“This is an example of a type of ecosystem that could be active on Enceladus or Europa right this second,” microbiologist William Brazelton told Anna Kusmer of The Smithsonian in 2018.
The towers of pale carbonate that are almost 700 meters into the Atlantic near the peak of a submerged mountain mimic the remnants of a structure in the beams of an ROV. The Lost City Hydrothermal Field was discovered in 2000 and is neither a smouldering volcanic smelter, as are the more famous “black smokers.” It is a gradual, constant chemical engine-an environment, which has expelled over 120,000 years, the longest-lived of all the hydrothermal systems known in the ocean.
The construction of Lost City is serpentinized: the seawater moves through uplifted mantle rocks, the minerals in the rocks restructure, and the alkaline fluids-modified by alkaline fluids move back to the sea floor with hydrogen, methane, and other dissolved gases. The plume is not scalding but can be as warm as 40degC, though the system will be producing chemically strong fluids. The reaction provides the “fuel”of life in the absence of sunlight, oxygen, and a nearby magma chamber, and uses the mantle of the Earth represented by the seawater instead. With time, the minerals solidify and form chimneys which may take several millennia to grow with a monolith that exceeds 60 meters high called Poseidon.
It is important that chemistry has to be involved at all since the building blocks are not stolen by the surface world. Scientists have demonstrated that hydrocarbons can be produced by seawater, which reacts with rocks under the vent field, which does not require photosynthesis. Fissures and porous carbonate provide microbial communities in the Lost City transforming the compounds into metabolism creating an ecosystem where standard food webs would not operate. Snails and crustaceans cluster in the vents which “weeping” ; the larger animals are more occasional, yet the field still shows as being alive busy, patched and strange.
A factor that made Lost City draw scientists back is the difference it has with the black smokers, both in ingredients and implications. Black smokers are iron and sulfur-rich in minerals and may have an extreme temperature release. The carbonate chimneys of Lost City by comparison are connected to fluids that produce much more hydrogen and methane, which have been reported as 10 to 100 times more than typical black smoker systems, and thus makes it an interesting model of early life on Earth and of ocean planets where rock and water are brought together in the dark.
In 2024, scientists announced the largest recovery ever made at the site: a 1,268-meter (4,500 ft) core of mantle rock that drilled out of the Lost City region. Hopefully such material would preserve the mineral conditions that might have contributed to the formation of the earliest organic chemistry and allow investigators to test theories of the evolution of life origin in rock-based processes instead of in sunlit surface waters.
In the case of Lost City, however, protection is not merely a theoretical discussion, as this is in the high seas- no longer ruled by any individual nation. It is located in an Ecologically or Biologically Significant Marine Area and has been considered as a potential World Heritage site but the management has been complicated. Fishing is not the prevailing industrial issue in the region but the exploration of mines along the Mid-Atlantic Ridge whereby plumes of sediment and discharges can move long distances beyond a drill site as well as drift across habitats never to be charted in any intensive manner.
The most disturbing aspect of Lost City is, perhaps, its rarity: decades of ocean exploration were spent, but it is, nonetheless, the only hydrothermal field of its type that has been confirmed and examined with the help of ROVs. Within an ocean where most of the mountains are never visited, the white towers serve as a reminder that the most significant chemistry of the planet can go unexplored, hidden out of view, and decisions on the sea bottom around the towers can be determined many miles above.
