AN ASTROBIOLOGY
STRATEGY FOR THE

Search for
Life in the Universe

Committee on Astrobiology Science Strategy for the Search for Life in the Universe

Space Studies Board

Division on Engineering and Physical Sciences

A Consensus Study Report of

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This study is based on work supported by the Contract NNH17CB02B with 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 any organization or agency that provided support for the project.

International Standard Book Number-13: 978-0-309-48416-9
International Standard Book Number-10: 0-309-48416-2
Digital Object Identifier: https://doi.org/10.17226/25252

Cover: Background photo is of the Milky Way over the Stirling Ranges in Western Australia. The photo was taken by Trevor Dobson on July 2, 2018, 400 km north of Perth, Australia. Original photo can be found online: https://www.flickr.com/photos/trevor_dobson_inefekt69/42428966514/.

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Suggested Citation: National Academies of Sciences, Engineering, and Medicine. 2019. An Astrobiology Strategy for the Search for Life in the Universe. The National Academies Press, Washington, D.C. https://doi.org/10.17226/25252.

COMMITTEE ON ASTROBIOLOGY SCIENCE STRATEGY FOR THE SEARCH FOR LIFE IN THE UNIVERSE

BARBARA SHERWOOD LOLLAR, University of Toronto, Chair

SUSHIL K. ATREYA, University of Michigan

ALAN P. BOSS, Carnegie Institution of Washington

PAUL G. FALKOWSKI, NAS,¹ Rutgers, State University of New Jersey, New Brunswick

JACK D. FARMER, Arizona State University

OLIVIER GUYON, University of Arizona

GERALD F. JOYCE, NAS/NAM,² Salk Institute for Biological Studies

JAMES F. KASTING, NAS, Pennsylvania State University

VICTORIA S. MEADOWS, University of Washington

PHILIP M. NECHES, NAE,³ Entrepreneurs Roundtable Accelerator

CARL B. PILCHER, Blue Marble Space Institute of Science

NILTON O. RENNÓ, University of Michigan

KARYN L. ROGERS, Rensselaer Polytechnic Institute

BRITNEY E. SCHMIDT, Georgia Institute of Technology

ROGER SUMMONS, Massachusetts Institute of Technology

FRANCES WESTALL, Centre National de la Recherche Scientifique

SHELLEY A. WRIGHT, University of California, San Diego

Staff

DAVID H. SMITH, Senior Program Officer, Study Director

SARAH C. BROTHERS, Associate Program Officer

ANESIA WILKS, Program Coordinator

MIA BROWN, Research Associate

LAURA CUMMINGS, Lloyd V. Berkner Space Policy Intern

CARSON BULLOCK, Lloyd V. Berkner Space Policy Intern

JONATHAN LUTZ, Lloyd V. Berkner Space Policy Intern

___________________

¹ Member, National Academy of Sciences.

² Member, National Academy of Medicine.

³ Member, National Academy of Engineering.

SPACE STUDIES BOARD

FIONA HARRISON, NAS,¹ California Institute of Technology, Chair

JAMES H. CROCKER, NAE,² Lockheed Martin Space Systems Company (retired), Vice Chair

GREGORY P. ASNER, NAS, Carnegie Institution for Science

JEFF M. BINGHAM, Consultant

ADAM BURROWS, NAS, Princeton University

MARY LYNNE DITTMAR, Dittmar Associates

JEFF DOZIER, University of California, Santa Barbara

JOSEPH FULLER JR., Futron Corporation (retired)

SARAH GIBSON, National Center for Atmospheric Research

VICTORIA HAMILTON, Southwest Research Institute

CHRYSSA KOUVELIOTOU, NAS, George Washington University

DENNIS P. LETTENMAIER, NAE, University of California, Los Angeles

ROSALY M. LOPES, Jet Propulsion Laboratory

STEPHEN J. MACKWELL, Universities Space Research Association

DAVID J. MCCOMAS, Princeton University

LARRY PAXTON, Johns Hopkins University, Applied Physics Laboratory

ELIOT QUATAERT, University of California, Berkeley

BARBARA SHERWOOD LOLLAR, University of Toronto

HARLAN E. SPENCE, University of New Hampshire

MARK H. THIEMENS, NAS, University of California, San Diego

ERIKA WAGNER, Blue Origin

PAUL WOOSTER, Space Exploration Technologies

EDWARD L. WRIGHT, NAS, University of California, Los Angeles

Staff

MICHAEL H. MOLONEY, Director (until March 2, 2018)

RICHARD ROWBERG, Interim Director (March 2 to August 6, 2018)

COLLEEN HARTMAN, Director (from August 6, 2018)

CARMELA J. CHAMBERLAIN, Administrative Coordinator

TANJA PILZAK, Manager, Program Operations

CELESTE A. NAYLOR, Information Management Associate

MARGARET KNEMEYER, Financial Officer

___________________

¹ Member, National Academy of Sciences.

² Member, National Academy of Engineering.

Preface

Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. It is an inherently interdisciplinary field that encompasses astronomy, biology, geology, heliophysics, and planetary science, including complementary laboratory activities and field studies conducted in a wide range of terrestrial environments. Combining inherent scientific interest and public appeal, the search for life in the solar system and beyond provides a scientific rationale for many current and future activities carried out by the National Aeronautics and Space Administration (NASA) and other national and international agencies and organizations.

In 2017, Congress directed NASA to enter into an arrangement with the National Academies of Sciences, Engineering, and Medicine to develop a science strategy for astrobiology that would outline key scientific questions, identify the most promising research in the field, and indicate the extent to which the mission priorities in existing decadal surveys address the search for life’s origin, evolution, distribution, and future in the universe (see Appendix A). In response to this congressional mandate, NASA’s associate administrator for the Science Mission Directorate approached the Space Studies Board (SSB) with a request to carry out this study (see Appendix B). While retaining the core language of the law, the statement of task ultimately agreed upon between SSB and NASA incorporated additional tasks relating to the specific programmatic and scientific context of the agency’s various astrobiology-related endeavors, which are most prominently detailed in the 2015 NASA Astrobiology Strategy.¹ Indeed, both the SSB and NASA regarded the nature and timing of the request to be particularly fortuitous in that the results of the study would provide important input to the next decadal surveys in astronomy and astrophysics and planetary sciences, due to start in 2018 and 2020, respectively. Doubly fortuitous was the fact that the same congressional language also mandated that a similar strategy be developed for exoplanet exploration. Given close scientific ties between the astrobiology and exoplanet community, as well as the parallel timelines of the dual studies, the SSB and NASA agreed that the astrobiology and exoplanet committees should collaborate to the maximum degree feasible.

The discussions between NASA and the National Academies on the details of the task to be undertaken by the SSB converged on the following charge:

___________________

¹ NASA, NASA Astrobiology Strategy 2015, https://nai.nasa.gov/media/medialibrary/2016/04/NASA_Astrobiology_Strategy_2015_FINAL_041216.pdf.

To address this statement of task, the National Academies formally established the Committee on Astrobiology Science Strategy for the Search for Life in the Universe in the fall of 2017. The committee held its first meeting at the National Academies’ Beckman Center in Irvine, California, on January 16-18, 2018. Subsequent meetings were held in Washington, D.C., at the National Academy of Sciences and the Keck Center on March 6-8 and April 25-27, respectively.

In addition, the committee solicited community input in the form of white papers (see Appendix C). A total of 53 white papers originating from members of academia, employees of the federal government, and members of the general public were received and considered by the committee.

The astrobiology committee was able to have a significant degree of engagement and coordination with the exoplanet committee during the study. A co-chair of the exoplanet committee attended the first meeting of the astrobiology committee. Subsequently, a joint session of both committees was held on March 7, 2017, during the astrobiology committee’s second and the exoplanet committee’s first meeting. In addition, one member of the astrobiology committee also served as a member of the exoplanet committee, and SSB staff associated with the study attended the meetings of both committees. Furthermore, a working group composed of four members of each committee held three closed-session teleconferences to exchange ideas and review relevant parts of each report.

A complete draft of the committee’s report was sent to external reviewers for comment on June 20. A revised draft was assembled in July and August and was approved for release by the National Academies on September 20, 2018.

This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process.

We thank the following individuals for their review of this report: John Baross, University of Washington; Courtney Dressing, University of California, Berkeley; Colin Goldblatt, University of Victoria, Canada; Martha Grover, Georgia Institute of Technology; Jonathan Lunine, NAS,² Cornell University; Paul Mahaffy, NASA

___________________

² Member, National Academy of Sciences.

Goddard Space Flight Center; John Rummel, SETI Institute; Gary Ruvkun, NAS/NAM,³ Harvard Medical School, Massachusetts General Hospital; and Norman H. Sleep, NAS, Stanford University.

Although the reviewers listed above provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations of this report nor did they see the final draft before its release. The review of this report was overseen by Louis J. Lanzerotti, NAE,⁴ New Jersey Institute of Technology. He was responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies.

___________________

³ Member, National Academy of Medicine.

⁴ Member, National Academy of Engineering.

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Contents

SUMMARY

1 THE SEARCH FOR LIFE IN THE UNIVERSE: PAST, PRESENT, AND FUTURE

The Space Age, Planetary Science, Exobiology, and the Origins of Astrobiology

Astrobiology Roadmaps and Strategies

Forward from NASA’s Astrobiology Strategy 2015

Astrobiology: A Systems-Level Science

Organization of This Report

References

2 DYNAMIC HABITABILITY

A Thermodynamic Perspective on Life’s Origin

The Dynamic Early Earth and Life’s Emergence

Examples of Recent Advances in Understanding Dynamic Habitability

References

3 COMPARATIVE PLANETOLOGY AND MULTIPARAMETER HABITABILITY ASSESSMENT

Terrestrial Exoplanets and the Search for Habitability

Evolution from Habitable Zones to Multiparameter Habitability Assessment

Comparative Planetology

References

4 BIOSIGNATURE IDENTIFICATION AND INTERPRETATION

Identifying Novel Biosignatures to Improve Reliability

Agnostic Biosignatures

Survivability of Biosignatures

Detectability of Biosignatures

Toward a Comprehensive Framework for Integration of Biosignatures

References

5 EVOLUTION IN THE TECHNOLOGY AND PROGRAMMATIC LANDSCAPE

Technology for Searching for Life on Nearby Exoplanets

Technology for Sample-Based Life Detection

Programmatic Challenges and Opportunities

Developments in Drilling Technology and Sample Handling

Big Data Analysis Techniques

References

6 THE SEARCH FOR LIFE IN THE COMING DECADES

The Physical and Chemical Evolution of the Early Solar System and Prebiotic Earth

Dynamic Habitability: Coevolution of Life and Environment

Diverse Habitable Conditions and Subsurface Worlds

Astrobiology Goals for Exoplanet Missions

Understanding Biosignatures in the Context of Their Environment

A New Generation of Missions

References

7 LEVERAGING PARTNERSHIPS

Potential of the Commercial Sector

Increasing Philanthropic Investment

Managing Public-Private Partnerships

Unified Interagency Investment Strategies

International Opportunities

References

APPENDIXES

A Congressional Mandate and Letter of Request

B Statement of Task

C List of White Papers

D Biographies of Committee Members

E Glossary and Acronyms