Find a purple planet, and you may have spotted alien life. Some of the first Earthlings were purple bacteria that ruled the planet about 3 billion years ago. If any Earth-like exoplanets host similar microbes, their distinctive hue will be visible from space.
Previous work showed that we might be able to detect the infrared signature of vegetation on exoplanets, based on the signal given off by trees and other plants on modern Earth. Other studies suggest sniffing for gases in alien atmospheres that would only be given off by life.
But we are more likely to find microbial aliens than other kinds, because these life forms thrived on Earth for aeons before larger life forms evolved, and they will survive long after complex life dies out. Esther Sanromá at the Institute of Astrophysics of the Canary Islands and her colleagues wondered if the types of microbes that existed in our planet's past would give off a unique signature when seen from afar. If so, perhaps we could detect signs of similar microbes living on distant worlds.
Just watch out for those one-eyed, one-horned, flyin' purple people eaters! ;-) To read more, click here.