The origin of life and oxygenic photosynthesis
Speaker: Mike Russell (Jet Propulsion Laboratory, NASA)
The early Earth was a “water world”—one ocean enveloped the entire planet. The atmosphere then consisted mostly of the greenhouse gas, CO2. Warm alkaline springs continually exhaled into this carbonated ocean carrying that most effective of fuels, hydrogen. The H2 and CO2 reacted together, and with hydrothermal ammonia, to produce organic molecules in one of the many mounds precipitated at these springs on the seafloor. The organic molecules so produced then reacted together to form ever more complex organic molecules, eventually reproducing as the first organic cells within this hydrothermal hatchery. The acetate and methane wastes generated during this early biosynthesis were discharged into the ocean. Bacteria migrated from the mound into the deep biosphere where some were carried by ocean floor spreading into the photic zone. Here a few managed to exploit the solar flux, even gaining H2 for biosynthesis from the photolysis of water.