Planning Considerations Related to the Organic Contamination of Martian Samples and Implications for the Mars 2020 Rover
Abstract
Table of Contents 1. Executive Summary 2. Introduction 2.1. Introduction to the Mars 2020 OCP 2.1.1. Mars and the potential for habitability 2.1.2. Charge to the OCP 2.1.3. Introduction to the proposed Mars 2020 Mission 2.1.4. Definition of "organic contamination" 2.1.5. A note about units 2.2. Previous work on organic contamination control of acquired samples 2.3. Key concepts 2.3.1. Terrestrial microbial life forms (alive or dead) as sources of organic molecular contaminants 2.3.2. Analytical method limits of detection and contamination limits 2.3.3. Not all contaminants are equal 2.3.4. Contamination control versus contamination knowledge 2.4. Science and PP objectives both drive need for organic analyses 3. Sample-Based Investigations and Measurements 3.1. Need for early survey measurements 3.2. Potential analytical methods for returned samples 3.3. Survey versus targeted analytical methods 3.4. Survey analytical methods 4. Sample-Based Contaminants of Concern 4.1. General considerations 4.1.1. Selection criteria for choosing contaminants of concern 4.1.2. S/N threshold for acceptable contamination 4.1.3. Limits for TOC, individual molecules, or particles 4.1.4. Alive versus dead microbial contamination 4.1.5. The possibility of reproduction of Earth-sourced microbial contaminants in sealed sample tubes 4.2. Considerations related to specific contaminants 4.2.1. Which contaminants? 4.2.1.1. Tier-I contaminants 4.2.2. Allowable levels of contamination 4.2.2.1. What analyte concentrations do we expect? 4.2.2.2. What concentrations can we measure? 4.2.2.3. What level of cleanliness can we achieve? 4.2.3. Conclusions for specific compound levels 4.3. Considerations related to TOC 4.3.1. Allowable levels of contamination 4.3.1.1. What analyte concentrations do we expect? 4.3.1.2. What concentrations can we measure? 4.3.1.3. What level of cleanliness can we achieve? 4.3.1.3.1. Contamination pathways 4.3.1.4. Contamination transfer from sample-contacting surfaces 4.3.2. Conclusions for TOC levels 4.4. Considerations related to particulate organic matter 4.4.1. Introduction 4.4.2. Analytical approaches to measuring particulates on Earth 4.4.3. Limits on organic particulates 4.4.4. Conclusions and recommendations for particulates 4.5. Implementation 4.5.1. Strategy for implementing contaminant requirements 5. Strategies for Recognizing and Characterizing Organic Contamination 5.1. Introduction 5.2. Witness plates 5.3. Blanks and blank standards 5.4. Archive of organic and trace biological materials 5.5. Spatially resolved measurements on returned samples 6. Discussion and Proposals for Future Work 6.1. The case for cleaner 6.2. Summary and conclusions 6.3. Topics for future work Acknowledgments References A. Appendices and Supporting Files A.3. Appendix 3: Definitions of terms A.4. Appendix 4: Summary of instruments and measurements available as of 2014 for investigating organic molecules in rock and soil samples A.4.1. Notes regarding detection limits and capability of surface spectroscopic techniques