Deep beneath the Atlantic Ocean, a landscape of jagged spires, small mounds, and monumental towers is home to a community of microbes, snails, and crustaceans. They all live at the bottom of the sea, some without any oxygen in the cracks and crevices of the hot springs forming these mounds, at temperatures reaching up to 104 degrees Fahrenheit. As absurd as it sounds, the Lost City Hydrothermal Field, as it is called, is real; it has been known to be located west of the Mid-Atlantic Ridge since the year 2000. The carbonate stacks and spires act as part of a huge vent system that spews hydrogen, methane, and other gases into the water around it.
The tallest vent chimney is named Poseidon, standing at 200 feet tall and emitting hot fluids (liquids and gases) from multiple outlets. There is huge variability in the sizes of the towers; next to Poseidon is a small one named Beehive that measures just three feet tall, and on its other side is a 26-foot-tall block named IMAX that has a large protruding lip and stalagmite-like growths. No sunlight reaches these rocks; anything that manages to live amongst them must do so with an alternate energy source.
The creatures that live in the Lost City are all extremophiles: they thrive in environments that are hostile to much of the life on Earth we are familiar with. Plants and animals we see on the surface of the Earth and in shallower waters all get their energy from the sun, directly or indirectly (i.e., by eating other organisms that got energy from sunlight). Energy cannot be created or destroyed; life forms are just converting it from one form to another. Plants like trees, ferns, and grass, for example, take light energy and convert it into chemical energy, which is a more usable form for them. Animals then consume the chemical energy stored in plants, thus indirectly accessing energy that came to Earth from the sun. The creatures in the Lost City, however, have been living off of the hydrocarbons coming from the carbonate chimneys. The nutrients they depend on were produced not by interactions with sunlight, but by reactions underneath the ocean floor.
This characteristic of the Lost City’s inhabitants means that it might be a good model for how life could exist on other planets. For example, Enceladus—a moon of Saturn with a liquid ocean beneath an icy outer layer—may have such an environment on one of its ocean floors. Even more intriguing is that this form of life may give us clues about how life first formed on Earth billions of years ago. Life back then was very different from the life we know now, but basic mechanisms for catalyzing chemical reactions (essential for metabolism) and passing on genetic information must have existed in some form. The origins of life is an elusive, difficult field to study, and any clues that can help us piece together how biological systems came about from inorganic molecules are exciting steps for the scientific community.
Although the Lost City was discovered decades ago, a study was published this July in Geochemistry, Geophysics, Geosystems reporting on a 1268-meter-deep (4160 feet) borehole sample that was drilled right next to the hydrothermal field. Studying the rock and seawater below it is what yields information about what environment and reactions produced the hydrothermal fluids ejected by the chimneys. As beautiful and intriguing as this underwater fantasy landscape is, the fluids it produces and the ecosystem it feeds can teach us even more intriguing things about the nature and origin of life.
