Detecting pyrolysis products from bacteria on Mars

A pyrolysis/sublimation technique was developed to isolate volatile amine c ompounds from a Mars soil analogue inoculated with similar to 10 billion Es cherichia coli cells. In this technique, the inoculated soil is heated to 5 00 degreesC for several seconds at Martian ambient pressure and the sublima te, collected by a cold finger, then analyzed using high performance liquid chromatography. Methylamine and ethylamine, produced from glycine and alan ine decarboxylation, were the most abundant amine compounds detected after pyrolysis of the cells. A heating cycle similar to that utilized in our exp eriment was also used to release organic compounds from the Martian soil in the 1976 Viking gas chromatography/mass spectrometry (GC/MS) pyrolysis exp eriment. The Viking GC/MS did not detect any organic compounds of Martian o rigin above a level of a few parts per billion in the Martian surface soil. Although the Viking GC/MS instruments were not specifically designed to se arch for the presence of living cells on Mars, our experimental results ind icate that at the part per billion level, the degradation products generate d from several million bacterial cells per gram of Martian soil would not h ave been detected. (C) 2001 Elsevier Science B.V. All rights reserved.