The detection of optical asymmetry in biogenic molecules by gas chromatography for extraterrestrial space exploration: sample processing studies.

Life detection instrumentation proposed for space missions is necessarily based on fundamental properties of life as we know it. Most biological life detection experiments attempt to elicit biological activity such as metabolism, growth, or reproduction. In addition to these approaches, which could be definitive, it is desirable to attack the problem of life detection as depending on some chemical attribute, since it may be most difficult to elicit a biological response. Fortunately, the property of natural optical activity in organics is synonymous with life, and can be measured by physicochemical methods. The phenomenon of optical activity arising from the selection of one of two possible isomers in living systems has been explained previously. Its detection in extraterrestrial samples would be prima facie evidence for the existence of life. For this reason, among others, gas chromatographic methods for the detection of optical asymmetry have been investigated and developed in recent years. We have preferred the diastereomeric route using (+)-2-butyl derivatives of amino acids and recently we have successfully made and separated derivatives of carbohydrates from glyceraldehyde through some hexoses. A scheme for isolating, purifying and derivatizing amino acids from soils has been devised and applied to rich and poor soils alike. Since the operations involved are simple as shown schematically, the utility of automated wet chemical approaches in space exploration is a distinct possibility.