Probabilistic approach to planetary protection

Abstract

The Mars Science Laboratory (MSL) is the next generation Mars surface exploration mission proposed to launch in 2009. MSL faces a new and complex set of planetary protection (PP) and contamination control issues. MSL will carry a scientific payload capable of making geochemical and biochemical measurements never before attempted on another planet. MSL is designed to access most of the surface of Mars at any season for as much as a full Mars year through the use of radioisotope power. The combination of the science goals, use of radioisotope power, new measurements and theories about the presence of ice, and the requirement to evaluate off-nominal landings have forced the MSL project to develop a new approach to PP. Well, not so new, the project's strategy is the go back to the Viking probabilistic approach as the basis for its planetary protection categorization request. With the newest knowledge of Mars and detailed failure scenarios the project is preparing a very detailed set of analyses to show there is an acceptably low probability of contaminating Mars in the event an off-nominal landing. This paper discusses the formulation of the probabilistic approach and the latest results. Included is a summary of the various analyses that are required to support the probabilistic analysis including: entry and aerothermal breakup, terminal impact and breakup, thermo-fluid dynamics of icy soil in the presence of a perennial heat source to create liquid water, biologic reproduction potential and redistribution. This work is being closely coordinated with the NASA Planetary Protection Officer and is recognized as path finding for future Mars surface missions.