Assessment of Planetary Protection
Requirements for Spacecraft Missions to

ICY
SOLAR SYSTEM
BODIES

 

 

 

 

Committee on Planetary Protection Standards for Icy Bodies in the Outer Solar System

Space Studies Board

Division on Engineering and Physical Sciences

NATIONAL RESEARCH COUNCIL
                 OF THE NATIONAL ACADEMIES

THE NATIONAL ACADEMIES PRESS
Washington, D.C.
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Committee on Planetary Protection Standards for Icy Bodies in the Outer Solar System Space Studies Board Division on Engineering and Physical Sciences

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THE NATIONAL ACADEMIES PRESS 500 Fifth Street, NW Washington, DC 20001 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This study is based on work supported by Contract NNH06CE15B between the National Academy of Sciences and the National Aeronautics and Space Administration. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the agency that provided support for the project. Cover: Cover design by Penny E. Margolskee. The false-color mosaic image of the “tiger stripe” fractures in the southern polar region of Saturn’s moon Enceladus was constructed from data collected at ultraviolet, green, and near-infrared wavelengths by the Cassini spacecraft during its close flyby of Enceladus on August 11, 2008. Enceladus’s striking plumes emanate from discrete locations along the “tiger stripes.” Courtesy of NASA/Jet Propulsion Laboratory (JPL)/Space Science Institute. Inset, left: An artist’s impression of the New Horizons spacecraft during its flyby of the Pluto-Charon system in July 2015. Courtesy of Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. Inset, center: Enigmatic plumes of ice particles, water vapor, and trace organic compounds emanate from the southern polar region of Saturn’s moon Enceladus. This false-color image was created from data collected by the Cassini spacecraft on November 27, 2005, when it was 148,000 km from Enceladus. Courtesy of NASA/JPL/Space Science Institute. Inset, right: An artist’s impression of the proposed Europa Clipper spacecraft. This Jupiter-orbiting spacecraft is designed to undertake intensive observations of Europa during a series of close flybys. Courtesy of NASA/JPL. International Standard Book Number-13: 978-0-309-25675-9 International Standard Book Number-10: 0-309-25675-5 Copies of this report are available free of charge while supplies last from: Space Studies Board National Research Council 500 Fifth Street, NW Washington, DC 20001 Additional copies of this report are available from the National Academies Press, 500 Fifth Street, NW, Keck 360, Washington, DC 20001; (800) 624-6242 or (202) 334-3313; http://www.nap.edu. Copyright 2012 by the National Academy of Sciences. All rights reserved. Printed in the United States of America.

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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in sci - entific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad com - munity of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the gov - ernment, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. www.nationalacademies.org

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OTHER REPORTS OF THE SPACE STUDIES BOARD Assessment of a Plan for U.S. Participation in Euclid (Board on Physics and Astronomy [BPA] and Space Studies Board [SSB], 2012) Earth Science and Applications from Space: A Midterm Assessment of NASA’s Implementation of the Decadal Survey [prepublication] (SSB, 2012) Report of the Panel on Implementing Recommendations from the New Worlds, New Horizons Decadal Survey (BPA and SSB, 2012, released in 2010) Technical Evaluation of the NASA Model for Cancer Risk to Astronauts Due to Space Radiation (SSB, 2012) Assessment of Impediments to Interagency Collaboration on Space and Earth Science Missions (SSB, 2011) Panel Reports—New Worlds, New Horizons in Astronomy and Astrophysics (BPA and SSB, 2011) Recapturing a Future for Space Exploration: Life and Physical Sciences Research for a New Era (SSB, 2011) Sharing the Adventure with the Public—The Value and Excitement of “Grand Questions” of Space Science and Exploration: Summary of a Workshop (SSB, 2011) Vision and Voyages for Planetary Science in the Decade 2013-2022 (SSB, 2011) Capabilities for the Future: An Assessment of NASA Laboratories for Basic Research (Laboratory Assessments Board with SSB and Aeronautics and Space Engineering Board [ASEB], 2010) Controlling Cost Growth of NASA Earth and Space Science Missions (SSB, 2010) Defending Planet Earth: Near-Earth-Object Surveys and Hazard Mitigation Strategies: Final Report (SSB with ASEB, 2010) An Enabling Foundation for NASA’s Space and Earth Science Missions (SSB, 2010) Forging the Future of Space Science: The Next 50 Years (SSB, 2010) Life and Physical Sciences Research for a New Era of Space Exploration: An Interim Report (SSB with ASEB, 2010) New Worlds, New Horizons in Astronomy and Astrophysics (BPA and SSB, 2010) Revitalizing NASA’s Suborbital Program: Advancing Science, Driving Innovation, and Developing a Workforce (SSB, 2010) America’s Future in Space: Aligning the Civil Space Program with National Needs (SSB with ASEB, 2009) Approaches to Future Space Cooperation and Competition in a Globalizing World: Summary of a Workshop (SSB with ASEB, 2009) Assessment of Planetary Protection Requirements for Mars Sample Return Missions (SSB, 2009) Near-Earth Object Surveys and Hazard Mitigation Strategies: Interim Report (SSB with ASEB, 2009) A Performance Assessment of NASA’s Heliophysics Program (SSB, 2009) Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration (SSB with ASEB, 2009) Launching Science: Science Opportunities Provided by NASA’s Constellation System (SSB with ASEB, 2008) Opening New Frontiers in Space: Choices for the Next New Frontiers Announcement of Opportunity (SSB, 2008) Limited copies of these reports are available free of charge from: Space Studies Board National Research Council The Keck Center of the National Academies 500 Fifth Street, NW, Washington, DC 20001 (202) 334-3477/ssb@nas.edu www.nationalacademies.org/ssb/ssb.html iv

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COMMITTEE ON PLANETARY PROTECTION STANDARDS FOR ICY BODIES IN THE OUTER SOLAR SYSTEM MITCHELL L. SOGIN, Marine Biological Laboratory, Chair GEOFFREY COLLINS, Wheaton College, Vice Chair AMY BAKER, Technical Administrative Services JOHN A. BAROSS, University of Washington AMY BARR, Brown University WILLIAM V. BOYNTON, University of Arizona CHARLES S. COCKELL, University of Edinburgh MICHAEL J. DALY, Uniformed Services University of the Health Sciences JOSEPH R. FRAGOLA, Valador Incorporated ROSALY M.C. LOPES, Jet Propulsion Laboratory, California Institute of Technology KENNETH H. NEALSON, University of Southern California DOUGLAS S. STETSON, Space Science and Exploration Consulting Group MARK H. THIEMENS, University of California, San Diego Staff DAVID H. SMITH, Senior Program Officer, Study Director CATHERINE A. GRUBER, Editor RODNEY N. HOWARD, Senior Project Assistant HEATHER D. SMITH, National Academies Christine Mirzayan Science and Technology Policy Fellow ANNA B. WILLIAMS, National Academies Christine Mirzayan Science and Technology Policy Fellow KATIE DAUD, Lloyd V. Berkner Space Policy Intern DANIELLE PISKORZ, Lloyd V. Berkner Space Policy Intern MICHAEL H. MOLONEY, Director, Space Studies Board v

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SPACE STUDIES BOARD CHARLES F. KENNEL, Scripps Institution of Oceanography, University of California, San Diego, Chair JOHN KLINEBERG, Space Systems/Loral (retired), Vice Chair MARK R. ABBOTT, Oregon State University STEVEN J. BATTEL, Battel Engineering YVONNE C. BRILL, Aerospace Consultant ELIZABETH R. CANTWELL, Oak Ridge National Laboratory ANDREW B. CHRISTENSEN, Dixie State College and The Aerospace Corporation ALAN DRESSLER, The Observatories, Carnegie Institution for Science JACK D. FELLOWS, University Corporation for Atmospheric Research HEIDI B. HAMMEL, Association of Universities for Research in Astronomy, Inc. FIONA A. HARRISON, California Institute of Technology ANTHONY C. JANETOS, University of Maryland JOAN JOHNSON-FREESE, Naval War College ROBERT P. LIN, University of California, Berkeley MOLLY K. MACAULEY, Resources for the Future JOHN F. MUSTARD, Brown University ROBERT T. PAPPALARDO, Jet Propulsion Laboratory, California Institute of Technology JAMES PAWELCZYK, Pennsylvania State University MARCIA J. RIEKE, University of Arizona DAVID N. SPERGEL, Princeton University WARREN M. WASHINGTON, National Center for Atmospheric Research CLIFFORD M. WILL, Washington University THOMAS H. ZURBUCHEN, University of Michigan MICHAEL H. MOLONEY, Director CARMELA J. CHAMBERLAIN, Administrative Coordinator TANJA PILZAK, Manager, Program Operations CELESTE A. NAYLOR, Information Management Associate CHRISTINA O. SHIPMAN, Financial Officer SANDRA WILSON, Financial Assistant vi

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Preface In a letter sent to the National Research Council’s (NRC’s) Space Studies Board (SSB) Chair Charles F. Kennel on May 20, 2010, Edward J. Weiler, NASA’s associate administrator for the Science Mission Directorate (SMD), explained that understanding of the planetary protection requirements for spacecraft missions to Europa and the other icy bodies of the outer solar system should keep pace with our increasing knowledge of these unique planetary environments. Specific advice regarding planetary protection requirements for Europa is contained in the 2000 NRC report Preventing the Forward Contamination of Europa.1 NRC advice concerning other icy bodies is either nonexistent or contained in reports that are now outdated. As NASA and other space agencies prepare for future missions to the icy bodies of the outer solar system, it is appropriate to review the findings of the 2000 Europa report and to update and extend its recommendations to cover the entire range of icy bodies—i.e., asteroids, satellites, Kuiper belt objects, and comets. These considerations led Dr. Weiler to request that the NRC revisit the planetary protection requirements for missions to icy solar system bodies in light of current scientific understand - ing and ongoing improvements in mission-enabling technologies. In particular, the NRC was asked to consider the following subjects and make recommendations: • The possible factors that usefully could be included in a Coleman-Sagan formulation describing the prob- ability that various types of missions might contaminate with Earth life any liquid water, either naturally occurring or induced by human activities, on or within specific target icy bodies or classes of objects; • The range of values that can be estimated for the above factors based on current knowledge, as well as an assessment of conservative values for other specific factors that might be provided to missions targeting individual bodies or classes of objects; and • Scientific investigations that could reduce the uncertainty in the above estimates and assessments, as well as technology developments that would facilitate implementation of planetary protection requirements and/or reduce the overall probability of contamination. In response to this request, the Committee on Planetary Protection Standards for Icy Bodies in the Outer Solar System was established in September 2010. The committee held organizational teleconferences on November 17 and December 15 in 2010. The committee’s first meeting to hear presentations relating to its task took place at 1 National Research Council, Preventing the Forward Contamination of Europa, National Academy Press, Washington, D.C., 2000. vii

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viii PREFACE the National Academies’ Keck Center in Washington, D.C., on January 31 through February 2, 2011. Additional presentations and discussions were heard during a meeting held at the Arnold and Mabel Beckman Center of the National Academies in Irvine, California, on March 16-18 and during a teleconference held on May 13. The com - mittee’s final meeting was held at the Beckman Center on June 14-16. The work of the committee was made easier thanks to the important help, advice, and comments provided by numerous individuals from a variety of public and private organizations. These include the following: Douglas Bernard (Jet Propulsion Laboratory), Brent Christner (Louisiana State University), Benton C. Clark (Space Sci - ence Institute), Karla B. Clark (Jet Propulsion Laboratory), Catharine A. Conley (NASA Headquarters), Steven D’Hondt (University of Rhode Island), Will Grundy (Lowell Observatory), Torrence V. Johnson (Jet Propulsion Laboratory), Ralph D. Lorenz (Johns Hopkins University, Applied Physics Laboratory), Wayne L. Nicholson (University of Florida), Curt Niebur (NASA Headquarters), Robert T. Pappalardo (Jet Propulsion Laboratory), Chris Paranicas (Johns Hopkins University, Applied Physics Laboratory), P. Buford Price, Jr. (University of California, Berkeley), Louise Prockter (Johns Hopkins University, Applied Physics Laboratory), John D. Rummel (East Carolina University), Daniel F. Smith (Advanced Sterilization Products), John Spencer (Southwest Research Institute), J. Andrew Spry (Jet Propulsion Laboratory), Elizabeth Turtle (Johns Hopkins University, Applied Physics Laboratory), Christopher R. Webster (Jet Propulsion Laboratory), and Yuri Wolf (National Library of Medicine, National Institutes of Health). This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the authors and the NRC in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. The committee wishes to thank the following individuals for their participation in the review of this report: John R. Battista, Louisiana State University; Chris F. Chyba, Princeton University; Gerald W. Elverum, TRW Space Science and Defense; Kevin P. Hand, Jet Propulsion Laboratory; Margaret G. Kivelson, University of California, Los Angeles; Christopher P. McKay, NASA Ames Research Center; Ronald F. Probstein, Massachusetts Insti- tute of Technology; John D. Rummel, East Carolina University; and Yuri I. Wolf, National Library of Medicine, National Institutes of Health. Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Larry W. Esposito, University of Colorado, Boulder. Appointed by the NRC, he was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.

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Contents SUMMARY 1 1 CURRENT STATUS OF PLANETARY PROTECTION POLICIES FOR ICY BODIES 5 Context, 5 COSPAR Response to NRC Recommendations, 8 Implementing Planetary Protection Policies, 8 Why This Study Is Timely, 9 References, 11 2 BINARY DECISION TREES 13 Problems with Coleman-Sagan Calculations, 13 COSPAR’s Simplified Version of the Coleman-Sagan Approach, 16 An Alternative to the Coleman-Sagan Formulation, 17 Conclusions and Recommendations, 18 References, 18 3 HIERARCHICAL DECISIONS FOR PLANETARY PROTECTION 19 Decision Points, 19 Conclusions and Recommendations, 21 References, 22 4 A GEOPHYSICAL PERSPECTIVE AND INVENTORY OF HABITABLE ENVIRONMENTS 23 ON ICY BODIES Geophysical Bottlenecks, 23 Potentially Habitable Environments, 24 Observed Geologic Activity on Icy Bodies, 29 Conclusions and Recommendations, 34 References, 34 ix

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x CONTENTS 5 MICROBIAL METABOLISM AND PHYSIOLOGY 41 Decision Points 1, 2, and 3, 42 Decision Point 4—Chemical Energy, 43 Decision Point 6—Complex Nutrients, 43 Decision Point 7—Minimal Planetary Protection, 47 Conclusions and Recommendations, 48 Notes and References, 50 6 NECESSARY RESEARCH 55 Heat Resistance of Cold-Loving Spores, 55 Enhanced Resistance of Biofilms, 56 Imaging Methodology to Determine Bioload, 56 Availability of Biologically Important Elements, 57 Global Material Transport, 57 References, 58 APPENDIXES A Letter Requesting This Study 61 B Current and Prospective Missions to Icy Bodies of Astrobiological Interest 64 C Event Sequence Diagram for the Determination of Planetary Protection Measures for Missions to Icy Bodies 70 D Committee and Staff Biographical Information 74 E Glossary and Abbreviations 79