Abstract

The possibility that the positive outcome of the Viking Labeled Release Experiment (LR) had resulted from the presence of extant Martian microorganisms in samples examined on Mars was dismissed based largely on the failure of the Viking Gas Chromatograph-Mass Spectrometer (GCMS) to demonstrate the presence of organic mole-cules. More recent findings suggesting that the Viking GCMS would have missed such molecules if present necessitates a re-evaluation of the Viking LR data as well as a continued search for organic material and life at the Martian surface. In addition to advanced mass spectrometers to look for organic signatures of biological processes, future lander missions may use biological techniques, such as immunoassay, to directly detect bio-organic molecules. Meanwhile, several decades in advance of any planned sample return missions, the examination of Mars samples already present on Earth in the form of the SNC meteorites indicates that organic matter has existed in the Martian upper crust. It is concluded that a biological interpretation of the LR on Mars cannot be dismissed and should now be considered at least as plausible as a non-biological interpretation until more complete studies of the Martian sur-face are carried out.