How did Earth transform from a hostile, acidic ocean world to one that nurtured life?
Scientists at Yale and in Singapore have developed a groundbreaking model to estimate how ocean acidity evolved over time.
Unraveling Earth’s Habitability Through Ocean Acidity
Scientists at Yale and Singapore’s Nanyang Technological University have developed a groundbreaking model to estimate when and how Earth became habitable, with a key focus on ocean acidity.
This new theoretical model builds on previous Yale-led research, incorporating a wide range of geological and atmospheric processes. It offers one of the most detailed views yet of how Earth evolved to support life.
Connecting Surface and Deep Earth Processes
“This is a tour-de-force theoretical endeavor, bridging a longstanding gap between surface processes and processes deep in the Earth,” said Jun Korenaga, a professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences, and co-author of a new study in the journal Nature Geoscience is a monthly peer-reviewed scientific journal published by the Nature Publishing Group that covers all aspects of the Earth sciences, including theoretical research, modeling, and fieldwork. Other related work is also published in fields that include atmospheric sciences, geology, geophysics, climatology, oceanography, paleontology, and space science. It was established in January 2008.
” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Nature Geoscience. “This work presents by far the most comprehensive whole-Earth system model to estimate how ocean pH likely evolved during Earth’s history.”
pH, or “potential of hydrogen,” measures the concentration of hydrogen ions in water. A lower pH means higher acidity. A solution with a pH lower than 7 is considered acidic. While modern seawater has a pH of about 8, scientists believe Earth’s ancient oceans were much more acidic, which would have made it difficult for life to emerge.
The Complexity of Modeling Ocean pH
“To understand the origin of life, it becomes important to understand when and how Earth began hosting an ocean with a more neutral pH,” said Meng Guo, a former Yale graduate student in Korenaga’s lab who is now a presidential postdoctoral fellow at Nanyang Technological University in Singapore and first author of the new study.
“But modeling the long-term evolution of ocean pH is a notoriously difficult problem, as it involves almost all of the components of the Earth system: the atmosphere, the ocean, the crust, and the mantle,” Guo said.
How Atmospheric CO2 Shapes Ocean Chemistry
For example, ocean pH depends to a large extent on atmospheric carbon dioxide (CO2), which, in turn, is influenced by a variety of other factors. The concentration of CO2 decreases, for instance, as a result of its chemical reaction with continents, deep-sea oceanic crust — and its eventual plunge into Earth’s interior via subduction. But levels of atmospheric CO2 increase when there is volcanic activity.
For their study, Korenaga and Guo carefully calibrated and set parameters for how each of these components functioned — and then had them interact. The researchers were guided by a series of early Earth studies previously published from Korenaga’s group.
“I think the main reason why we are able to do this modeling now is that our understanding of early Earth tectonics has been drastically improved in the last few years,” Korenaga said. “That work concentrated on the evolution of continental crust and the physics of magma oceans.”
How Long Did It Take for Earth to Support Life?
Using their new model, Korenaga and Guo estimated that it would have taken Earth 500 million years to neutralize ocean acidity enough to support life. Pockets of water with more neutral pH levels may have existed earlier, but not on a large enough scale for life to take hold.
The researchers said their findings can shed light not only on early Earth processes, but also on the role those processes play in modern-day climate.
Reference: “Rapid rise of early ocean pH under elevated weathering rates” by Meng Guo, and Jun Korenaga, 10 February 2025, Nature Geoscience.
DOI: 10.1038/s41561-025-01649-9
The research was supported, in part, by a NASA astrobiology grant.
