A volcanic field in the deep Atlantic
The Lucky Strike hydrothermal field rests on the summit of a volcano nearly 1,700 meters below the ocean surface. Located on the Mid-Atlantic Ridge southwest of the Azores, the site was discovered in 1992. It is one of the largest known vent fields, covering roughly one square kilometer inside a depression formed by three volcanic cones. This depression holds a fossil lava lake, and the field contains at least 25 active vent sites.
The vents, known as "black smokers," are mineral chimneys that blast out geothermally heated seawater. The exiting fluid can reach temperatures of 333°C. As this superheated, mineral-rich water mixes with the near-freezing deep-sea water, dissolved minerals precipitate, building the chimney structures. One of The most prominent structure, a 20-meter-high spire, is named "Eiffel Tower". The entire field is a changing environment, geologically influenced by its position near the Azores hotspot, a region of high volcanic activity. Since 2010, the site has been continuously monitored by the EMSO-Azores deep-sea observatory, which tracks seismic activity, fluid chemistry, and biological changes.
An ecosystem powered by chemistry
In the complete absence of sunlight, life at Lucky Strike depends on chemosynthesis. Bacteria and other microbes convert chemicals from the vents, like hydrogen sulfide, into energy. This process forms the foundation of a unique food web. The dominant animal is the mussel Bathymodiolus azoricus, which forms dense beds covering the vent structures. These mussels have symbiotic bacteria in their gills that produce food for them.
The ecosystem's most unusual resident is the shrimp Rimicaris exoculata. These shrimp are eyeless, an adaptation to the darkness. They congregate in dense swarms on the sides of the hot smoker chimneys. To navigate this extreme environment, the shrimp have a specialized sensory organ on their dorsal side, just beneath their carapace. This organ contains a high concentration of the light-sensitive pigment rhodopsin. It cannot form images but is extremely sensitive to the faint thermal radiation—a dim glow emitted by the 300°C vent water. This allows the shrimp to stay close enough to the vents to feed on the chemosynthetic bacteria without being cooked. Other animals found in this habitat include the shrimp Mirocaris fortunata, various species of gastropods like Protolira valvatoides, and occasionally sea urchins.