Language related to planetary protection was incorporated into Article IX of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (known as the Outer Space Treaty), which entered into force in 1967:

States Parties to the Treaty shall pursue studies of outer space, including the moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter and, where necessary, shall adopt appropriate measures for this purpose.6

The United States signed and ratified the Outer Space Treaty in 1967, and so is legally bound by the treaty’s requirement to avoid harmful contamination of the Moon and other celestial bodies. The treaty was the second so-called non-armament treaty of the Cold War and was in some respects modeled on its predecessor, the Antarctic Treaty, which entered into force in 1961 (U.S. Department of State, 2004). Article IX of the Antarctic Treaty called for states that are parties to the treaty to recommend measures to further “the preservation and conservation of living resources in Antarctica.” Article IX of the Outer Space Treaty, however, is ambiguous with respect to whether its focus is on protecting celestial bodies themselves or the scientific interests of those countries exploring them.

A policy review of the Outer Space Treaty concluded that, while Article IX “imposed international obligations on all state parties to protect and preserve the environmental integrity of outer space and celestial bodies such as Mars,” there is no definition as to what constitutes harmful contamination, nor does the treaty specify under what circumstances it would be necessary to “adopt appropriate measures” or which measures would in fact be “appropriate” (Goh and Kazeminejad, 2004, p. 219). An earlier legal review, however, argued that “if the assumption is made that the parties to the treaty were not merely being verbose” and “harmful contamination” is not simply redundant, “harmful” should be interpreted as “harmful to the interests of other states,” and since “states have an interest in protecting their ongoing space programs,” Article IX must mean that “any contamination which would result in harm to a state’s experiments or programs is to be avoided” (Cypser, 1993, pp. 324-325). Both reviews, and their interpretations, are unofficial.

Current NASA policy states that the goal of NASA’s forward contamination planetary protection policy is the protection of scientific investigations (Rummel and Billings, 2004), declaring explicitly that “the conduct of scientific investigations of possible extraterrestrial life forms, precursors, and remnants must not be jeopardized” (NASA, 1999). This has been the approach taken by COSPAR for the past four decades, most obviously with respect to its idea of a finite “period of biological exploration” beyond which planetary protection measures need not extend.7 Consistent with this approach, the protection of the ability to perform scientific measurements without confounding them with false positives has been the focus of past National Research Council (NRC) examinations of forward contamination planetary protection policy for Mars. In its 1992 report Biological Contamination of Mars: Issues and Recommendations, the Space Studies Board (SSB) Task Group on Planetary Protection emphasized that “the philosophical intent of the 1978 committee [the SSB committee that had previously addressed the topic] to protect Mars from terrestrial contamination so as not to jeopardize future life-detection experiments on Mars is still profoundly important” (NRC, 1992, p. 57).

The present committee’s statement of task reads in part, “To the maximum possible extent, the [committee’s] recommendations should be developed to be compatible with an implementation that will use the regulatory framework for planetary protection currently in use by NASA and COSPAR,”8 which the committee understood as


The full text of the treaty, its membership, and related documents such as the Antarctic Treaty appear in Rauf et al. (2000), pp. 138-142 (treaty text) and pp. 241-247 (membership).


The period of biological exploration is referred to as either a defined number of years or the time to completion of a series of robotic missions to, or experiments on, Mars, during which strict planetary protection practices must be followed to protect the planet for the conduct of scientific investigations, including the search for life.


See the committee’s statement of task, reproduced in the Preface to this report.

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