Planetary Protection Concepts in the Context of the Evolvable Mars Campaign

Spacefaring nations have committed to protecting solar system objects from harmful contamination resulting from the activities of interplanetary spacecraft, and of similarly protecting the Earth from uncontrolled release of a putative extra-terrestrial organism from returned extra-terrestrial samples. Planetary protection policies to achieve these goals are mature for outbound missions performing robotic exploration of Mars, having been updated and refined over time as more became understood about the martian environment. Similarly, increased understanding of the limits and capabilities of terrestrial life on Earth continues to inform planetary protection policy. In considering the future human exploration of Mars, it is clear that the bioburden requirements historically used for robotic missions (<5x105 microbial spores/mission) would not be sustainable for a crewed mission (~1x1014 microorganisms/astronaut in a complex internal and external community related to digestion and a plethora of other functions). This does not mean that the current planetary protection paradigm would be discarded. On the contrary, the intent to prevent harmful contamination would remain, with safeguarding the Earth from potential backward contamination continuing to be the highest planetary protection priority. It is widely accepted that the greater capability of human explorers can only be beneficial to the astrobiological exploration of Mars if human-associated contamination is controlled and understood, yet for landed missions conducting surface operations, it is likely not practicable for all human-associated processes and mission operations to be conducted within entirely closed systems. Additionally, based on the lunar experiences of the Apollo astronauts, the exposure of crewmembers exploring Mars (and their support infrastructure) to martian materials would be inevitable.