The Timeframe when Ocean Acidity Favorable for Life's Origin
Earth's ancient oceans, about 4.1 billion years ago, harbored pockets of liquid water. However, these oceans were highly acidic, stunting life's development on our planet for its initial 500 million years. Meng Guo, a former Yale graduate student now at Nanyang Technological University in Singapore, tackles this issue as the first author of a new study. Guo explained that an acidic pH lower than 7 can disrupt the synthesis of organic molecules and harm living tissue. Modern seawater boasts a neutral pH of roughly 8.
Addressing the importance of understanding when Earth hosted a more neutral ocean pH, Guo stated that modeling its long-term evolution is challenging due to the intricate entanglement of Earth components - atmosphere, ocean, crust, and mantle. Jun Korenaga, a Yale professor, further explained that this theoretical undertaking bridged the divide between surface processes and deep Earth processes.
Ocean pH is significantly impacted by atmospheric CO2 levels, affected by volcanic degassing, weathering, and erosion. Improved understanding of early Earth tectonics, particularly the formation of continental crust and the physics of magma oceans, enabled researchers to generate a more detailed model of ocean pH evolution.
Using this model, Guo and Korenaga discovered that it took Earth roughly 500 million years to neutralize its ocean acidity, allowing for life to flourish. The oldest confirmed life signs on Earth date back to 3.5 billion years, while some experts believe that microbial fossils may be present in older hydrothermal veins. However, the model suggests that it's unlikely that these concretions are real fossils.
In conclusion, Guo and Korenaga's findings highlight the importance of early Earth processes in shaping its habitability and impacting modern-day climate. Their research not only focuses on life's emergence but also aids in predicting climate changes, potentially offering insights into mitigating ongoing and future changes.
The study led by Meng Guo suggests that science and innovation in understanding Earth's history can reveal how long it took for seawater to become less acidic, approximately 500 million years. This shift in pH, from highly acidic to neutral, was crucial for the innovation of complex life forms. The increase in ocean pH can be attributed to changes in Earth's tectonics and the formation of a less acidic crust, a significant finding in the field of DNL (Darwinian natural selection).
