Progress in Planetary Protection Development for Crewed Mars Missions

It is widely accepted that the current Planetary Protection (PP) paradigm developed for robotic spacecraft needs to change ahead of the first crewed mission to Mars. Assessing spacecraft microbial cleanliness against a quantitative bioburden threshold at launch is just not relevant for the habitable spacecraft environments that would be introduced to the Martian surface, when the astronauts themselves each have circa eight orders of magnitude more microorganisms on and in their bodies than would be permitted for a typical robotic Mars lander mission. The international COSPAR PP policy recognizes this, but also states that; “the intent of planetary protection is the same whether a mission to Mars is conducted robotically or with human explorers. Accordingly, planetary protection goals should not be relaxed to accommodate a human mission to Mars. Rather, they become even more directly relevant to such missions — even if specific implementation guidelines should differ.” The goals that are to remain the same (as described in Article IX of the 1967 Outer Space Treaty) are: i) to avoid the harmful contamination of the target solar system body (Mars in this case), and ii) to avoid adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter. But what then are the implementation guidelines that should differ? The NASEM CoPP in its recent (2021) “Evaluation of Bioburden Requirements for Mars Missions” report declined to recommend relaxation of the present robotic requirements, noting that for such relaxation to be acceptable, any landing site needs “to be a conservative distance from any subsurface access point”, and that such a determination would also need to consider wind conditions for the location and season, and best estimates of microorganism survival time in the surface UV environment. This knowledge is simply not available at present, but this paper will provide an update on these and other “knowledge gaps” identified in a workshop series on PP for crewed Mars missions. Additionally, the paper will describe progress to incorporate the addressing of PP constraints in ongoing activities within NASA as the Moon to Mars architecture is matured. Finally, because the scientific community has been unable to provide a consensus answer to the question “How much is too much?”, in regard to the contamination that a crewed spacecraft mission might introduce to Mars, the paper will describe work to model and quantitate the microbial bioburden associated with the hardware and operations of NASA's crewed Mars surface mission concepts.