EXOPLANET
SCIENCE
STRATEGY
Committee on Exoplanet Science Strategy
Space Studies Board
Board on Physics and Astronomy
Division on Engineering and Physical Sciences
A Consensus Study Report of
THE NATIONAL ACADEMIES PRESS
Washington, DC
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This study is based on work supported by Contract NNH11CD57B with the National Aeronautics and Space Administration. Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any agency or organization that provided support for the project.
International Standard Book Number-13: 978-0-309-47941-7
International Standard Book Number-10: 0-309-47941-X
Digital Object Identifier: https://doi.org/10.17226/25187
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Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2018. Exoplanet Science Strategy. Washington, DC: The National Academies Press. https://doi.org/10.17226/25187.
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COMMITTEE ON EXOPLANET SCIENCE STRATEGY
DAVID CHARBONNEAU, NAS,1 Harvard University, Co-Chair
B. SCOTT GAUDI, Ohio State University, Co-Chair
FABIENNE A. BASTIEN, Pennsylvania State University
JACOB BEAN, University of Chicago
JUSTIN R. CREPP, University of Notre Dame
ELIZA KEMPTON, University of Maryland
CHRYSSA KOUVELIOTOU, NAS, The George Washington University
BRUCE A. MACINTOSH, Stanford University
DIMITRI P. MAWET, California Institute of Technology
VICTORIA S. MEADOWS, University of Washington
RUTH MURRAY-CLAY, University of California, Santa Cruz
EVGENYA L. SHKOLNIK, Arizona State University
IGNAS SNELLEN, Leiden University
ALYCIA J. WEINBERGER, Carnegie Institution of Washington
Staff
NATHAN J. BOLL, Associate Program Officer, Study Director (after May 2018)
DAVID B. LANG, Senior Program Officer, Study Director (until May 2018)
ARTHUR A. CHARO, Senior Program Officer
CHRISTOPHER J. JONES, Program Officer
DIONNA WISE, Program Coordinator
LAURA J. CUMMINGS, Berkner Space Policy Intern
MICHAEL H. MOLONEY, Director, Aeronautics and Space Engineering Board and Space Studies Board (until April 2018)
RICHARD ROWBERG, Interim Director, Aeronautics and Space Engineering Board and Space Studies Board (April 2018 through July 2018)
COLLEEN HARTMAN, Director, Aeronautics and Space Engineering Board and Space Studies Board (after July 2018)
JAMES C. LANCASTER, Director, Board on Physics and Astronomy
___________________
1 Member, National Academy of Sciences.
SPACE STUDIES BOARD
FIONA A. 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, Inc.
JOSEPH FULLER, JR., Futron Corporation
SARAH GIBSON, National Center for Atmospheric Research
VICTORIA HAMILTON, Southwest Research Institute
CHRYSSA KOUVELIOTOU, NAS, The George Washington University
DENNIS P. LETTENMAIER, NAE, University of California, Los Angeles
ROSALY M. C. LOPES, Jet Propulsion Laboratory
STEPHEN J. MACKWELL, Universities Space Research Association
DAVID J. McCOMAS, Princeton University
LARRY PAXTON, Johns Hopkins University
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 B. WAGNER, Blue Origin, LLC
PAUL D. WOOSTER, Space Exploration Technologies
EDWARD L. WRIGHT, NAS, University of California, Los Angeles
Staff
MICHAEL H. MOLONEY, Director (until April 2018)
RICHARD ROWBERG, Interim Director (April 2018 through July 2018)
COLLEEN HARTMAN, Director (after July 2018)
CARMELA J. CHAMBERLAIN, Administrative Coordinator (until June 2018)
TANJA PILZAK, Manager, Program Operations
CELESTE A. NAYLOR, Information Management Associate
MARGARET A. KNEMEYER, Financial Officer
ANTHONY BRYANT, Financial Associate (until August 2018)
___________________
1 Member, National Academy of Sciences.
2 Member, National Academy of Engineering.
BOARD ON PHYSICS AND ASTRONOMY
BARBARA V. JACAK, NAS,1 Lawrence Berkeley National Laboratory, Chair
ABRAHAM LOEB, Harvard University, Vice Chair
LOUIS F. DIMAURO, The Ohio State University
FRANCIS J. DISALVO, NAS, Cornell University
NATHANIEL J. FISCH, Princeton University
DANIEL S. FISHER, NAS, Stanford University
WENDY L. FREEDMAN, NAS, University of Chicago
TIMOTHY M. HECKMAN, NAS, Johns Hopkins University
WENDELL T. HILL III, University of Maryland
ALAN HURD, Los Alamos National Laboratory
BARBARA A. JONES, IBM Almaden Research Center
ANDREW J. LANKFORD, University of California, Irvine
NERGIS MAVALVALA, NAS, Massachusetts Institute of Technology
LYMAN A. PAGE, JR., NAS, Princeton University
STEVEN M. RITZ, University of California, Santa Cruz
Staff
JAMES C. LANCASTER, Director
DONALD SHAPIRO, Senior Scholar
CHRISTOPHER J. JONES, Program Officer
NEERAJ GORKHALY, Associate Program Officer
HENRY KO, Research Associate
LINDA WALKER, Program Coordinator
BETH DOLAN, Financial Associate
___________________
1 Member, National Academy of Sciences.
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Preface
The NASA Transition Authorization Act of 2017 directed the National Aeronautics and Space Administration (NASA) to engage the National Academies of Sciences, Engineering, and Medicine in the development of a science strategy for the study and exploration of extrasolar planets in preparation for, and as an input to, the upcoming decadal surveys in astronomy and astrophysics and in planetary science. The NASA Science Mission Directorate then enlisted the Space Studies Board (SSB) and the Board on Physics and Astronomy to establish the Committee on Exoplanet Science Strategy. This committee was charged with surveying the status of the field and outlining key scientific questions for future research, as well as identifying opportunities for coordination with international, commercial, and not-for-profit partners. The complete statement of task is reprinted in Appendix A.
To address its task, the committee convened three in-person meetings and numerous teleconferences during its work from December 2017 through August 2018. The meetings included extensive conversations with the exoplanet science community, including leadership from NASA and the National Science Foundation, and featured presentations from a broad range of stakeholders, including mission scientists, individual investigators, international representatives, and philanthropic organizations. In addition, the committee issued a broad call for white papers that was targeted at the astronomy community, but open to anyone who wished to provide input to the study process. The complete white paper call and a list of the submitted white papers are reprinted in Appendix B. The full text of the submitted white papers is also available on the committee’s website. Throughout this process, the committee coordinated its work with the concurrent National Academies Committee on the State of the Science of Astrobiology.
The committee would like to thank the many generous individuals throughout the exoplanet science community and its supporting institutions who contributed to the study process through presentations, written input, and discussions. A special thanks goes to the staff from the National Academies: David Lang, Nathan Boll, Chris Jones, Art Charo, Dionna Wise, Jim Lancaster, Richard Rowberg, Colleen Hartman, and former SSB director Michael Moloney.
Dave Charbonneau and Scott Gaudi, Co-Chairs
Committee on Exoplanet Science Strategy
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Acknowledgment of Reviewers
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:
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 Marcia J. Rieke, NAS, University of Arizona. She 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.
___________________
1 Member, National Academy of Engineering.
2 Member, National Academy of Sciences.
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Contents
2 THE STATE OF THE FIELD OF EXOPLANETS
Methods of Detecting and Characterizing Exoplanets: Applications, Biases, and Limitations
What Has Been Learned About Exoplanets in the Past 30 Years?
The Demographics of Exoplanets
Exoplanet Atmospheres and Interiors
The Search for Life on Exoplanets
3 OUTLINING THE EXOPLANET SCIENCE STRATEGY
Characterizing Planets and Planetary Systems
Toward a More Complete Statistical Census of Exoplanets
Characterizing the Atmospheres and Interiors of a Diversity of Exoplanets
Understanding the Factors That Affect Habitability and How to Measure Them
Discovering Potentially Habitable Planets and Searching for Life on Them
4 IMPLEMENTING THE EXOPLANET SCIENCE STRATEGY
Expanding the Statistical Census of Exoplanets in the Galaxy
Opportunities to Characterize Planets Through Transits
Planet Discoveries Through Transits
Atmospheric Characterization Through Transit Spectroscopy
The Need for Detailed Stellar Characterization
Connecting the Exoplanet and Stellar Astrophysics Communities
Theory of Exoplanet Evolution, Interiors, Surfaces, and Atmospheres
Specific Scientific Challenges in the Theory of Exoplanets
Observations and Studies to Support the Search for Habitable Environments and Life
Mechanisms to Achieve Interdisciplinarity
Reducing Barriers to Scientific Excellence
Areas Needing Further Research
6 TIMELINE FOR THE EXOPLANET SCIENCE STRATEGY