National Aeronautics and Space Administration Astrobiology

Ask most anyone whether life exists on other planets and moons, and the answer you’ll get is a confident “yes!” Going back decades (and in many ways generations), we’ve been introduced to a menagerie of extraterrestrials good and bad. Their presence suffuses our entertainment and culture, and we humans seem to have an almost innate belief-or is it a hope-that we are not alone in the universe. But that extraterrestrial presence on regular display is, of course, a fiction. No life beyond Earth has ever been found; there is no evidence that alien life has ever visited our planet. It’s all a story. This does not mean, however, that the universe is lifeless. While no clear signs of life have ever been detected, the possibility of extraterrestrial biology – the scientific logic that supports it – has grown increasingly plausible. That is perhaps the single largest achievement of the burgeoning field of astrobiology, the broad-based study of the origins of life here and the search for life beyond Earth. By exploring and illuminating the world of extreme life on Earth, by experimenting with how life here began, by understanding more about the chemical makeup of the cosmos, by testing for habitability on missions to Mars, Jupiter’s moon Europa, Saturn’s moon Titan, and beyond, an enormous body of science is being assembled to analyze and explain the origins, characteristics and possible extraterrestrial dimensions of life. And unlike the ETs and star-ship invaders of popular culture, these discoveries are, and will be, real.