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The Astrophysical Context of Life The Astrophysical Context of Life Committee on the Origins and Evolution of Life Space Studies Board Division on Engineering and Physical Sciences Board on Life Sciences Division on Earth and Life Studies NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES THE NATIONAL ACADEMIES PRESS Washington, D.C. www.nap.edu
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The Astrophysical Context of Life THE NATIONAL ACADEMIES PRESS 500 Fifth Street, N.W. 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 task group responsible for the report were chosen for their special competences and with regard for appropriate balance. Support for this project was provided by Contract NASW 01001 between the National Academy of Sciences and the National Aeronautics and Space Administration. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor. Cover: Design by Penny E. Margolskee. Background image of a portion of the Large Magellanic Cloud near the Tarantula Nebula. Courtesy of the European Southern Observatory. International Standard Book Number 0-309-09627-8 Copies of this report are available free of charge from: Space Studies Board National Research Council The Keck Center of the National Academies 500 Fifth Street, N.W. Washington, DC 20001 Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu. Copyright 2005 by the National Academy of Sciences. All rights reserved. Printed in the United States of America
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The Astrophysical Context of Life THE NATIONAL ACADEMIES Advisers to Nation on Science, Engineering, and Medicine 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 M. 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. Wm. 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. 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 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 M. Alberts and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council. www.national-academies.org
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The Astrophysical Context of Life OTHER REPORTS OF THE SPACE STUDIES BOARD AND THE AERONAUTICS AND SPACE ENGINEERING BOARD Review of Progress Toward the Decadal Vision in Astronomy and Astrophysics: Letter Report (SSB with Aeronautics and Space Engineering Board, 2005) Science in NASA’s Vision for Space Exploration (SSB, 2005) Assessment of Options for Extending the Life of the Hubble Space Telescope: Final Report (SSB with Aeronautics and Space Engineering Board, 2004) Exploration of the Outer Heliosphere and the Local Interstellar Medium: A Workshop Report (SSB, 2004) Issues and Opportunities Regarding the U.S. Space Program: A Summary Report of a Workshop on National Space Policy (SSB with Aeronautics and Space Engineering Board, 2004) Plasma Physics of the Local Cosmos (SSB, 2004) Review of Science Requirements for the Terrestrial Planet Finder: Letter Report (SSB, 2004) Solar and Space Physics and Its Role in Space Exploration (SSB, 2004) Understanding the Sun and Solar System Plasmas: Future Directions in Solar and Space Physics (SSB, 2004) Utilization of Operational Environmental Satellite Data: Ensuring Readiness for 2010 and Beyond (SSB with Aeronautics and Space Engineering Board and Board on Atmospheric Sciences and Climate, 2004) Assessment of NASA’s Draft 2003 Earth Science Enterprise Strategy: Letter Report (SSB, 2003) Assessment of NASA’s Draft 2003 Space Science Enterprise Strategy: Letter Report (SSB, 2003) Satellite Observations of the Earth’s Environment: Accelerating the Transition of Research to Operations (SSB with Aeronautics and Space Engineering Board and Board on Atmospheric Sciences and Climate, 2003) Steps to Facilitate Principal-Investigator-Led Earth Science Missions (SSB, 2003) The Sun to the Earth—and Beyond: Panel Reports (SSB, 2003) Assessment of Directions in Microgravity and Physical Sciences Research at NASA (SSB, 2002) Life in the Universe: An Assessment of U.S. and International Programs in Astrobiology (SSB with Board on Life Sciences, 2002) New Frontiers in the Solar System: An Integrated Exploration Strategy (SSB, 2002) The Sun to Earth—and Beyond: A Decadal Research Strategy in Solar and Space Physics (SSB, 2002) Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques (SSB with Board on Life Sciences, 2001) Astronomy and Astrophysics in the New Millennium (Board on Physics and Astronomy with SSB, 2000) Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary Bodies (SSB, 2000) A Strategy for Research in Space Biology and Medicine in the New Century (SSB, 1998) Limited copies of SSB reports are available free of charge from: Space Studies Board National Research Council The Keck Center of the National Academies 500 Fifth Street, N.W., Washington, DC 20001 (202) 334-3477 firstname.lastname@example.org www.nationalacademies.org/ssb/ssb.html NOTE: Listed according to year of approval for release.
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The Astrophysical Context of Life COMMITTEE ON THE ORIGINS AND EVOLUTION OF LIFE JACK W. SZOSTAK, Massachusetts General Hospital, Co-chair J. CRAIG WHEELER, University of Texas, Co-chair STEVEN A. BENNER,* University of Florida JOSEPH A. BERRY,* Carnegie Institution/Stanford University RUTH BLAKE, Yale University WENDY M. CALVIN,* University of Nevada, Reno MICHAEL J. DALY, Uniformed Services University of the Health Sciences KATHERINE H. FREEMAN,* Pennsylvania State University J. PETER GOGARTEN,* University of Connecticut JAMES F. KASTING, Pennsylvania State University ANTHONY KEEFE, Archemix Corporation MARTIN KELLER, Diversa Corporation SANDRA PIZZARELLO,* Arizona State University JANET L. SIEFERT, Rice University ROGER SUMMONS, Massachusetts Institute of Technology NEVILLE J. WOOLF, University of Arizona LUCY M. ZIURYS,* University of Arizona Staff DAVID H. SMITH, Study Director ROBERT L. RIEMER, Senior Staff Officer RODNEY N. HOWARD, Senior Project Assistant CATHERINE A. GRUBER, Assistant Editor * Former member.
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The Astrophysical Context of Life SPACE STUDIES BOARD LENNARD A. FISK, University of Michigan, Chair GEORGE A. PAULIKAS, The Aerospace Corporation (retired), Vice Chair DANIEL N. BAKER, University of Colorado ANA P. BARROS, Duke University RETA F. BEEBE, New Mexico State University ROGER D. BLANDFORD, Stanford University RADFORD BYERLY, JR., University of Colorado JUDITH A. CURRY, Georgia Institute of Technology JACK D. FARMER, Arizona State University JACQUELINE N. HEWITT, Massachusetts Institute of Technology DONALD INGBER, Harvard Medical Center RALPH H. JACOBSON, The Charles Stark Draper Laboratory (retired) TAMARA E. JERNIGAN, Lawrence Livermore National Laboratory MARGARET G. KIVELSON, University of California, Los Angeles CALVIN W. LOWE, Bowie State University HARRY Y. McSWEEN, JR., University of Tennessee BERRIEN MOORE III, University of New Hampshire NORMAN NEUREITER, Texas Instruments (retired) SUZANNE OPARIL, University of Alabama, Birmingham RONALD F. PROBSTEIN, Massachusetts Institute of Technology DENNIS W. READEY, Colorado School of Mines ANNA-LOUISE REYSENBACH, Portland State University ROALD S. SAGDEEV, University of Maryland CAROLUS J. SCHRIJVER, Lockheed Martin Solar and Astrophysics Laboratory HARVEY D. TANANBAUM, Smithsonian Astrophysical Observatory J. CRAIG WHEELER, University of Texas A. THOMAS YOUNG, Lockheed Martin Corporation (retired) JOSEPH K. ALEXANDER, Director
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The Astrophysical Context of Life BOARD ON LIFE SCIENCES COREY S. GOODMAN, Renovis, Inc., Chair RUTH L. BERKELMAN, Emory University R. ALTA CHARO, University of Wisconsin, Madison DENNIS CHOI, Merck Research Laboratories JEFFREY L. DANGL, University of North Carolina, Chapel Hill PAUL R. EHRLICH, Stanford University JAMES M. GENTILE, Hope College ED HARLOW, Harvard Medical School DAVID HILLIS, University of Texas, Austin KENNETH H. KELLER, University of Minnesota, Minneapolis RANDALL MURCH, Institute for Defense Analyses GREGORY A. PETSKO, Brandeis University STUART L. PIMM, Duke University BARBARA A. SCHAAL, Washington University JAMES M. TIEDJE, Michigan State University KEITH R. YAMAMOTO, University of California, San Francisco FRANCES E. SHARPLES, Director
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The Astrophysical Context of Life To astronomers, biologists, chemists, and geologists who have caught the astrobiology bug
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The Astrophysical Context of Life Preface This study addresses issues raised in the recent assessment of astrobiology programs at the National Aeronautics and Space Administration (NASA)—Life in the Universe: An Assessment of U.S. and International Programs in Astrobiology.1 The authors of that report found that research in certain key areas of astrophysics relevant to understanding the astronomical environment in which life arose on Earth (and, potentially, elsewhere in the universe) was not well represented within the broad range of issues being addressed by NASA’s astrobiology program. This report is intended to highlight the contributions astronomers can make to the field of astrobiology. Life on Earth originated more than 3.5 billion years ago and has since then evolved in a complex and highly variable astronomical environment. Earth was assembled from interstellar gas already enriched in prebiotic molecules that were themselves the product of generations of stellar nucleosynthesis and chemical evolution in interstellar matter. Asteroid and comet impacts, some perhaps triggered by the random passage of another star, have evidently altered the course of evolution. Long-lived radioactive elements from stellar explosions have contributed heat to Earth’s molten core, helping to drive plate tectonics. Life on or near the surface of Earth is strongly affected by the evolving output of radiation from the Sun, interrupted by solar flares. The flux of cosmic rays that can induce mutations and perhaps affect climate has probably varied significantly over geological time. Earth is estimated to have been exposed to perhaps thousands of jolts of potentially biologically significant radiation from supernovas, and more exotic events such as gamma-ray bursts have been considered. Other solar system bodies and extrasolar planets that might harbor life have similar histories, but the effects of these events will be varied in import and detail. Thus, there are compelling reasons to argue that a full and complete picture of the origin and evolution of life must take into account its astrophysical context. 1 National Research Council. 2003. Life in the Universe: An Assessment of U.S. and International Programs in Astrobiology. Space Studies Board and Board on Life Sciences. The National Academies Press, Washington, D.C.
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The Astrophysical Context of Life One of the goals of the burgeoning intellectual field of astrobiology is to integrate the core sciences of biology, biochemistry, chemistry, physics, and geology into the broadest appropriate context of astronomy. Conversely, relevant aspects of astronomy should inform the biology, chemistry, and geology in order to facilitate intellectual exchange between those fields and to maximize the synergism within this innately multidisciplinary field. An example of the mutual interchange among these fields arises when we attempt to define “habitable zones.” Classic habitable zones are planetary environments where radiation from a host star results in surface temperatures commensurate with the existence of liquid water. Even hyperthermophilic microorganisms require a temperature and pressure realm where liquid water persists. On a broader scale, there have been attempts to define the locations and temporal stability of habitable zones within galaxies. The issues here include the abundance of heavy elements required to support the growth of terrestrial planets and the degree to which the galactic setting remains sufficiently stable to permit the emergence and continuance of life. In response to these opportunities, the Space Studies Board (SSB) charged the Committee on the Origins and Evolution of Life, one of its standing committees, with investigating ways to expand and integrate astronomy and astrophysics into astrobiology—in particular, into NASA’s astrobiology program and into relevant programs in other federal agencies. The goals of this study are as follows: Identify areas where there can be especially fruitful collaboration between astrophysicists, biologists, biochemists, chemists, and planetary geologists. Define areas where astrophysics, biology, chemistry, and geology are ripe for mutually beneficial interchanges and define areas that are likely to remain independent for the near future. Suggest areas where current activities of the National Science Foundation (NSF) and other federal agencies might augment NASA programs. Although some preliminary work on this study was undertaken during the committee meeting in October 2002, the study was not formally initiated until the committee met at the National Academies’ Keck Center in Washington, D.C., in March 2003. Work continued at meetings held at the Desert Research Institute in Reno, Nevada, and at the National Academies’ Beckman Center in Irvine, California, in July and October 2003, respectively. An initial draft of the report was assembled in December 2003 and extensively revised during a meeting of the committee held at the University of Arizona, in Tucson, in January 2004. A new draft was created in February 2004 and circulated to the committee. It was revised in March and sent out for external review in April. The committee’s work in drafting this report was made easier thanks to the input provided by many individuals, including the following: Ariel Anbar (University of Rochester), David Archer (University of Chicago), Charles Beichman (Jet Propulsion Laboratory), Alan Boss (Carnegie Institution of Washington), William Boynton (University of Arizona), Roger Buick (University of Washington), Philippe Crane (NASA Headquarters), Pascale Ehrenfreund (Leiden Observatory), Guillermo Gonzalez (Iowa State University), Andrew Gould (Ohio State University), Rosalind Grymes (NASA Astrobiology Institute), Frank Kyte (University of California, Los Angeles), Jonathan Lunine (University of Arizona), Michael Meyer (NASA Headquarters), Michael New (NASA Headquarters), Carl Pilcher (NASA Headquarters), Stefan Rahmstorf (Potsdam Institute for Climate Impact Research), Lynn Rothschild (NASA Ames Research Center), Bruce Runnegar (University of California, Los Angeles), Nir Shaviv (Hebrew University), and Bruce Wielicki (NASA-Langley Research Center).
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The Astrophysical Context of Life 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 contents 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: David W. Deamer, University of California, Santa Cruz, James P. Ferris, Rensselaer Polytechnic Institute, Donald Ingber, Children’s Hospital/Harvard Medical School, Victoria S. Meadows, Jet Propulsion Laboratory, Simon Conway Morris, University of Cambridge, England, Sara P. Seager, Carnegie Institution of Washington, Norman H. Sleep, Stanford University, Virginia Trimble, University of California, Irvine, and Nicolle E.B. Zellner, Lawrence Livermore National Laboratory. 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 Leslie Orgel, Salk Institute for Biological Studies. 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 task group and the institution.
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The Astrophysical Context of Life Contents EXECUTIVE SUMMARY 1 1 INTRODUCTION 7 The Astronomical Perspective, 7 Goals of the Current Study, 10 2 RELATED EFFORTS 11 National Research Council’s Life in the Universe Report, 11 National Aeronautics and Space Administration, 11 Origins Roadmap, 11 Cosmochemistry, 12 Space Radiation and Human Health, 12 Other Agencies, 13 National Science Foundation, 13 Department of Energy, 14 Astrobiology in Europe, 14 3 NASA EFFORTS IN ASTROPHYSICS FOR ASTROBIOLOGY 15 What Is Astronomy? What Is Astrobiology? 15 Astrophysical Research at NASA, 16 NASA Astrobiology Institute, 16 Other NASA Programs, 18 Broadening the Range of This Research, 19 4 AREAS THAT COULD BENEFIT FROM AUGMENTATION AND INTEGRATION 21 Galactic Environment, 22 Current Work and Gaps, 22 Areas of Relevant Independent Astronomical Research, 23
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The Astrophysical Context of Life Areas of Potential Interdisciplinary Interaction, 24 Missions, Role of Other Agencies, 24 Cosmic, Solar, and Terrestrial Irradiation, 25 Current Work and Gaps, 25 Areas of Relevant Independent Astronomical Research, 27 Areas of Potential Interdisciplinary Interaction, 28 Missions, Role of Other Agencies, 33 Interstellar and Protostellar Nebular Chemistry, 33 Current Work and Gaps, 33 Areas of Relevant Independent Astronomical Research, 34 Areas of Potential Interdisciplinary Interaction, 35 Missions, Role of Other Agencies, 35 Bombardment, 36 Current Work and Gaps, 36 Areas of Relevant Independent Astronomical Research, 38 Areas of Potential Interdisciplinary Interaction, 39 Missions, Role of Other Agencies, 40 Prebiotic Chemistry and Photosynthesis, 41 Current Work and Gaps, 41 Areas of Relevant Independent Astronomical Research, 44 Areas of Potential Interdisciplinary Interaction, 45 Missions, Role of Other Agencies, 47 Molecular Evolution in a Variable Astronomical Context, 48 Current Work and Gaps, 48 Areas of Relevant Independent Astronomical Research, 50 Areas of Potential Interdisciplinary Interaction, 50 Programs of Other Agencies, 51 5 INTEGRATING ASTRONOMY WITH THE OTHER DISCIPLINES OF ASTROBIOLOGY 52 Common Goals and Interests, 52 Common Language, 53 Background and Education, 53 Student Research Training, 53 Graduate Student Exchange Program, 54 Postdoctoral Fellowships, 54 Faculty Enrichment, 55 Recommendations, 55 APPENDIXES A Context and Statement of Task 59 B Related Reports and Programmatic Activities 62 C Glossary 70 D Committee Member and Staff Biographies 75