Earth's oceans once had a completely different color 🌊

Earth's oceans may have displayed a very different color several billion years ago. This hypothesis emerges from a recent study conducted by a Japanese team.

Researchers from Nagoya University explored how cyanobacteria, among the first photosynthetic organisms, influenced the color of Archean oceans. Their work, published in Nature Ecology & Evolution, suggests these microorganisms thrived in iron-rich waters.


During the Archean era, oceans contained high concentrations of iron from hydrothermal systems. Cyanobacteria, by producing oxygen, transformed soluble iron into insoluble iron, precipitating as hydroxides. This process altered the light passing through water, favoring green wavelengths.

These microorganisms then evolved to exploit this green light, developing red pigments like phycoerythrin. This adaptation allowed them to thrive under unique conditions, marking a turning point in life's history.

The oceans thus became the stage for a coevolution between red life and a green environment. This interaction paved the way for more complex life forms to follow. Researchers' simulations confirm these mechanisms played a key role in early life evolution.


This discovery opens new perspectives for extraterrestrial life research. Green, iron-rich oceans could indicate similar biological processes on other planets. Future space missions might target these color signatures.

The study illustrates how life and its environment interact to shape a planet's characteristics. Cyanobacteria not only transformed Earth's atmosphere but also its oceans' appearance, marking a crucial step in Earth's history.

Taro Matsuo, the study's lead, emphasizes the importance of field observations. The green waters around Iwo Island served as a model to understand Archean ocean conditions. This research fills a gap in our understanding of Earth's early evolution.