Earth’s oceans may have been green for billions of years
The sea around Iwo Island, one of the Satsunan Islands off the coast of Japan, is green because of high levels of iron
Taro Matsuo et al. (2025)
For a long stretch of Earth’s history, our planet might have looked green from a distance, instead of the pale blue dot we know today.
Earth’s green period, which lasted from around 3 billion years to 600 million years ago, probably shaped the evolution of the cyanobacteria that filled the atmosphere with breathable quantities of oxygen, says Taro Matsuo at Nagoya University in Japan.
