Green oceans on early Earth, shaped by iron, pushed microbes to evolve light-absorbing tools that worked in green light.

Researchers have found that Earth’s first oceans may not have been blue at all like today. Instead, they may have gleamed in shades of green for billions of years. Although Earth formed about 4.5 ...

But Japanese researchers have made a compelling case that Earth’s oceans were once green, in a study published in Nature. The reason Earth’s oceans may have looked different in the ancient ...