New research from Nagoya University reveals that Earth's early oceans were likely green rather than blue, suggesting potential markers of early life.

These findings, published in Nature Ecology & Evolution, focus on the role of cyanobacteria during the Great Oxidation Event approximately 2.4 billion years ago.

Taro Matsuo, the lead researcher, transitioned from skepticism to belief in the green ocean hypothesis after field surveys showed iron-rich waters similar to those of early Earth.

Advanced simulations indicated that the high levels of ferrous iron in the Archaean oceans altered light absorption, resulting in a green hue due to the absorption of blue and red light by iron-rich particles.

The study emphasizes the co-evolution of Earth's environment and photosynthetic organisms, highlighting the intricate relationship between life and geological processes.

Matsuo's research highlights that cyanobacteria adapted to absorb green light, allowing them to thrive in these iron-rich oceans.

Unlike modern plants that primarily rely on chlorophyll, early cyanobacteria utilized both chlorophylls and phycobilins, which facilitated their adaptation to the environment.

During this period, cyanobacteria initiated oxygenic photosynthesis, significantly transforming Earth's atmosphere and paving the way for the evolution of oxygen-dependent life forms.

Matsuo also noted that the green waters observed around Iwo Island could be detectable from a distance, potentially aiding in the search for extraterrestrial life.

The implications of this research suggest that searching for green oceans on other planets may help identify signs of primitive life.