Mars Sample Return backward contamination – Strategic advice and requirements Report from the ESF-ESSC Study Group on MSR Planetary Protection Requirements European Science Foundation (ESF) European Space Sciences Committee (ESSC) The European Science Foundation (ESF) is an The European Space Sciences Committee (ESSC), independent, non-governmental organisation, the established in 1975, grew from the need to give members of which are 72 national funding agencies, European space scientists a voice in the space arena research performing agencies and academies from 30 at a time when successive US space science missions countries. and NASA’s Apollo missions dominated space The strength of ESF lies in its influential membership research. More than 35 years later, the ESSC actively and in its ability to bring together the different domains collaborates with the European Space Agency (ESA), of European science in order to meet the challenges of the European Commission, national space agencies the future. and the ESF Member Organisations. This has made Since its establishment in 1974, ESF, which has its ESSC a reference name in space sciences within headquarters in Strasbourg with offices in Brussels Europe. and Ostend, has assembled a host of organisations The mission of the ESSC today is to provide an that span all disciplines of science, to create a independent forum for scientists to debate space common platform for cross-border cooperation in sciences issues. The ESSC is represented ex officio Europe. in all ESA’s scientific advisory bodies, in ESA’s High- ESF is dedicated to promoting collaboration in level Science Policy Advisory Committee advising scientific research and in funding of research and its Director General, it has members in the EC’s FP7 science policy across Europe. Through its activities space advisory group, and it has observer status in and instruments, ESF has made major contributions to ESA’s Ministerial Council. At the international level, science in a global context. ESF covers the following ESSC maintains strong relationships with the National scientific domains: Humanities, Life, Earth and Research Council’s (NRC) Space Studies Board in the Environmental Sciences, Medical Sciences, Physical US. and Engineering Sciences, Social Sciences, Marine The ESSC is the European Science Foundation’s (ESF) Sciences, Materials Science and Engineering, Nuclear Expert Committee on space sciences and the ESF’s Physics, Polar Sciences, Radio Astronomy, Space interface with the European space community. Sciences. www.esf.org/essc www.esf.org The European Science Foundation hosts six Expert Authors Boards and Committees: Walter Ammann, John Baross, Allan Bennett, • The European Space Sciences Committee (ESSC) Jim Bridges, Joseph Fragola, Armel Kerrest, • The Nuclear Physics European Collaboration Karina Marshall-Bowman, Hervé Raoul, Petra Rettberg, Committee (NuPECC) John Rummel, Mika Salminen, Erko Stackebrandt, • The Marine Board-ESF (MB-ESF) Nicolas Walter • The European Polar Board (EPB) • The Committee on Radio Astronomy Frequencies (CRAF) ESF Support Staff • The Materials Science and Engineering Expert Committee (MatSEEC) Nicolas Walter, Senior Science Officer Karina Marshall-Bowman, Junior Science Officer In the statutory review of the Expert Boards Johanne Martinez-Schmitt, Administrator and Committees conducted in 2011, the Review Panel concluded unanimously that all Boards and Committees provide multidisciplinary scientific Contact services in the European and in some cases global framework that are indispensable for Europe’s Nicolas Walter scientific landscape, and therefore confirmed the need Senior Science Officer for their continuation. Physical, Engineering and Space Sciences Unit The largely autonomous Expert Boards and Tel: +33 (0)3 88 76 71 66 Committees are vitally important to provide in-depth Email: [email protected] and focused scientific expertise, targeted scientific and policy advice, and to initiate strategic developments in areas of research, infrastructure, environment and society in Europe. Cover picture: ISBN: 978-2-918428-67-1 European Space Agency Printing: Ireg – Strasbourg September 2012 Contents Foreword: Mission Statement 3 1. Mars Sample Return Mission and planetary protection – background 5 1.1 Planetary protection regulatory framework 5 1.2 Mars Sample Return Mission concept 6 1.3 Sterilisation: concept, methods and limitations 7 1.4 Summary of advice from past committees 9 2. From remote exploration to returning samples 10 2.1 New missions for new knowledge 10 2.2 The importance of not compromising the sample and the Mars surface 11 2.3 The challenge raised by a returned sample 11 2.4 Considering backward contamination through particle size 12 3. Life as we know it and size limits 14 3.1 Life as we know it 14 3.2 Approaching the issue of minimum size limit for life 14 3.3 Characteristics of the smallest cells 15 3.4 Viruses 17 3.5 Gene transfer agents (GTAs) 18 3.6 From new knowledge to new requirements 19 3.7 Perspectives for the future 21 4. Defining the adequate level of assurance for a non-release 22 4.1 From risk to level of assurance 22 4.2 Approaching the unknown and considering consequences 22 4.3 The Precautionary Principle in the context of MSR 25 4.4 Emission optimisation strategies 25 4.5 Quantitative risk levels used by regulators 27 4.6 Updating the appropriate level of assurance 31 4.7 Potential verification methods 32 5. From release to risk: a framework to approach the consequences 33 5.1 The sequence of events leading to environmental consequences 33 5.2 Estimate of the overall risk 35 5.3 Direct consequences for human health 35 5.4 Being prepared 38 6. Perceived risk: differences between the general public and experts 39 7. Regulatory and legal aspects of a Mars Sample Return Mission 42 7.1 Obligation to prevent pollution/contamination of Outer Space and the Earth 42 7.2 Responsibility and liability of States 43 7.3 The necessity/utility to give some legal value to measures preventing damage 44 8. Study Group findings and recommendations 45 8.1 Mars exploration and sample return 45 8.2 Uncertainties, Precautionary Principle and optimisation 45 8.3 On particle size 46 8.4 Public perception 47 8.5 On the required level of assurance 47 8.6 Implication for design 48 8.7 Accompanying measures 48 References 50 Annex 1: ESF-ESSC Study Group composition 57 Annex 2: Risk perception workshop – participation, consensus statements and recommendations 58 Foreword: Mission Statement l l l As planetary protection regulations have a signifi- The mandate of the Study Group was to: 3 cant impact on mission design, engineering and “Recommend the level of assurance for the exclu- overall cost, it is critical that the guidelines are sion of an unintended release of a potential Mars implemented with proper justification and are re- life form into the Earth’s biosphere for a Mars evaluated on a regular basis. Sample Return mission”. In June 2011, the European Space Agency The starting point of this activity was the asked the European Science Foundation (ESF) in requirement used since the late 1990s specifying coordination with its European Space Sciences that: ‘the probability that a single unsterilised particle Committee (ESSC) to perform a study regarding of 0.2 micron diameter or greater is released into the planetary protection regulations for a Mars Sample Earth environment shall be less than 106’. Return (MSR) mission. Specifically, ESF was asked The value for the maximum particle size was to perform a study on the level of assurance of derived from the NRC-SSB 1999 report ‘Size Limits preventing an unintended release of Martial par- of Very Small Microorganisms: Proceedings of a ticles into the Earth’s biosphere in the frame of an Workshop’, which declared that 0.25 ± 0,05 µm MSR mission. ESF commissioned a study group of was the lower size limit for life as we know it (NRC, 12 high-level, international and multidisciplinary 1999). However, the past decade has shown enor- experts (see Annex 1 for Study Group composi- mous advances in microbiology, and microbes in tion) to evaluate the current requirements, and to the 0.10–0,15 µm range have been discovered in provide new insights and recommendations where various environments. Therefore, the value for the applicable. The Study Group was formed following maximum particle size that could be released into a call for nominations addressed to several research the Earth’s biosphere is revisited and re-evaluated organisations in Europe and beyond as well as to in this report. Also, the current level of assurance the ESF standing committees on Life, Earth and of preventing the release of a Mars particle is recon- Environmental Sciences (LESC), Medical Research sidered. (EMRC), Physical and Engineering Sciences (PESC) To complete its mandate, the Study Group met as well as Social Sciences (SCSS) and Humanities on three occasions between June and November (SCH). 2011 and commissioned the organisation of a work- Mars Sample Return backward contamination – Strategic advice and requirements shop dedicated to risk perception held in January 2012. The outcome and recommendations from the risk perception workshop (see Annex 2 for details) were used as direct inputs in the formulation of the advice contained in this report. 1. Mars Sample Return Mission and planetary protection – background l l l 5 1.1 Planetary protection regulatory policy, while also providing guidelines to spacefar- framework ing nations. Planetary protection considers two