Tuesday, April 14, 2015

A Possible Site For the Origin of Life

Scientists have proposed different theories about where life originated. Proposed sites for life’s origin range from deep sea thermal vents to subglacial lakes to exoplanets. Today I will introduce one of the theories, the “hydrothermal vent” theory.

Before introducing this theory for the origin of life, I would like to first introduce the concept of “extremophiles.” Extremophiles are organisms that can survive in and even favor extreme environments. For example, there are thermophiles that can thrive at temperatures between 45–122 °C, and xerophiles that can grow in extremely dry conditions. Since these extremophiles can live in such environments, they indicate the range of conditions suitable for life, and thus they provide precious clues for scientists who are investigating the possible environments in which life may have originated.

Hydrothermal vents

The proponents of the hydrothermal theory believe that the complex, high-pressure environment around deep-ocean vents may have been where life began. In 1977, a warm spring on the seafloor hosting a rich ecosystem was discovered by researchers using the submarine Alvin. Two years later, researchers on-board Alvin found a hydrothermal vent, an ancient chimney-like structure that enriched the surrounding seawater with minerals and heated it to 340°C. Around the vent was a prosperous biological community, which was unexpected because of the lack of sunlight and the extreme water pressure. Before the discovery, most scientists thought that life could not exist without the energy of the sun. However, this oasis had rich amounts of clams, crabs, sea anemones, and bacteria which have evolved their own ways to survive in the deep, cold environment without exposure to daylight. Because this discovery was totally unexpected, many scientists began to consider whether hydrothermal vents were where life might have originated on earth.

Therefore, these scientists started to carefully investigate the organisms living in the ecosystem around the hydrothermal vents. These organisms are thermophiles. During the investigation, the scientists found a thermophilic bacteria, A. Pyrophilus, that seems to be the closest living relative to LUCA (the Last Universal Common Ancestor). This finding suggests that life might originally have arisen under high-temperature conditions, perhaps in deep-sea hydrothermal vents.

The existence of organisms that are able to survive under extreme conditions has given scientists added motivation to explore the mystery of the origin of life. By understanding and researching extremophiles, scientists might be able to find the truth of the origin of life.


- Cora Wu