When Cooking Up Planets, Ice Grains Add Dash of Life

Article excerpt

Life's origin on Earth inspires a lot of scientific speculation. How did molecules get together and decide to start self-reproducing? If they had known ahead of time what life would ultimately be doing, would they have changed their minds? Would they be annoyed by someone talking about mindless molecules as if they could make choices to begin with?

Obviously, the first molecules on the newborn Earth didn't possess self-awareness--or the self-replicating survival strategies that got life going. Scientists have ideas about how that might have happened but haven't succeeded in establishing any one scenario as the likely real story. But there may be an answer to another crucial question about life's origin: Where did the raw material molecules come from in the first place?

Life's key molecules--proteins and nucleic acids--are made from the complex organic molecules known as amino acids (the links in the molecular chains composing proteins) and nucleobases (ring-shaped molecules that make up DNA and RNA). Scientists can make those molecules in the lab from simpler molecules including water, carbon dioxide and ammonia. So maybe some alien chemist concocted an organic soup and delivered it to Earth once the planet was safe enough for molecules to start families. …