Earth's oceans may have been green for billions of years until the first photosynthetic organisms flooded our atmosphere with oxygen.

For most of human history, Earth has been known as the “Pale Blue Dot,” a term popularized by astronomer Carl Sagan when referring to the iconic 1990 image taken by Voyager 1. But for billions of ...

St. Patrick’s Day usually conjures images of partying, Catholicism, Irish nationalism and, perhaps most famously, the color ...