![]() Various airlock designs have been relied on in the past decades 12. Risks are exacerbated by the fact that scientific and maintenance needs of crewed missions to Mars are expected to lead to a much higher frequency of EVAs than in the current ISS program, increased from an average of around 10 EVAs a year to perhaps 3 to 6 a week 11. Conversely, backward contamination (the contamination of astronauts, or later of terrestrial ecosystems, by extant Martian life) would be most likely during ingress. Forward contamination could occur during egress, when aerosols from inside the habitat will be most prone to leaking, and during operations in a potentially contaminated suit. Planetary protection technologies should, in particular, mitigate the risks posed by extravehicular activities (EVAs). There is some urgency: dedicated technologies should be designed this decade if they are to stand a chance of being integrated into missions foreseen for the next. Strategic choices-e.g., avoiding the Special Regions (where terrestrial organisms are likely to replicate, or which have a high potential for hosting indigenous life), if some are identified, until adequately sterilized rovers have determined a near-absence of risk can be instrumental in meeting planetary protection goals, but they cannot in themselves ensure compliance to stringent bioburden requirements. One more viable approach to this problem could lie in providing space actors with pragmatic solutions to accommodate planetary protection concerns. If planetary protection recommendations are seen as too restrictive, they may be passed over. ![]() Most entities involved in space exploration have been largely compliant so far but one cannot ascertain that this will remain the case. ![]() ![]() It is, however, an advisory committee, and to date no country has integrated its recommendations into national law. COSPAR is offering more detailed guidelines. All major spacefaring countries are parties to the 1967 Outer Space Treaty, which is formally binding and whose Article IX stipulates that the harmful contamination of celestial bodies should be avoided but, as pointed out by Fairén and Schulze-Makuch 5, 10, what constitutes “harmful contamination” (or what standards should be held) is not defined, which limits the guidance and constraints this rule provides. While deciding on stringent bioburden requirements may, at first glance, seem like the safest option, it critically depends on compliance from the entities involved in space exploration. An example of the arguments put forward is that either Mars can support terrestrial life, in which case the later has most likely colonized it already (after reaching it through natural panspermia or with contaminated spacecraft), or the biocidal factors in the Martian environment 6, 7, 8, 9 are lethal to any terrestrial life form and would promptly inactivate microbial contaminants. At the other end of the debate, it has been argued that current planetary protection measures are excessive even for robotic missions 5. Deciding for the former would, it seems, mean giving up on crewed missions to Mars for the foreseeable future. Whether those goals justify retaining the limits on bioburden defined for hardware, or whether a reassessment of the risks may lead to milder requirements, is still being debated. ![]() The principles and guidelines for human missions to Mars given by COSPAR’s Policy on Planetary protection 1 include a statement that “planetary protection goals should not be relaxed to accommodate a human mission to Mars”. We suggest a concrete concept for such an adapted airlock, believing that only practical and implementable solutions will be followed by human explorers in the long run. We therefore propose to adapt airlocks specifically to the goals of planetary protection. In our view, the one nominal mission activity that is most prone to introducing terrestrial microbes into the Martian environment is when humans leave their habitat to explore the Martian surface, if one were to use state-of-the-art airlocks. With this paper, we attempt to reconcile these two conflicting goals: the human exploration of Mars and its protection from biological contamination. However, while companies and space agencies aim at getting to Mars within ambitious timelines, the state-of-the-art planetary protection measures are only applicable to uncrewed spacecraft. Protecting the Martian environment from contamination with terrestrial microbes is generally seen as essential to the scientific exploration of Mars, especially when it comes to the search for indigenous life. ![]()
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