A REEXAMINATION OF AMINO-ACIDS IN LUNAR SOILS - IMPLICATIONS FOR THE SURVIVAL OF EXOGENOUS ORGANIC MATERIAL DURING IMPACT DELIVERY

Using a sensitive high performance liquid chromatography technique, we have analyzed both the hot water extract and the acid hydrolyzed hot water extract of lunar soil collected during the Apollo 17 mission. Bo th free amino acids and those derived from acid labile precursors are present at a level of roughly 15 ppb. Based on the D/L amino acid rati os, the free alanine and aspartic acid observed in the hot water extra ct can be entirely attributed to terrestrial biogenic contamination. H owever, in the acid labile fraction, precursors which yield amino acid s are apparently present in the lunar soil. The amino acid distributio n suggests that the precursor is probably solar wind implanted HCN. We have evaluated our results with regard to the meteoritic input of int act organic compounds to the moon based on an upper limit of less than or equal to 0.3 ppb for alpha-aminoisobutyric acid, a non-protein ami no acid which does not generally occur in terrestrial organisms and wh ich is not a major amino acid produced from HCN, but which is a predom inant amino acid in many carbonaceous chondrites. We find that the sur vival of exogenous organic compounds during lunar impact is less than or equal to 0.8%. This result represents an example of minimum organic impact survivability. This is an important first step toward a better understanding of similar processes on Earth and on Mars, and their po ssible contribution to the budget of prebiotic organic compounds on th e primitive Earth.