JPL Publication 06-5, Rev A Earth-Like Exoplanets: The Science of NASA’s Navigator Program Edited by: P. R. Lawson and W. A. Traub National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California October 16, 2006 This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement by the United States Government or the Jet Propulsion Laboratory, California Institute of Technology. ii A BSTRACT Abstract This book outlines the exoplanet science content of NASA’s Navigator Program, and it identifies the exoplanet research priorities. The goal of Navigator Program missions is to detect and characterize Earth- like planets in the habitable zone of nearby stars and to search for signs of life on those planets. The Navigator Program includes the ground-based Keck Interferometer and the Large Binocular Telescope Interferometer, designed to measure the inner and outer dust disks of nearby stars. The Navigator Program also includes three space-based missions: Space Interferometry Mission (SIM) PlanetQuest, Terrestrial Planet Finder Coronagraph (TPF-C), and Terrestrial Planet Finder Interferometer (TPF-I). The scientific goals of these missions are complementary: SIM will determine the orbits and masses of nearby planets, down to about one Earth-mass; TPF-C and TPF-I will detect Earth-like planets in the habitable zone of nearby stars and will measure the colors and spectra of these planets, in the visible and infrared respectively, to characterize them and look for signs of life. Each mission measures unique properties of exoplanets. Together the missions build a synergistic picture of exoplanets. No single mission can do this. We describe expected progress in exoplanet science research. We highlight areas worthy of investment by NASA. We list opportunities for funding from NASA and other agencies. This book also serves a programmatic purpose. The science priorities described here are tied to the development phases of individual Navigator missions. Preparatory science conducted by observational and theoretical research is essential to help define future missions, to aid our understanding of the planets that could be discovered, and to better understand the star systems that these missions will study. The programmatic gates and preparatory science requirements are listed for SIM PlanetQuest, TPF-C, and TPF-I. We will annually review and update this book as needed. The current edition is available online at http://planetquest.jpl.nasa.gov/documents/NavigatorScience2006.pdf. iii A PPROVALS Approvals Released by: ___________________ ______ JPL Peter R. Lawson date Science Architect, Navigator Program Approved by: ___________________ ______ Approved by: ___________________ ______ JPL Wesley A. Traub date NASA HQ Lia LaPiana date Chief Scientist, Program Executive, Navigator Program Navigator Program Approved by: ___________________ ______ Approved by: ___________________ ______ JPL Michael Devirian date NASA HQ Stephen Ridgway date Manager, Program Scientist, Navigator Program Navigator Program Approved by: ___________________ ______ Approved by: ___________________ ______ JPL Jakob van Zyl date NASA HQ Richard Howard date Director, JPL Astronomy & Physics Director, Directorate Astronomy and Physics Division v C ONTENTS Contents Approvals ........................................................................................................................... v Contents............................................................................................................................vii Preface ............................................................................................................................... xi 1 Introduction................................................................................................................... 1 1.1 Exoplanet Science: A New Interdisciplinary Field........................................................................... 1 1.2 The State of Exoplanet Science ........................................................................................................ 1 1.3 References......................................................................................................................................... 4 2 NASA Missions and the Search for Earth-Like Planets .......................................... 9 2.1 Fundamental Questions..................................................................................................................... 9 2.2 Study the Formation and Evolution of Planetary Systems.............................................................. 10 2.3 Explore the Diversity of Other Worlds........................................................................................... 12 2.4 Search for Habitable Planets and Life............................................................................................. 15 2.5 Navigator Program.......................................................................................................................... 21 2.6 Summary of Contributing NASA Missions.................................................................................... 28 3 Frequency of Terrestrial Planets............................................................................... 33 3.1 Objectives of Precursor Science ..................................................................................................... 33 3.2 Observational Programs.................................................................................................................. 36 3.3 Theory and Modeling...................................................................................................................... 45 3.4 Summary: Opportunities, Risk, and Priorities ................................................................................ 51 3.5 References....................................................................................................................................... 53 4 Exozodiacal Dust......................................................................................................... 55 4.1 Objectives of Precursor Science ..................................................................................................... 55 4.2 Observational Programs.................................................................................................................. 58 4.3 Theory and Modeling...................................................................................................................... 63 4.4 Summary: Opportunities, Risk, and Priorities ................................................................................ 67 4.5 References....................................................................................................................................... 68 vii C ONTENTS 5 Target Stars ................................................................................................................. 71 5.1 Objectives of Precursor Science ..................................................................................................... 71 5.2 Observational Programs.................................................................................................................. 74 5.3 Theory and Modeling...................................................................................................................... 77 5.4 Target Stars and Mission Studies.................................................................................................... 78 5.5 Summary: Opportunities, Risk, and Priorities ................................................................................ 83 5.6 References....................................................................................................................................... 83 6 Signs of Life ................................................................................................................. 87 6.1 Objectives of Precursor Science ..................................................................................................... 87 6.2 Observational Programs.................................................................................................................. 90 6.3 Theory and Modeling...................................................................................................................... 94 6.4 Summary: Opportunities, Risk, and Priorities .............................................................................. 100 6.5 References..................................................................................................................................... 101 7 Astrophysics and Exoplanets ................................................................................... 105 7.1 Capabilities ................................................................................................................................... 108 7.2 General Astrophysics Objectives.................................................................................................. 109 7.3 Formation and Evolution of Stars ................................................................................................. 110 7.4 Formation and Evolution