A human-occupied vehicle (HOV) probing the deep Pacific Ocean has cast a light upon a massive undersea ‘metropolis’.
The tortuous system of deep craters and dolomite walls blows the Atlantic Ocean’s famous ‘Lost City’ out of the water.
Through a curtain of falling marine ‘snow’, the ghostly carbonate walls and jagged rocks around twenty hydrothermal vents shimmer in the heat – almost as if they were a deep-sea mirage.
At 11.1 square kilometers (4.3 square miles), the newly discovered hydrothermal field is over a hundred times larger than its Atlantic counterpart.
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The Lost City, with its jagged landscape of towers and turrets, was discovered near the mid-Atlantic ridge in 2000, and it was once the largest field of hydrothermal vents known anywhere in the world.
Related: ‘Lost City’ Deep Beneath The Ocean Is Unlike Anything We’ve Seen Before on Earth
It now lies in the shadow of another major aggregation of vents discovered on the whole other side of the world, northeast of Papua New Guinea.
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Researchers at Laoshan Laboratory and the Chinese Academy of Sciences (CAS) have named the Pacific counterpart the Kunlun hydrothermal field.
Like the Lost City, their discovery is a rarity, and it may be an even better example of how life first started on Earth.
Kunlun’s unique seafloor is gushing hydrogen-rich fluids at temperatures under 40°C – much colder than the ‘black smokers‘ of other hydrothermal vents, which resemble underwater chimneys.
Kunlun’s rich hydrogen fluids are thought to resemble the ‘hot soups’ that existed on Earth billions of years ago, when life first began. This makes the location a perfect backdrop for further research on how biological life may form from inorganic matter.
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“What’s particularly fascinating is the ecological potential,” says marine geochemist Weidong Sun from CAS.
“We observed diverse deep-sea life thriving in this environment, including shrimp, squat lobsters, anemones, and tubeworms – species that may rely on hydrogen-driven chemosynthesis.”
Based on an analysis of the hydrothermal field, researchers estimate that Kunlun contributes up to 8 percent of the flux in abiotic hydrogen across all the world’s submarine sources.
That is a huge contribution from just one system, according to Sun and colleagues, led by marine geologists Lianfu Li and Hongyun Zhang from the Laoshan Laboratory.
Unlike the Lost City, which is marked by thin, jagged towers of dolomite, the craters at Kunlun can stretch hundreds of meters in diameter and plummet more than 100 meters deep. Even the shallower depressions are typically deeper than 30 meters.
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“Compared to the carbonate towers formed in the Lost City, these pipes/pits provide a more sustained and stable evolutionary time frame, offering a potentially more suitable environment for the evolution of early life,” the team argues.
The Kunlun pipes were formed when seawater penetrated Earth’s mantle, the interaction between fluid and rock releasing heat and hydrogen. The first stage of formation would have probably resulted in a major explosion, creating a crater. Then, as fractures formed in the rock, more saltwater reactions led to more hydrogen.
Over time, carbonate sediment gradually sealed these channels until the hydrogen started to accumulate again, causing more minor explosions.
The vents are expected to eventually go ‘extinct’ once seawater can no longer probe the depths and interact with hydrogen-rich materials below.
To date, scientists have discovered most hydrogen-rich vents near spreading tectonic plates. Kunlun, however, sits 80 kilometers west of a trench, within the Carolina Plate.
The researchers note that this system, flourishing with deep-sea life, may also be an “ideal target” for retrieving deep-sea hydrogen as an energy source.
“The Kunlun system is unique not just because of the exceptionally high hydrogen flux we observed, but also because of its scale and geological setting,” says Sun.
“It demonstrates that serpentinization-driven hydrogen generation can occur far from mid-ocean ridges, challenging previous assumptions.”
Perhaps there are more undersea metropolises like Kunlun waiting to be found in the ocean’s abyss.
The study was published in Science Advances.
