The goal of planetary protection is to control, to the degree possible, the biological cross-contamination of planetary bodies. Two accepted rationales support this objective. Planetary protection policies seek, first, to preserve the ability to conduct future studies relating to the origin of life and prebiotic chemical evolution in extraterrestrial environments, and second, to protect the Earth’s biosphere from potential harm arising from the return to Earth of possibly hazardous materials—for example, replicating biological entities—from other planetary bodies. Other, but equivalent, formulations of these twin rationales exist.
BACKGROUND TO THIS STUDY
The Space Studies Board (SSB) of the National Academies of Sciences, Engineering, and Medicine has been involved in producing reports on planetary protection for 60 years. NASA’s planetary protection policies have codified much of the scientific and technical advice contained in these reports.
At the international level, the Committee on Space Research (COSPAR) of the International Science Council develops and maintains consensus planetary protection guidelines. Not surprisingly, many if not most of COSPAR’s guidelines are built on NASA policy and the SSB’s recommendations.
In the last half-dozen years or so, concerns arose that new space developments were stressing existing planetary protection policies and the policy development process. Such developments included planning for challenging robotic missions to Mars and the outer solar system addressing important astrobiology goals, the plans and missions of new national and international space agencies, the increasing private-sector space activities, and planning for the resumption of human exploration activities on the Moon and, eventually, on Mars.
Against this backdrop, NASA requested that the SSB undertake a comprehensive review of the planetary protection policy development process. The resulting report, Review and Assessment of Planetary Protection Policy Development Processes1 (hereinafter the “2018 report”), was completed in the late spring of 2018. Partially in response to the 2018 report and partially in response to concerns raised by private-sector space enterprises, NASA’s Advisory Council (NAC) recommended that the agency establish an internal group “to develop U.S. policies that properly balance the legitimate need to protect against the harmful contamination of the Earth or
1 National Academies of Sciences, Engineering, and Medicine (NASEM), Review and Assessment of Planetary Protection Policy Development Processes, The National Academies Press, Washington, D.C., 2018.
other celestial bodies with the scientific, social, and economic benefits of public and private space missions” (see Appendix D). The resulting report of the Planetary Protection Independent Review Board (PPIRB)2 was completed in the early autumn of 2019 (hereinafter the “PPIRB report”). A few weeks prior to the completion of the PPIRB report, NASA’s Science Mission Directorate requested that the SSB undertake a study (Appendix A) to assess the consistency between the findings and recommendations in the 2018 report (Appendix B) and those in the PPIRB report (Appendix C). The Committee to Review the Report of the NASA Planetary Protection Independent Review Board (hereafter the committee) was established in the autumn of 2019 to complete the comparative review of the two reports (Preface and Appendix A).
Additional background information relating to planetary protection and the initiation of this study is found in Chapter 1.
ASSESSMENT OF THE PPIRB REPORT
The PPIRB report contains 77 findings and recommendations organized into seven thematic sections. Chapter 2 contains the committee’s point-by-point assessment of each of the PPIRB’s findings and recommendations. The committee sorted the 77 findings and recommendations into three categories: (1) where the PPIRB and 2018 reports are consistent, (2) where the reports are inconsistent, and (3) where the two reports are not comparable because the PPIRB introduced a new idea, issue, or approach not discussed in the 2018 report. Sorting the PPIRB’s findings and recommendations in this way and organizing the results under the PPIRB report’s seven thematic sections yields Table S.1.
The PPRIB and 2018 reports have few inconsistencies (9 percent). A majority (58 percent) of the findings and recommendations of both reports are consistent. However, almost one-third (32 percent) of the PPIRB’s findings and recommendations touch on issues not discussed in the 2018 report.
However, the boundaries of the PPIRB report’s thematic sections are somewhat porous and create some issues for comparison with the 2018 report. The committee identified some inconsistencies within the PPIRB report between findings and recommendations in different thematic sections. Moreover, some of the PPIRB’s findings and recommendations combine multiple topics, some of which are consistent with the 2018 report and others are inconsistent. In its more granular analysis in Chapter 2, the committee addresses these inconsistencies and their implications for its comparative analysis.
Areas of Consistency
Areas where the PPIRB and 2018 reports are consistent include the following:
- The importance of U.S. leadership in the development of planetary protection science, approaches, technologies, and policy in keeping with the obligations contained in the Outer Space Treaty;3
- Planetary protection policies are equally applicable to both government and nongovernment missions;4
- Existence of lack of agreement about the implementation of planetary protection policies and associated requirements for private-sector space missions and, in particular, the need to identify, in domestic law, a federal agency to regulate nongovernmental entities on planetary protection;5
- The importance of international cooperation and recognition of COSPAR’s historical role;6
2 Planetary Protection Independent Review Board (PPIRB), NASA Planetary Protection Independent Review Board (PPIRB): Report to NASA/SMD: Final Report, NASA, Washington, D.C., 2019, https://www.nasa.gov/sites/default/files/atoms/files/planetary_protection_board_report_20191018.pdf. For ease of reference, the findings and recommendations contained in the PPIRB report have been numbered sequentially by the committee (see Appendix C) and are referred to in brackets.
3 See PPIRB, 2019  (albeit with a different approach to compliance than that supported by NASEM, 2018) and  (albeit with a different approach to U.S. leadership than contemplated in NASEM, 2018).
4 See PPIRB, 2019 .
5 See PPIRB, 2019 [10, 11, 53, 58].
6 See PPIRB, 2019 [18, 76].
TABLE S.1 Findings and Recommendations of the PPIRB Report Sorted According to Their Consistency or Otherwise with the 2018 Report
|Major Sections of the PPIRB Report||Consistent||Inconsistent||Not Comparable|
|Planetary Protection Categorization||1||0||5|
|Human Space Flight||9||0||2|
|Private Sector Initiatives and Missions||6||1||1|
|Robotic Mars Sample Return||5||0||4|
|Ocean World Exploration||0||0||4|
- Changes in exploration and uses of space affecting planetary protection policies:
- Need for reassessment of planetary protection policies in order to respond to the changes in the context of space activities:
- Reorganization of NASA’s Office of Planetary Protection,10
- Incorporation of new science and technology,11
- Definition of human exploration zones on Mars,12 and
- Planetary protection policy for the human exploration of Mars;13
- The need to resolve issues arising from the application of planetary protection policies to private-sector space activities;14
- Need for timely definition of planetary protection requirements;15
- Need for input from all stakeholders in the development of planetary protection policies and through advisory processes;16 and
- Clear public communication of planetary protection policies, issues, and mission-implementation strategies.17
Areas of Inconsistency and Concern
Areas where the PPIRB and 2018 reports are inconsistent or raise concerns—because they highlight in different ways the contexts in which government and private-sector stakeholders confront a lack of clarity about the development, application, and implementation of planetary protection policy concerns—include the following:
7 See PPIRB, 2019 [1, 52, 57].
8 See PPIRB, 2019 .
9 See PPIRB, 2019 [62, 63, 65].
10 See PPIRB, 2019 [8, 9].
11 See PPIRB, 2019 [5, 20, 21, 22, 23, 24]. However, the following thematically related findings and recommendations relate to topics not discussed in NASEM, 2018: PPIRB, 2019 [69, 70, 72].
12 See PPIRB, 2019 .
13 See PPIRB, 2019 [43, 45, 46, 49, 50]. However, the following thematically related recommendation relates to topics not discussed in NASEM, 2018: PPIRB, 2019 .
14 See PPIRB, 2019 . However, the following thematically related recommendation relates to areas not discussed in NASEM, 2018: PPIRB, 2019 .
15 See PPIRB, 2019 [13, 14, 15, 25, 26].
16 See PPIRB, 2019 [6, 7, 27, 48, 58, 59, 68]. However, the following thematically related finding is inconsistent with NASEM, 2018: PPIRB, 2019 .
17 See PPIRB, 2019 [42, 44, 64].
- The respective roles of COSPAR and the UN Committee on the Peaceful Uses of Outer Space in the development of planetary protection policies;18
- The legal relevance of the obligations in the Outer Space Treaty for private-sector space missions;19
- The idea of needing to balance planetary protection and various mission objectives as if they were competing aims;20 and
- The term “planetary protection” is confusing.21
Areas Not Comparable
As mentioned above, almost one-third of the PPIRB’s findings and recommendations address topics not discussed in the 2018 report. These findings and recommendations are concerned with topics such as the following:
- Recategorization of spacecraft missions to the Moon, Mars, and small solar system bodies (e.g., asteroids);22
- The potential cost challenges for small,23 low-cost spacecraft (e.g., SmallSat and CubeSat) missions in implementing planetary protection measures;24
- NASA’s potential role in providing planetary protection assistance to new, private-sector space activities;25
- Opportunities for future NASA contracts as a means of enforcing planetary protection policies;26
- Sanctions for private-sector actors that do not follow planetary protection policies;27
- What martian meteorites can potentially reveal about planetary protection policies designed to protect Earth from back contamination;28
- Impact of bioload-reduction sterilization techniques on science;29 and
- Whether Mars is already contaminated by previous robotic missions and whether the impacts of future robotic and human missions are “likely to be minimal.”30
AREAS OF STRATEGIC IMPORTANCE
From its comparative review of the PPIRB and 2018 reports, and its examination of the topics considered only in the PPIRB report, the committee identified the following areas of strategic importance in the development of future planetary protection policy common to both reports:31
- Establishing a new advisory process;
- Clarifying legal and regulatory issues; and
- Building the scientific and technical foundations of planetary protection policies for human missions to Mars.
Subsequent sections cover each of these strategic areas in turn.
18 See PPIRB, 2019 [32, 33].
19 See PPIRB, 2019 .
20 See PPIRB, 2019 .
21 See PPIRB, 2019 . However, the thematically related recommendation  is not discussed in NASEM, 2018.
22 See PPIRB, 2019 [35, 36, 37, 39, 71].
23 The committee defines a small spacecraft as one with a mass of less than 600 kg.
24 See PPIRB, 2019 [28, 29].
25 See PPIRB, 2019 .
26 See PPIRB, 2019 [16, 17].
27 See PPIRB, 2019 [30, 31].
28 See PPIRB, 2019 [19, 60, 61].
29 See PPIRB, 2019 [66, 67].
30 See PPIRB, 2019 [40, 51].
Establishing a New Advisory Process for Planetary Protection Policy
The PPIRB and 2018 reports, independently and together, make the persuasive case for NASA to establish a new process for gathering input on planetary protection policy from all relevant stakeholders. Such an advisory process is necessary to ensure that the planetary protection policy comprehensively reflects the new environment of public and private space activities, contributes to the success of government and private-sector space missions, and reinforces U.S. leadership on planetary protection.
Recommendation: NASA should establish a new, permanent, and independent advisory body formally authorized to provide NASA with information and formulate advice from representatives of the full range of stakeholders relevant to, or affected by, planetary protection policy.
The execution of planetary protection policy necessarily requires international coordination. However, the United States has shown leadership in developing planetary protection policy and most, if not all, of these policies have been adopted internationally. However, there are U.S. issues—for example, back contamination associated with current planning for a robotic Mars sample return mission in this decade and the complex scientific, technical, and policy ramifications that must be addressed to enable the human exploration of Mars in the next decade—that require immediate attention.
Recommendation: The initial focus of the new advisory body should be on the needs of upcoming private-sector and government missions.
Clarifying Legal and Regulatory Issues Concerning Planetary Protection
The persistence of disagreements about how the United States fulfills its obligations under the Outer Space Treaty in connection with private-sector space activities with planetary protection implications creates uncertainty for the private sector and potentially harms the objective of the U.S. government to facilitate exploration and uses of space by the private sector.32,33
Recommendation: NASA should work with other agencies of the U.S. government, especially the U.S. Department of State, to provide the private sector with a clear and authoritative explanation of the U.S. government’s obligations under the Outer Space Treaty to authorize and continually supervise the space activities of nongovernmental entities that raise planetary protection issues.
Problems persist with whether and how U.S. federal law regulates private-sector space activities for planetary protection purposes concerning launch, on-orbit, and re-entry activities.34 These problems create challenges for U.S. compliance with the Outer Space Treaty’s obligations concerning the authorization and continual supervision of activities of nongovernmental entities. The problems also undermine the private sector’s need for a transparent and efficient legal and regulatory framework to support expanding private-sector exploration and uses of space.
Recommendation: NASA should work with other agencies of the U.S. government, especially the Federal Aviation Administration, to produce a legal and regulatory guide for private-sector actors planning space activities that implicate planetary protection but that do not involve NASA participation. The guide should clearly identify where legal authority for making decisions about planetary
33 National Space Council, Space Policy Directive-2, Streamlining Regulations on Commercial Use of Space, Executive Office of the President, Washington, D.C., May 24, 2018.
protection issues resides, how the United States translates its obligations under the Outer Space Treaty into planetary protection requirements for nongovernmental missions, what legal rules apply to private-sector actors planning missions with planetary protection issues, and what authoritative sources of information are available to private-sector actors that want more guidance on legal and regulatory questions.
Building the Scientific and Technological Foundation for Planetary Protection Policy on Human Missions to Mars
Although NASA recognizes that existing planetary protection policy is inappropriate for human missions to Mars, it has not developed a strategy for producing practical planetary protection measures for such human missions.35 The lack of a strategy arises, in large measure, because NASA has not conducted the research and development needed to build the scientific and technological foundation for planetary protection measures designed specifically for human missions to Mars.36 For example, the current state of research is not yet adequate to determine whether there are regions on Mars where human explorers or commercial missions might land with minimal planetary protection implications.
Recommendation: NASA should make the development and execution of a strategy to guide the adoption of planetary protection policy for human missions to Mars a priority.
Essential elements of such a strategy could include the following:37
- A process to identify the most promising concepts for achieving planetary protection objectives in the context of human missions, such as high-priority astrobiological zones and human exploration zones, building upon the work done to date by COSPAR, NASA and the European Space Agency (ESA);
- Establishment of an adequately funded program of research and development to answer questions and address challenges raised by the most promising concepts for integrating planetary protection measures in human missions; and
- A plan to develop planetary protection policy for human missions to Mars on a timeline that permits the integration of such research and development into mission planning and implementation at the earliest possible stages.
The committee has chosen to emphasize the need for a strategy for humans to Mars because of the magnitude of the task and because this topic is emphasized in both the PPIRB and 2018 reports. However, it could be argued that the same kind of effort will be needed to address topics not discussed in the 2018 report and, thus, technically beyond the scope of the current study. Such topics include, for example, relaxing the planetary protection requirements for large areas of the Moon and thus opening them up to private-sector missions and addressing other planetary protection issues associated with the future exploration of ocean worlds and other astrobiologically significant environments.
EXPEDITING THE DEVELOPMENT OF NEW APPROACHES TO PLANETARY PROTECTION
The committee recognizes that NASA needs time to implement fully the recommendations contained in the PPIRB and 2018 reports and those offered above. However, NASA has an opportunity to make some rapid progress on important aspects of a new approach to planetary protection policy by leveraging the potential that small,
low-cost spacecraft offer for governmental, academic, and private-sector exploration and utilization of space. The PPIRB report drew attention to the challenges that small spacecraft missions can present in terms of the costs of compliance with planetary protection measures, even for Category II mission requirements38 related to undertaking trajectory analysis and completing an organic inventory for a spacecraft. Because of limited budget resources and time, small spacecraft require a more refined balance between risk and cost than is typical for large spacecraft. The committee agrees with the PPIRB’s emphasis on this issue and notes that small, low-cost spacecraft present an ideal environment for experimentation and innovation in the implementation of specific planetary protection policies.39