Harmful Contamination

Under article IX of the OST, States are obligated to avoid the harmful contamination of space. This concept is generally understood in a broad sense, covering all possible changes of the outer space environment —unintentional or deliberate— that would result in harm to the activities of other actors. In this sense, the creation of space debris would be an example of a form of harmful contamination. It should be noted, however, that article IX does not specify what measures would be appropriate to avoid harmful contamination and when such measures should be adopted, that is to say, what degree or level of care is required of States to avoid harmful contamination.

Harmful contamination can also refer more specifically to adversely changing outer space and celestial bodies with contaminants from Earth. Similarly, article IX of the OST establishes the obligation of avoiding “adverse changes” to Earth’s environment through the introduction of extraterrestrial matter. Some consider harmful contamination and adverse changes to be separate legal concepts —the former referring exclusively to space and celestial bodies, and the latter referring only to Earth— however there are others that consider both of these concepts to be contained under the umbrella of harmful contamination; having distinguished between two types of contamination stakeholders should be aware of and seek to avoid:

• Forward contamination refers to the introduction of Earth microbes to other planets.
• Backward contamination refers to bringing extraterrestrial matter back to planet Earth in manner that would create “adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter”.