"Life exists on Earth because of a delicate combination of chemical
ingredients. Using a theoretical model, Glaser is hypothesizing the
existence of adenine in interstellar dust clouds. Those same clouds
may have showered young Earth with adenine as it began cooling
billions of years ago, and could potentially hold the key for
initiating a similar process on another planet."

http://www.sciencedaily.com/releases...1002113036.htm

Double-A