The sea around Iwo Island, one of the Satsunan Islands off the coast of Japan, is green because of high levels of ironTaro Matsuo et al. (2025)For a long stretch of Earths history, our planet might have looked green from a distance, instead of the pale blue dot we know today.Earths 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.