Scientists from Yale University and Singapore have developed a new model to estimate when Earth’s oceans became less acidic, allowing life to begin.

Their research connects many complex Earth processes to paint a clearer picture of how our planet became habitable.

“This study bridges a big gap between surface changes and deep Earth processes,” said Jun Korenaga, a Yale professor and co-author of the study published in Nature Geoscience.

“It’s the most detailed model yet for understanding how ocean acidity changed over time.”

Acidity is measured by pH, which tells us how many hydrogen ions are in water.

A lower pH means higher acidity. Modern seawater has a pH of about 8, but scientists believe Earth’s early oceans were much more acidic.

Since life struggles to form in highly acidic environments, it’s important to know when and how ocean pH became more neutral.

Meng Guo, the study’s lead author and a researcher at Nanyang Technological University in Singapore, explained the challenge. “Modeling ocean pH over long periods is difficult because it involves almost everything—the atmosphere, oceans, Earth’s crust, and even its deep interior.”

One key factor is carbon dioxide (CO2) in the atmosphere. CO2 affects ocean acidity and is influenced by many things. For example, CO2 reacts with land and ocean rocks, pulling it out of the air. However, volcanic eruptions release more CO2, raising acidity.

To build their model, the researchers carefully analyzed how these processes worked together over time. They used recent studies on early Earth tectonics (movement of Earth’s crust) and magma oceans (molten rock covering the planet’s surface in its early days).

Their results suggest that Earth took about 500 million years to make its oceans neutral enough for life to thrive. While small pockets of neutral water may have existed earlier, they weren’t widespread enough to support life on a large scale.

This research not only helps us understand the origins of life on Earth but also gives insight into modern climate changes. The processes that shaped Earth’s early environment still play a role in today’s climate system.

The study was supported in part by a NASA astrobiology grant, showing its importance in understanding both our past and the potential for life on other planets.