Earth's oceans were once green, according to a new study. Carl Sagan, the host of the popular TV show Cosmos, once described Earth as a 'pale blue dot' when explaining an image taken by Voyager 1.

The study suggests that the oceans were not blue, as they are today, but rather a vibrant green. The study, published in Nature, focuses on a critical period in Earth’s history: the Archaean eon ...