Billions of years ago, our planet looked very different, including its coloring. New research suggests that early oceans were ...

Blue-green algae, also called cyanobacteria, were one of the earliest life forms on Earth and contributed heavily to the oxygenation of the planet.

Were Earth’s oceans once green? (Image credit: 100Y Design via Shutterstock) Nearly three fourths of Earth is covered by oceans, making the planet look like a pale blue dot from space.

Nearly three fourths of Earth is covered by oceans, making the planet look like a pale blue dot from space. But Japanese researchers have made a compelling case that Earth’s oceans were once ...