New research suggests Earth was once a purple planet. Early microbes used retinal, not chlorophyll, for photosynthesis.

While fields, forests and jungles have made green the color most associated with ... ludicrous to think that another habitable planet could be, say, purple. Start the day smarter.

Recent research suggests that astronomers should focus on detecting purple hues to identify potential signs of life on distant planets. The study reveals that light signals from exoplanets lacking ...