Origins, Worlds, and Life

A Decadal Strategy for Planetary Science and Astrobiology 2023–2032

Committee on the Planetary Science and Astrobiology Decadal Survey

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 Contract No. NNH17CB02B/NNH17CB01T with the National Aeronautics and Space Administration and Grant No. 2040016 with the National Science Foundation. 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: 978-0-309-47578-5
International Standard Book Number-10: 0-309-47578-3
Digital Object Identifier: https://doi.org/10.17226/26522
Library of Congress Control Number: 2023938864

Cover: Design by Paul Byrne.
Images: Foreground waves: Conrad Ziebland; protoplanetary disk: ESO/L. Calçada; Saturn: NASA; Earth: ESA/OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA/Gordan Ugarković; magma ocean world: ESA/Hubble, M. Kornmesser; comet: NASA/ESA/Hubble Heritage Team (STScI-AURA); hydrothermal vent: MARUM–Zentrum für Marine Umweltwissenschaften, Universität Bremen; starfield: ESO/S. Brunier.

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Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2023. Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023–2032. Washington, DC: The National Academies Press. https://doi.org/10.17226/26522.

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COMMITTEE ON THE PLANETARY SCIENCE AND ASTROBIOLOGY DECADAL SURVEY

Steering Group

ROBIN M. CANUP, NAS,¹ Southwest Research Institute, Co-Chair

PHILIP R. CHRISTENSEN, Arizona State University, Co-Chair

MAHZARIN R. BANAJI, NAS, Harvard University

STEVEN J. BATTEL, NAE,² Battel Engineering

LARS E. BORG, Lawrence Livermore National Laboratory

ATHENA COUSTENIS, National Centre for Scientific Research, Paris Observatory

JAMES H. CROCKER, NAE, Lockheed Martin Space Systems Company

BRETT W. DENEVI, Johns Hopkins University Applied Physics Laboratory

BETHANY L. EHLMANN, California Institute of Technology

LARRY W. ESPOSITO, University of Colorado Boulder

ORLANDO FIGUEROA, Orlando Leadership Enterprise

JOHN M. GRUNSFELD, Endless Frontier Associates

JULIE HUBER, Woods Hole Oceanographic Institution

KRISHAN KHURANA, University of California, Los Angeles

WILLIAM B. McKINNON, Washington University in St. Louis

FRANCIS NIMMO, NAS, University of California, Santa Cruz

CAROL RAYMOND, Jet Propulsion Laboratory

BARBARA SHERWOOD LOLLAR, NAS/NAE, University of Toronto

AMY SIMON, NASA Goddard Space Flight Center

Panel on Giant Planet Systems

JONATHAN I. LUNINE, NAS, Cornell University, Chair

AMY SIMON, NASA Goddard Space Flight Center, Vice Chair

FRANCES BAGENAL, NAS, University of Colorado Boulder

RICHARD W. DISSLY, Ball Aerospace and Technologies Corporation

LEIGH N. FLETCHER, University of Leicester

TRISTAN GUILLOT, Nice Observatory

MATTHEW HEDMAN, University of Idaho

RAVIT HELLED, University of Zurich

KATHLEEN E. MANDT, Johns Hopkins University Applied Physics Laboratory

ALYSSA RHODEN, Southwest Research Institute

PAUL M. SCHENK, Lunar and Planetary Institute

MICHAEL H. WONG, SETI Institute

Panel on Mars

VICTORIA E. HAMILTON, Southwest Research Institute, Chair

BETHANY L. EHLMANN, California Institute of Technology, Vice Chair

WILLIAM B. BRINCKERHOFF, NASA Goddard Space Flight Center

TRACY K.P. GREGG, University of Buffalo

JASPER S. HALEKAS, University of Iowa

JOHN “JACK” W. HOLT, University of Arizona

JOEL HUROWITZ, Stony Brook University

___________________

¹ Member, National Academy of Sciences.

² Member, National Academy of Engineering.

BRUCE M. JAKOSKY, University of Colorado Boulder

MICHAEL MANGA, NAS, University of California, Berkeley

HARRY Y. MCSWEEN, NAS, University of Tennessee

CLAIRE E. NEWMAN, Aeolis Research

ALEJANDRO M. SAN MARTIN, NAE, Jet Propulsion Laboratory

KIRSTEN L. SIEBACH, Rice University

AMY WILLIAMS, University of Florida

ROBIN D. WORDSWORTH, Harvard University

Panel on Mercury and the Moon

TIMOTHY L. GROVE, NAS, Massachusetts Institute of Technology, Chair

BRETT W. DENEVI, Johns Hopkins University Applied Physics Laboratory, Vice Chair

JAMES DAY, University of California, San Diego

ALEXANDER J. EVANS, Brown University

SARAH FAGENTS, University of Hawaii at Manoa

WILLIAM M. FARRELL, NASA Goddard Space Flight Center

CALEB I. FASSETT, NASA Marshall Space Flight Center

JENNIFER L. HELDMANN, NASA Ames Research Center

MASATOSHI HIRABAYASHI, Auburn University

JAMES TUTTLE KEANE, Jet Propulsion Laboratory

FRANCIS MCCUBBIN, NASA Johnson Space Center

MIKI NAKAJIMA, University of Rochester

MARK P. SAUNDERS, Independent Consultant

SONIA M. TIKOO-SCHANTZ, Stanford University

Panel on Ocean Worlds and Dwarf Planets

ALEXANDER G. HAYES, Cornell University, Chair

FRANCIS NIMMO, NAS, University of California, Santa Cruz, Vice Chair

MORGAN L. CABLE, Jet Propulsion Laboratory

ALFONSO DAVILA, NASA Ames Research Center

GLEN FOUNTAIN, Johns Hopkins University Applied Physics Laboratory

CHRISTOPHER R. GERMAN, Woods Hole Oceanographic Institution

CHRISTOPHER R. GLEIN, Southwest Research Institute

CANDICE HANSEN, Planetary Science Institute

EMILY S. MARTIN, National Air and Space Museum, Smithsonian Institution

MARC NEVEU, University of Maryland

CAROL S. PATY, University of Oregon

LYNNAE C. QUICK, NASA Goddard Space Flight Center

JASON M. SODERBLOM, Massachusetts Institute of Technology

KRISTA M. SODERLUND, University of Texas Institute for Geophysics

Panel on Small Solar System Bodies

NANCY L. CHABOT, Johns Hopkins University Applied Physics Laboratory, Chair

CAROL RAYMOND, Jet Propulsion Laboratory, Vice Chair

PAUL A. ABELL, NASA Johnson Space Center

WILLIAM F. BOTTKE, Southwest Research Institute

HAROLD C. CONNOLLY, JR., Rowan University

THOMAS D. JONES, Association of Space Explorers

STEFANIE N. MILAM, NASA Goddard Space Flight Center

EDGARD G. RIVERA-VALENTÍN, Lunar and Planetary Institute

DANIEL J. SCHEERES, NAE, University of Colorado Boulder

RHONDA STROUD, Naval Research Laboratory

MEGAN BRUCK SYAL, Lawrence Livermore National Laboratory

MYRIAM TELUS, University of California, Santa Cruz

AUDREY THIROUIN, Lowell Observatory

CHAD TRUJILLO, Northern Arizona University

BENJAMIN P. WEISS, Massachusetts Institute of Technology

Panel on Venus

PAUL K. BYRNE, Washington University in St. Louis, Chair

LARRY W. ESPOSITO, University of Colorado, Vice Chair

GIADA N. ARNEY, NASA Goddard Space Flight Center

AMANDA S. BRECHT, NASA Ames Research Center

THOMAS E. CRAVENS, University of Kansas

KANDIS-LEA JESSUP, Southwest Research Institute

JAMES F. KASTING, NAS, The Pennsylvania State University

SCOTT D. KING, Virginia Polytechnic Institute and State University

BERNARD MARTY, Université de Lorraine

THOMAS NAVARRO, University of California, Los Angeles

JOSEPH G. O’ROURKE, Arizona State University

JENNIFER M. ROCCA, Jet Propulsion Laboratory

ALISON R. SANTOS, Wesleyan University

JENNIFER L. WHITTEN, Tulane University

Staff

DAVID H. SMITH, Senior Program Officer, Space Studies Board, Study Director

DWAYNE A. DAY, Senior Program Officer, Aeronautics and Space Engineering Board

DANIEL NAGASAWA, Program Officer, Space Studies Board

JORDYN WHITE, Program Officer, Committee on National Statistics

CARL-GUSTAV ANDERSON, Associate Program Officer, Board on Mathematical Sciences and Analytics

MIA BROWN, Research Associate, Space Studies Board

MEGAN A. CHAMBERLAIN, Senior Program Assistant, Space Studies Board

GAYBRIELLE HOLBERT, Program Assistant, Space Studies Board

DIONNA ALI, Associate Program Officer, Intelligence Community Studies Board

ELI NASS, Research Assistant, Division on Engineering and Physical Sciences

KATHERINE DZURILLA, Temporary Research Assistant, Space Studies Board

LUCIA ILLIARI, Temporary Research Assistant, Space Studies Board

JEAN DE BECDELIEVRE, Christine C. Mirzayan Science and Technology Policy Fellow (2021)

JACOB N.H. ABRAHAMS, Lloyd V. Berkner Space Policy Intern (2021)

TARINI KONCHADY, Lloyd V. Berkner Space Policy Intern (2021)

DYLAN PITTS, Lloyd V. Berkner Space Policy Intern (2023)

COLLEEN N. HARTMAN, Director, Space Studies Board

SPACE STUDIES BOARD

MARGARET G. KIVELSON, NAS, University of California, Los Angeles, Chair

GREGORY P. ASNER, NAS, Carnegie Institution for Science

ADAM BURROWS, NAS, Princeton University

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

JEFF DOZIER, University of California, Santa Barbara

M. DARBY DYAR, Mount Holyoke College

ANTONIO L. ELIAS, NAE, Orbital ATK (retired)

VICTORIA E. HAMILTON, Southwest Research Institute

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

ROSALY M. LOPES, Jet Propulsion Laboratory

STEPHEN J. MACKWELL, American Institute of Physics

DAVID J. MCCOMAS, Princeton University

LARRY J. PAXTON, Johns Hopkins University

ELIOT QUATAERT, University of California, Berkeley

MARK SAUNDERS, Independent Consultant

BARBARA SHERWOOD LOLLAR, NAS/NAE, University of Toronto

HOWARD SINGER, National Oceanic and Atmospheric Administration

ERIKA B. WAGNER, Blue Origin

PAUL D. WOOSTER, Space Exploration Technologies

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

Staff

COLLEEN N. HARTMAN, Director

CARMELA J. CHAMBERLAIN, Administrative Coordinator

TANJA PILZAK, Manager, Program Operations

CELESTE A. NAYLOR, Information Management Associate

MARGARET KNEMEYER, Financial Officer

Preface

The Planetary Science Division (PSD) of NASA’s Science Mission Directorate (SMD) is the primary source of funding for planetary science, astrobiology, and planetary defense activities in the United States. In addition, the National Science Foundation (NSF) provides modest, but highly important, support for a variety of supporting ground-based activities, most notably access to world-class, ground-based optical and radio telescopes.

The allocation of resources within and among spacecraft missions, supporting research activities, and technology development is determined to a major extent via a relatively mature strategic planning process that relies heavily on inputs from the scientific community to establish the scientific basis and direction for its space-science flight- and ground-research programs and technology development activities.

The primary sources of this guidance are the independent scientific analyses and recommendations provided by reports of the National Academies of Sciences, Engineering, and Medicine (e.g., by the Space Studies Board [SSB] and its committees) and, to a lesser extent, by parallel inputs coming from community-based, but NASA-organized, analysis/assessment groups (e.g., the Mars Exploration Program Analysis Group and the Outer Planets Assessment Group). The science strategies developed by the SSB and the analysis/assessment groups form input to subsequent program development activities conducted by the FACA-chartered NASA Advisory Council and its associated committees (e.g., NASA’s Planetary Science Advisory Committee).

The SSB’s primary vehicles for the provision of strategic advice to NASA are the space science decadal surveys. The National Academies decadal surveys are widely recognized among policymakers and program managers as key resources in determining where a field of research is and where it is headed. Indeed, the decadal survey process has proved so useful that Section 1104 of the NASA Authorization Act of 2008 requires that the NASA “Administrator shall enter into agreements on a periodic basis with the National Academies for independent assessments, also known as decadal surveys, to take stock of the status and opportunities for Earth and space science discipline fields and aeronautics research and to recommend priorities for research and programmatic areas over the next decade.”

The most recent effort for planetary science and astrobiology resulted in the publication of Vision and Voyages for Planetary Science in the Decade 2013–2022 in 2011. While it is generally regarded that Vision and Voyages was especially successful in its outcomes—as witnessed by the facts that the survey’s top two large-class mission priorities are both under development and that PSD’s annual budget has doubled over the past decade—a new survey is needed to address the challenges of the coming decade.

Following informal requests in the early months of 2019 from the director of PSD, the SSB and its Committee on Astrobiology and Planetary Science (CAPS) began the task of defining the specific actions and issues that

needed to be address in a new decadal survey. CAPS’s activities culminated in the convening of a decadal survey organizing meeting, held at the California Institute of Technology’s Keck Institute for Space Studies in September 2019. Negotiations between NASA and the SSB continued through the final months of 2019 and eventually settled on a statement of task calling for a decadal survey that provided a clear exposition of the following:¹

1. An overview of planetary science, astrobiology, and planetary defense: what they are, why they are compelling undertakings, and the relationship between space- and ground-based research.
2. A broad survey of the current state of knowledge of the solar system.
3. The most compelling science questions, goals, and challenges that should motivate future strategy in planetary science, astrobiology, and planetary defense.
4. A coherent and consistent traceability of recommended research and missions to objectives and goals.
5. A comprehensive research strategy to advance the frontiers of planetary science, astrobiology, and planetary defense during the period 2023–2032 that will include identifying, recommending, and ranking the highest priority research activities (research activities include any project, facility, experiment, mission, or research program of sufficient scope to be identified separately in the final report). For each activity, consideration should be given to the scientific case, international and private landscape, timing, cost category and cost risk, as well as technical readiness, technical risk, lifetime, and opportunities for partnerships. The strategy should be balanced by consideration of large, medium, and small research activities for both ground and space.
6. Recommendations for decision rules, where appropriate, for the comprehensive research strategy that can accommodate significant but reasonable deviations in the projected budget or changes in urgency precipitated by new discoveries or technological developments.
7. An awareness of the science and space mission plans and priorities of NASA human space exploration programs and potential foreign and U.S. agency partners reflected in the comprehensive research strategy and identification of opportunities for cooperation, as appropriate.
8. The opportunities for collaborative research that are relevant to science priorities among SMD’s four science divisions (for example, comparative planetology approaches to exoplanet or astrobiology research); between NASA SMD and the other NASA mission directorates; between NASA and the NSF; between NASA and other U.S. government entities; between NASA and private sector organizations; and between NASA and its international partners.
9. The state of the profession, including issues of diversity, inclusion, equity, and accessibility; the creation of safe workspaces; and recommended policies and practices to improve the state of the profession. Where possible, provide specific, actionable, and practical recommendations to the agencies and community to address these areas.

In response to this request, the National Academies established the Committee on the Planetary Science and Astrobiology Decadal Survey (hereafter, the “survey committee” or the “committee”) consisting of a 19-member steering group and 78 additional experts organized into six topical panels. The co-chairs of the survey committee were appointed in May 2020, and the members of the panels were identified and appointed in the subsequent spring and summer months.

The steering group held its first meeting on September 30, 2020, and held its 22nd and final meeting on November 2, 2021. The six panels each held at least 20 meetings during the period October 2020 to September 2021. Notably, each and every single meeting was held virtually because of the ongoing COVID-19 pandemic. The work of the survey committee can be divided into three distinct phases: the last 3 months of 2020, the first 9 months of 2021, and late summer/early autumn of 2021.

In phase one, the steering group deliberated on and defined the key science questions around which the report would be structured. In parallel, the panels ingested and assessed candidate missions already studied, and identified additional concepts deemed worthy of study. Phase one ended with the development of two key items: first, a cross-survey consensus that the most appropriate key questions had been identified, and second, the prioritization

___________________

¹ See Appendix A for the letter requesting this study, the full text of the statement of task, and additional, nonbinding guidelines.

by the steering group of 10 new mission concepts worthy of additional study. These 10 new concepts were subsequently forwarded to NASA for detailed study. To ensure that the panels would perform their initial task in an expeditious manner, they were organized and appointed so that each would have responsibility for different portions of the solar system—that is, Mercury and the Moon, Venus, Mars, giant planet systems, ocean worlds and dwarf planets, and small solar system bodies.

During the second phase, the panels worked with mission-design teams at the Jet Propulsion Laboratory, NASA Goddard Space Flight Center, and at the Johns Hopkins University Applied Physics Laboratory to develop the 10 new mission concepts. In parallel, a series of approximately 20 informal, cross-survey writing groups—each consisting of 5–10 members from the steering group and the panels—were established to create the initial drafts of the chapters in this report devoted to the key science questions and to programmatic issues such as the state of the profession, research and analysis, and technology development. Once the additional mission studies were completed, their sponsoring panels performed a comparative assessment of the degree to which the new concepts and other proposed and studied missions could address the survey’s key science questions. This phase of the survey ended with the completion of the initial drafts of 20 of this report’s 23 chapters and the prioritization by the steering group of 17 mission concepts (some new and some old) for detailed technical risk and cost evaluation (TRACE) by the Aerospace Corporation.

Phase three involved the scheduling of some 20 survey-wide “summit meetings,” during which the text produced by each writing group was subjected to intense comment, review, and subsequent revision. In parallel, the steering group assessed the results of the TRACE analyses, selected the most promising ones, prioritized them, and, thus, established the survey’s list of recommended mission activities for the coming decade. In addition, the steering group worked with the leaders of each writing group to integrate the draft text of the various chapters into a self-consistent and coherent program of activities for the next decade. The final task performed was the drafting by the steering group of the summary and the chapter describing the recommended program of activities for the period 2023–2032.

Final sections of the report were drafted, assembled, and integrated in October and November 2021. The text was sent to external reviewers in December, was revised between January and February 2022, was formally approved for release by the National Academies on March 24, 2022, and was publicly unveiled on April 19, 2022.

The work of the committee was made easier thanks to the important help given by individuals too numerous to list—indeed, printing just the names of those individuals who made public presentations to the survey committee would require two full pages of text—at a variety of public and private organizations, who made presentations at committee meetings, drafted white papers, and participated in mission studies. Important contributions were also made by the TRACE team at the Aerospace Corporation, led by Russell Persinger, Justin Yoshida, and Mark Barrera. Last, the survey committee thanks Kellie Mendelow for her invaluable record keeping, file management, and editorial assistance.

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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:

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¹ Member, National Academy of Sciences.

² Member, National Academy of Medicine.

Although the reviewers listed above have 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 Rosaly M. Lopes, Jet Propulsion Laboratory, and Norman H. Sleep, NAS, Stanford University. They were 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 of the report rests entirely with the authoring committee and the National Academies.

___________________

³ Member, National Academy of Engineering.

Contents

SUMMARY

1 INTRODUCTION TO PLANETARY SCIENCE, ASTROBIOLOGY, AND PLANETARY DEFENSE

Planetary Science and Astrobiology

Planetary Defense

The Relationship Between Ground- and Space-Based Research

Support for Planetary Science and Astrobiology

International Cooperation

Planetary Science Decadal Surveys and Related Reports

Scientific Scope of This Report

A Guide to Reading This Report

References

2 TOUR OF THE SOLAR SYSTEM: A TRANSFORMATIVE DECADE OF EXPLORATION

Mercury

The Moon

Venus

Mars

Small Solar System Bodies

Giant Planet Systems

Ocean Worlds and Dwarf Planets

References

3 PRIORITY SCIENCE QUESTIONS

4 QUESTION 1: EVOLUTION OF THE PROTOPLANETARY DISK

Q1.1 What Were the Initial Conditions in the Solar System?

Q1.2 How Did Distinct Reservoirs of Gas and Solids Form and Evolve in the Protoplanetary Disk?

Q1.3 What Processes Led to the Production of Planetary Building Blocks—That Is, Planetesimals?

Q1.4 How and When Did the Nebula Disperse?

Supportive Activities for Question 1

References

5 QUESTION 2: ACCRETION IN THE OUTER SOLAR SYSTEM

Q2.1 How Did the Giant Planets Form?

Q2.2 What Controlled the Compositions of the Material That Formed the Giant Planets?

Q2.3 How Did Satellites and Rings Form Around the Giant Planets During the Accretion Era?

Q2.4 How Did the Giant Planets Gravitationally Interact with Each Other, the Protosolar Disk, and Smaller Bodies in the Outer Solar System?

Q2.5 How Did Processes in the Early Outer Solar System Produce the Structure and Composition (Surface and Interior) of Pluto and the Trans-Neptunian Objects?

Q2.6 How Did the Orbital Structure of the Trans-Neptunian Belt, the Oort Cloud, and the Scattered Disk Originate, and How Did Gravitational Interactions in the Early Outer Solar System Lead to Scattering and Ejection?

Supportive Activities for Question 2

References

6 QUESTION 3: ORIGIN OF EARTH AND INNER SOLAR SYSTEM BODIES

Q3.1 How and When Did Asteroids and Inner Solar System Protoplanets Form?

Q3.2 Did Giant Planet Formation and Migration Shape the Formation of the Inner Solar System?

Q3.3 How Did the Earth–Moon System Form?

Q3.4 What Processes Yielded Mars, Venus, and Mercury and Their Varied Initial States?

Q3.5 How and When Did the Terrestrial Planets and Moon Differentiate?

Q3.6 What Established the Primordial Inventories of Volatile Elements and Compounds in the Inner Solar System?

Supportive Activities for Question 3

References

7 QUESTION 4: IMPACTS AND DYNAMICS

Q4.1 How Have Planetary Bodies Collisionally and Dynamically Evolved Throughout Solar System History?

Q4.2 How Did Impact Bombardment Vary with Time and Location in the Solar System?

Q4.3 How Did Collisions Affect the Geological, Geophysical, and Geochemical Evolution and Properties of Planetary Bodies?

Q4.4 How Do the Physics and Mechanics of Impacts Produce Disruption of and Cratering on Planetary Bodies?

Supportive Activities for Question 4

References

8 QUESTION 5: SOLID BODY INTERIORS AND SURFACES

Q5.1 How Diverse Are the Compositions and Internal Structures Within and Among Solid Bodies?

Q5.2 How Have the Interiors of Solid Bodies Evolved?

Q5.3 How Have Surface/Near-Surface Characteristics and Compositions of Solid Bodies Been Modified by, and Recorded, Interior Processes?

Q5.4 How Have Surface Characteristics and Compositions of Solid Bodies Been Modified by, and Recorded, Surface Processes and Atmospheric Interactions?

Q5.5 How Have Surface Characteristics and Compositions of Solid Bodies Been Modified by, and Recorded, External Processes?

Q5.6 What Drives Active Processes Occurring in the Interiors and on the Surfaces of Solid Bodies?

Supportive Activities for Question 5

References

9 QUESTION 6: SOLID BODY ATMOSPHERES, EXOSPHERES, MAGNETOSPHERES, AND CLIMATE EVOLUTION

Q6.1 How Do Solid Body Atmospheres Form and What Was Their State During and Shortly After Accretion?

Q6.2 What Processes Govern the Evolution of Planetary Atmospheres and Climates over Geologic Timescales?

Q6.3 What Processes Drive the Dynamics and Energetics of Atmospheres on Solid Bodies?

Q6.4 How Do Planetary Surfaces and Interiors Influence and Interact with Their Host Atmospheres?

Q6.5 What Processes Govern Atmospheric Loss to Space?

Q6.6 What Chemical and Microphysical Processes Govern the Clouds, Hazes, Chemistry, and Trace Gas Composition of Solid Body Atmospheres?

References

10 QUESTION 7: GIANT PLANET STRUCTURE AND EVOLUTION

Q7.1 What Are Giant Planets Made of and How Can This Be Inferred from Their Observable Properties?

Q7.2 What Determines the Structure and Dynamics Deep Inside Giant Planets and How Does It Affect Their Evolution?

Q7.3 What Governs the Diversity of Giant Planet Climates, Circulation, and Meteorology?

Q7.4 What Processes Lead to the Dramatically Different Outcomes in the Structure, Content, and Dynamics of the Outer Planets’ Magnetospheres and Ionospheres?

Q7.5 How Are Giant Planets Influenced by, and How Do They Interact with, Their Environment?

Supportive Activities for Question 7

References

11 QUESTION 8: CIRCUMPLANETARY SYSTEMS

Q8.1 How Did Circumplanetary Systems Form and Evolve over Time to Yield Different Planetary Systems?

Q8.2 How Do Tides and Other Endogenic Processes Shape Planetary Satellites?

Q8.3 What Exogenic Processes Modify the Surfaces of Bodies in Circumplanetary Systems?

Q8.4 How Do Planetary Magnetospheres Interact with Satellites with Rings, and Vice Versa?

Q8.5 How Do Rings Evolve and Coalesce into Moons?

Supportive Activities for Question 8

References

12 QUESTION 9: INSIGHTS FROM TERRESTRIAL LIFE

Q9.1 What Were the Conditions and Processes Conducive to the Origin and Early Evolution of Life on Earth, and What Do They Teach Us About the Possible Emergence and Evolution of Life on Other Worlds?

Q9.2 What Is the Diversity, Distribution, and Range of Possible Metabolic Strategies of Life in Terrestrial Environments (Surface, Subsurface, Atmosphere) and How Did They Evolve Through Time?

Q9.3 How Do Investigations of Earth’s Subsurface Environments Inform What Habitability and/or Life on Other Worlds Might Look Like?

Q9.4 How Can Our Knowledge of Life and Where and How It Arises and Is Sustained on Earth Illuminate the Search for Life Beyond Earth?

Q9.5 How Do Record Bias, Preservational Bias, False Negatives, and False Positives Play a Role in Biosignature Detectability and Reliability on Earth, and What Are the Implications for Targets Beyond?

References

13 QUESTION 10: DYNAMIC HABITABILITY

Q10.1 What Is Habitability?

Q10.2 Where Are or Were the Solar System’s Past or Present Habitable Environments?

Q10.3 Water Availability: What Controls the Amount of Available Water on a Body over Time?

Q10.4 Organic Synthesis and Cycling: Where and How Are Organic Building Blocks of Life Synthesized in the Solar System?

Q10.5 What Is the Availability of Nutrients and Other Inorganic Ingredients to Support Life?

Q10.6 What Controls the Energy Available for Life?

Q10.7 What Controls the Continuity or Sustainability of Habitability?

Supportive Activities for Question 10

References

14 QUESTION 11: SEARCH FOR LIFE ELSEWHERE

Q11.1 Path to Biogenesis: What Is the Extent and History of Organic Chemical Evolution, Potentially Leading Toward Life, in Habitable Environments Throughout the Solar System? How Does This Inform the Likelihood of False Positive Life Detections?

Q11.2 Biosignature Potential: What Is the Biosignature Potential in Habitable Environments Beyond Earth? What Are the Possible Sources of False Positives and False Negatives?

Q11.3 Life Detection: Is or Was There Life Elsewhere in the Solar System?

Q11.4 Life Characterization: What Is the Nature of Life Elsewhere, If It Exists?

References

15 QUESTION 12: EXOPLANETS

Q12.1 Evolution of the Protoplanetary Disk

Q12.2 Accretion in the Outer Solar System

Q12.3 Origin of Earth and Inner Solar System Bodies

Q12.4 Impacts and Dynamics

Q12.5 Solid Body Interiors and Surfaces

Q12.6 Atmosphere and Climate Evolution on Solid Bodies

Q12.7 Giant Planet Structure and Evolution

Q12.8 Circumplanetary Systems

Q12.9 Insights from Terrestrial Life

Q12.10 Dynamic Habitability

Q12.11 Search for Life Elsewhere

Supportive Activities for Question 12

References

16 STATE OF THE PROFESSION

Introduction

Implicit and Systemic Bias

The Evidence

White Papers Submitted to the Survey

Summary of Findings

Recommendations

References

17 RESEARCH AND ANALYSIS

What Is R&A?

The Internal Scientist Funding Model

Virtual Institutes and Research Coordination Networks

Is the R&A Portfolio Optimized for NASA’s Scientific Needs?

R&A Proposal Review Process

Trends in PSD R&A Funding and Programs Through Time

Recommended Funding for NASA Planetary R&A

The Size of the Planetary Research Community

NASA-NSF Partnerships

References

18 PLANETARY DEFENSE: DEFENDING EARTH THROUGH APPLIED PLANETARY SCIENCE

NEO Detection, Tracking, and Characterization

NEO Modeling, Prediction, and Information Integration

NEO Deflection and Disruption Missions

International Cooperation on NEO Preparation

NEO Impact Emergency Procedures and Action Protocols

Conclusions

References

19 HUMAN EXPLORATION

The Pivotal Role of Science in Human Exploration

Science Enabled by Human Explorers

Near-Term Human Exploration Plans, Relationship to Science, and In Situ Resource Utilization

Integrating Science into Human Exploration

NASA Programmatic Considerations for Artemis and Beyond: Challenges of Integrating Science and Human Exploration

Scientific and Human Exploration of Mars

A Tale of Two Orbiters: LRO and IMIM

Research Programs to Enable and Optimize Human Exploration

Role of Commercial Space and Human-Scale Vehicle Capabilities

External Cooperation

References

20 INFRASTRUCTURE FOR PLANETARY SCIENCE AND EXPLORATION

NASA Infrastructure

Supporting NSF Infrastructure

Intra-Agency, Interagency, and International Collaborations

References

21 TECHNOLOGY

Technology Development in NASA

Technologies for This Decade and Beyond

Instrumentation

General Technology Areas

Disruptive and Game-Changing Trends in Technologies

References

22 RECOMMENDED PROGRAM: 2023–2032

Scientific Themes and Priority Science Questions

Ongoing Missions and Existing Programs

Discovery, New Frontiers, and Flagship Recommendations for the Decade 2023–2032

Representative Flight Programs for the Decade

State of the Profession

Other Key Programmatic Recommendations

References

23 THE FUTURE

Continuing Oversight

The Midterm Review

Preparing for the Next Decadal Survey

References

APPENDIXES

A Letter of Request, Statement of Task, and Other Guidance

B White Papers Received

C Technical Risk and Cost Evaluation of Priority Missions

D Missions Studied but Not Sent for TRACE

E Panel Missions Not Selected for Additional Study

F Glossary and Acronyms

G Biographical Information for Committee Members

Dedication

This report is dedicated to the memory of H. Jay Melosh (1947–2020)
who had agreed to play an important role in this study.

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