Planetary Protection: An Integral Part of Mission Preparations

Since the early years of the space program, scientists have expressed concern about planetary protection –that is, the prevention of human-caused biological cross-contamination between Earth and other bodies in the solar system. “Hitchhiker” bacteria and other organisms on spacecraft and equipment might cause irreversible changes in the environments of other planets or interfere with scientific exploration on them. In practical terms, the concerns are twofold: avoiding (1) forward contamination, the transport of terrestrial microbes on outbound spacecraft, and (2) back contamination, the introduction onto Earth of contamination or life-forms that could be returned from space. Both concerns are covered in provision of the Outer Space Treaty of 1967, as well as in NASA policies and requirements.