A Forward-Looking Perspective for the COSPAR Planetary Protection Policy for Mars

Kurzfassung

Mars exploration is entering a new era, transitioning from exclusively scientific robotic missions to include prospects for crewed and commercial missions. This shift introduces new mission architectures, longer operational timescales, and planetary protection challenges regarding human-derived contamination. In this context, the COSPAR Panel on Planetary Protection continuously evaluates and refines the COSPAR Planetary Protection Policy to reflect evolving mission needs and advances in scientific understanding, enabling future exploration. Initial guidelines for missions to Mars were based on a probabilistic approach (1 x 10-4) that used a Period of Biological Exploration (PBE) of 20 years, with an assumption of 100 missions, later extended to 50 years. Post-Viking, spore counts were incorporated into the policy as a practical proxy for bioburden limits. This change reflected the conclusion that Mars was less hospitable to terrestrial life than initially believed, and that applying a purely probabilistic approach was challenging due to uncertainties in key parameters. At the time, this shift led to the adoption of a simplified mission–target categorisation scheme, which has remained the foundation of planetary protection policy for Mars to this day. Spore-count values are assigned to each category for forward missions to Mars, and for Category III (Fly-by, gravity assist manoeuvres), a probability of impact is included as an alternative approach. Recent advancements in probabilistic risk assessment modelling have enabled the resolution of uncertainties through increasingly sophisticated modelling—an approach effectively demonstrated in the planetary protection plan for the Europa Clipper mission. Therefore, as we look to the future, it is now time to consider including a probabilistic approach for lander missions (Categories IVa, b, and c) for Mars. In this presentation, we will highlight the time-critical importance of adopting a probabilistic risk assessment approach for Mars and show how recent advances in scientific understanding and modelling now support us to overcome earlier limitations and enable future missions.