Preventing the Forward Contamination of Mars

Recent spacecraft and robotic probes to Mars have yielded data that are changing our understanding significantly about the possibility of existing or past life on that planet. Coupled with advances in biology and life-detection techniques, these developments place increasing importance on the need to protect Mars from contamination by Earth-borne organisms. To help with this effort, NASA requested that the NRC examine existing planetary protection measures for Mars and recommend changes and further research to improve such measures. This report discusses policies, requirements, and techniques to protect Mars from organisms originating on Earth that could interfere with scientific investigations. It provides recommendations on cleanliness and biological burden levels of Mars-bound spacecraft, methods to reach those levels, and research to reduce uncertainties in preventing forward contamination of Mars. Table of ContentsFront MatterExecutive Summary1 Introduction2 Policies and Practices in Planetary Protection3 Future Mars Exploration: The Rolling Wave4 Environments on Mars Relative to Life5 Expanding Our Knowledge of the Limits of Life on Earth6 Advances in Technologies for Life Detection and Bioburden Reduction7 Assessing Non-Living Contaminants of Concern8 A Path Forward for Planetary Protection in the 21st Century9 Transition Process and Time LineAppendix A Biographical Sketches of Committee Members and StaffAppendix B Recommendations from Two Previous NRC Reports on Forward ContaminationAppendix C Summary of Procedures Currently Used to Assess Bioburden in Spacecraft Assembly Clean Rooms and on SpacecraftAppendix D History of Recommended Values for Probability of GrowthAppendix E Approaches to Bioburden Reduction for Lander Missions to Mars Appendix F Ambiguities in Geomorphic Interpretation: Martian GulliesAppendix G Spacecraft Propellant and By-Products as Potential ContaminantsAppendix H Acronyms and Abbreviations