aliquots of the samples should be released from the confines of the Mars Quarantine Facility unless warranted by ongoing biological studies, and the samples are sterilized.

COMPLEX anticipates that even if the martian samples are found to contain viable life, certain types of studies in specialized laboratories outside the quarantine facility will be desirable. Samples should be removed from the quarantine facility for this purpose only after they have been sterilized and effective sterilization has been certified (Chapter 5).

No Evidence of Biological Activity

The samples returned from Mars may be shown to be altogether barren of organic matter, containing no detectable organic carbon compounds and displaying no evidence of metabolic-like activities or potential infectivity, or any other evidence of past or present biologic activity. In this event, certification of unsterilized aliquots of the samples for release and study beyond the confines of the quarantine facility would be justified.

Uncertain Evidence (Considered the Most Likely Case)

The samples returned from Mars may be shown to contain small amounts of organic matter and/or evidence suggestive of viable or recently dead microbial life. Given the difficulties inherent in achieving and maintaining a stringently sterile and organically clean environment, such evidence of biological activity might represent terrestrial contamination, introduced during sample collection and/or processing. But because the nature of martian life (if any) is completely unknown, the source of the biological signal would have to be rigorously ascertained. Until the possibility of martian life is ruled out, unsterilized aliquots of the samples should not be released for study outside the quarantine facility.

This is by far the most likely outcome of the preliminary examination of the Mars samples. In the climate of desire to find life in the samples, researchers examining them will be reluctant to declare them unmistakably barren of viable entities, organic matter, or structures that might be fossils. The samples will be sufficiently complex to contain equivocal evidence of life, even if it is spurious. There will be ample latitude for disagreement among workers as to the biological significance of observations made. It is quite possible that a time will never come when everyone knowledgeable about the samples is satisfied that they do not contain evidence of life. An example of this depressing state of uncertainty is seen in the recent history of study of (Antarctic) Mars meteorite ALH84001: More than 5 years after possible evidence of life in the meteorite was published,2 agreement still has not been reached on the significance of the observations.

The remainder of this chapter describes a strategy designed for the anticipated “uncertain” case: The samples do not contain unequivocal evidence of life, but the possibility of life also cannot be firmly ruled out.


This strategy for quarantine and distribution assumes that the Mars samples are found to be neither manifestly barren of organic matter nor obviously the bearers of live or recently dead organisms. The condition researchers are most likely to find is ambiguity about the evidence or lack of it for life in the samples. Because ambiguity of this sort can persist for a very long time (e.g., the debate about the significance of putative artifacts of life in martian meteorite ALH84001, just referred to), COMPLEX considers it undesirable to delay the release of returned samples in any form from quarantine for a period that will be indefinite but measured in years. Scientists who have prepared their laboratories and staffs to study the samples should be allowed to begin work on them, and the results of their studies will provide important feedback for the planning of later Mars missions. Studies in specialized laboratories outside the quarantine facility will also be essential to the continuing search for evidence


McKay, D.S., Gibson, Jr., E.K., Thomas-Keprta, K.L., Vali, H., Romanek, C.S., Clemett, S.J., Chiller, X.D.F., Maechling, C.R., and Zare, R.N. 1996. Search for past life on Mars: Possible relic biogenic activity in martian meteorite ALH84001. Science 273:924.

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