Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies

Framework for Decision Making

Task Group on Sample Return from Small Solar System Bodies

Space Studies Board

Commission on Physical Sciences, Mathematics, and Applications

National Research Council

NATIONAL ACADEMY PRESS
Washington, D.C. 1998



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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies Framework for Decision Making Task Group on Sample Return from Small Solar System Bodies Space Studies Board Commission on Physical Sciences, Mathematics, and Applications National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1998

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making 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 task group responsible for the report were chosen for their special competences and with regard for appropriate balance. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific 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. Bruce Alberts 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. William A. Wulf 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. Kenneth I. Shine 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 community 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 government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council. This study was supported by Contract No. NASW-96013 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 author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for this project. Library of Congress Catalog Card Number 98-85797 International Standard Book Number 0-309-06136-9 Cover design by Penny Margolskee. Comet photo courtesy of Dennis di Cicco. Asteroid and Europa images courtesy of NASA/JPL/Caltech. Additional copies of this report are available from: National Academy Press 2101 Constitution Ave., NW Box 285 Washington DC 20055 800-624-6242 202-334-3313 (in the Washington metropolitan area) http://www.nap.edu Copyright © 1998 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making TASK GROUP ON SAMPLE RETURN FROM SMALL SOLAR SYSTEM BODIES LESLIE ORGEL, Salk Institute for Biological Studies, Chair MICHAEL A'HEARN, University of Maryland JEFFREY BADA, University of California, San Diego JOHN BAROSS, University of Washington CLARK CHAPMAN, Southwest Research Institute MICHAEL DRAKE, University of Arizona JOHN KERRIDGE, University of California, San Diego MARGARET S. RACE, SETI Institute MITCHELL SOGIN, Marine Biological Laboratory, Woods Hole STEVEN SQUYRES, Cornell University JOSEPH L. ZELIBOR, JR., Study Director JACQUELINE ALLEN, Project Assistant

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making SPACE STUDIES BOARD CLAUDE R. CANIZARES, Massachusetts Institute of Technology, Chair MARK R. ABBOTT, Oregon State University DANIEL N. BAKER, University of Colorado LAWRENCE BOGORAD, Harvard University DONALD E. BROWNLEE, University of Washington GERARD W. ELVERUM, JR., TRW Space and Technology Group ANTHONY W. ENGLAND, University of Michigan MARILYN L. FOGEL, Carnegie Institution of Washington RONALD GREELEY, Arizona State University BILL GREEN, former member, U.S. House of Representatives ANDREW H. KNOLL, Harvard University ROBERTA BALSTAD MILLER, CIESIN BERRIEN MOORE III, University of New Hampshire MARY JANE OSBORN, University of Connecticut Health Center SIMON OSTRACH, Case Western Reserve University MORTON B. PANISH, AT&T Bell Laboratories (retired) CARLÉ M. PIETERS, Brown University THOMAS A. PRINCE, California Institute of Technology PEDRO L. RUSTAN, JR., U.S. Air Force (retired) JOHN A. SIMPSON, Enrico Fermi Institute GEORGE L. SISCOE, Boston University EDWARD M. STOLPER, California Institute of Technology RAYMOND VISKANTA, Purdue University ROBERT E. WILLIAMS, Space Telescope Science Institute MARC S. ALLEN, Director (through December 12, 1997) JOSEPH K. ALEXANDER, Director (as of February 17, 1998)

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND APPLICATIONS ROBERT J. HERMANN, United Technologies Corporation, Co-chair W. CARL LINEBERGER, University of Colorado, Co-chair PETER M. BANKS, ERIM International, Inc. WILLIAM BROWDER, Princeton University LAWRENCE D. BROWN, University of Pennsylvania RONALD G. DOUGLAS, Texas A&M University JOHN E. ESTES, University of California at Santa Barbara MARTHA P. HAYNES, Cornell University L. LOUIS HEGEDUS, Elf Atochem North America, Inc. JOHN E. HOPCROFT, Cornell University CAROL M. JANTZEN, Westinghouse Savannah River Company PAUL G. KAMINSKI, Technovation, Inc. KENNETH H. KELLER, University of Minnesota KENNETH I. KELLERMANN, National Radio Astronomy Observatory MARGARET G. KIVELSON, University of California at Los Angeles DANIEL KLEPPNER, Massachusetts Institute of Technology JOHN KREICK, Sanders, a Lockheed Martin Company MARSHA I. LESTER, University of Pennsylvania NICHOLAS P. SAMIOS, Brookhaven National Laboratory CHANG-LIN TIEN, University of California at Berkeley NORMAN METZGER, Executive Director

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making Foreword For the first time since the Apollo program, NASA has specific plans to bring samples to Earth from elsewhere in the solar system. The earliest mission, Stardust, is scheduled to be launched in 1999 and return approximately 7 years later with a collection of cometary and interplanetary material. Other missions in various stages of definition would gather bits from Mars, an asteroid, or the satellites of Jupiter. Prudence demands giving proper attention to handling extraterrestrial samples so that they pose no risk to Earth's biosphere. At the same time, an unreasonable level of concern could needlessly escalate the cost of sample handling or obviate such missions altogether. Since Mars is the place most often considered as a possible host of past or present microbial life forms and one from which samples will surely be returned within the next decade, it has received the greatest amount of attention, including a recent study by a task group of the Space Studies Board (National Research Council, 1997, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington D.C.). The present report broadens the scope of consideration to encompass the other bodies in the solar system. The report finds that the degree of caution required in handling material depends on its site of origin. To a high degree of confidence, some returned samples do not need special handling precautions. Others might be in this category, but the degree of confidence is lower. For still others, the samples should be handled with the same degree of containment as would be applied to material from Mars. In addition, the report considers further research that would inform this issue and reduce areas of uncertainty. Learning how some of Earth's hardier microbes would fare under the extreme conditions of radiation and temperature can help increase our understanding of the sterilization processes that occur naturally in parts of the solar system. Since NASA has plans to bring Mars rocks back to Earth within a decade, the proper procedures for handling the most suspect samples must be put in place. This report shows that the full machinery of containment will also be required for some material, but certainly not everything, collected in our neighborhood. Claude R. Canizares, Chair Space Studies Board

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making Preface The National Research Council's Space Studies Board provides guidance to NASA on planetary protection, which is the effort to preserve conditions for future biological and organic exploration on planets and other solar system objects and to protect Earth and its biosphere from potential extraterrestrial sources of contamination. In 1997, the Space Studies Board produced the report Mars Sample Return: Issues and Recommendations, which assessed the potential for a viable exogenous biological entity to be included in a sample returned to Earth from Mars as well as the potential for large-scale effects if such an entity were inadvertently introduced into Earth's biosphere. The report provides justification for and recommendations on procedures for the quarantine of samples returned from Mars. Given the prospect of sample return missions from various small solar system bodies in the next decade, NASA then requested that the Board assess the potential for a living entity to be present in or on samples returned from small solar system bodies such as planetary satellites, asteroids, and comets. Guidance from the new study would extend and generalize to other solar system bodies the published advice regarding Mars. In response to NASA's request, the Space Studies Board convened the Task Group on Sample Return from Small Solar System Bodies to assess the potential for a living entity to be present in or on samples returned from small solar system bodies by addressing the following: The potential for a living entity to be contained in or on samples returned from planetary satellites or small solar system bodies, such as asteroids, comets, and meteoroids; Detectable differences among small solar system bodies that would affect the above assessment; Scientific investigations that need to be conducted to reduce the uncertainty in the above assessment; and The potential risk posed by samples returned directly to Earth from spaceflight missions, as compared to the natural influx of material that enters Earth's atmosphere as interplanetary dust particles, meteorites, and other small impactors. The task group met three times over an 11-month period, reviewed relevant reports, was briefed by representatives from NASA and expert researchers and practitioners on topics related to sample return, and held a workshop to obtain a wide spectrum of perspectives. The task group considered in some detail the following topics: The possibility that, at some time in the past, life originated on a body from which a sample might be taken, or that life was transported there from elsewhere in the solar system;

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making The possibility that life still exists on the body either in active or in reactivatable form; and The potential hazard to terrestrial ecosystems from extraterrestrial life if it exists in a returned sample. The central concern addressed by the task group in this report is the possibility that samples returned to Earth from small solar bodies might harbor living entities that could harm terrestrial living organisms or disrupt their ecosystems. The primary audience for the task group's report is NASA, those who have a stake in sample return missions and planetary protection, and the public at large. The task group members wish to thank those individuals who made presentations at the task group meetings, including Sherwood Chang, NASA-Ames; Christopher Chyba, University of Arizona; Ben Clark, Lockheed-Martin; John Cronin, Arizona State University; James Ferris, Rensselaer Polytechnic Institute; Marina Fomenkova, University of California, San Diego; Ted Roush, San Francisco State University; and Perry Stabekis, Lockheed-Martin. Special thanks are given to John Rummel and Michael Meyer for serving as the project's points of contact at NASA and for their presentations to the task group.

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making Acknowledgment of Reviewers This report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council's (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 the 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 content of the review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their participation in the review of this report: Rita R. Colwell, University of Maryland; Ellis Cowling, North Carolina State University; Michael Gaffey, Rensselaer Polytechnic Institute; Donald M. Hunten, University of Arizona; Marsha I. Lester, University of Pennsylvania; Harry Y. McSween, Jr., University of Tennessee; Norman R. Pace, University of California, Berkeley; Everett L. Shock, Washington University; and John A. Wood, Harvard University. Although the individuals listed above provided many constructive comments and suggestions, responsibility for the final content of this report rests solely with the authoring task group and the NRC.

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making Contents     EXECUTIVE SUMMARY   1 1   INTRODUCTION   8     Scope and Approach of This Study   9     Current Understanding of Origins, Continuance, and Survival of Terrestrial Life Forms—A Synopsis   10     Early Earth as a Model for the Origins of Self-replicating Life Forms   10     Viability of Microorganisms   11     Factors That Influence the Survival of Metabolically Active Cells   11     Factors That Affect the Survival of Dormant Microorganisms   15     Questions Appropriate for Assessing the Biological Potential of Small Bodies   16     Content and Organization of This Report   17     References   19 2   NATURAL INFLUX AND CROSS-CONTAMINATION   21     Natural Influx to Earth   21     Processes of Delivery from Diverse Parent Bodies   23     Cross-Contamination   24     Summary   25     References   25 3   PLANETARY SATELLITES INSIDE JUPITER'S ORBIT   26     Origin, Composition, and Environmental Conditions of Satellites Examined   26     The Moon   26     The Satellites of Mars   27     The Galilean Satellites of Jupiter   29

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making     Potential for a Living Entity to Be in or on Samples Returned from Planetary Satellites   35     Scientific Investigations to Reduce the Uncertainty in the Assessment of Planetary Satellites   36     Phobos and Deimos   36     Europa   36     Ganymede   37     Callisto   37     Summary   37     References   37 4   ASTEROIDS AND METEORITES   40     Undifferentiated, Primitive (C-Type) Asteroids   43     Undifferentiated, Metamorphosed Asteroids   45     Differentiated Asteroids   46     Potential for a Living Entity to Be in or on Samples Returned from Asteroids   47     Scientific Investigations to Reduce the Uncertainty in the Assessment of Asteroids   49     Summary   50     References   50 5   COMETS   52     Origin   52     Place of Formation   52     Nebular Processes and Accretion   52     Gravitational Scattering   53     Early Heating and Melting   54     Composition   55     Physical Characteristics   55     Chemical Composition   56     Past and Present Environmental Conditions   58     Delivery of Samples to Earth   59     Potential for a Living Entity to Be in or on Samples Returned from Comets   60     Scientific Investigations to Reduce the Uncertainty in the Assessment of Comets   62     Summary   62     References   63 6   COSMIC DUST   64     Natural Infall of Dust to Earth   65     Potential for a Living Entity to Be in or on Returned Samples of Cosmic Dust   66     Scientific Investigations to Reduce the Uncertainty in the Assessment of Cosmic Dust   66     Summary   67     References   67 7   CONSIDERING THE POTENTIAL RISKS FROM RETURNED SAMPLES   69     Likelihood of Finding and Including a Living Organism in Samples from Different Solar System Bodies   70     Anticipating the Putative Nature of Life from Small Solar System Bodies   71     Concerns About Potential Biohazards and Adverse Effects   71

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Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making     Containment and Quarantine Facilities   72     Testing of Returned Samples   72     Summary   73     References   74 8   CONCLUSIONS AND RECOMMENDATIONS   75     Assessment of Potential for a Living Entity to Be Present in or on Samples Returned from Small Solar System Bodies   75     Planetary Satellites   75     Asteroids   77     Comets   78     Cosmic Dust   78     Containment and Handling of Returned Samples   79     Scientific Investigations to Reduce Uncertainty   81     Reference   81     APPENDIXES   83     A Biographical Sketches of Task Group Members   85     B Letter of Request   89     C Additional Perspectives on Contamination from Space   93     D Planetary Protection Policy—NASA and COSPAR   95     E Glossary   99

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