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Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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22

Recommended Program: 2023–2032

This chapter outlines a prioritized program of research activities to advance the frontiers of planetary science, astrobiology, and planetary defense in the 2023–2032 decade. The recommended program, traced directly from the priority science questions, defines an integrated portfolio of flight projects, high-priority research activities, and technology development that will produce transformative advances in our knowledge and understanding. The program is shown to be achievable within realistic funding profiles, and decision rules are identified to accommodate budgetary changes or new scientific or technical developments. The recommended program is balanced across activities of varied scale and scientific focus and includes key areas for cooperation with NASA’s human exploration program and U.S. agency, industry, and international partners. This chapter addresses items three through nine1 in the Statement of Task (see Appendix A).

The chapter begins with background on approaches and definitions and an assessment of key elements of NASA’s ongoing missions and existing programs and activities. This discussion is followed by recommendations and prioritizations of future missions, and a detailed description of the recommended overall program for representative budgetary profiles, including decision rules. The final sections provide recommendations on major aspects of NASA’s activities that have broad importance for both the recommended program and the continued success of the nation’s planetary science and astrobiology efforts, informed by key findings and recommendations detailed in Chapters 1621.

SCIENTIFIC THEMES AND PRIORITY SCIENCE QUESTIONS

This decadal report is the first to be organized according to significant, overarching science questions. The committee first identified three high-level scientific themes2 as intellectual drivers for the pursuit of planetary science and astrobiology:

Origins: How did the solar system and Earth originate, and are systems like ours common or rare in the universe?

Worlds and Processes: How did planetary bodies evolve from their primordial states to the diverse objects seen today?

Life and Habitability: What conditions led to habitable environments and the emergence of life on Earth, and did life form elsewhere?

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1 Note: this chapter only includes summary discussions of and key recommendations for the state of the profession (Chapter 16), research and analysis (Chapter 17), planetary defense (Chapter 18), infrastructure (Chapter 20), and technology (Chapter 21). Readers interested in more details on any and all of these topics should consult the relevant chapter.

2 It is from these themes that the report’s title—Origins, Worlds, and Life—is derived.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

Across these themes, the committee defined 12 priority science questions, shown in Table 22-1, each comprised of a single overarching topic and a brief description of the question’s scope. Chapters 3 through 15 describe these priority questions, as well as specific sub-questions and strategic research activities for each that would provide substantial advances in understanding over the next decade. The strategic research activities span basic theory and modeling, laboratory and experimental work, ground-based observations, and spacecraft measurements and investigations.

TABLE 22-1 The Twelve Priority Science Question

Scientific Themes Priority Science Question Topics and Descriptions
(A) Origins Q1. Evolution of the protoplanetary disk. What were the initial conditions in the solar system? What processes led to the production of planetary building blocks, and what was the nature and evolution of these materials?
Q2. Accretion in the outer solar system. How and when did the giant planets and their satellite systems originate, and did their orbits migrate early in their history? How and when did dwarf planets and cometary bodies orbiting beyond the giant planets form, and how were they affected by the early evolution of the solar system?
Q3. Origin of Earth and inner solar system bodies. How and when did the terrestrial planets, their moons, and the asteroids accrete, and what processes determined their initial properties? To what extent were outer solar system materials incorporated?
(B) Worlds and Processes Q4. Impacts and dynamics. How has the population of solar system bodies changed through time, and how has bombardment varied across the solar system? How have collisions affected the evolution of planetary bodies?
Q5. Solid body interiors and surfaces. How do the interiors of solid bodies evolve, and how is this evolution recorded in a body’s physical and chemical properties? How are solid surfaces shaped by subsurface, surface, and external processes?
Q6. Solid body atmospheres, exospheres, magnetospheres, and climate evolution. What establishes the properties and dynamics of solid body atmospheres and exospheres, and what governs material loss to space and exchange between the atmosphere and the surface and interior? Why did planetary climates evolve to their current varied states?
Q7. Giant planet structure and evolution. What processes influence the structure, evolution, and dynamics of giant planet interiors, atmospheres, and magnetospheres?
Q8. Circumplanetary systems. What processes and interactions establish the diverse properties of satellite and ring systems, and how do these systems interact with the host planet and the external environment?
(C) Life and Habitability Q9. Insights from terrestrial life. What conditions and processes led to the emergence and evolution of life on Earth; what is the range of possible metabolisms in the surface, subsurface, and/or atmosphere; and how can this inform our understanding of the likelihood of life elsewhere?
Q10. Dynamic habitability. Where in the solar system do potentially habitable environments exist, what processes led to their formation, and how do planetary environments and habitable conditions co-evolve over time?
Q11. Search for life elsewhere. Is there evidence of past or present life in the solar system beyond Earth, and how do we detect it?
Cross-cutting A–C linkage Q12. Exoplanets. What does our planetary system and its circumplanetary systems of satellites and rings reveal about exoplanetary systems, and what can circumstellar disks and exoplanetary systems teach us about the solar system?
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Topics that appear frequently in the science question chapters include:

  • The central role of sample return and in situ analyses for providing breakthrough science and ground-truth constraints;
  • The dearth of knowledge of the ice giant3 systems, which may represent the most common class of exoplanets, and the importance of ice versus gas giant comparative studies;
  • Effects of nebular processes on compositional mixing and the formation of planetary building blocks and primitive bodies, and the need for further constraints on the solar system’s dynamical evolution, from primordial planet migration to ongoing bombardment;
  • The complex interplay of internal and external processes—many still ongoing—that affect planets, moons, rings, and small bodies, and the factors responsible for the varied initial states and divergent evolutionary paths of our terrestrial planets;
  • The conditions that led to the emergence of life on Earth, and the compelling rationale for understanding habitability beyond Earth, particularly at Mars and icy ocean worlds; and
  • A strong desire in the coming decade to make substantive progress in understanding whether life existed (or exists) elsewhere in the solar system.

These topics figured prominently in the committee’s discussions and provided a backdrop for the committee’s work in developing a balanced portfolio of recommended research activities and missions.

Program Evaluation Approach

The committee developed its recommended program by evaluating potential research activities against several general criteria. First and foremost was the capacity to deliver breakthrough science return as a function of activity cost level and technical readiness. Science return was judged with respect to the priority scientific questions4 (Q1 through Q12), while cost and technical readiness were assessed through an independent evaluation process, described below. A second criterion was programmatic balance across the priority science questions and target destinations, together with an appropriate mix of small, medium, and large activities. Other criteria included the potential for cooperation with planned human exploration efforts and other key partners, as well as the availability of trajectory opportunities within the period 2023–2032. There was not a fixed weighting for each of these criteria: for example, for a mission that uniquely addresses a crucial science question, science was considered a proportionally larger factor, while for a mission without a viable trajectory, technical feasibility was proportionally more important. Committee decisions considered the state of science, technology, and mission studies at the time of this report’s writing.

Definition of Mission Classes and Mission Lines

The statement of task calls for the evaluation of NASA’s planetary missions in three separate cost classes—small, medium, and large. The Discovery program supports small missions, while the New Frontiers program supports medium-class missions. Large missions are commonly referred to as Flagship missions. Any mission class may also be supported through destination-specific programs within NASA’s Planetary Science Directorate (PSD), namely the Mars Exploration and Lunar Discovery and Exploration programs. Small- and medium-class missions may either be led by a principal investigator (PI) or be strategically directed by NASA; large missions are strategically directed by NASA and are not PI-led. Mission classes are differentiated not only by their costs but also by their timescale of execution, span of technology, and involvement of the scientific community.

The Discovery program supports PI-led missions that address focused science objectives, with each mission selected through a competitive process. Rapid mission development (3–5 years) is feasible and desirable, and

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3 While the mass of a gas giant (e.g., Jupiter or Saturn) is dominated by hydrogen and helium, the mass of an ice giant (e.g., Uranus or Neptune) is dominated by heavier elements (e.g., carbon, nitrogen, and oxygen), some portion of which is in the form of ices.

4 Priority science questions, detailed in Chapters 4 through 15, are referenced by question number as Q1 to Q12, respectively.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

emphasis is placed on maintaining a high cadence of launches on average every 24 months. The Discovery program does not specify mission objectives or destinations, and proposers may address any science that can be accommodated within a specified cost cap. The overall program structure allows Discovery missions to rapidly respond to new discoveries and nimbly address changing scientific priorities, while encouraging creative new ideas and approaches to maximizing science return per dollar. The program has been remarkably successful, with 13 launches since its initiation, and remains a vibrant and highly valuable component of NASA’s planetary mission portfolio.

New Frontiers (NF) missions address a broader suite of science goals than those that can be implemented within Discovery but are still more scientifically focused than Flagship missions. NF missions can be executed on timescales of less than a decade, and while they are complex and challenging, they typically take advantage of technological developments from prior missions. NF missions, like those in Discovery, are PI-led and are selected via a competitive process, a model proven effective in maximizing innovation and community involvement. In contrast to the Discovery program, NF solicitations have been more strategic, restricting proposals to a small number of specific mission themes identified primarily through decadal surveys.

Flagship missions (e.g., Viking, Voyager, Galileo, Cassini, Mars Science Laboratory, Mars 2020, Europa Clipper, and subsequent missions in the Mars Sample Return campaign) have an approximately 10-year development cycle. These missions address a wide range of important scientific objectives at high priority targets and utilize sophisticated instrument payloads that involve some degree of new technology development. Flagship missions typically require very capable launch vehicles, large teams of investigators, and a complex organization of supporting institutions, often with multi-agency and international involvement. Because of their scientific breadth, high cost, technical complexity, and high strategic importance to NASA and the nation, flagship missions are directed missions, typically with PI-led individual instruments selected through open competition. Although large in cost, Flagship missions have consistently proven to have a high science return per dollar and have engaged a large fraction of the planetary science community (NASEM 2017b).

Program Balance Considerations

The prior decadal survey, Vision and Voyages (NRC 2011), provided a strong rationale for the importance of balance across mission cost classes when defining a mission portfolio to maximize overall scientific return. Its logic remains pertinent today. A program consisting of a single Flagship per decade would be unable to respond to ongoing scientific developments and result in long stretches of time with relatively little new data, whereas a portfolio of only Discovery-class missions could not address the most complex science questions that require an integrated suite of sophisticated instruments, complex mission designs, long duration investigations, and/or travel to distant targets. The former could lead to stagnant science and engineering communities, while the latter could fail to yield transformative scientific advances.

The past 30 years of planetary robotic exploration has generally followed a progression of mission types—from reconnaissance flybys, to orbital investigations, to in situ exploration, to sample return—at a growing number of target destinations. Each step along this progression allows us to address more sophisticated and challenging scientific questions, with a commensurate increase in mission and instrumentation complexity and cost. Different objects in the solar system are currently at different stages in this exploration continuum, and as such a balanced portfolio will naturally contain a range of mission classes. For example, as described below, sample return from Mars is planned for the same overall timeframe as the initial flyby reconnaissance of the distant Trojan asteroids.

Vision and Voyages provided the following criteria by which a flight program may be assessed:

  • Capacity to make steady progress—Does the proposed program make reasonable progress toward the scientific goals set forth in the decadal survey? Are the cadence of missions and the planning process such that new scientific discoveries can be followed up rapidly with new missions, such as small missions in the Discovery program? Does the program smoothly match and complement programs initiated by prior decadal surveys?
  • Stability—Can one construct an orderly sequence of missions, meeting overarching scientific goals, developing advanced technology, sizing and nurturing the research and technical community, and providing
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×
  • for appropriate interactions with the international community? Is the program stable under the inevitable budgetary perturbations as well as the occasional mission failures?
  • Balance—Is the program structured to contain a mix of small, medium, and large missions that together make the maximum progress toward the scientific goals envisioned by this decadal survey? Can some of the scientific objectives be reached or approached via missions of opportunity and by means of piggyback or secondary flights of experiments on other NASA missions?
  • Robustness—Is the program robust in that it provides opportunities for the training and development of the next generation of planetary scientists? Is it robust in that it lays the technological foundation for a period longer than the present decade?

The criteria cited above are not orthogonal. “Balance” in various guises permeates the other three criteria. For example, a balanced portfolio of missions enhances overall program stability, and provides better assurance of a continuing stream of new results. A balanced portfolio also helps prevent large excursions in workforce demands and cost, therefore fitting more easily into the relatively smooth year-to-year NASA budget.

Recommendation: NASA’s suite of planetary missions should continue to consist of a balanced mix of small, medium, and large missions, enabling both a steady stream of new discoveries and the capability to make major scientific and technical advances, as well as the needed training of future generations of planetary scientists.

ONGOING MISSIONS AND EXISTING PROGRAMS

The overall goal of this report is to recommend an integrated portfolio of flight projects, technology development, and supporting research activities to maximize the advancement of planetary science and astrobiology, as well as planetary defense, over the next decade. Recommended future activities need to be considered within the context of the existing planetary exploration program. In this section, the committee discusses and provides recommendations related to existing activities, including (1) operating missions; (2) missions and international contributions in development; (3) Mars Sample Return; and (4) the existing Mars Exploration, Lunar Discovery and Exploration, Research and Analysis, Astrobiology, and Planetary Defense programs.

Operating Missions

NASA has been remarkably successful in launching and operating planetary missions in the past decade. Currently operating PSD spacecraft include the ongoing Mars orbiter missions, the Curiosity and Perseverance Mars rovers, the Lunar Reconnaissance Orbiter, the InSight and Lucy Discovery missions, and the New Horizons, Juno, and OSIRIS-REx New Frontiers missions. These missions are at varied stages of operation, ranging from newly launched to those in extended mission phases. Extended missions can provide important new data and scientific insights with high science value per additional dollar expended (NASEM 2016). Another important aspect of extended missions is their role in providing mission experience and leadership for the development of the next generation of scientists and engineers who will lead the missions of the future. To ensure appropriate and high-value scientific return, NASA evaluates missions proposing to enter into or operating within an extended mission phase through the Senior Review process.

Finding: The committee endorses the Senior Review process for evaluation of the merit of extended missions and supports continued operation of missions prioritized by the Senior Review as representing high scientific return and/or programmatic importance.

New Frontiers, Discovery, and SIMPLEx Missions in Development

Vision and Voyages recommended a total of seven New Frontiers mission themes: five for the New Frontiers 4 (NF-4) call, and two to be added to the New Frontiers 5 (NF-5) call. NASA subsequently added an ocean worlds mission theme to NF-4. NASA selected the Dragonfly mission to Titan in NF-4, which is currently in development.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

In development Discovery missions include the Psyche mission to the asteroid Psyche, and the DAVINCI and VERITAS missions to Venus. Four small satellite missions under the recently introduced Small Innovative Missions for Planetary Exploration (SIMPLEx) line are also in development.

Finding: The committee strongly endorses the continued development of the Dragonfly, Psyche, DAVINCI, VERITAS, and small satellite missions. The committee finds the projected costs of these missions to be commensurate with their expected scientific return.

Contributions to International Missions in Development

NASA is providing hardware and other contributions to a variety of international space missions, including, for example, the ESA-led JUICE mission to Ganymede and the Jupiter system, the ESA-led ENVISION mission to Venus, and the JAXA-led MMX mission to the small moons of Mars.

Finding: The committee strongly endorses NASA’s partnerships with international space agencies and recognizes the benefits these bring to the U.S. space science community.

Europa Clipper

The second highest priority Flagship mission identified in Vision and Voyages was the Jupiter Europa Orbiter (JEO). NASA followed the decadal survey’s recommendations to descope the mission, which will now perform multiple flybys rather than orbit Europa, and to use solar rather than radioisotope thermoelectric power. The resulting Europa Clipper Flagship mission is in development, with a planned launch in October 2024. This mission will provide a critical foundation for the exploration of ocean worlds through its focused exploration of an important target of high astrobiological interest. As a large Flagship class mission, its budgetary growth has the potential to undercut other parts of the planetary program if not closely monitored and thoughtfully controlled (NASEM 2018b).

Recommendation: NASA should continue the development of the Europa Clipper mission and closely monitor the mission’s cost.

Mars Sample Return

The prior decadal survey recommended a Mars sample caching rover as its top priority Flagship mission, and as the first step in a campaign to return martian samples to Earth. Vision and Voyages envisioned Mars Sample Return as being “broken into three separate missions that can be spaced out over two or even three decades, reducing the per-year costs, and thus making it easier for programmatic balance to be maintained.” Following the recommendations of Vision and Voyages, the Mars Astrobiology Explorer-Cacher (MAX-C) mission was redesigned to include a single rover, allowing the reuse of existing Mars landing technologies. NASA implemented this recommendation with the successful landing of the Perseverance rover on Mars on February 18, 2021, which has begun its primary mission goal of acquiring and caching high-quality samples for return to Earth.

In 2017, NASA SMD introduced a concept to commence Mars Sample Return (MSR) through a “focused and rapid” campaign with essential participation from ESA; planning and implementation of this concept has proceeded subsequently. NASA asked the committee to assess whether NASA’s MSR plans play an appropriate role in the research strategy for the next decade (see “Considerations for Planetary Defense Flight Programs” in Appendix A), and, as appropriate, to provide recommendations related to the plans themselves.

While many science questions remain to be explored from orbit and the surface (e.g., MASWG 2020), key scientific objectives for Mars and, more broadly, for planetary and astrobiological science, can only be achieved via study of carefully selected martian samples in terrestrial laboratories. The Perseverance rover is collecting samples from Jezero crater, a former lake basin with a feeding channel system that was carved into Noachian (>3.7 Ga) stratigraphy. Distinct types of sedimentary, igneous, water-altered, and impact-formed rocks accessible in this region will provide a geological record of a time interval particularly important for

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

understanding Mars’s environmental evolution and, potentially, its biology. Sample return will provide geologic materials that are not represented among martian meteorites (e.g., sediments and water-altered rocks), and whose volatile, organic, and secondary mineral components have not been altered by impact. Sample context—location and stratigraphic position—will enable a chronology and age-dating of key episodes in Mars’s evolution and calibrate timings inferred from crater size frequency distributions that constrain the early impactor flux in the inner solar system.

The scientific impact of sample return is broad, both because of the types of samples to be collected and the measurements possible in laboratories on Earth (iMOST 2019). Certain types of measurements (e.g., phase-specific stable and radiogenic isotopes, trace elements, nanometer-scale composition and texture, and precise organics characterization) cannot be done remotely because they require sample preparations and analytical precisions only possible in specialized laboratories. Key science investigations that will be conducted on the returned samples include:

  • Coordinated analyses in the search for life, including analyzing potential biosignatures and inventories of prebiotic organic molecules; measuring compound-specific isotopic compositions and chirality; and establishing that such features are indigenous through preprocessing, nanometer-scale textural interrogation and follow-up observations with multiple methods.
  • Constraining the nature and longevity of environments with liquid water and assessing habitability and volatile inventory. Samples of ancient atmosphere (trapped in inclusions in minerals/glasses) will allow measurements of elements and rare isotopes (e.g., noble gases) that cannot be determined remotely (iMOST 2019). Samples of modern atmosphere will allow noble and trace gas measurement (Jakosky et al. 2020).
  • Determining radiometric ages, critical trace element abundances, nucleosynthetic isotope anomalies, and paleomagnetic properties to quantify and further understand Mars’s origin, differentiation, and geologic evolution, as well as compositional heterogeneity and dynamical mixing in the early solar system.

In addition, sample return will allow for future analyses by instruments and techniques not yet developed. As has been the case with the Apollo samples from the Moon, future analyses are expected to yield profound results for many decades after sample return.

Finding: The committee reaffirms the broad and fundamental scientific importance of Mars Sample Return recognized in Vision and Voyages, the 2018 Decadal Midterm Review (NASEM 2018a), and the 2020 Independent Review Board Report (NASA 2020b). MSR will enable investigations to address many fundamental issues, including crucial elements of Q3 through Q6, Q10, and Q11. MSR will also provide an invaluable sample collection to the benefit of future generations. As such, the committee finds that the aspirational, groundbreaking MSR campaign plays an appropriately central role in the research strategy for planetary science and astrobiology in the next decade.

NASA’s plans for MSR were extensively reviewed by an Independent Review Board (IRB) in December 2020. This technically demanding endeavor includes three interconnected missions: Perseverance, an Earth Return Orbiter (ERO), and a Sample Retrieval Lander (SRL). The SRL will carry a Sample Fetch Rover and Sample Transfer Arm to be supplied by the European Space Agency (ESA), as well as a Mars Ascent Vehicle to be developed and provided by NASA. The ERO is being developed by ESA. While the IRB concluded that decades of Mars exploration and years of preliminary planning have prepared NASA and ESA to undertake MSR, they found the plan they reviewed to be high-risk. The IRB identified several options to reduce both technical and programmatic risks, including a replan for SRL and ERO launches in 2028 (a shift from a baseline 2026 launch plan), a budgetary increase, further exploration of mission architectural and vehicle options, and simplification/consolidation of MSR organizational and management structures. The overall IRB recommendation was that MSR proceed, owing to its extraordinary scientific value and potential for world-changing discoveries. The committee endorses the findings and recommendations of the December 2020 IRB report on the MSR Program.

Recommendation: The highest scientific priority of NASA’s robotic exploration efforts this decade should be completion of Mars Sample Return as soon as is practicably possible with no increase or decrease in its current scope.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

The IRB described MSR as “arguably the most technically difficult and operationally demanding robotic space mission NASA and ESA have ever undertaken,” and asserted that, given its ambitious goals and complexity, it is essential that MSR be conducted with mission success as its top priority. In such a situation, there is clearly potential for mission cost growth, particularly if the 2026–2028 launch window is not achieved. Given the financial scale of MSR, cost growth has the potential to impact other NASA planetary science programs severely.

Mars exploration has historically figured prominently in NASA’s planetary program, and annual funding for Mars exploration has varied from ~25 to ~35 percent of the PSD budget over the past three decades. The representative PSD programs presented later in this chapter (Table 22-2) adopt a total MSR cost of $5.3 billion (this includes NASA’s contribution to a Sample Receiving Facility),5 and restrict funding for the Mars Exploration Program (MEP) to a relatively low level until the end of the decade when MSR’s annual costs decrease. The resulting decade-long total for Mars exploration in these plans, including both MSR and MEP, is ~20 percent of the total PSD budget over the decade, and ≤30 percent in any single year, which is lower than over the past several decades. Even with up to an additional 20 percent growth in MSR’s total cost, the next decade’s funding for Mars exploration would remain at or below previous percentage levels. However, cost growth of MSR at this level would, without an associated budget augmentation, undermine the programmatic balance across the priority scientific questions, mission classes, and target destinations, damaging the health of NASA’s overall planetary science program. Delaying the completion of MSR would undoubtably increase its total cost, which would also negatively impact the long-term health of the planetary program. Therefore, the completion of MSR as rapidly and efficiently as possible is highly desirable. The committee also notes that further reductions in the MEP program beyond that in the Level Program outlined here (Table 22-2) could not offset significant MSR cost growth without severely impacting the long-term health of the nation’s strategic program at Mars.

Recommendation: Mars Sample Return is of fundamental strategic importance to NASA, U.S. leadership in planetary science, and international cooperation, and should be completed as rapidly as possible. However, its cost should not be allowed to undermine the long-term programmatic balance of the planetary portfolio. If the cost of MSR increases substantially (≥20 percent) beyond the $5.3 billion level adopted here, or goes above ~35 percent of the PSD budget in any given year, NASA should work with the Administration and Congress to secure a budget augmentation to ensure the success of this strategic mission.

Key Existing Programs and Activities

In this section, the committee discusses prominent programs and activities within NASA’s PSD, including the Mars Exploration and Lunar Discovery and Exploration programs, the Research and Analysis and Astrobiology programs, and the Planetary Defense Coordination Office.

Throughout the history of planetary exploration NASA has used a variety of approaches for mission selection and development, from typically decade-long, or longer, flagship missions that address a broad suite of fundamental science questions to smaller, higher cadence Discovery missions that address focused questions at diverse targets. In addition, NASA has created programs to define and coordinate its efforts for scientific exploration of particular objects that have broad importance across a combination of scientific and programmatic priorities, including coordination with NASA’s human exploration plans.

The Mars Exploration Program (MEP) is a scientific success story, providing stability across decades to support long-term, strategic science planning; coordination across multiple missions and assets (often operating simultaneously and in support of each other); development of a multi-generational science community that defines the goals and priorities of the program; international coordination and involvement; infrastructure and technology development; and development of scientific connections to human exploration plans. The relatively short travel times to Mars have allowed for a structured, multi-mission approach, with each mission building on its predecessor and addressing science questions of increasing sophistication. The 2019 formation of the Lunar Discovery and Exploration Program (LDEP) has the potential to emulate the successful MEP model by supporting activities focused on the Moon such as those listed above for Mars. The Moon’s greater proximity and accessibility affords

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5 All dollar amounts are in real-year dollars unless specified otherwise.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

tremendous opportunities for frequent missions with increasingly sophisticated payloads, growing commercial and international partnerships, and advancement of decadal-level science6 through coordination with near-term human exploration activities planned for the next decade.

Finding: Mars and the Moon are currently unique in the breadth of activities focused on them. Further, they each provide the opportunity to investigate a wide range of priority science questions at destinations that are relatively easy to reach. These aspects justify the existence of MEP and LDEP as dedicated programs and their associated administrative costs.

Other objects or classes of objects in the solar system, while currently not subject to the same breadth of activity as Mars and the Moon, also merit coordinated, strategic scientific planning. As the number of NASA and international missions to specific destinations or classes of objects increases, such as has recently occurred in the selection of three missions to Venus and increased interest in ocean world missions, the need for coordination and the opportunities for collaboration also increase. Scientific exploration strategies may consider, for example, (1) coordination within NASA to support key research topics encompassing remote-sensing, laboratory, theoretical, and ground- and space-based telescopic investigations focused on upcoming missions; (2) a technology development plan to enable future missions; and (3) collaboration on possible future activities between U.S. and international and commercial partners to maximize NASA’s investments, aid in the selection of an optimal suite of missions, and enhance the exchange of scientific knowledge and data.

Recommendation: NASA should develop scientific exploration strategies, as it has for Mars, in areas of broad scientific importance, for example, Venus and ocean worlds that have an increasing number of U.S. missions and international collaboration opportunities.

Mars Exploration Program

Over the past three decades, MEP has maintained a portfolio of small to large Mars science missions. As detailed in the MASWG 2020 report, three attributes drive the programmatic approach at Mars:

  • Scientific: Mars is a key destination in the search for past and present extraterrestrial life. It provides the opportunity to search for extant life and, thanks to its 4.5-billion-year-old rock record that includes a relatively pristine record of the first billion years of solar system history, it offers a unique opportunity to investigate the full range of interacting processes on habitable terrestrial planets (e.g., geoscience, climate/atmosphere, space weather, and potentially biology) under different conditions from Earth (see priority science questions 5, 6, 10, and 11).
  • Programmatic: Mars is accessible, allowing multiple mission classes to explore different components of the martian environment and their interactions, including access to the surface and near subsurface.
  • Exploration: Mars is NASA’s stated long-term destination for human exploration. Mars is also a destination of rapidly increasing interest for multiple international space agencies (including those of Europe, China, Japan, India, UAE, and Russia), as well as commercial entities, with whom our scientific understanding will benefit from long-term coordination.

The committee reaffirms findings of the Vision and Voyages midterm review (NASEM 2018a) regarding the importance of coordinating Mars exploration and managing the MEP as a program, rather than just as a series of missions, to optimize science at the architectural level.

Finding: MEP has a record of success, and it has advanced our understanding of Mars and the evolutionary paths of terrestrial planets while also fostering, for example, technological developments, identification of opportunities for joint mission implementation, and public enthusiasm for planetary science.

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6 Decadal-level science is that which results in significant, unambiguous progress in addressing at least one of the survey’s 12 priority science questions.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

The committee recommends above that completion of MSR be the top priority for NASA’s scientific exploration of Mars in the next decade. MSR is managed as a separate program outside of MEP, a logical approach given the size and complexity of this international endeavor.

Finding: Maintaining strong scientific, programmatic, and strategic connections between the MEP and MSR will provide the scientific leadership for MSR and ensure the feed forward from the sample-return campaign to future Mars science activities.

There remain many fundamental science questions at Mars beyond those addressed by MSR. Many of these require a series of measurements that build on prior data, and/or measurements at varied locations, times, or parts of the Mars system. Thanks to Mars’s relative accessibility, international partners eager to pursue partnerships with NASA, and increasing capabilities of small spacecraft, effective coordination by MEP this decade can support a mission cadence to enable ongoing discovery along multiple arcs of priority science goals (see MASWG 2020). New, rapid, and low-cost exploration techniques using proven technology advancements—such as innovative landing methods, small satellites, and aerial vehicles—can be part of the MEP strategy to advance scientific and human exploration goals. MEP may also have opportunities this decade to prioritize science on future human exploration missions (see Chapter 19).

Recommendation: NASA should maintain the Mars Exploration Program, managed within the PSD, that is focused on the scientific exploration of Mars. The program should develop and execute a comprehensive architecture of missions, partnerships, and technology development to enable continued scientific discovery at Mars.

As highlighted in community documents (MEPAG 2020), certain high-priority science objectives at Mars—including subsurface ice composition, detailed organics characterization to search for modern biosignatures, and in situ stable and radiogenic isotopic measurements of rocks—likely require medium-class mission implementations. The committee considered a range of medium-class Mars mission concepts and whether such missions are best performed under the auspices of MEP or included in the New Frontiers program.

Finding: Retaining medium-class Mars missions within MEP affords key advantages for coordination across multiple missions and international partnerships, and for fostering development and utilization of common enabling technological aspects.

The committee considered four medium-class Mars missions (two studied by NASA prior to the survey and two identified and studied during the survey) and prioritized two of these for TRACE: the Mars Life Explorer (MLE) and In Situ Mars Geochronology (see Appendixes C and D, respectively). The committee ranked MLE as the highest priority medium-class mission for the MEP. “Are we alone?” is one of the most profound questions that can be addressed by solar system exploration (Q11). Ancient biosignatures are a focus of Perseverance and MSR, and multiple types of past habitable environments with liquid water and organic matter have been discovered on Mars (Q10). Mars has subsequently undergone profound climate change (Q6), and key questions are whether any habitable environments persist to the present and whether they are inhabited. The focus of Mars Life Explorer is to seek extant life and assess modern habitability.7 The notional mission concept examines Mars’s lowest latitude ice deposits that preserve a record of recent climate change and may provide a recent habitat for life. MLE would land and drill into the ice to characterize and quantify organics, trace gases, and isotopes at a fidelity suitable for biosignature detection. It would also assess ice habitability and the question of modern liquid water via analysis of elemental chemistry, salts, conductivity, and ice thermophysical properties. Long-term atmospheric measurements over a martian year would determine the current stability versus instability of the ice deposits.

Recommendation: Subsequent to the peak-spending phase of MSR, the next priority medium-class mission for MEP should be Mars Life Explorer.

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7 The full Mars Life Explorer mission study report is available at https://tinyurl.com/2p88fx4f.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

The complex interplay among Mars science, human exploration, and international partnerships requires carefully crafted collaborations. High potential synergy of objectives exists between the science of martian climate change (Q5, Q6, and Q10) and human exploration efforts relating to in situ resource utilization (ISRU), including the desire to map near-surface ice on Mars. The international Mars Ice Mapper (iMIM), in pre-Phase A at the time of this writing, was proposed by NASA as a mission with priorities for human exploration and multiple international partners. However, as presently articulated, iMIM measurements only minimally address the science goals and measurement requirements for Mars ice mapping defined in community documents and by planetary mission concept studies prepared for this decadal survey (see Appendixes C and D). NASA is in the process of convening a Measurement Definition Team (MDT); however, this activity postdates the basic international agreements, including a choice of a specific radar instrument. The MDT needs to include stakeholders from both the Mars science and human exploration communities. With incorporation of measurement requirements based on current state-of-the-art in understanding Mars’s crustal properties and Mars science, iMIM could address priority science questions related to Mars climate while also realizing human exploration objectives (see Chapter 19 for further discussion).

Finding: While leveraging international partnerships can potentially lower NASA mission costs, coordination is necessary to achieve priority science. Stronger programmatic coupling is needed between science and human exploration communities to ensure that precursor missions, such as iMIM and eventual human missions to Mars, achieve decadal-level science.

Recommendation: The development of the goals and measurement requirements for missions addressing both science and human exploration interests should be developed to meet the objectives of both communities.

Recommendation: NASA should consider implementation of an ice mapping mission that prepares for ISRU by humans and addresses the priority climate science questions at Mars related to near-surface ice.

Lunar Discovery and Exploration Program

The 2017 Space Policy Directive-1 (SPD-1) instructed NASA to explore the Moon with commercial and international partners and to return humans to the Moon for long-term exploration and resource utilization to achieve sustainable human presence. The Lunar Discovery and Exploration Program (LDEP), begun in 2019 in response to this directive, is intended to support commercial partnerships and innovative approaches to accomplish lunar exploration and science goals. LDEP is executed through the Exploration Science Strategy and Integration Office (ESSIO) and integrates and coordinates the Artemis science efforts across the SMD divisions, across NASA directorates, and with other U.S. and international partners.

DEP has implemented new research and technology developments; established the Commercial Lunar Payload Services (CLPS) program for lunar landing services; and supported the development of lunar science instruments, lunar CubeSats and SmallSats, and the development of lunar rovers. There are currently two LDEP flight projects managed by PSD. The Volatiles Investigating Polar Exploration Rover (VIPER) is a lunar volatiles detection and measurement mission that will be launched as a payload on a CLPS to the lunar south pole, characterizing the distribution and physical state of lunar polar water and other volatiles in lunar cold traps and studying the potential for in situ resource utilization from the Moon’s polar regions. Lunar Trailblazer, a SmallSat orbiter selected in the SIMPLEx program, will characterize the form, abundance, distribution, and time variability of H2O/OH in sunlit terrains and ice in permanently shadowed regions.

Commercial Lunar Payload Services Program

The goal of the CLPS program is to enable reliable and affordable access to the lunar surface by helping to establish a viable commercial lunar sector. Like the Commercial Cargo and Crew programs, NASA pays CLPS providers for services rather than spacecraft. These services include delivery to the lunar surface from Earth (launch vehicle and spacecraft), and ground systems. Thus far, NASA has contracted eight CLPS deliveries to the lunar surface, the largest being for the VIPER rover, although no landings have yet occurred. CLPS capabilities

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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are currently limited but have the potential to meet additional NASA needs such as lunar night survival, mobility, delivery of larger payloads, and sample return. The CLPS model for purchasing delivery services to the Moon, once landing systems have proven to be reliable, is a promising and innovative procurement model within SMD that can benefit planetary science, if used as one component of a PSD-integrated program to accomplish important science objectives. Competition and firm fixed-price contracts incentivize the commercial sector to keep costs low, allowing for a higher mission cadence and a larger acceptance of risk. The higher cadence will provide opportunities to test and advance new technology, address focused science questions, and train new scientists and engineers.

Recommendation: NASA should continue to support commercial innovation in lunar exploration. Following demonstrated success in reaching the lunar surface, NASA should develop a plan to maximize science return from CLPS by, for example, allowing investigators to propose instrument suites coupled to specific landing sites. NASA should evaluate the future prospects for commercial delivery systems within other mission programs and consider extending approaches and lessons learned from CLPS to other destinations, for example, Mars and asteroids.

Structuring LDEP to Achieve Decadal-Level Science

LDEP is funded within the PSD budget, but the responsibility for its budget is split between PSD and ESSIO. ESSIO is focused primarily on inter-division activity coordination and commercial partnerships, whereas PSD is responsible for accomplishing lunar science goals. LDEP funds many (but not all) lunar programs in PSD but does not currently manage or coordinate them. In the current LDEP organizational structure, no single organizational chain has authority for executing lunar science missions and accomplishing lunar science. Further, there is as of yet no overall strategy for lunar scientific exploration or a program director or chief scientist to lead such a plan. As a result, despite substantial investment and tremendous potential for innovative lunar exploration, LDEP activities are not well coordinated or optimized to accomplish high-priority planetary science goals at the Moon.

Recommendation: PSD should execute a strategic program to accomplish planetary science objectives for the Moon, with an organizational structure that aligns responsibility, authority, and accountability.

The 2007 report, The Scientific Context for the Exploration of the Moon, provided a set of lunar science concepts, goals, and recommendations that have informed subsequent studies and lunar community activities (NRC 2007). More recently, the Lunar Exploration Analysis Group (LEAG) charged the Advancing Science of the Moon Specific Action Team (ASM-SAT) with evaluating progress made in accomplishing lunar science goals and identifying key directions for future research. The resulting 2018 ASM-SAT report (LEAG 2018) highlighted three additional science concepts beyond those in the 2007 report. Given that the National Academies has not addressed the most compelling science goals to be addressed at the Moon since 2007, Box 22-1 outlines current priority lunar science themes identified by the committee.

In recognition of the wide range of current and planned lunar exploration activities, it is now essential that a prioritized set of objectives and measurements to address decadal-level science questions at the Moon be developed. The scientific success of MEP provides an example of the utility and impact of having well-defined goals, prioritized science questions, specific measurements to address those questions, and a long-term plan. The MEPAG “goals document” was begun in the 1990s and has continuously evolved via sustained and well-organized inputs from the Mars science community through workshops and committees.

Finding: A structured approach to setting science goals and measurement objectives at the Moon, led by the lunar science community in a manner similar to that led by the Mars community, would allow for scientific prioritization and coordination of lunar missions, instrumentation, landing site selections, and other activities performed within LDEP.

Lunar science can benefit enormously from available and planned robotic, commercial, and human implementation options. Managing these different assets through a well-coordinated Science Mission Directorate/Exploration Systems Development Mission Directorate program would maximize synergy among existing and future domestic

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

and international missions, execute a healthy and comprehensive technology pipeline at the architectural (versus individual mission) level, and ensure sustenance of foundational infrastructure.

NASA’s Artemis Plan (NASA 2020a) calls for landing humans near the Moon’s south pole within the 2020s and ultimately developing a basecamp to support sustainable exploration and longer stays. NASA’s historic investment in the Artemis program merits a substantive scientific component capable of transforming our understanding of the Earth-Moon and the early solar system. The successful integration of science into programs of human exploration has historically been a challenge and remains so for Artemis (Beattie 2001; see Chapter 19). Currently, science requirements do not drive the Artemis capabilities. However, in the committee’s view, it is imperative that Artemis support breakthrough, decadal-level science, as outlined in Box 22-1. To not do so would be a missed opportunity for NASA and the nation that would undermine the value of the envisioned long-term Artemis program.

Recommendation: The advancement of high priority lunar science objectives, as defined by PSD based on inputs from this report and groups representing the scientific community, should be a key requirement of the Artemis human exploration program. Design and implementation of an integrated plan responsive to both NASA’s human exploration and science directorates, with separately appropriated funding lines, presents management challenges; however, overcoming these is strongly justified by the value of human-scientific and human-robotic partnerships to the agency and the nation.

Transformative Science Enabled by a Synergistic Robotic-Human Partnership

While the Discovery, current CLPS, and SIMPLEx programs provide opportunities to address focused science objectives at the Moon, broader science goals require more ambitious and complex missions. A fundamental science goal is to utilize the Moon to investigate the early dynamical and impact history of the solar system (see Box 22-1). Impacting comets and asteroids are thought to have substantially influenced the origin and early evolution of life on Earth through, for example, the delivery of water, key elements, and organics; effects on geologic and climate evolution; and impact-driven mixing and energy deposition. An impact on the Moon created its oldest and largest known basin, the roughly 2,500 km South Pole–Aitken (SPA) basin, and excavated the Moon’s interior, potentially exposing lunar mantle materials. There are no known mantle samples in Apollo or lunar meteorite collections; analysis of such material would provide crucial new understanding of the Moon’s bulk composition and interior structure, which in turn are key constraints on Earth-Moon system origin and the Moon’s primordial evolution (Moriarty et al. 2021). The record of early impacts preserved on the Moon can be used to test hypotheses of early solar system evolution, including models of the migration of the giant planets that sent asteroids and comets on collision courses with Earth and other planets. Understanding early bombardment and its implications has been the longstanding highest priority for planetary science and astrobiology at the Moon. Furthermore, the lunar geologic record provides a basis for understanding how large terrestrial bodies evolve through time forming crusts, mantle, and cores.

The committee studied two mission concepts designed to address this highest priority lunar science, which would revolutionize our understanding of the Moon and the early history of the solar system recorded in its most ancient impact basin. Both concepts, Endurance-R and Endurance-A, utilize a CLPS-delivered rover to traverse nearly 2,000 km of diverse terrains within the SPA basin.8 The rover conducts in situ measurements and collects samples for return to Earth for detailed analyses in existing and future laboratories. The first concept, Endurance-R, requires two medium-class missions to robotically collect and return about ~2 kg of total sample mass. This mission was viewed by the committee as too costly given the small returned sample mass.

The second concept, Endurance-A, involves a single medium-class mission to robotically collect 100 kg of samples, which are delivered to a location where they can be collected by astronauts for return to Earth. Retrieval and return of substantial Endurance-A samples by Artemis astronauts would be the ideal synergy between NASA’s human and scientific exploration of the Moon, producing flagship-level science at a fraction of the cost to PSD

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8 The full report of the Endurance mission concept studies is available at https://tinyurl.com/2p88fx4f.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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through strategic coordination with Artemis exploration efforts. This would be a forward-looking, inspirational partnership to deliver ground-breaking science not possible through the local collection of limited samples.

Science objectives of Endurance-A include determining:

  • The age of the largest and oldest impact structure on the Moon, SPA basin, to anchor the earliest impact history of the solar system;
  • When post-SPA farside basins formed to test the giant planet migration and terminal cataclysm hypotheses, and to better constrain the inner solar system impact chronology used to date the surfaces of other planetary bodies;
  • The age and mineralogical and geochemical composition of deep and crustal materials exposed in SPA to understand the bulk composition of the Moon, its primordial differentiation and geologic evolution, and the significance of chronologic measurements completed on nearside samples for timing lunar solidification;
  • The age and nature of volcanic features and compositional anomalies on the lunar farside to characterize the thermochemical evolution of terrestrial worlds and constrain the origin of the Moon’s nearside-farside asymmetry; and
  • The geologic diversity of the SPA Terrane to provide geologic context for returned samples, ground truth for orbital measurements, and characterize the surface processes that shape planetary bodies.

Recommendation: Endurance-A should be implemented as a strategic medium-class mission as the highest priority of the Lunar Discovery and Exploration Program. Endurance-A would utilize CLPS to deliver the rover to the Moon, a long-range traverse to collect a substantial mass of high-value samples, and astronauts to return them to Earth.

If timelines or plans for Artemis render this partnership infeasible, NASA, with guidance from CAPS,9 could evaluate options for a robotic return of the minimum set of samples needed to accomplish the core science objectives, leveraging international partnerships and commercial capabilities as appropriate, while maintaining life cycle costs to NASA commensurate with a medium class mission.

Research and Analysis

Research and analysis (R&A) activities are the foundation for advancing the scientific knowledge from NASA’s missions and projects, training and maintaining a diverse science and engineering workforce to meet NASA’s needs, and preparing for the Agency’s future activities. The fraction of the NASA PSD budget devoted to R&A decreased from 14 percent in 2010, to 8 percent in 2019, to a projected level of 7.7 percent by FY 2023 (see Figure 17-1 of the Research and Analysis chapter). Negative impacts on the community, and the portion of time spent writing and reviewing proposals instead of doing science, have greatly increased of late, as evidenced by multiple white papers and presentations to the committee that characterize the current situation as a crisis. Reversing this trend of decreasing proportional investment in R&A is essential to maintaining the health of the nation’s planetary science efforts (see Chapter 17 for detailed discussion).

Finding: Robotic exploration of the solar system is driven by the desire to increase scientific knowledge. Strong, steady investment in R&A is needed to ensure that the scientific return from past and ongoing missions is maximized; that new data drives the development of improved understanding and novel, testable hypotheses; and that these advances feed into the development of innovative techniques and future mission concepts that will deliver breakthrough, high-impact scientific results.

PSD R&A efforts include a variety of programs. Among these, it is the openly competed R&A programs—to which any PI may propose and whose funds are awarded through a highly competitive, peer-review process—that

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9 The Committee on Astrobiology and Planetary Sciences, https://www.nationalacademies.org/our-work/committee-on-astrobiology-andplanetary-sciences.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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are best suited for driving innovation, responding rapidly to new developments, identifying the most meritorious ideas worthy of support, and attracting new and increasingly diverse individuals into the field. These programs are identified in Table 17-1 of the Research and Analysis chapter.

Finding: Rigorous peer-review and open, equitable competitions are fundamental to NASA’s success and to maximizing excellence in its activities and its workforce. The openly competed R&A programs drive innovation, direct funding to the most meritorious ideas, and encourage broad access and participation.

The committee recommends that PSD’s investment in R&A activities be tied to the scale of the PSD program, a logic similar to that used in industry to establish investment levels for supportive research and development activities. The past decade has been enormously successful for PSD, accompanied by an approximate doubling of its annual budget. This reflects broad-based expansion across most of the primary PSD budgetary categories, with flagship (MSR and Europa Clipper) and the Discovery/New Frontiers mission lines approximately doubling from 2018 to 2023, in addition to proportionally even larger growth in planetary defense and LDEP during this period. However, proportional investments in R&A have not kept up with this growth in PSD activities. Recent levels in the 8 to 9 percent range threaten the continued scientific payoff from NASA’s mission investments. Returning the annual PSD percentage investment in R&A activities to ≥10 percent through an increase in support to the openly competed programs would represent an approximately 40 percent increase in those programs relative to their recent levels. This illustrates that a relatively small increase in fractional PSD investment into R&A would strongly (and disproportionately) enhance the value delivered by R&A to its flight programs. Adjustments in R&A funding are ideally managed over a multi-year period to smooth out annual fluctuations, either upward are downward, with the goal of maintaining the stability of the workforce, associated national technical capabilities, and the pool of high-quality R&A proposals. The committee repeats here the following recommendation from Chapter 17:

Recommendation: PSD should increase its investment in R&A activities to achieve a minimum annual funding level of 10 percent of the PSD total annual budget. This increase should be achieved through a progressive ramp-up in funding allocated to the openly competed R&A programs, as defined in this decadal survey. Mid-decade, NASA should work with an appropriately constituted independent group to assess progress in achieving this recommended funding level.

Chapter 17 also presents recommendations that relate to specific large programs within PSD R&A, and to R&A proposal submission and evaluation processes. While planetary science and astrobiology R&A is funded primarily through NASA’s PSD, NSF also provides related support, primarily within its Division of Astronomical Sciences (AST). NSF-AST supports ground-based astronomy as well as basic planetary science research. Ground-based observations are an important complement to data returned by planetary missions (see Telescopic Observations section later in this chapter). Other relevant activities at NSF, such as support of and access to field site for analog studies in extreme Earth environments, are detailed in Chapter 1.

Recommendation: NASA and NSF would realize greater return on their R&A investments by working together to streamline the mechanisms by which researchers can propose and conduct science that is of benefit to both agencies.

Astrobiology Program

Astrobiology encompasses a diverse set of topics, ranging from the study of prebiotic chemistry, terrestrial life’s origin and evolution, the co-evolution of planets and life, and the search for habitability and for life elsewhere in the solar system and beyond to the exoplanets (see Q9 through Q11, Chapters 12, 13, and 14, respectively). Astrobiology is thus an inherently interdisciplinary field involving integrative study of physical, chemical, biological, geologic, planetary, and astrophysical systems. Over the past 25 years, astrobiology has become a crucial element of NASA’s planetary program and is the central scientific motivation for large strategic missions currently in development (MSR and Europa Clipper), and a compelling component of many New Frontiers and Discovery

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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mission themes. Significant advances have occurred in astrobiology over the past decade, as discussed in the NASA Astrobiology Strategy (NASA 2015) and the Astrobiology Strategy for the Search for Life in the Universe (NASEM 2019a). Three ideas advanced in these reports are particularly relevant to the coming decade of exploration of the solar system:

  • Dynamic habitability and the co-evolution of planets and life (see Q9, Chapter 12) are key concepts to be addressed in the next decade, requiring integration across the planetary science and astrobiology communities because they involve the study of terrestrial environments, solar system bodies, and exoplanets.
  • Understanding life in extreme environments on Earth is highly relevant to the next decade of solar system exploration. First, life in isolated refugia and ephemeral environments on Earth (e.g., in terrestrial deserts) implies that habitability is a continuum defined over varying time and spatial scales. Second, awareness of the habitability of saline and hypersaline terrestrial environments, together with the discovery of potential brines on Mars, has led to a resurgence of the idea of life adapted to saline fluids. Third, discovery of life in the ocean floor subsurface and continental lithosphere provides new models for rock-hosted, chemosynthetic life that might exist elsewhere in the solar system, for example, in ocean worlds.
  • The search for life hinges on the ability to validate potential biosignatures, building on what has been discovered to date regarding life on Earth. Issues related to record bias, preservational bias, false negatives, and false positives all play a role in biosignature detectability and interpretation. However, the planning, implementation, and operations of planetary exploration missions with astrobiological objectives have tended to be more strongly defined by geological perspectives than by astrobiology-focused strategies.

As a result of these factors, the committee specifically endorses the following three recommendations from the 2019 National Academies’ report:

Recommendation: NASA and other relevant agencies should catalyze research focused on emerging systems-level thinking about dynamic habitability and the coevolution of planets and life, with a focus on problems and not disciplines—that is, using and expanding successful programmatic mechanisms that foster interdisciplinary and cross-divisional collaboration.

Recommendation: NASA’s programs and missions should reflect a dedicated focus on research and exploration of subsurface habitability in light of recent advances demonstrating the breadth and diversity of life in Earth’s subsurface, the history and nature of subsurface fluids on Mars, and potential habitats for life on ocean worlds.

Recommendation: To advance the search for life in the universe, NASA should accelerate the development and validation, in relevant environments, of mission-ready, life detection technologies. In addition, it should integrate astrobiological expertise in all mission stages—from inception and conceptualization to planning, development, and operations.

Ongoing NASA and NSF research activities on Earth are also essential to progress in astrobiology (see Chapter 17).

Planetary Defense Program

NASA’s Planetary Defense Program coordinates and supports activities to protect our world from asteroid and comet impacts. Its charter, per congressional mandate, is to detect and track all near-Earth objects and assess the threat and consequences of Earth impact. As awareness of the hazard posed to life and property by Earth-approaching asteroids and comets has grown, the U.S. Congress and presidential administrations have directed NASA, NSF, and other government agencies to pursue activities in support of planetary defense (NSTC 2018). The establishment of NASA’s Planetary Defense Coordination Office (PDCO) in 2016 brought leadership and strategic direction to national planetary defense efforts. The placement of PDCO within the Planetary Science Directorate reflects a

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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synergistic relationship, wherein scientific knowledge about the characteristics and population of small bodies, as well as experience in successful implementation of small body space missions, is applied to developing methods to assess the risk, and protect the planet from, hazardous objects. While not primarily science-driven missions, NASA’s recently launched Double Asteroid Redirection Test (DART) kinetic-impactor demonstration—in conjunction with ESA’s Hera follow-up assessment mission, and the Near-Earth Object Surveyor Mission (NEO Surveyor)—exemplify this synergy (e.g., NASEM 2019b).

Chapter 18 provides a detailed discussion of planetary defense for the next decade and includes 38 findings and 11 recommendations. Here the committee presents several of the key elements and recommendations from that chapter.

Finding: A dedicated space-based mid-infrared survey is the most effective architecture to accomplish congressionally directed NEO survey goals. NEO Surveyor, currently pending confirmation, will conduct that survey and provide real-time information on object diameter, critical for rapid impact hazard assessment.

Recommendation: NASA should fully support the development, timely launch, and subsequent operation of NEO Surveyor to achieve the highest priority planetary defense NEO survey goals.

A critical next step is to develop a flexible implementation approach to quickly characterize threatening objects via reconnaissance missions in order to plan for mitigation if needed. After NEO Surveyor, the next priority planetary defense mission is a rapid-response, flyby reconnaissance of an object representative of the most hazardous class of objects (~50 to 100 m diameter; see Chapter 18). A rapid response capability may also provide a template for responding to newly identified, high-value science targets such as interstellar objects or dynamically new comets.

Recommendation: In the coming decade, NASA should develop an approach for a rapid-response, flyby characterization of emerging, short-warning-time (<3 years) threats and science opportunities.

DISCOVERY, NEW FRONTIERS, AND FLAGSHIP RECOMMENDATIONS FOR THE DECADE 2023–2032

In this section, the committee first addresses issues related to the Discovery and New Frontiers programs, including cost structure, cadence, and, in the case of New Frontiers, whether mission themes will continue to be specified. It then describes the process by which candidate medium and large missions were studied and assessed, followed by a prioritization of such missions.

In its guidelines to the committee, NASA provided cost definitions for three mission classes, each of which was exclusive of the launch vehicle and mission operations (i.e., Phase E-F) costs: less than ~$500 million for small missions, between $500 million and $900 million for medium missions, and more than $900 million for large, strategic missions. The committee carefully evaluated these cost classes and recommends revisions to the cost structures for the Discovery and New Frontiers programs, as specified below, based on several considerations: (1) growing trajectory, instrumentation, and technology requirements needed to address decadal-level science questions, as evidenced both by recent mission selections and results of independent mission concept analyses; (2) the different roles played by each program within NASA’s planetary mission portfolio; (3) a desire to more clearly anticipate mission life cycle cost, both for community awareness and for NASA budgetary planning; and (4) effects of inflation.

Discovery and SIMPLEx Missions

The Discovery program was initiated in 1990 as a means to ensure frequent access to space for planetary science investigations through competed PI-led missions (Table 22-1). The low cost and short development times of Discovery missions provide flexibility to address new scientific discoveries on a timescale significantly less than 10 years. Identification of specific Discovery missions is outside the scope of decadal recommendations, but the overall program warrants evaluation and recommendations.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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TABLE 22-2 Discovery Program Mission Selections to Date

Year of AO Mission Selected Launch Date Description
n/a Near-Earth Asteroid Rendezvous February 17, 1996 Asteroid orbiter and rendezvous
n/a Mars Pathfinder December 4, 1996 Mars lander and Sojourner rover
1994 Lunar Prospector January 6, 1998 Lunar orbiter
1994 Stardust February 7, 1999 Comet particle sample return
1996 Genesis August 8, 2001 Solar wind sample return.
1996 CONTOUR July 3, 2002 Comet nuclei flybys (lost contact 6 weeks after launch)
1998 MESSENGER August 3, 2004 Mercury orbiter
1998 Deep Impact January 12, 2005 Comet impactor and flyby
2000 Dawn September 27, 2007 Orbit of asteroid Vesta and dwarf planet Ceres
2000 Kepler March 6, 2009 Extrasolar planets telescope
2004 No Selection
2006 GRAIL September 9, 2011 Lunar orbiters for gravity mapping
2010 InSight May 5, 2018 Terrestrial planet seismicity
2014 Lucy October 16, 2021 Trojan asteroid tour
2014 Psyche 2023 Psyche asteroid rendezvous
2018 DAVINCI 2028–2030 Venus entry probe
2018 VERITAS 2028–2030 Venus orbiter

The strategic research activities given in Chapters 415 demonstrate that many science questions can be addressed at multiple destinations and provide examples of the rich array of science that can be addressed with future Discovery missions. Primitive body investigations are ideally suited for Discovery missions. The vast number and diversity of asteroids and comets provide opportunities to benefit from frequent launches. The proximity of some targets allows missions that can be implemented within the context of the Discovery program. Near the limit of the Discovery cost cap, it may be possible to collect and return samples from nearby objects. The diversity of targets means that proven technologies may be reflown to new targets, reducing mission risk and cost. And the population of scientifically compelling targets is not static but is continually increasing because of discoveries in the supporting research and analysis programs. Opportunities for lunar Discovery missions could build on the success of the CLPS program and incorporate more sophisticated instrumentation and/or longer-lived missions. Missions to Mars can benefit from collaboration with international and commercial partners and innovative approaches and technologies that could provide more affordable access to the martian surface and expand the geologic diversity of sites that have been visited. Even the outer solar system can be accessible in the Discovery program, as evidenced by the 2021 launch of Lucy to the Trojan asteroids and the selection of the Io Volcano Observer and the Trident mission to Triton for Phase A studies following the most recent call for Discovery missions. Thus, there is still much compelling science that can be addressed by Discovery missions.

Recommendation: The Discovery program has made important and fundamental contributions to planetary exploration and should continue to be supported in the coming decade.

The SIMPLEx program of very small, low-cost missions that is managed within the Discovery program takes advantage of recent advances in small spacecraft technologies and/or ride-share opportunities on other launches. Inclusion of this innovative program promises to increase launch cadence overall within the Discovery program and provides flexibility to achieve a balanced portfolio across targets and maintain a continuous stream of new data to the planetary science community. The combination of higher risk tolerance and shorter mission lifetimes complements the Discovery mission line by embracing rapidly improving commercial deep space SmallSats capabilities and

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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allowing infusion of new technologies that will ultimately benefit larger missions. In addition, SIMPLEx represents an entry-level mission that could allow early career scientists and nontraditional institutions to participate and gain experience in the NASA mission process.

Finding: SIMPLEx plays a unique role within the PSD mission portfolio that capitalizes on new technology and innovative launch strategies at modest cost. It is well-placed within the Discovery management structure, where it can be flexibly accommodated as budgets and ride-share opportunities allow.

However, the challenging budgets, schedules, and coordination of rideshares or small launch procurement for SIMPLEx missions requires strong NASA stakeholder engagement with the mission team. Five SIMPLEx missions have been selected to date, with the latest SIMPLEx round having a mission cost cap of $55 million. In development SIMPLEx missions are the LunaHMap mission to map hydrogen at the lunar south pole, the Janus mission to send twin spacecraft to explore two binary asteroid systems, the Lunar Trailblazer mission to provide maps of water abundance on the Moon, and the ESCAPADE mission to study the martian upper atmosphere. These missions provide high science value, but may represent the “low-hanging fruit” at the current cost cap. A higher cost cap would enhance the potential of the program to achieve decadal-level science and drive innovation across more destinations.

Recommendation: NASA should provide a ~50 percent increase in the SIMPLEx cost cap for future calls to expand the range of possible destinations and increase the scientific return from this program.

Discovery Program Cost Structure and Cadence

The Discovery program was designed to support a high cadence of missions within a specified cost cap but without science or target constraints. This structure encourages innovation to maximize science return per dollar. The first generations of Discovery missions targeted objects and material in the inner solar system (see Table 22-2). Recently, Discovery has supported missions to targets in the outer solar system, including both proposals selected for Phase A study (e.g., the Io Volcano Observer and the Trident mission to Triton) and for flight (Lucy, which will study Jupiter’s Trojan asteroid swarms). This evolution reflects a natural and beneficial progression of scientific discovery. It is highly desirable that the Discovery mission class retain the ability to access objects in the outer solar system, while continuing to prioritize launch cadence and maximal science return per dollar—core attributes of this program.

Vision and Voyages recommended a Phase A–F Discovery cost cap, exclusive of the launch vehicle, that is equivalent to ~$700 million when inflated to FY 2025 dollars. The most recent Discovery competitions had a cost cap of ~$500 million for the hardware development phases (Phase A–D), with the mission operations phase (Phase E) and launch vehicle costs excluded from the cost cap. By excluding Phase E from the cap, this cost structure allowed for missions to outer solar system targets—which generally have longer trajectories and higher Phase E costs—to be competitive within Discovery, a very favorable outcome. However, estimated total mission costs for selections made with this cost structure (Psyche and Lucy) proved to be roughly twice the original cost cap once Phase E and launch vehicle costs were included. Such a large difference between the original cost cap and the actual life cycle cost is problematic: it makes budgetary forecasting challenging, while also introducing a potential mismatch between community expectations for launch cadence and realities of program budgetary constraints. Launch vehicle costs are largely outside of a proposing team’s control (and are relatively predictable by NASA), and the committee reaffirms Vision and Voyages arguments that launch vehicles be excluded from the Discovery cost cap. However, Phase E costs can vary substantially across different missions. Excluding Phase E costs from the cost cap makes it challenging to assess the science return per true total mission cost and also undermines budgetary forecasting needed to maintain a predictable cadence of frequent selections and launches.

The committee carefully weighed the cost cap for Discovery going forward, considering several factors. Addressing many of the priority science questions identified in this survey will require higher levels of instrumentation and/or mission complexity, and potentially longer missions (including notably to outer solar system objects), than were required in the past. Indeed, as Discovery missions accomplish many of the high-priority science

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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objectives achievable at the current cost, a larger cost cap will be needed to ensure the breadth of breakthrough science that has driven the success of the Discovery program.

Finding: A single Discovery cost cap that covers Phase A–F activities will allow each proposing team to allocate their costs between hardware development and operations in a manner that best suits the specific mission and maximizes the science that is achieved.

Recommendation: The Discovery Phase A through F cost cap should be $800 million in FY 2025 dollars, exclusive of the launch vehicle, and periodically adjusted throughout the decade to account for inflation. This cap will enable the Discovery Program to continue to support missions that address high-priority science objectives, including those that can reach the outer solar system.

A key element for a vibrant planetary exploration program is the regular acquisition of new information to test hypotheses, and mission cadence is an essential element of the Discovery Program. Discovery Announcements of Opportunity (AOs) have been released in 1994 (two selected), 1996 (two selected), 1998 (two selected), 2000 (two selected), 2004 (no selection), 2006 (one selected), 2010 (one selected), 2014 (two selected), and 2018 (two selected) (see Table 22-2). The preparation and review of Discovery proposals is time and resource intensive, and many high-quality proposals are received in each competition. In each of the past two Discovery competitions, NASA selected two missions. Although this increased the length of time between Discovery AOs, an overall high cadence of launches has generally been maintained.

Finding: The committee commends NASA for maintaining a high cadence of Discovery mission opportunities and finds that the selection of two Discovery missions per announcement of opportunity is a good approach to maximizing return on the substantial time and costs associated with proposal preparation and reviews.

Finding: The interval from release of the announcement of opportunity to launch has recently increased from 4 to 9 years. This increase appears to be owing to a combination of factors, including delayed selections, funding availability, unforeseen schedule delays, and growing technical complexity. The trend toward a longer implementation time is cause for concern because it undercuts the scientific responsiveness of the Discovery program.

New Frontiers Program and Cost Structure

NASA asked the committee to consider whether specific flight investigations in New Frontiers will ideally continue to be specified or whether this mission class be open like the Discovery program (see “Considerations” in Appendix A). New Frontiers missions address broader and/or more technically challenging scientific questions than Discovery-class missions. They are complex, may have a large suite of instruments and/or complex mission operations, and can be managed by only one of three centers (JPL, APL, and GSFC). Extensive time and resources go into planning and proposing NF missions, and only a relatively small number of concepts can be developed by each of the centers. The higher cost of NF missions also means that a single mission can consume a significant fraction of the planetary science budget and that they occur infrequently. It is therefore essential that NF missions be strategically designed to address the most important questions put forward by the science community. Decadal surveys provide the opportunity for a large, diverse group of scientists that represent the broad science community to devote significant time and resources to the evaluation and prioritization of candidate mission themes to best address priority science questions.

Recommendation: Mission themes for the NF-6 and NF-7 calls should continue to be specified by the decadal survey. Additional concepts that may arise mid-decade owing to new discoveries should be evaluated by an appropriately constituted group representing the scientific community and considered for addition to NF-7.

Mission life cycle costs are the primary factor in determining launch cadence for a cost-bounded program like New Frontiers. In evaluating the NF cost structure, the committee prioritized enabling access to all targets across the solar system at the potential expense of launch cadence. Missions to the outer (and innermost) solar system can have very long cruise phases to reach their target(s); sample return missions can also require long cruise phases to

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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return their samples to Earth. Even in a quiet cruise operational mode (defined below), these durations can result in significantly higher costs than for missions to nearby objects with comparable cost instrument suites. Further, while the committee’s recommended cost structure for Discovery can support targeted outer solar system science, accomplishing much of this science requires a medium-class mission. As with Discovery, the committee carefully weighed the option of separating the NF Phase A–D and Phase E–F costs, and again concluded that leaving the development and operational phases together in a single cost cap provides the greatest flexibility for mission teams to maximize scientific return.

Recommendation: New Frontiers should have a single cost cap that includes both Phase A–D and the primary mission Phase E–F costs, with a separate, additional cost cap allocation for a mission’s quiet cruise phase. This approach will enable the NF Program to optimize mission science, independent of cruise duration.

Vision and Voyages recommended a New Frontiers Phase A-F cost cap (excluding launch vehicle) equivalent to $1.34 billion in FY 2025 dollars. This recommendation merits reassessment based on actual and projected NF mission costs. The initial reconnaissance of the solar system has demonstrated its remarkable diversity and complexity, raising questions in planetary and astrobiological science of increasing sophistication that require increasingly advanced instrumentation and/or mission design. The exciting and aspirational Dragonfly mission selected in NF-4—involving a drone that lands on Titan and then performs multiple flights to explore varied regions and perform in situ analyses—is an example case. While the NF-4 competition had a Phase A-D cost cap equivalent to $1.14 billion in FY 2025 dollars, the NASA prelaunch budget for Dragonfly through FY 2026 is about $1.7 billion (launch is planned for 2027), suggesting that the total life cycle mission cost will likely be significantly higher than the original cost cap. As indicated earlier in this chapter, the committee endorses the Dragonfly mission at this budgetary level. Indeed, its costs are not too dissimilar from those of the scientifically compelling NF mission concepts considered by the committee, which had independently estimated (see next section) Phase A–D costs in the $1.2 billion to $2 billion range (FY 2025 dollars). These missions are representative of the nature and breadth of the science that will optimally be accomplished in the NF program in the coming decade, and a Phase A–D cost of some $1.5 billion is thus representative of the associated hardware costs. A nominal 2-year NF primary mission with a cost of $80 million per year would yield a primary mission Phase E cost of $160 million. Examination of recent Discovery and NF cruise costs indicates that a representative quiet cruise phase costs approximately $30 million per year.

Recommendation: The NF Phase A-F cost cap, exclusive of quiet cruise phase and launch vehicle costs, should be increased to $1.65 billion in FY 2025 dollars. A quiet cruise allocation of $30 million per year should be added to this cap, with quiet cruise to include normal cruise instrument checkout and simple flyby measurements, outbound and inbound trajectories for sample return missions, and long transit times between objects for multiple-target missions.

Mission Study Process and Technical Evaluation

The program portfolio recommended below was designed to achieve an appropriate balance among mission classes. To maintain this balance, it is crucial that all missions be initiated with a reasonable understanding of their probable costs. This decadal survey, like its predecessor, has placed considerable emphasis on cost realism, and the technical and cost evaluation process used in this decadal survey was specifically designed to provide a realistic assessment of mission costs. The committee has relied on detailed mission studies and cost estimates derived using a methodology designed to quantify the technical, schedule, and cost risks that are inherent in concepts with modest degrees of technical maturity (see Appendix C).

Prior to the start of this decadal survey, NASA undertook the selection and study of a suite of candidate missions through the Planetary Mission Concept Study (PMCS) program.10 This program completed 11 Center-led studies (Appendix C) whose final reports were made available to the science community. The committee examined the PMCS studies, together with missions recommended by Vision and Voyages and existing concepts explored

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10 The final report of each of the PMCS concepts is available at https://science.nasa.gov/solar-system/documents.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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by science definition teams and identified additional mission concepts needed to address the full breadth of the priority science questions, including input from white papers submitted by the scientific community (Appendix B). The committee prioritized these gap-filling candidate missions and commissioned 11 additional mission studies (Appendix C).11 Each study was overseen by one or more committee members, selected based upon their expertise, who acted as “science advocates” for the missions during the study. The studies were conducted by the Jet Propulsion Laboratory (JPL), the Applied Physics Laboratory (APL), or the Goddard Space Flight Center (GSFC) and were funded by NASA and delivered to the agency, which then delivered them to the decadal survey. Although NASA was aware of the contents of the studies, the Agency was not involved in their prioritization.

Seventeen of the available mission studies were prioritized by the committee for further Technical, Risk, and Cost Evaluation (TRACE) using criteria described at the beginning of this chapter. This independent evaluation was performed by The Aerospace Corporation, a contractor to the National Academies. The TRACE process is designed to provide an independent assessment of the technical feasibility of the mission candidates, as well as to produce a rough estimate of their costs. The process considers many factors when evaluating a mission’s potential costs, including the actual costs of analogous previous missions. It therefore reflects cost impacts that may be beyond the control of project managers and principal investigators. It includes a probabilistic model of cost growth owing to technical and schedule risks, and hence projects cost growth resulting from insufficient technical maturity. Appendix C discusses the TRACE process in more detail.

The TRACE process typically resulted in cost estimates that were higher than the estimates produced by the study teams, driven in large part by inclusion of costs related to probable threats to technical implementation and schedule. Independent cost estimates based on analogue missions, and independent risk assessment attempt to remove biases inherent in advocate estimation processes. Only the independently generated cost estimates were used in evaluation of the candidate missions by the committee in formulating the final recommendations.

It is stressed that the studies carried out were of specific “point designs” for the mission concepts. They provide a proof-of-concept demonstration that a mission is feasible and provide a basis for developing a cost estimate for the purpose of this decadal survey and are only intended to be representative of a potential implementation approach.

Prioritized New Large Strategic Missions

The decadal survey considered six candidate flagship missions for the decade 2023–2032 that were judged to have exceptional scientific merit, based on their ability to address priority science questions Q1 through Q12. In alphabetical order, these are the Enceladus Orbilander, the Europa Lander, the Mercury Lander, the Neptune-Triton Odyssey Flagship, the Uranus Orbiter and Probe, and the Venus Flagship.12 TRACE analyses were performed on all six, which were found to have medium-low to medium technical risk, except for the Venus Flagship, which has numerous system elements that increased its technical risk to medium-high (Appendix C). Three of the missions proposed—Europa Lander, the Enceladus Orbilander, and the Neptune Odyssey Flagship—require the SLS launch vehicle, but options are available for launch on a heavy lift vehicle with the inclusion of a solar-electric propulsion stage and/or a Jupiter gravity assist (if available). The TRACE cost estimates in FY 2025 dollars for these missions were $4.9 billion for Enceladus Orbilander, $5.8 billion for Europa Lander, $2.8 billion for Mercury Lander, $5.2 billion for Neptune-Triton Odyssey, $4.2 billion for the Uranus Orbiter and Probe, and $7.8 billion for the Venus Flagship.

Uranus and Neptune, the so-called “ice giants”—although whether they are predominantly ice versus rock remains uncertain (see Q2 and Q7)—are the only planets that have never been studied with a dedicated orbital tour. An ice giant system mission was judged to be the top priority flagship for the next decade, primarily for its ability to produce transformative, breakthrough science across a broad range of topics and key science questions. A secondary consideration was that the system-oriented, multi-target emphasis of such a mission is programmatically complementary to the flagships currently under way (MSR and Europa Clipper) that focus on

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11 The full mission study reports examining the concepts identified by the decadal survey are available at https://tinyurl.com/2p88fx4f.

12 The mission study reports for Enceladus Orbilander, Mercury Lander, Neptune-Triton Odyssey, and Venus Flagship are available at https://science.nasa.gov/solar-system/documents.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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single targets. As part of the prioritization process, the committee carefully considered flagship missions to perform system science at either Uranus or Neptune. While missions to both systems have outstanding scientific merit, the committee concluded that a Uranus mission is favored because an end-to-end mission concept exists that can be implemented in the 2023–2032 decade on currently available launch vehicles. Neptune Odyssey does not have demonstrated viable trajectories for a launch within the decade covered by this survey on currently available launch vehicle configurations, and there is a potential need for modifications to existing fairings. In addition, there are uncertainties in power requirements and the possible need for solar electric propulsion to reach Neptune if neither the SLS nor a Jupiter gravity assist are available. The Uranus mission has flexible trajectory opportunities, with the ability to be initiated at times throughout the decade including a launch as early as 2031.

The highest priority new Flagship mission for the decade 2023–2032 is the Uranus Orbiter and Probe mission. The Uranus Orbiter and Probe (UOP) will deliver an in situ atmospheric probe and conduct a multi-year orbital tour that would transform our knowledge of ice giants in general and the uranian system in particular. Uranus itself is one of the most intriguing bodies in the solar system: an extreme axial tilt; low internal energy; high speed winds and active atmospheric dynamics; and complex magnetic field all present major puzzles. It is unclear when and where Uranus formed, or if it swapped positions with Neptune during early solar system migration. It has been proposed that an early catastrophic impact caused the planet’s extreme tilt and odd characteristics, possibly forming its rings and satellites, but this has yet to be validated. Uranus’s large ice-rock satellites represent potential ocean worlds that could have astrobiological importance. Some of these moons display surprising degrees of geological activity or evidence of past internal heat release, particularly Ariel and Miranda, and yet they are part of the least explored regular satellite system. Detailed study of an ice giant system will provide vital ground-truth to exoplanetary science, given that exoplanets with similar masses are perhaps the most abundant class of exoplanet, and an inherently different class of planet than gas-rich Jupiter and Saturn. The committee’s prioritization of the UOP mission reaffirms its identification in Vision and Voyages as the next highest priority flagship after MAX-C and the Jupiter Europa Orbiter, whose derivative missions (Perseverance and Europa Clipper) are already in operation or development. The TRACE found UOP to have medium-low technical risk, the only flagship concept to receive this rating among those studied.

Key science questions for the Uranus Orbiter and Probe are:

  1. Origin, Interior, and Atmosphere (Q1, Q2, Q7, Q12):
    • How does atmospheric circulation function, from interior to thermosphere, in an ice giant?
    • What is the 3D atmospheric structure in the weather layer?
    • When, where, and how did Uranus form, how did it evolve both thermally and spatially, including migration, and how did it acquire its retrograde obliquity?
    • What is Uranus’s bulk composition and its depth dependence?
    • Does Uranus have discrete layers or a dilute core, and can this be tied to its formation and tilt?
    • What is the true rotation rate of Uranus, does it rotate uniformly, and how deep are the winds?
  2. Magnetosphere (Q7):
    • What dynamo process produces Uranus’s complex magnetic field?
    • What are the plasma sources and dynamics of Uranus’s magnetosphere and how does it interact with the solar wind, Uranus’s upper atmosphere, and satellite surfaces?
  3. Satellites and rings (Q2, Q4, Q5, Q8, Q10)
    • What are the internal structures and rock-to-ice ratios of the large uranian moons and which moons possess substantial internal heat sources or possible oceans?
    • How do the compositions and properties of the uranian moons constrain their formation and evolution?
    • What geological history and processes do the surfaces record and how can they inform outer solar system impactor populations? What evidence of exogenic interactions do the surfaces display?
    • What are the compositions, origins and history of the uranian rings and inner small moons, and what processes sculpted them into their current configuration?

The Uranus Orbiter and Probe mission will deliver an in situ probe into Uranus’s atmosphere, then complete a multi-year orbital tour of all aspects of the uranian system including the atmosphere, interior, magnetosphere, rings,

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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and satellites. The orbital science on the study payload includes visible and thermal imaging, visible/near-infrared imaging spectroscopy, fields and particles science, and radio/gravity science. The probe instruments measure atmospheric composition and isotopic ratio profiles, provide critical ground truth for the hydrogen ortho-para fraction and the vertical temperature profile, and determine abundances of the noble gases and their isotopes, as well as the vertical wind profile, parameters inaccessible to remote sensing. For more detail, refer to the complete science traceability matrix in the full mission study report.13 UOP can be launched on an existing heavy lift expendable rocket, with or without a Jupiter gravity assist. The primary and secondary launch opportunities occur in June 2031 and April 2032, and both benefit from a Jupiter gravity assist available at those times to place ~5,000 kg in orbit at Uranus after a ~13-year cruise. These optimal launch and cruise times could be achieved with a FY 2024 start of the UOP mission, as is included in the committee’s Recommended Flight Program (see Table 22-3 and Figure 22-1 below). Other launch opportunities from 2032 through 2038 (and beyond) utilize multiple inner solar system gravity assists (including a Venus flyby) to place up to 5,900 kg in orbit with an increased ~15-year cruise time. These diverse launch opportunities provide significant schedule flexibility and were considered by the committee to be a major strength of the Uranus mission concept. Further, international interest in an ice giant mission offers the opportunity for partnership, in analogy to the highly successful Cassini/Huygens partnership between NASA and ESA. Indeed, the 2021 report of the Voyage 2050 Senior Committee (ESA 2021) recommends that ESA pursue a substantial, medium class contribution to an ice giant orbiter mission led by an international partner.

The second highest priority new Flagship mission for the decade 2023–2032 is the Enceladus Orbilander. Enceladus is a small, active ice world in which gas and particles from its subsurface ocean are being jetted into space. Conditions at Enceladus thus allow for direct investigation of the habitability of an ocean world and assessment of whether it is inhabited. This addresses one of the most fundamental questions in solar system science: is there life beyond Earth and if not, why not?

Direct in situ sampling of plume materials by Cassini showed evidence of water vapor, carbon dioxide, methane, ammonia, complex organic molecules, and various salts, and ongoing hydrothermal activity in Enceladus’s rocky core is inferred. However, Cassini flyby velocities were high, leading to fragmentation of large molecules, and ambiguity as to the precise identity of the parent organic compounds.

Enceladus Orbilander will sample an extant subsurface ocean through study of freshly ejected plume material originating from a well-characterized location.14 Orbilander will execute a 1.5-year set of orbits of Enceladus, collecting plume samples from orbit, prior to a 2-year landed mission when more voluminous plume material is acquired in both passive and active (i.e., scooping) modes. Approximately ~300 μl of sample can be passively collected in ~10 days on the surface or in a single scoop. There are two main science objectives: (1) to search the plume materials for evidence of life (e.g., via multiple complementary approaches including the detection of amino acids, lipids, polyelectrolyte, and cell-like morphologies) at the level of fidelity necessary for biosignature detection (Q10, Q11, Q12); and (2) to obtain geochemical and geophysical context for life detection experiments (e.g., conditions in the ocean, structure/dynamics of the interior, and the structure of the jet vents; Q5, Q8). In addition to life detection, landed science includes a seismometer and radio science. Orbital science includes laser altimetry, radar sounding, gravity/radio science, thermal and visible imaging, and landing site reconnaissance. Viable launch opportunities on existing heavy-lift launch vehicles occur in 2037, 2038, and during the 2040s; these lead to Enceladus landing during favorable south pole illumination and Earth-communication conditions that begin in the early 2050s. The committee’s Recommended Program starts Orbilander in FY 2029 (see Table 22-3 and Figure 22-1), in support of these launch times.

The remaining four Flagship missions are described next in unranked, alphabetical order.

  • Europa Lander—This mission would characterize the biological potential of Europa’s ocean through direct study of any chemical, geological, and possibly biological, signatures as expressed at the surface of Europa. The search for signs of life on Europa’s surface would incorporate an analytical payload to perform quantitative organic compositional, microscopic, and spectroscopic analysis on five samples acquired from

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13 The full mission study report is available at https://tinyurl.com/2p88fx4f.

14 The Enceladus Orbilander mission study report is available at https://science.nasa.gov/solar-system/documents.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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  • centimeters beneath the icy surface, with supporting context imaging observations. This mission would significantly advance our understanding of Europa as an ocean world, even in the absence of any definitive signs of life, and would provide the foundation for the future robotic exploration of Europa. However, it was considered to be a lower priority than Enceladus Orbilander because of challenges associated with a short surface mission lifetime, effects of extensive radiolytic processes, and a lack of known continuously active, large volume plumes to supply fresh material from the underlying ocean. The committee notes that NASA’s investments in Europa Lander studies have advanced the concepts and technology for landing and conducting surface operations on an icy body. They have also aided the maturation of instruments and tools for surface science on icy worlds. Continuing work in these areas will support a potential future landed mission to Europa as well as to other ocean worlds.
  • Mercury Lander—This mission, as proposed, would deliver a lander with a suite of instruments to the surface of the innermost planet to gain insight into the original distribution of elements in the earliest stages of solar system development and to learn how planets and exoplanets form and evolve near to their host stars. The Mercury Lander would investigate: (1) the chemistry and mineralogy of Mercury’s extremely reduced and unexpectedly volatile-rich surface, (2) Mercury’s interior structure and magnetic field, (3) the active processes that produce Mercury’s exosphere and alter its regolith, and (4) the geologic processes that have shaped its evolution. It was ranked lower in priority because of the narrower scientific scope of the mission as proposed compared to an ice giant system mission, and the high priority placed on the transformative science possible with the astrobiologically focused Enceladus Orbilander. The Mercury Lander concept would benefit from development work to enable enhanced spacecraft thermal control and high-temperature subsystems that would allow for longer duration surface operations and cost-effective circular and low-altitude orbits. Further, mission concept development to broaden the science goals, for example, to enable characterization of isotopic composition, would be valuable.
  • Neptune-Triton Odyssey—This mission would deliver an orbiter and atmospheric probe to the Neptune-Triton system to study an ice giant planet, its rings, small satellites, space environment, and its large irregular moon, Triton, using a single launch of the SLS or, for example, heavy lift with a Jupiter gravity assist or a solar-electric propulsion kick stage. The mission would address: (1) how the interiors and atmospheres of ice giant (exo)planets form and evolve; (2) what causes Neptune’s strange magnetic field, and how its magnetosphere and aurora work; (3) whether Triton is an ocean world, what causes its plumes, and the nature of its atmosphere; (4) how Triton’s geophysics and composition can expand our knowledge of dwarf planets like Pluto; and (5) the connections between Neptune’s rings, its small inner satellites, and Triton’s orbital evolution. The Neptune-Triton flagship was ranked lower than the Uranus Orbiter and Probe primarily owing to the lack of demonstrated viable trajectories to Neptune for a launch within the decade covered by this survey on available launch vehicles, uncertainties in heavy lift launch vehicle accommodation, and the potential need for solar-electric propulsion to reach Neptune if neither the SLS nor a Jupiter gravity assist is available. The concept would benefit from a new mission study in which a Jupiter gravity assist is not assumed, and existing launch vehicles and power systems are utilized. Such a study will likely require consideration of the technological feasibility of solar electric propulsion, identification of any technology developments required, and prioritization of potential science descopes while retaining Flagship-level science.
  • Venus Flagship—This mission would deliver an orbiter, lander, variable-altitude aerobot, and two small satellites on a single launch that will use multiple instruments to probe and measure the exosphere, atmosphere, and surface at multiple scales with high precision. The science goals would be to (1) understand the history of volatiles and liquid water on Venus and determine if Venus has ever been habitable, (2) understand the composition and climatological history of the surface of Venus and the present-day couplings between the surface and atmosphere, and (3) understand the geologic history of Venus and whether Venus is active today. West Ovda Regio tessera would be the nominal landing site to examine rocks considered to be among the most likely to have formed in a habitable climate regime. The Venus Flagship included multiple elements and was intended to operate in a challenging environment. The committee’s assessment was that critical, flagship-class science advances could be made from the lander and a descoped
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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  • orbiter/lander mission was evaluated. However, the TRACE cost of the descoped mission is estimated to be $5.7 billion (see Box C-2), which is significantly higher than the other prioritized flagship missions. Its relatively high cost, together with the technical risk of landing on a challenging surface environment and sample handling at the Venus surface, led to the Venus Flagship being ranked lower than the top two prioritized flagship missions. It is possible that its science objectives could be met by landing in the plains, at a lower risk and cost. The concept would benefit from a study to assess the scientific rationale and the technical and cost feasibility of such an approach.

Prioritized New Frontiers Missions

New Frontiers (NF) Announcement of Opportunities (AOs) have included a list of mission themes that each specify destination and primary science objectives, with proposals required to address one of the themes. In general, the NF mission themes have been specified by decadal surveys, although subsequent to Vision and Voyages NASA added an Ocean Worlds (Titan and/or Enceladus) theme to the NF-4 call. Per above, the committee recommends that the New Frontiers Program continue to specify mission themes in future calls, and in this section the committee describes its related recommendations.

New Frontiers 5

In a November 5, 2020, Community Announcement, NASA indicated an October 2022 (target) release date for the NF-5 AO, and that the NF-5 mission themes would be (parenthetical words are NASA’s):

  • Comet Surface Sample Return (CSSR)
  • Lunar South Pole–Aitken Basin (SPA) Sample Return (pending Artemis landing site selection(s) and science objectives)
  • Ocean Worlds (only Enceladus)
  • Saturn Probe
  • Venus In Situ Explorer
  • Io Observer (pending flight selection(s) for the Discovery program)
  • Lunar Geophysical Network (LGN)

Midway through the decadal process, on May 12, 2021, NASA issued a Community Announcement that the NF-5 announcement of opportunity (AO) was to be delayed until a target release of October 2024. That announcement indicated that NASA intended to use the results of this survey to guide the NF-5 AO. However, when the National Academies initiated this decadal survey, it was with the understanding that the NF-5 mission themes would not be determined by the survey committee. Therefore, committee membership was not designed nor vetted to provide impartial findings and recommendations on NF-5. On May 25, 2021, the survey chairs released a letter notifying the community that the committee would not adjust the mission themes for NF-5 and would retain those listed above.

New Frontiers 6 and 7

The committee prioritized 13 (potentially) medium-class missions for TRACE (see Appendix C): Calypso Uranus and KBO flyby, Triton Ocean World Surveyor, Enceladus Multiple Flyby (EMF), Intrepid lunar rover, Endurance lunar rover, INSPIRE lunar polar volatiles rover, Titan Orbiter, Titan Orbiter and Probe, Ceres Sample Return, Mars Life Explorer (MLE), Centaur Orbiter and Lander (CORAL), Mercury Lander, and Mars In Situ Geochronology. An additional 6 medium-class missions were considered that had undergone independent cost and technical evaluation as part of Vision and Voyages: Venus in situ explorer, Lunar SPA Sample Return, LGN, CSSR, Io Observer, and Saturn probe. As indicated above, the committee recommends that Mars Life Explorer and Endurance-A be supported through MEP and LDEP, respectively, and the Mercury Lander

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

was ultimately considered as a flagship mission, leaving a total of 16 mission concepts to be considered for inclusion in New Frontiers.

The panels prioritized NF mission themes based on how well each would address the priority science questions. Using the panel scientific prioritizations as key input, the steering group then prioritized themes based on a combination of science merit, programmatic balance across different science questions and destination class, cost, and technical readiness. Careful consideration was given to the number of NF mission themes to be prioritized. NF-4 and NF-5 calls had, or will have, six and seven mission themes, respectively. As emphasized by Vision and Voyages, “Because preparation and evaluation of New Frontiers proposals places a substantial burden on the community and NASA, it is important to restrict each New Frontiers solicitation to a manageable number of candidate missions.” Indeed, with only three major design centers (APL, JPL, GSFC) that can manage NF missions and proposals, a restricted list is needed so they can appropriately allocate resources. On the other hand, after the NF-5 selection, six mission themes from the prior decade will remain unselected. Adding themes based on concepts studied in this survey, which is desirable to ensure that the NF list continues to address the currently highest priority science, then requires increasing the number of mission themes and/or removing some of the prior themes. In consideration of this balance, the committee decided to recommend eight NF themes per call.

In nonprioritized order, the mission themes recommended for New Frontiers 6 are:

  • Centaur Orbiter and Lander (CORAL)
  • Ceres Sample Return
  • Comet Surface Sample Return (CSSR)
  • Enceladus Multiple Flyby (EMF)
  • Lunar Geophysical Network (LGN)
  • Saturn Probe
  • Titan Orbiter
  • Venus In Situ Explorer (VISE)

If one of the above mission themes is selected in NF-5, it would be removed from the NF-6 list.

The mission themes recommended for New Frontiers 7 include all nonselected mission themes from the NF-6 list above, with the addition of:

  • Triton Ocean World Surveyor

The following provides descriptions for the NF-6 and NF-7 mission themes in alphabetical order, as well as additional contextual information in some cases. The listed science objectives reflect the judgment of the committee and are not necessarily identical to those identified in the mission concept studies.

CORAL investigates a Centaur from orbit and in situ, exploring one of a population of dynamically evolved but compositionally primitive small icy bodies from the Kuiper belt that currently reside between Jupiter and Neptune. The proximity of Centaurs provides an opportunity to conduct a comprehensive study of the geochemical and physical properties of primordial ice-rich planetesimals, which trace the composition of nebular volatiles such as H2O, CO2, CO, and NH3, revealing the nature of early solar system compositional reservoirs. The mission will map the surface and measure the ices and organics in situ.15

Science Objectives:

  • Determine the chemical and physical properties of a Centaur to understand the nature of primitive planetesimals.

___________________

15 The full mission study report is available at https://tinyurl.com/2p88fx4f.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×
  • Perform in situ elemental, isotopic, and organic analyses of a Centaur to develop a comprehensive understanding of the composition and initial conditions of the protoplanetary disk.
  • Determine the shape, topography, geological landforms, and density of a Centaur to understand the evolutionary history of this population of objects.
  • Determine degree of aqueous alteration on a Centaur to investigate the biologic potential of icy planetesimals and potential brine reservoirs.

The mission shall address all four objectives.

Ceres Sample Return focuses on quantifying Ceres’s current habitability potential and its origin, which is important for understanding habitability of mid-sized planetary bodies. Habitability is addressed through orbital and in situ investigation of the surface and subsurface environment around a hypothesized brine extrusion zone and via detailed compositional investigations in Earth labs of a returned samples. These samples will be collected from young carbonate salt deposits, typified by those identified by the Dawn mission at Occator crater, as well as some of Ceres’s typical dark materials. A sample of adequate mass to achieve the science objectives, acquired in pristine condition and returned at a temperature of lower than –20°C to prevent alteration, would allow investigations of the origin and evolution of Ceres’s organic matter, its brine chemistry and sources, and its accretional environment.

Science Objectives:

  • Characterize the depth and extent of potential deep brine layer(s) to determine whether liquid exists beneath Ceres today near hypothesized brine extrusion zones.
  • Characterize the nature of Ceres’s brines from salt deposits to determine the chemistry of waters and their potential habitability.
  • Determine the composition, structure, and isotopic composition of Ceres’s organics to understand processes of abiotic organic synthesis and evolution.
  • Determine the elemental abundances and isotopic ratios of Ceres’s materials via measurements on returned samples to determine its accretional environment.

The mission shall address all four objectives.

Comet Surface Sample Return seeks to understand the nature of cometary formation and mixing of materials in the protosolar nebula; compositional reservoirs present in the early solar system; the role of comets in the delivery of water and organic molecules to the early Earth, terrestrial planets and satellites; and evolutionary processes spanning from the protoplanetary disk to current cometary activity. The mission will map the nucleus of a Jupiter family comet, select an optimal sampling site, and acquire a sample from the surface for return to Earth for laboratory analysis. The sample will be acquired and transported in a manner that preserves organics and prevents aqueous alteration of the sample. Volatile material will be characterized via onboard analysis and/or by capture and return at noncryogenic temperatures.

Science Objectives:

  • Determine the elemental, isotopic, and structural composition of the organic and inorganic components of a comet nucleus to understand early compositional reservoirs.
  • Sample, preserve, and analyze cometary organic material to determine how complex organic molecules form and evolve in interstellar, nebular, and planetary environments.
  • Determine the isotopic composition of cometary water to address the role of comets in delivering volatiles to Earth’s atmosphere and interior.
  • Determine if cometary organic matter contributed significantly to prebiotic chemistry and homochirality of life on Earth.

The mission shall address all four objectives.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

Enceladus Multiple Flyby seeks to characterize Enceladus’s habitability and look for evidence of life via multiple flybys and analysis of plume material. Enceladus, an active icy moon with a subsurface ocean in a relatively benign radiation environment, provides the best opportunity to directly sample a potential habitable subsurface ocean. Prior Cassini observations demonstrate the presence of alkali and carbonate salts and complex organic molecules in plume icy grains; gas-phase nitrogen- and oxygen-bearing as well as aliphatic and aromatic organic molecules; redox couples (e.g., H2 and CO2), habitable temperature, salinity, and pH; alkaline hydrothermal activity; and water–rock reactions. However, Cassini flyby velocities were high, leading to fragmentation of large compounds, and ambiguity as to the precise identity of the parent organic molecules.16

Science Objectives:

  • Search for and identify complex organic molecules in Enceladus plume materials, with velocities <4 km/s and sample volume >1 μl with appropriate contamination control to enable life-detection investigations.
  • Determine the composition, energy sources, and physicochemical conditions of Enceladus’s ocean to assess its habitability.
  • Characterize Enceladus’s cryovolcanic activity to determine spatial and compositional variations in plume activity and the processes causing ocean material ejection and modification.

The mission shall address all three objectives.

The question of whether Enceladus harbors life merits study and would be best addressed by the Orbilander flagship mission (above), which would provide high fidelity in situ analyses for life detection. However, budgetary constraints might not allow for a second new flagship in this decade. Given this, the committee includes the Enceladus Multiple Flyby mission theme in NF, providing an alternative pathway for progress this decade on this crucial question, albeit with smaller sample volume and relatively high sample collection velocity. There are two principal differences between Orbilander and the NF Enceladus Multiple Flyby mission. First, EMF would likely be restricted to a limited number of passes at high velocity (~4 km/s), thus greatly restricting the sample volume available and possibly increasing sample degradation. Conversely, Orbilander in its landed and active scooping mission phase can acquire sample volumes 102–104 times larger. Second, EMF would have a much smaller instrument component, which reduces the number of orthogonal or cross-checking life-detection techniques available, as well as the geological and geophysical context that can be provided. If the Enceladus Orbilander flagship can be initiated this decade as recommended, then EMF would be removed from the NF-6 and NF-7 lists.

Lunar Geophysical Network examines the physical properties of the present-day Moon by deploying a global, long-lived (≥6 years) network of geophysical instruments on its surface. Although all large terrestrial bodies are thought to form cores, mantles, and primordial crusts through solidification of magma oceans, the Moon retains the most faithful record of the nature of this process. LGN will reveal the nature and evolution of the lunar interior and facilitate understanding of the initial solidification and primordial geologic processes that have shaped all terrestrial bodies. These measurements (e.g., seismic, heat flow, laser ranging, and magnetic-field/electromagnetic sounding) will allow the bulk composition of the Moon to be calculated, elucidate the dynamical processes that are active during the early history of terrestrial planets, provide new constraints on the collision process that generated our unique Earth-Moon system, and illuminate processes currently active on the Moon.

Science objectives:

  • Determine the internal structure and size of the crust, mantle, and core to constrain the composition, mineralogy, and lithologic variability of the Moon.
  • Determine the distribution and origin of lunar seismic activity in order to better understand the origin of moonquakes and provide insights into the current dynamics of the lunar interior and the interplay with external phenomena such as tidal interactions with Earth.

___________________

16 The full mission study report is available at https://tinyurl.com/2p88fx4f.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×
  • Determine the global heat-flow budget for the Moon in order to constrain more precisely the distribution of heat-producing elements in the crust and mantle, the origin and nature of the Moon’s asymmetry, its thermal evolution, and the extent it was initially melted.

The mission shall address all three objectives.

Saturn Probe obtains in situ measurements of the atmosphere from an entry probe. Understanding the initial conditions in the protosolar nebula requires measurements of each of the giant planets’ elemental and isotopic compositions. Constraining giant planet formation mechanisms is particularly dependent on knowing when and where Saturn formed, over how long, and if its orbit has migrated over time to stop Jupiter’s inward movement. Noble gas abundances are also crucial for determining if helium rain has prolonged Saturn’s thermal evolution. Additionally, comparisons of what governs the diversity of giant planet climates, circulation, and meteorology require constraints on the vertical temperature and wind profiles, as well as vertical circulation. Although some measurements may be obtained via remote sensing, many of the science objectives require in situ sampling.

Science Objectives:

  • Determine the in situ noble gas, elemental, and isotopic abundances to understand conditions in the protosolar nebula, as well as constrain Saturn’s formation, evolution, and migration.
  • Determine the in situ tropospheric temperature-pressure profile to quantify Saturn’s heat transport and convective stability.
  • Determine the in situ vertical wind shear to characterize Saturn’s tropospheric circulation and meteorology.
  • Constrain vertical mixing in Saturn’s troposphere to bound transport from the deeper interior

The mission shall address all four objectives.

Titan Orbiter globally characterizes Titan’s dense N2 atmosphere that harbors prebiotic molecules, its Earth-like methane hydrological cycle and seas, and its subsurface liquid water ocean, including how they evolve over time, in order to assess Titan’s potential habitability. Cassini flybys revealed complex organic chemistry, methane-ethane lakes and seas, and meteorology on Titan; however, these processes could not be thoroughly studied owing to instrumentation and flyby coverage limitations. Titan orbiter will investigate how the organic chemical factory on Titan works, both in the atmosphere and on the surface, providing important context for data from Dragonfly and complementary global measurements.17

Science Objectives:

  • Determine Titan’s internal structure, the depth and thickness of the ice shell and subsurface ocean, and whether the former is convecting; and determine rates of interior-surface solid or gas interchange.
  • Characterize Titan’s global geology and its landscape-shaping processes.
  • Characterize Titan’s global methane hydrological and sedimentological system, including surface transport/flow rates and cloud distributions.
  • Quantify the production, transport and fate of organic molecules in Titan’s upper atmosphere and atmospheric and climate evolution in general.

The mission shall address all four objectives.

The CAPS 2020 report on NF-5 (NASEM 2020) stated “With the selection of Dragonfly in the NF-4 competition and now under development, reconsideration by NASA of including a Titan mission in the NF-5 call under the Ocean Worlds mission theme is warranted on programmatic grounds and removing Titan from the list of potential targets would be appropriate. The next steps for Titan exploration are best evaluated and prioritized by the upcoming planetary science and astrobiology decadal survey.” The committee evaluated these issues and concluded that Titan Orbiter provides important and complementary science to Dragonfly, including global-scale monitoring of the atmosphere, seasons, and surface geologic processes, versus the several hundreds of kilometers

___________________

17 The full mission study report is available at https://tinyurl.com/2p88fx4f.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

to be studied by Dragonfly along its flightpath. Cassini was not a Titan orbiter and did not achieve global coverage, and Titan’s upper atmospheric composition is not known and will not be measured by Dragonfly. Vision and Voyages evaluated the Titan Saturn System Mission (TSSM), which addressed a wide range of science goals, and Titan Orbiter in combination with Dragonfly would cover most of the science envisaged for TSSM, which was broader in scope than the NF-4 Ocean Worlds Titan mission theme.

Triton Ocean World Surveyor orbits Neptune and performs multiple flybys of its largest and retrograde orbiting satellite, Triton. Triton is likely a captured KBO and a candidate ocean world with a geologically young surface and active geysers. It has a hazy atmosphere like Pluto’s and a uniquely strong ionosphere.

Proposed Science Objectives:

  • Determine whether Triton is an ocean world, ascertain its interior structure, and decide whether Triton’s ice shell is in hydrostatic equilibrium and decoupled from the interior.
  • Characterize Triton’s surface composition and geology, and look for changes, including plumes and their composition.
  • Determine the nature of the moon–magnetosphere interaction at Triton.
  • Determine the composition, density, temperature, pressure, and spatial/temporal variability of Triton’s atmosphere.

The mission shall address all four objectives.

The recommendation that Triton Ocean World Surveyor be delayed until NF-7 took into consideration launch trajectories, which benefit from a Jupiter gravity assist likely available in the NF-7 timeframe.

Venus In Situ Explorer (VISE) investigates the processes and properties of Venus that cannot be characterized from orbit or from a single descent profile. These include (1) complex atmospheric cycles (e.g., radiative balance; chemical cycles, atmospheric dynamics, variations of trace gases, light stable isotopes, and noble gas isotopes, and the couplings between these processes); (2) surface–atmosphere interactions (e.g., physical and chemical weathering at the surface, near-surface atmospheric dynamics, and effects upon the atmosphere by any ongoing geological activity); and (3) surface properties (e.g., elemental and mineralogical composition of surface materials, heat flow, seismic activity, and any magnetization). VISE will provide breakthrough information on the origin of the terrestrial planets, the evolution of their interiors and surfaces, atmospheric evolution and climate, and critical insights into the nature and habitability of exoplanets.

Science objectives:

  • Characterize past or present large-scale spatial and temporal (global, longitudinal and/or diurnal) processes within Venus’s atmosphere.
  • Investigate past or present surface–atmosphere interactions at Venus.
  • Establish past or present physical and chemical properties of the Venus surface and/or interior.

The mission shall address at least two of these three objectives.

Two missions on the NF-5 list of mission themes do not appear on the above lists for NF-6 and NF-7: Io Observer and SPA Sample Return. The committee carefully considered the Io Observer NF theme in light of the success of the IVO Discovery mission in reaching Phase A. CAPS 2020 stated the following: “If NASA’s exploration of Io proceeds via the selection of the IVO Discovery mission, then based on the IVO Step 1 proposal, inclusion of Io Observer would be redundant scientifically and its inclusion in NF5 would strongly warrant reconsideration.” The committee reaffirms the importance of Io as a unique body. Not only is it important to understanding tidal dissipation and resulting active volcanic, tectonic, and plasma processes, but also, for example, to providing an important analog to young terrestrial planets and tidally heated exoplanets. The committee anticipates that Io Observer will have an opportunity to compete in NF-5. The selection of IVO for Phase A study demonstrates that fundamental Io science can also be achieved via the Discovery program, and this may be increasingly true with

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

time as power systems and launch vehicles continue to evolve. These factors placed this theme at lower priority for NF-6 and NF-7 than other themes that clearly require a medium-class mission to complete their core science.

The SPA Sample Return mission addresses the highest priority lunar science. However, achieving the top science objectives with a fixed lander, as has been typically envisioned, is challenging. The committee concluded that the Endurance-A rover mission is a superior approach for acquiring abundant samples across diverse terrains to address multiple top-level science questions for the Moon and the solar system. The committee recommends that NASA pursue Endurance-A as a strategic medium-class mission within LDEP (see LDEP section above).

REPRESENTATIVE FLIGHT PROGRAMS FOR THE DECADE

Following the recommendations, priorities, and decision rules outlined in this report, the committee developed two representative program portfolios—Recommended and Level—for solar system exploration in the decade 2023–2032. The Level Program is designed to fit within the decadal funding projected for PSD, calculated by inflating the FY 2023 NASA planetary science budget by 2 percent per year through the remainder of the decade. The Recommended Program describes a vision to address the priority questions identified in this report and can be met with a total decade budget that is ~17.5 percent higher than the Level Program.

Both programs:

  • Continue support for missions in operation and in development.
  • Continue the Mars Sample Return campaign as currently planned.
  • Initiate the Uranus Orbiter and Probe Flagship mission.
  • Increase R&A funding to 10 percent or more of the annual PSD budget by mid-decade.
  • Continue support of the Mars (MEP) and Lunar (LDEP) Programs.
  • Return the MEP to its pre-MSR funding levels as MSR costs decrease, reaching a level of $500 million in FY 2032.
  • Incorporate the cost cap recommendations for Discovery and New Frontiers.
  • Incorporate cost realism from the TRACE studies.
  • Assume life cycle costs of a representative Discovery mission to be $900 million.
  • Assume a representative NF mission has an 11-year cruise and a life cycle cost of $2 billion in the first half of the decade and $2.2 billion in the second half.
  • Maintain support for Planetary Defense, enabling a new start, rapid-response flyby reconnaissance mission.
  • Sustain and increase plutonium production.

Table 22-3 summarizes the total decade funding levels recommended for each of the major programmatic elements in both the Recommended and Level Programs. Where the two programs differ most is in the level of support for new initiatives to address the science questions discussed in Chapters 415 (Tables 22-3 and 22-4). The Recommended Program captures the highest priorities of the community as outlined in this report and is both aspirational and inspirational. This program enables the robust training and development of diverse planetary science and engineering communities, drives technology development and implementation, and maintains U.S. leadership in exploration across the solar system. This program begins the highest-priority Flagship mission, the Uranus Orbiter and Probe, in FY 2024 with a launch in the early 2030s to take advantage of a Jupiter gravity assist that is available through 2032 to minimize cruise length and complexity. This UOP start date maintains the strategic mission funding as the MSR costs decrease (Figure 22-1). The Recommended Program also begins the second prioritized flagship, the Enceladus Orbilander in the latter part of the decade, allowing for state-of-the-art life detection techniques and sample volume that cannot be achieved in a medium-class mission. Orbilander provides an outstanding opportunity to explore the astrobiological conditions of ocean worlds and will revolutionize our understanding of these worlds. The Recommended Program restores the strong recommendation from Vision and Voyages, endorsed by this committee, for a cadence of two NF missions per decade. The NF-5 selection, which was to be the second NF mission from the decade of Vision and Voyages, would be completed early in the decade and would be followed by the selection of two NF missions in a mid-decade NF-6 opportunity. The Recommended Program increases the total funding for R&A across the decade by $1.25 billion relative to the current planned FY 2023 level adjusted

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

TABLE 22-3 Representative PSD Programs for the Decade

Program Element Recommended Program ($ million) Level Program ($ million)
R&Aa 3,870 3,350
Europa Clipper 1,700 1,700
Mars Sample Return 5,300 5,300
Discovery 5,250 5,250
New Frontiers 7,300 5,100
Mars Explorationb 2,850 2,650
Lunar Explorationc 4,760 4,760
Planetary Defense 1,700 1,700
Radioisotope power 1,750 1,750
Planetary Otherd 2,150 2,150
New Flagship #1 3,450 1,280
New Flagship #2 1,040
Total 41,120 34,990

NOTE: Costs are in real year dollars assuming 2 percent annual inflation.

a R&A budget levels reflect a 10 percent per year funding increase for openly competed R&A programs sufficient to bring the annual investment in R&A to ≥10 percent of the annual PSD budget by mid-decade; nonopenly competed R&A activities are increased by inflation at 2 percent/year; see “Recommended Funding for NASA Planetary R&A” section of Chapter 17 for details.

b MEP would support extended mission science and directed activities (e.g., small spacecraft missions, international collaborations, technology development, and/or execution of a science-enhanced iMIM) during the main MSR development phase, followed by a gradual ramp-up of the MEP yearly budget to its pre-MSR level by the decade’s end, and, in the Recommended Program, supporting initiation of a medium-class Mars mission.

c LDEP would support ongoing activities and Endurance-A.

d Other includes non-R&A elements in the Planetary Science Research line (e.g., planetary data system and astromaterial curation); management in the Discovery, MEP, and LDEP lines; international mission contributions in the Discovery and Outer Planets and Ocean Worlds lines; and icy satellites surface technology. It is increased by 2 percent/year relative to current levels to account for inflation. Technology development is included in most elements (e.g., R&A, Flagships, Mars Exploration, Lunar Exploration, and Planetary Other) and does not have a separate line in this table.

forward with inflation (see Chapter 17). Figure 22-1 shows the funding profile for the Recommended Program and Table 22-4 summarizes the primary differences between the two programs.

The Level Program can be conducted assuming the currently projected NASA budget (Table 22-3). The Level Program increases the total funding for R&A across the decade by $730 million relative to the current level including inflation. However, the Level Program budget profile (Figure 22-2) reveals several substantial disadvantages compared with the Recommended Program. This budget scenario does not include Enceladus Orbilander or MLE. The Uranus Orbiter and Probe Flagship mission could be initiated, but it would not begin until late in the decade, delaying its launch until 2038 or later, well into the decade beyond the horizon of this survey, and more than 14 years after the planned launch of Europa Clipper. Regular launch opportunities for UOP are available in this period but would have 2–3 years longer cruise durations and require Venus as well as Earth flybys. The program also loses the continuity of development begun in the Europa Clipper and MSR missions, with a drop in strategic mission funding from FY 2027 through FY 2030 raising the potential for loss of optimized workflow and/or critical expertise. Indeed, delay of UOP until the end of the decade would focus interim new developments

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×
Image
FIGURE 22-1 Recommended Program for the 2023 to 2032 decade. Costs are in real year dollars assuming 2 percent annual inflation. “Planetary Other” includes non-R&A elements in Planetary Science Research, management in Discovery, MEP, and LDEP; international mission contributions, and icy satellites surface technology.

TABLE 22-4 Comparison of Representative Programs

Recommended Program Level Program
Continue Mars Sample Return Continue Mars Sample Return
Five new Discovery selections at recommended cost cap Five new Discovery selections at recommended cost cap
Support LDEP with mid-decade start of Endurance-A Support LDEP with mid-decade start of Endurance-A
R&A increased by $1.25 billion R&A increased by $730 million
Continue Planetary Defense Program with NEO Surveyor and a follow-on NEO characterization mission Continue Planetary Defense Program with NEO Surveyor and a follow-on NEO characterization mission
Gradually restore MEP to pre-MSR level with late decade start of Mars Life Explorer Gradually restore MEP to pre-MSR level in late decade with no new start for Mars Life Explorer
New Frontiers 5 (1 selection) New Frontiers 5 (1 selection)
New Frontiers 6 (2 selections) New Frontiers 6 (late, or not included)
Begin Uranus Orbiter and Probe in FY 2024 Begin Uranus Orbiter and Probe in FY 2028
Begin Enceladus Orbilander in FY 2029 No new start for Enceladus Orbilander this decade
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×
Image
FIGURE 22-2 Level Program for the 2023 to 2032 Decade. Costs are in real year dollars assuming 2 percent annual inflation. “Planetary Other” includes non-R&A elements in Planetary Science Research, management in Discovery, MEP, and LDEP; international mission contributions, and icy satellites surface technology.

on smaller programmatic elements and maintaining the vitality of the whole program and the community in these circumstances may be very challenging. The first opportunity to select from the highly regarded new NF mission concepts studied in this report—including CORAL, Ceres Sample Return, and Titan Orbiter—will be in NF-6. In the Level Program, this selection would likely not occur until very late in the decade or in the next because of the delayed NF-5 selection and the funding required to complete Dragonfly.

This undermines the potential for high-impact science, including notably that involving outer solar system targets and/or sample return. In summary, the reductions associated with the Level Program would result in a less balanced portfolio with a significantly lower science return compared to the Recommended Program.

Budgetary Decision Rules

The committee strongly endorses the aspirational Recommended Program. The Level Program has been designed to fit within the projected PSD budget for the coming decade. However, if the budget is reduced below the Level Program budget then the committee has developed the following prioritized programmatic reductions to new initiatives to accommodate those changes. In priority order, with the first program element the first to be reduced, the committee recommends:

  1. Delay the start of the next Flagship mission;
  2. Reduce the number of new Discovery missions to four;
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×
  1. Reduce the funding level for Planetary Defense by removing the new-start mission after NEO Surveyor;
  2. Reduce the cadence of New Frontiers in the coming decade;
  3. Reduce the funding level for LDEP with a late-decade start of Endurance-A;
  4. Reduce the funding level for MEP below the Level program;
  5. Reduce the number of new Discovery missions to three; and
  6. Reduce R&A funding.

Science Traceability of Prioritized Large and Medium-Class Missions

The large- and medium-class strategic and PI-led missions prioritized and recommended in the preceding sections of this report were selected based on their ability to address the priority science questions, as well as programmatic balance, technical risk and readiness, and cost. After these missions had been selected, the committee evaluated this portfolio of new missions to assess how well they covered the breadth of the priority science questions (Q1–Q12) discussed in Chapters 415. The committee considered whether each mission would likely contribute to a “substantial,” “breakthrough,” or “transformative” advance for each of the sub-questions in Q1 through Q12. The tabulated and normalized results are displayed in a mission portfolio assessment matrix (Table 22-5) on a scale of modest (yellow) to high (dark green) contribution. This matrix illustrates that the collective suite of prioritized missions does an excellent job of addressing the full breadth of the priority planetary science questions and does so at a diverse set of destinations. The committee notes that Q9 focuses on terrestrial

TABLE 22-5 Mission Portfolio Assessment Matrix

Mission Name Priority Science Questions
1 2 3 4 5 6 7 8 9 10 11 12
Mars Sample Return
Uranus Orbiter and Probe
Enceladus Orbilander
Endurance-A
Mars Life Explorer
Centaur Orbiter and Lander
Ceres Sample Return
Comet Surface Sample Return
Enceladus Multiple Flyby
Lunar Geophysical Network
Saturn Probe
Titan Orbiter
Triton Ocean World Surveyor
Venus In Situ Explorer

NOTES: Assessment of the science questions addressed by MSR and each of the other large- and medium-class missions prioritized in this report. The top rows include MSR and the two new large strategic missions prioritized here. Endurance-A and Mars Life Explorer are highly ranked medium-class missions recommended for the LDEP and MEP programs, respectively. The remaining rows are the prioritized New Frontiers mission themes in alphabetical order. Yellow represents a modest contribution—typically a “substantial” advance in addressing one to a few of a priority science sub-questions—whereas the increasing intensity of green indicates increasing levels of “breakthrough” or “transformative” advances—that is, addressing an increasing number of sub-questions. Note that Q9 focuses on terrestrial life and is therefore not the primary focus of most planetary missions, but rather is supported through astrobiology research programs.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

life and is therefore not the primary focus of most planetary spacecraft missions, but rather is supported through astrobiology research programs. The committee further emphasizes that the table is not intended to, and should not be used to, prioritize between the missions; for example, a mission that definitively answers a single question can be as impactful as one that makes progress on several questions.

The Level Program would not include the Enceladus Orbilander or MLE, the Uranus Orbiter and Probe mission would be delayed, the sixth New Frontiers competition may not occur, and there would be fewer PI-led missions overall. These reductions would result in a less balanced portfolio with a significantly lower science return compared to the Recommended Program.

STATE OF THE PROFESSION

The committee’s Statement of Task explicitly requested an assessment of the state of the planetary science and astrobiology communities, and Chapter 16 is devoted to this topic. The state of the profession (SoP), including issues of diversity, equity, inclusivity, and accessibility (DEIA), is central to the success of the planetary science enterprise. Its inclusion here, for the first time in a planetary science decadal survey, reflects its importance and urgency.

Ensuring broad access and participation is essential to maximizing excellence in an environment of fierce competition for limited human resources, and to ensuring continued American leadership in planetary science and astrobiology (PS&AB). A strong system of equity and accountability is required to recruit, retain, and nurture the best talent into the PS&AB community. The committee applauds the hard-earned progress that has been made—most notably with respect to the entry and prominence of women in the field—as well as the exemplary goals and intentions of NASA science leadership with respect to DEIA. However, much work remains to be done, to address persistent and troubling issues of basic representation by race/ethnicity.

The committee’s eight SoP recommendations (see Chapter 16) address four primary topical areas:

  1. An evidence gathering imperative. Equity and accountability require accurate and complete data about the SoP. There is an urgent need for data concerning the size, identity, and demographics of the PS&AB community; and workplace climate. Without such data, it cannot be known if the best available talent is being utilized, nor how involvement may be undermined by adverse experiences.
  2. Education of individuals about the costs of bias and improvement of institutional procedures, practices, and policies. The committee recommends that the PSD adopt the view that bias can be both unintentional and pervasive, and provides actionable steps to assist NASA in identifying where bias exists and in removing it from its processes.
  3. Broadening opportunities to advance the SoP. Engaging underrepresented communities at secondary and college levels to encourage and retain them along PS&AB career pathways is essential to creating and sustaining a diverse community.
  4. Creating an inclusive and inviting community free of hostility and harassment. Ensuring that all community members are treated with respect, developing and enforcing codes of conduct, and providing ombudsperson support to address issues is important for maintaining healthy and productive work environments.

Together, the SoP findings and recommendations aim to assist NASA’s PSD in boldly addressing issues that concern its most important resource: the people who propel its planetary science and exploration missions. The reader is referred to Chapter 16 for detailed discussion of these important issues.

OTHER KEY PROGRAMMATIC RECOMMENDATIONS

Detailed rationales, findings, and recommendations for infrastructure, human exploration, and technology are given in their respective chapters. Key topics discussed in these three chapters and those recommendations having broad programmatic and budgetary implications are summarized below.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

Infrastructure

Chapter 20 provides a detailed discussion of PSD’s infrastructure needs for the next decade and includes 17 findings and 7 recommendations. Here the committee presents several of the key elements and recommendations from that chapter.

Mars Sample Receiving Facility

The processing and analysis of samples returned from Mars will occur in three separate stages: (1) initial receiving and characterization to verify that the samples can be safely distributed; (2) distribution to the science community for detailed analysis; and (3) long-term curation. An end-to-end plan is needed for all three of these elements, and this planning needs to include early engagement with the sample science community, government stakeholders, and the public. The samples will be initially delivered to the Mars Sample Receiving Facility (SRF), which will be the first facility since Apollo to implement planetary protection Category V, Restricted Earth Return requirements. These requirements include life detection, biohazard assessment, and, if necessary, sterilization procedures. Samples are anticipated from Mars in 2031 and the required biosafety level facility (BSL-4) can take up to 10 years to build (see Infrastructure chapter). Therefore, the finalization of requirements and the implementation of the SRF needs to begin immediately. Other government agencies have relevant BSL-4 facilities, and NASA can leverage this infrastructure and expertise to construct the SRF while minimizing cost. MSR/MEP and international participation and contribution in SRF requirements definition and funding is essential. Because the driving aim of MSR is analysis of samples by the science community, the SRF analysis capability needs to focus on the tools necessary to verify sample safety and does not need the full range of specialized microanalytical instrumentation available at other labs. The long-term curation of the Mars samples is best overseen by a NASA/ESA curatorial team. While MSR is driving the development schedule, it is prudent for NASA to consider needs beyond the MSR program, as the acquisition, curation, and analysis of samples is a many-decades-spanning investment and handling astrobiologically relevant samples from other destinations is an anticipated future need (see Infrastructure chapter).

Recommendation: NASA, in partnership with ESA and community stakeholders, should develop the plan for the end-to-end processing of samples returned from Mars. This plan should include the definition, design, and construction of the Mars Sample Receiving Facility to ensure that it is ready to receive the samples by 2031. The plan should also outline the approach for expeditiously distributing the samples to the scientific community for analysis and to a long-term curation facility.

Plutonium-238 Production

Plutonium-238 (238Pu) and Radioisotope Power Systems (RPS) are essential to the exploration of the solar system. Vision and Voyages recommended that NASA restart 238Pu production with a goal of producing 1.5 kg/year and the program is on track to reach this goal in 2026.

Recommendation: NASA should evaluate plutonium-238 production capacity against the mission portfolio recommended in this report and other NASA and national needs, and increase it, as necessary, to ensure a sufficient supply to enable a robust exploration program at the recommended launch cadence.

Recommendation: NASA should continue to invest in maturing higher efficiency radioisotope power system technology to best manage its supply of plutonium-238 fuel.

Launch Services

The capability, cost, and availability of launch vehicles are fundamental components of the timing and implementation of NASA’s planetary mission portfolio. The workhorse Atlas V and Delta IV vehicles are expected to be retired and will no longer be available for use by this survey’s prioritized missions. At the same time, new launch vehicle entrants—e.g., SpaceX Starship and Blue Origin New Glenn—are emerging from a variety of companies,

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

both established aerospace manufacturers and “new-space” enterprises. Some of these vehicles may have performance metrics suitable for planetary science missions on all scales. In particular, there may be opportunities for innovative solutions to sending missions on trajectories to the outer solar system. Experimental flight testing of new launch vehicles may also provide a mechanism for PSD technology flight validation missions.

Recommendation: NASA should develop a strategy to focus and accelerate development of high energy launch capability, or its equivalent, and in-space propulsion to enable robust exploration of all parts of the solar system. Any new systems that are developed should also build the pedigree to permit the launch of nuclear materials.

Telescopic Observations

Telescopic observations from space- and ground-based observatories provide essential support for planetary science and astrobiology through synergies with data returned from flight missions (see Chapter 20). Ground-based facilities have the benefit of longevity, and their capabilities can increase over time as science instruments can be upgraded, repaired, or replaced. Observations are utilized to monitor dynamic solar system phenomena, including planet and satellite atmospheres, comets, interstellar objects, and cryovolcanic/plume activity that can vary on timescales of hours to multiple decades. Occultations provide data important to understanding distant small body populations in general, and targets of planned space missions in specific. Such investigations are called out among the strategic research activities in priority science questions Q2 through Q8 (Chapters 511). Ground- and space-based observations of protoplanetary disks and exoplanetary systems provide crucial constraints to understanding how the solar nebula formed and ultimately evolved into our planetary system (see Q1–Q3 and Q12, Chapters 46 and 15, respectively).

Extremely large ground-based telescopes coming on-line late in the next decade will deliver advanced capabilities with angular resolution comparable to Voyager approach data. NASA investment in these observatories would enable new science and capabilities for spacecraft mission support. The NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab) provides the mainstay of ground-based telescopic science for astronomy. The Vera C. Rubin Observatory is currently being commissioned and will revolutionize planetary astronomy with an unprecedented inventory of solar system objects and time-domain observations. The next generation of extremely large optical telescopes will see first light in the next decade. Without NSF investment in guest observing programs at these next generation telescopes, the dramatically new science research that will be performed will only benefit from the skills, knowledge, and innovative perspectives from the subset of U.S. researchers. Construction of the next-generation VLA, planned to start in the next few years, promises major advances in planetary science, particularly for the giant planets and their largest moons (see Chapter 20). Planetary research at these future facilities will be aided by the inclusion of planetary astronomers within development teams and observatory staff.

Recommendation: NSF-supported, ground-based telescopic observations provide critical data needed to address important planetary science questions. The NSF should continue and, if possible, expand the funding to support the existing and future observatories, provide guest observer programs, and include planetary astronomers in future observatory development in order to maximize the science return from solar system observations

Planetary Radar

The loss of the Arecibo Observatory planetary radar facility has resulted in a significant gap in solar system observations, particularly in support of planetary defense. Radar observations are the most precise method for NEO astrometry, and provide important data needed to constrain small body size and spin states, improving our knowledge of the NEO population (see Chapters 7 and 18).

Recommendation: NASA and NSF should review the current radar infrastructure to determine how best to meet the community’s needs, including expanded capabilities to replace those lost at Arecibo Observatory.

Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
×

Human Exploration

Chapter 19 provides a detailed discussion of human exploration activities and includes 16 findings and 6 recommendations. Here the committee presents several of the key elements and recommendations from that chapter.

Human exploration is an aspirational and inspirational endeavor, and NASA’s Moon-to-Mars exploration plans hold the promise of broad benefits to the nation and the world. Human explorers can conduct cutting edge scientific investigations and collect carefully chosen samples, significantly enhancing quality of the science that can be achieved (see LDEP section above). In turn, a robust science program provides the motivating rationale for a sustainable human exploration program that will achieve the maximum return from programs such as Artemis at the Moon. The Human Exploration chapter provides a detailed discussion of the importance of science in human exploration and the need for an effective NASA organizational structure to maximize the scientific return from its human exploration endeavors. Here the committee presents two key recommendations from that chapter.

Recommendation: Conducting decadal-level science should be a central requirement of the overall human exploration program.

Recommendation: NASA should adopt an organizational approach in which SMD has the responsibility and authority for the development of Artemis lunar science requirements that are integrated with human exploration capabilities. NASA should consider establishing a joint program office at the associate administrator level for the purpose of developing Artemis program-level requirements across SMD, ESDMD, SOMD, and other directorates as appropriate.

Technology

Technology is the foundation of scientific exploration and significant technology investment by NASA is needed to ensure that the priority missions recommended by this survey can be accomplished. Within PSD, technology funding is included in the R&A program, Mars and lunar exploration, large mission development, the icy satellite surface technology program and elsewhere. Chapter 21 provides a detailed discussion of technology development needs and includes 44 findings and 7 recommendations to guide the necessary investments for the future. Here the committee presents the key budgetary recommendation from that chapter.

Recommendation: NASA PSD should strive to consistently fund technology advancement at an average of 6 to 8 percent of the PSD budget.

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Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 593
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 594
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 595
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 596
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 597
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 598
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 599
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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Page 600
Suggested Citation:"22 Recommended Program: 20232032." 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. doi: 10.17226/26522.
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The next decade of planetary science and astrobiology holds tremendous promise. New research will expand our understanding of our solar system's origins, how planets form and evolve, under what conditions life can survive, and where to find potentially habitable environments in our solar system and beyond. Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 highlights key science questions, identifies priority missions, and presents a comprehensive research strategy that includes both planetary defense and human exploration. This report also recommends ways to support the profession as well as the technologies and infrastructure needed to carry out the science.

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