The search for extraterrestrials must look beyond life as we know it, scientists have advised NASA. The space agency mostly hunts for life that, like on Earth, is based on water, carbon and DNA, a National Research Council committee found. The dozen committee members—specialists in genetics, chemistry, biology and other fields—instead recommend NASA consider what they call “bizarre life.” For instance, synthetic biology experiments have devised molecules that encode genetic data but that have more nucleotides than DNA or RNA do. Instead of water, aliens might employ ammonia or sulfuric acid as the basis for their life-sustaining biochemical reactions. Novel organisms might use minerals as catalysts, rather than enzymes. In their July 6 report, the council scientists singled out Saturn's moon Titan (photograph) as especially deserving of a follow-up mission because of evidence of mixtures of liquid ammonia and water in its interior.
This article was originally published with the title "Life Not as We Know It" in Scientific American 297, 3, 34 (September 2007)