Detecting Non-Terran Life: Possible Biosignatures and Alternative Biological Lexicons of Extraterrestrial Life

Confirming the existence of extant, or extinct, life on planets or satellites other than Earth (non-Terran life) is of fundamental interest to human society, but is not a stratight-forward endeavor even when studying bodies within our own Solar System. The most likely type of life that may be found would be microbial, but it is likely that such microbial life would have evolved very differently than life on Earth. The conservative hypothesis when considering extraterrestrial ife is that such life would require (or have required) liquid water to evolve, but may have evolved a very different lexicon of builiding blocks that do not include the 5 nucleotides (for DNA and RNA) and 20 proteinogenic amino acids (for proteins) that all life on Earth uses. The selection of this chemical lexicon for life on Earth is hypothesized to be due to a combination of components available during the origin of life and the billions of years of selection pressure that Earth's particular environment imposed. Neither of these factors (initial components available and environmental conditions) would be the same for non-Earth locations, and this combined with experimental evidence showing that alternative nucleotides and amino acids can be used to build functional biological polymers and microbes, strongly suggest that non-Terran life may look very different than life as we know it. This presentation will review current strategies for detecting extraterrestrial life, including agnostic biosignatures, and summarize the work our laboratory is pursing analyzing unnatural amino acid stability and terrestrial analogue sites in relation to detecting life as we don't know it.