlike the more commonly known black smoker vents, which rely on magma to heat surrounding water, the Lost City’s ecosystem thrives in a completely different way. Chemical reactions deep within the Earth’s mantle drive the formation of hydrogen and methane, the essential ingredients for life, making this hydrothermal field a  scientific marvel. Strands of bacteria living on a calcite vent in the Lost City. Chimneys spewing gases as hot as 40 °C (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. Despite the extreme nature of the environment, it appears to be teeming with life, and researchers think it's worth our attention and protection. But the Lost City is more than just an awe-inspiring geological wonder. Within the cracks and crevices of its towering chimneys, strands of bacteria cling to the mineral surfaces, feeding on hydrocarbons which emerge from the vents. This ecosystem, fuelled not by sunlight but by chemical reactions, is one of the most extreme and alien environments known on Earth. And according to some scientists, it may not be limited to our planet.

In 2024 researchers announced a record-breaking recovery of mantle rock in the form of a 1,268-meter-long core sample dug from the Lost City Hydrothermal Field. 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. While other hydrothermal fields like this one probably exist elsewhere in the world's oceans, this is the only one remotely operated vehicles have been able to find thus far. The Lost City is remarkable not just for what it reveals about life in Earth’s depths, but for what it might tell us about life elsewhere in the universe. Scientists believe that environments like this could exist on distant ocean worlds, including the icy moons Europa (Jupiter) and Enceladus (Saturn), both of which harbour vast subsurface oceans beneath their frozen exteriors.

The hydrocarbons produced by the Lost City's vents were not formed from atmospheric co2 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. And not just on our own planet. "This is an example of a type of ecosystem that could be active on Enceladus or Europa right this second," microbiologist William Brazelton said The Smithsonian in 2018, referring to the moons of Saturn and Jupiter. These moons have conditions strikingly similar to those found in the Lost City, cracks in their icy crusts where chemical-rich water may be venting into the oceans below, creating the perfect environment for life to take hold. “And maybe Mars in the past.” This statement suggests an even greater possibility, that long ago, when Mars had more liquid water, similar hydrothermal systems could have supported microbial life beneath its surface. The implications are staggering: if the Lost City can sustain life in complete darkness, powered only by deep-sea chemical reactions, then perhaps similar life-forms exist in the hidden oceans of other worlds.

Unlike underwater volcanic vents called black smokers, which have also been named as a possible first habitat, the Lost City's ecosystem doesn't depend on the heat of magma. Black smokers produce mostly iron- and sulfur-rich minerals, whereas the Lost City's chimneys produce up to 100 times more hydrogen and methane. The calcite vents of the Lost City are also much, much larger than black smokers, which suggests they've been active for longer. What makes the Lost City even more extraordinary is the delicate, otherworldly structures forming around its vents. Researchers from the University of Washington have described how these vents appear to be “weeping” with fluid, creating “clusters of delicate, multi-pronged carbonate growths that extend outward like the fingers of upturned hands.” This eerie formation adds to the alien-like nature of this deep-sea realm, making it one of the most visually stunning environments ever encountered by marine scientists.

The tallest of the monoliths is named Poseidon, after the Greek god of the sea, and it stretches more than 60 meters high. Just northeast of the tower, meanwhile, is a cliffside with short bursts of activity. Unfortunately, scientists aren't the only ones beckoned by that unusual terrain. Unlike the black smoker vents found elsewhere in the ocean, which are fuelled by magma and tend to be short-lived, the Lost City is far older and more stable. Its chimneys have been active for at least 120,000 years, and possibly much longer, providing an unparalleled look into Earth’s geological past. These vents continuously pump out hydrogen and methane, key building blocks of life, at rates far greater than those found in volcanic hydrothermal systems. This unique process may explain why the Lost City has remained active for so long, and why its discovery is so important for understanding Earth’s deep history. In 2018, it was announced that Poland had won the rights to mine the deep sea around The Lost City. While there are no precious resources to be dredged up in the actual thermal field itself, the destruction of the city's surroundings could have unintended consequences. Any plumes or discharges, triggered by the mining, could easily wash over the remarkable habitat, scientists warn. Some experts are therefore calling for the Lost City to be listed as a World Heritage site, to protect the natural wonder before it's too late. For tens of thousands of years, the Lost City has stood as a testament to the enduring force of life. Despite its  scientific importance, the Lost City faces an unexpected and urgent threat, deep-sea mining. Although the hydrothermal field itself does not contain valuable resources like gold or rare metals, large-scale mining operations nearby could create plumes of sediment that drift into the Lost City, smothering its fragile ecosystem. With deep-sea mining projects expanding worldwide, researchers are calling for urgent protection measures to preserve this rare and ancient environment. Many experts believe the Lost City should be designated as a World Heritage Site to ensure its survival. If action isn’t taken soon, this scientific treasure, one that could hold the key to understanding both Earth’s past and the possibility of life beyond it, may be lost forever.

Key Findings 

No Magma Required Unlike black smokers, the Lost City does not rely on volcanic activity but instead forms through chemical reactions between seawater and the Earth’s mantle.

Longest-Lived Venting System The Lost City has been continuously active for at least 120,000 years, making it the longest-known venting system in the ocean.

Thriving Microbial Life Microbial communities flourish in the cracks of the vents, surviving without sunlight or atmospheric carbon dioxide.

Towering Carbonate Structures The Lost City features towering white and blue carbonate formations, with some as tall as 60 m (200 ft).

Rich in Hydrogen and Methane The vents release hydrogen and methane, key ingredients that could have played a role in the origins of life.

Potential Clue to Alien Life Similar hydrothermal conditions could exist on Enceladus (Saturn) and Europa (Jupiter), raising the possibility of extra terrestrial life.

For now, the Lost City Hydrothermal Field remains a living testament to the power of Earth’s geology and the resilience of life in the most extreme environments. It has stood for over 120,000 years, quietly shaping our understanding of deep-sea ecosystems, the origins of life, and the search for extra terrestrial organisms. As exploration technology advances, scientists are eager to unlock even more of its secrets, before human interference threatens its existence. Whether the Lost City will continue to inspire and reveal the mysteries of our planet and beyond depends on the decisions we make today. Hidden beneath the waves, untouched by time, the Lost City may hold the answers to some of the greatest questions in  science.