Hydrothermal Vents - A New Theory for the Origin of Life

Earth science

Photo by: Mandy Guo

Hydrothermal vents, first discovered in 1977 near the Galapagos islands, have sparked new discussions among earth scientists, chemists, and biologists about the origin of life. Found near mid-ocean ridges in areas that are volcanically active, hydrothermal vents form when seawater percolates into the earth's crust through cracks and porous rocks. The water is heated by underlying magma, causing high-temperature chemical reactions that remove oxygen, magnesium, and sulphates from the water. The fluids also become warmer and more acidic, causing metals such as iron and zinc to be leached from the surrounding rocks. As the heated fluids reach 400°C, they rise back through cracks and fissures in the seafloor, causing further chemical reactions to occur as they interact with the cold oxygenated seawater. Precipitates of sulphur and other materials start to form and produce metallic towers up to 55 meters tall.

Scientists were astonished to find a huge range of life present in the harsh environmental conditions of hydrothermal vents. Over 300 species have been identified, with 95% of these unique to the vent ecosystem. Certain species, such as the Tube Worm, have no close evolutionary relationship with any other species, meaning they have evolved independently over millions of years. However, a question still remains about how these life forms can survive in the absence of light needed to power photosynthesis. The answer comes from a process called chemosynthesis.

Chemosynthesis is when organisms use the energy released by inorganic chemical reactions to form sugars that can be used in respiration. Hydrothermal vents are abundant in hydrogen sulphide, and bacteria utilize this by oxidizing the hydrogen sulphide, adding carbon dioxide and oxygen to produce sugar, sulfur, and water (CO2 + 4H2S + O2 -> CH20 + 4S + 3H2O).

University College London (UCL) has become a leader in researching whether the origin of life was possible in hydrothermal vents, specifically looking at the formation of protocells. Protocells are cell-like compartments that attempt to mimic the early stages and functioning of cellular life. The researchers wanted to prove that protocells could be formed in a high-temperature, alkaline environment synonymous with that of a hydrothermal vent. The team created the protocells using a different combination of fatty acids and fatty alcohols than previously used, as this was more representative of the diverse natural environment. The researchers found that these harsh environmental conditions may be favourable for producing protocells as molecules with larger carbon chains needed heat to form protocells, and the alkaline environment was necessary for the newly formed protocells to keep their electric charge. They also discovered that the saline environment allowed the fat molecules to bond more tightly, leading to the protocells becoming more stable.

Researchers from UCL have provided evidence that life may have originated in hydrothermal vents, contrary to the main theory that suggests life began in shallow pools. Dr Sean Jordan, the study's lead author, explains, "We still don't know where life first formed, but our study shows that the possibility of deep-sea hydrothermal vents cannot be ruled out." This discovery is significant as similar environments to hydrothermal vents are present on the moons of Jupiter and Saturn, making it relevant in the search for extraterrestrial life forms. Major space agencies, such as NASA, are now closely examining this finding to bring us closer to discovering diverse forms of life beyond Earth's atmosphere.