Biology on Mars; Before and After Viking

The data accumulated by the Viking landers failed to provide convincing evidence for the presence of an extant biota on Mars. Instead, several different experiments conducted on samples of the Martian regolith strongly suggested the presence of one or more oxidants in the surface material. These observations, together with extremely arid conditions, would appear to preclude the existence of indigenous organisms in that environment. Nevertheless, several hypothetical scenarios have been proposed for specialized environmental niches wherein microbial existence might still be occurring. Since no such niches have been identified, further in situ tests on surface material selected at random, or tests on returned samples from such sites, are not likely to yield definitive information indicating the presence of living organisms. On the other hand, with adequate instrumentation on remote-sensing and landed precursor missions, it is conceivable that one or more of the postulated specialized niches will be discovered. In that eventuality, it should be possible to devise experiments that specifically test for organisms adapted to living in those particular environments and thus avoid the ambiguity that marked some of the Viking data.

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Last Modified August 21, 1996