Recommendation. Samples returned from Mars by spacecraft should be contained1 and treated as though potentially hazardous until proven otherwise. No uncontained martian materials, including spacecraft surfaces that have been exposed to the martian environment, should be returned to Earth unless sterilized.

Recommendation. If sample containment cannot be verified en route to Earth, the sample, and any spacecraft components that may have been exposed to the sample, should either be sterilized in space or not returned to Earth.

Recommendation. Integrity of containment should be maintained through reentry of the spacecraft and transfer of the sample to an appropriate receiving facility.

Recommendation. Controlled distribution of unsterilized materials returned from Mars should occur only if rigorous analyses determine that the materials do not contain a biological hazard. If any portion of the sample is removed from containment prior to completion of these analyses, it should first be sterilized.

Samples returned from the martian surface, unless returned from sites specifically targeted as possible oases, are unlikely to harbor extant life as we know it, and there may be some pressure to reduce planetary protection requirements on subsequent sample-return missions if prior samples are found to be sterile. Presumably, however, subsequent missions will be directed toward locations on Mars where extant life is more plausible based on data acquired from an integrated exploration program, including prior sample-return missions. Thus, planetary protection measures may become more rather than less critical as the exploration program evolves. At some point it may be reasonable to relax the requirements, but this should only be done after careful scientific review by an independent body.

Recommendation. The planetary protection measures adopted for the first Mars sample-return missions should not be relaxed for subsequent missions without thorough scientific review and concurrence by an appropriate independent body.


Pathogenesis can be divided into two fundamental types: toxic and infectious. Generally, toxic effects of microorganisms are attributable to cell components or metabolic products that incidentally damage other organisms. Certain bacteria, algae, and fungi, as well as some animals and many plants, produce substances that interact with the nervous or immune systems of animals. This


The words “contained” and “containment” are used herein to indicate physical and biological isolation.

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