The planetary protection policy development process has evolved over decades of solar system exploration. National initiatives, such as the Apollo program and the Viking missions to Mars, were major influences early in the process of developing planetary protection policy, and a number of other national and international activities have influenced the process.1 This chapter summarizes roles and impacts of key elements of this history.
The international community expressed concern that space exploration could potentially contaminate planetary bodies, jeopardizing their biological exploration and posing risks to Earth’s biosphere, even before Sputnik began the spaceflight era. In 1956, the International Astronautical Federation (IAF) attempted to coordinate international efforts to prevent interplanetary contamination, and 2 years later the United Nations (UN) Committee on the Peaceful Uses of Outer Space (COPUOS) made initial attempts to deal with interplanetary contamination and spacecraft sterilization. In 1957, the U.S. National Academy of Sciences (NAS) urged that lunar and planetary studies avoid interplanetary contamination and asked the International Council for Science (ICSU) to assist in evaluating the possibilities of such contamination and developing means to prevent it. In 1958, the ICSU established an ad hoc Committee on Contamination by Extraterrestrial Exploration (CETEX), which in turn recommended establishing a code of conduct for space missions and research. In accepting the CETEX recommendations, ICSU established the Committee on Space Research (COSPAR) to coordinate worldwide space research.2
These organizations of the international scientific community had an early focus on planetary protection, among other issues. In 1961, ICSU declared that all countries launching space experiments that could have an adverse effect on other scientific research should provide ICSU and COSPAR with the information necessary to evaluate the potential contamination.3 In 1962, COSPAR organized a Consultative Group on Potentially Harmful
1 For a thorough discussion of the history of planetary protection through about 2011, see M. Meltzer, When Biospheres Collide: A History of NASA’s Planetary Protection Programs, NASA SP-2011-4234, U.S. Government Printing Office, Washington, D.C., 2011.
2 In 2017, COSPAR membership included 43 national member organizations—for example, the National Academies of Sciences, Engineering, and Medicine (NASEM) in the case of the United States—and 13 international scientific unions, and its various assemblies and topical meetings involve roughly 10,000 scientists from around the world.
Effects of Space Experiments to help conduct these evaluations. These actions set the foundations for the key role COSPAR has played in the international development of planetary protection policies.
With adoption of the Outer Space Treaty (OST)4 in 1967, planetary protection became part of international law and, with U.S. ratification of the treaty, federal law. For the past 50 years, the OST has been the most important international legal instrument regarding activities in space. All spacefaring countries to date are parties to the OST and are, thus, bound under international law to comply with the treaty. In 2017, congressional testimony confirmed the OST’s continuing importance to space activities.5
The OST contains many obligations on states parties, with the prohibition on the placement of nuclear weapons in space being one of the most important.6 In terms of planetary protection, the key provisions are Article IX, which is specific to planetary protection, and Article VI, which requires states parties to authorize and continually supervise the space activities of nongovernmental entities under their respective jurisdictions. Together, Articles IX and VI mean that states parties are required to address planetary protection issues for space activities of both governmental space agencies, such as NASA, and nongovernmental actors, such as private-sector enterprises.
To date, private-sector space activities have not raised planetary protection concerns, and, thus, Article IX implementation by states parties has not specifically addressed the private sector. However, states parties have a clear obligation under Article VI of the OST to authorize and continually supervise the space activities of nongovernmental entities.7 As this report discusses below,8 potential private-sector missions to Mars raise planetary protection questions, which Articles VI and IX of the OST require states parties to address.
The planetary protection obligations of Article IX provide that states parties shall conduct space exploration “so as to avoid harmful contamination” of celestial bodies and to avoid “adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter.” Thus, Article IX imposes obligations to avoid forward and backward contamination and provides that states parties “shall adopt appropriate measures” to do so.
These planetary protection provisions reflect the general duty in Article IX that states parties conduct space activities “with due regard to the corresponding interests of all other States Parties to the Treaty.” This due-regard obligation implements the principle in Article I of the OST that space “shall be free for exploration and use by all States,” including “free access to all areas of celestial bodies.”
The due-regard obligations on planetary protection do not impose specific requirements on space missions or the exploration of particular celestial bodies. What constitutes harmful contamination for one celestial body might not be relevant for another such body. Further, space exploration missions increase scientific knowledge about celestial bodies, permitting states parties to adapt their planetary protection approaches based on the best available science.9 Article IX requires states parties to evaluate harmful forward and backward contamination and,
4 Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, opened for signature January 27, 1967, 18 U.S.T. 2410, 610 U.N.T.S. 205 (hereinafter “Outer Space Treaty”).
5 See, for example, U.S. Senate Committee on Commerce, Science, and Transportation, “Reopening the American Frontier: Reducing Regulatory Barriers and Expanding American Free Enterprise in Space,” hearing of the Subcommittee on Space, Science, and Competitiveness, April 26, 2017, https://www.commerce.senate.gov/public/index.cfm/2017/4/reopening-the-american-frontier-reducingregulatory-barriers-and-expanding-american-free-enterprise-in-space.
6 Outer Space Treaty, Article IV.
7 In connection with proposed legislation in Congress, statements have been made asserting that the Outer Space Treaty does not directly apply to private-sector space activities (see, e.g., R. Kelly, Nemitz v. United States, A Case of First Impression: Appropriation, Private Property Rights and Space Law Before the Federal Courts of the United States, Journal of Space Law 30(2):297-309, 2004). These assertions fail to acknowledge that, under the Outer Space Treaty, the U.S. government is required to authorize and continually supervise the space activities of nongovernmental entities, including activities that raise planetary protection concerns under Article IX.
9 For example, scientific study of material returned from the Moon produced the conclusion that it posed no health or environmental threats on Earth. Thus, lunar missions that return such material to Earth are no longer classified as restricted Earth return in, for example, NASA and COSPAR planetary protection policies.
where necessary, adopt measures that appropriately manage such. Thus, the OST requires states parties to have a process or processes to identify planetary protection, design appropriate measures to address these, and implement the measures in space missions.
Article IX reinforces this requirement by stating that, in their space activities, states parties (1) “shall be guided by the principle of co-operation and mutual assistance”; and (2) “shall undertake appropriate international consultations” when a state party “has reason to believe that an activity or experiment planned by it or its nationals in outer space . . . would cause potentially harmful interference with the activities of other states parties in the peaceful exploration and use of outer space.”10 Further, Article IX permits a state party to request consultations if it has reason to believe the space activities of another state party might “cause potentially harmful interference with activities in the peaceful exploration and use of outer space.”11
Thus, when implementing their treaty obligations on planetary protection, states parties are required to consider the interests of other states parties in the exploration and use of space and consult with other states parties where these interests may be seriously affected.
For 50 years, states parties to the OST have implemented their Article IX obligations through planetary protection processes functioning at international and national levels. Internationally, states parties have used COSPAR to formulate consensus and science-based guidance on planetary protection objectives. Nationally, space agencies have developed their own planetary protection processes. Over time, the international and national planetary protection processes have influenced one another, reflecting Article IX’s emphasis on international consultation and cooperation.
To be clear, planetary protection guidance developed through COSPAR is not legally binding under the OST. COSPAR has no authority to compel OST states parties to implement its recommendations. Nor does the OST require states parties to use COSPAR in fulfilling Article IX obligations. However, states parties have, for five decades, implemented Article IX by using COSPAR and following its planetary protection guidance. For its part, the United States has exhibited sustained leadership within COSPAR and demonstrated commitment to COSPAR’s planetary protection guidance. Indeed, NASA requires that non-U.S. space agencies using NASA assets follow COSPAR guidance, thus actually enforcing the guidance that COSPAR produces. New spacefaring countries have also emphasized the importance of the COSPAR process and its recommendations to their efforts.12
Strong commitment to the COSPAR process and COSPAR guidance over 50 years helps explain why serious controversies about the meaning of, or compliance with, Article IX’s planetary protection provisions have not arisen. For example, the OST does not define “harmful contamination,” but states parties have so far not engaged in contentious debates about the meaning of this term. The area of planetary protection has not required international lawyers to apply the rules of treaty interpretation in response to problems among countries about what Article IX means.13 Compared to interpretation and compliance problems experienced in other areas of international law, what has transpired under the OST’s planetary protection provisions is impressive.
10 The inclusion of “its nationals” in this provision of Article IX underscores a state party’s obligation in Article VI to authorize and continually supervise space activities of nongovernmental entities.
11 The concept of “harmful interference” in Article IX is broader than “harmful contamination,” with the expanded scope incorporating matters than do not involve planetary protection. The harmful interference concept in Article IX arose from concerns that some space activities, such as the early 1960s launching of millions of small copper wires into orbit by the United States to enhance radio communication capabilities (Project West Ford, see, e.g., C. Peebles, High Frontier: The U.S. Air Force and the Military Space Program, Air Force History and Museums Program, 1997), could interfere with different space activities of other countries. Recent legislative proposals in the United States seeking to enhance private-sector space activities, such as asteroid mining, have raised unprecedented interpretations concerning the meaning of “harmful interference” in Article IX. See, for example, J. Gabrynowicz, “Hearings on Exploring Our Solar System: The ASTEROID Act as a Key Step,” testimony to the Subcommittee on Space of the Senate Committee on Science, Space, and Technology, September 10, 2014, https://science.house.gov/legislation/hearings/subcommittee-space-exploring-our-solar-system-asteroids-act-key-step.
12 See, for example, Omran Sharaf, “Planetary Protection in Emirates Mars Mission,” presentation to Legal Subcommittee, UN Committee on Peaceful Uses of Outer Space, Slides 17-18, March 2017, http://www.unoosa.org/documents/pdf/copuos/lsc/2017/tech-03.pdf.
13 The international legal rules on treaty interpretation are found in the Vienna Convention on the Law of Treaties (1969). Although the United States is not a party to the Vienna Convention, it considers the convention’s treaty interpretation rules to be binding on the U.S. government as customary international law.
The success, to date, of Article IX implementation has benefitted from important features of space exploration that have reduced the potential for controversy and conflict over implementation of the OST. These features include the following:
- A limited number of countries undertaking space missions that create planetary protection concerns;
- A predominant spacefaring nation, the United States, which supported planetary protection objectives through NASA and provided sustained leadership in COSPAR, as well as bilateral relations with other spacefaring countries;
- The focus on robotic planetary missions and the absence of human exploration activities after Apollo that limited the range of planetary protection concerns;
- The narrow focus on avoiding biological/organic contamination related to, among other things, the search for extraterrestrial life; and
- The absence of private-sector space activities that raise planetary protection concerns.
Changes in the nature of space exploration and use present challenges to planetary protection efforts. For example, private-sector missions to Mars would raise the issue of which agency of the U.S. government has the authority to regulate such missions, including for planetary protection compliance. Resolving where such authority resides cannot be ignored, because Article VI of the OST requires the United States to authorize and continually supervise the space activities on nongovernmental entities in the United States as well as U.S. government entities.14 Sending humans to Mars will also raise serious questions about what “harmful contamination” in Article IX of the OST means.15 Various concerns about the planetary protection policy processes in COSPAR and NASA regarding missions to Mars also raise questions related to the obligations in Article IX.
Although facing a potentially more challenging context, spacefaring nations remain bound under the OST’s Article IX provisions on planetary protection. The nature of these obligations provides states parties with ample opportunity to adjust their international cooperation and national activities to address new planetary protection issues. In this context, U.S. leadership on planetary protection becomes even more important.
Finding: The OST provides the critical and effective international legal framework for countries to identify risks of forward and backward contamination, formulate risk management strategies, and implement those strategies in space missions. States parties to the OST have not experienced serious disagreements on the meaning of, or compliance with, the treaty’s planetary protection provisions.
Finding: Planetary protection policies and requirements for forward and backward contamination apply equally to both government-sponsored and private-sector missions to Mars.
COSPAR is a scientific organization whose purpose is to “provide the world scientific community with the means whereby it may exploit the possibilities of satellites and space probes of all kinds for scientific purposes, and exchange the resulting data on a co-operative basis.”16 COSPAR promulgates guidelines from the international scientific community to assist national space agencies in developing their own policies and procedures.
NASA science and policy have, to date, provided the basis for practically all substantive COSPAR guidelines. For example, in 1963, on the basis of Space Studies Board (SSB)17 studies and advice, NASA adopted planetary protection policies for the Moon, Mars, and Venus. COSPAR followed U.S. policy in 1964 and established an
16 See, for example, A.W. Frutkin, International Cooperation in Space, Prentice-Hall, Englewood Cliffs, N.J., 1965, pp. 85-86.
17 Prior to 1988, the Space Studies Board was known as the Space Science Board.
interim quantitative framework for developing planetary protection standards that set limits on the probabilities of carrying viable organisms aboard spacecraft to planetary bodies or producing accidental impacts.
In 1969, COSPAR replaced the interim framework adopted in 1964 with guidelines that prescribed limits on the probability that a planet would be contaminated during the so-called period of biological exploration.18 Again, this decision reflected policies that NASA had recently adopted. Further following NASA’s lead, in 1970, COSPAR issued a statement of policy specifically recommending that the “Jovian planets be treated with the same quarantine requirements (for flybys, orbiters or entry probes) as currently apply to Mars . . . until further information is available.”19 Clearly, NASA policy was the driving factor in the development of international cooperation and harmonized guidelines on planetary protection within COSPAR.
This pattern continued in more recent decades. In 1982, acting on the SSB’s advice, NASA reviewed this quantitative policy and associated probabilistic approach to planetary protection requirements and implementation adopted in 1969 in light of new information obtained by planetary exploration and changes to, or uncertainties in, parameters used in the quantitative approach. On the basis of this review, NASA changed its policy and proposed that COSPAR adopt a new qualitative planetary protection policy. The new policy
- Established guidance for different combinations of target planet and mission type—i.e., orbiter, lander, etc. (see Table 2.1);
- Placed sample return missions in a separate category;
- Simplified documentation procedures; and
- Recommended implementing procedures (e.g., trajectory biasing, cleanroom assembly, spacecraft sterilization, etc.) if the planet–mission combination warranted such measures.
Similarly, NASA proposed the new planetary protection policy to COSPAR, and COSPAR adopted it in 1984 by amending its existing planetary protection guidelines by replacing “the basic probability of one in one thousand that a planet of biological interest will be contaminated shall be used as the guiding criterion during the period of biological exploration” with the mission/target categorization scheme outlined in Table 2.1.20,21
Again based on NASA input, COSPAR made the following changes to its planetary protection guidelines:
- In 1994, COSPAR amended the 1984 policy to include refinements of the Mars guidance.
- In 2002, COSPAR further refined these Mars recommendations and included guidance for the outer planets and icy moons and sample return missions.
- In 2008, COSPAR added explicit recommendations for individual target bodies and guidelines for human missions to Mars.
- In 2017, COSPAR updated the definition of Special Regions on Mars.
Finding: For five decades, the states parties to the OST have used COSPAR policy as part of complying with their planetary protection obligations under the treaty and, thus, have made COSPAR interdependent with their respective national rules, institutions, and processes on planetary protection.
Finding: All spacefaring nations, including new entrants to space exploration, have declared they will comply with COSPAR guidance on planetary protection. Such commitment highlights the importance of the COSPAR planetary policy development process to the behavior of spacefaring nations, including state party efforts to comply with their planetary policy obligations in the OST.
18 COSPAR, COSPAR Decision No. 16, COSPAR Information Bulletin, No. 50, pp. 15-16, 1969.
19 COSPAR, COSPAR Decision No. 14, COSPAR Information Bulletin, No. 54, p. 12, 1970.
20 COSPAR, COSPAR Internal Decision No. 7/84, Promulgated by COSPAR Letter 84/692-5.12.-G, July 18, 1984.
21 See, also, D.L. DeVincenzi, P.D. Stabekis, and J. Barengoltz, Refinement of planetary protection policy for Mars missions, Advances in Space Research 18:314, 1994.
TABLE 2.1 Mission Type Categories as Specified in COSPAR’s Planetary Protection Policy
|Mission Category||Mission Type||Planetary Bodies||Planetary Protection Requirements (Illustrative Examples)|
|I||Any||Bodies not of direct interest for understanding the process of chemical evolution or the origin of life (e.g., undifferentiated, metamorphosed asteroids, and others [to be determined]).||None.|
|II||Any||Bodies of significant interest relative to the process of chemical evolution and origin of life, but only a remote chance that contamination could compromise future investigations (e.g., comets, carbonaceous chondrite asteroids, outer solar system planets, Venus, the Moon, icy bodies of the outer solar system [note 1] and others [to be determined]).||Brief documentation only (except for missions to the Moon, which also require an inventory of all organic compounds present in excess of 1 kg).|
|III||Flyby, orbiter (no direct contact)||Bodies of significant interest to the process of chemical evolution and/or origin of life and where scientific opinion provides a significant chance that contamination could compromise future investigations (e.g., Mars [note 2], Europa, Enceladus, and others [to be determined]).||Documentation on contamination control and organics inventory, plus trajectory biasing, cleanroom assembly, bioload reduction.|
|IV||Lander, probe (direct contact)||Bodies of significant interest to the process of chemical evolution and/or origin of life and where scientific opinion provides a significant chance that contamination could compromise future investigations. (e.g., Mars [note 3], Europa, Enceladus, and others [to be determined]).||Documentation (as for Category III) plus microbial reduction plan; Category III procedures plus partial sterilization and bioassay monitoring.|
|V (unrestricted)||Earth return after contact with another body||Earth-return missions from bodies deemed by scientific opinion to have no indigenous life forms (e.g., Venus, Moon, and others [to be determined]).||None except for requirements for category above for outbound phase.|
|V (restricted)||Earth return after contact with another body||Earth-return missions from bodies deemed by scientific opinion to be of significant interest to the process of chemical evolution and/or origin of life (Mars, Europa, and others [to be determined]).||Same as for Category IV plus sterile or contained returned hardware and continual monitoring of project activities.|
|Note 1||Missions to Ganymede, Titan, Triton, Pluto/Charon, and Kuiper belt objects greater than half the diameter of Pluto can be assigned to Category II if they demonstrate by analysis their “remote potential for contamination of the liquid water environments that may exist beneath their surfaces (a probability of introducing a single viable terrestrial organism of <1 × 10−4) addressing both the existence of such environments and the prospects of accessing them.”|
|Note 2||Mars orbiters are required to meet an orbital lifetime requirement (20 or 50 years after launch with a probability ≥0.99 or 0.95, respectively. Lifetime requirements are not required if the orbiter meets a total bioburden level of ≤500,000 spores.|
|Note 3||Category IV missions to Mars are subdivided into IVa, IVb, and IVc. Category IVa missions—i.e., those not carrying instruments designed to investigate extant martian life—are restricted to a surface bioburden of ≤300,000 spores, and an average of ≤300 spores m−2. Category IVb missions—i.e., those carrying instruments designed to investigate extant martian life—must meet Category IVa requirements plus: “the entire landed system is restricted to a surface bioburden of ≤30 spores [note 4] or to levels of bioburden reduction driven by the nature and sensitivity of the particular life-detection system”; or “the subsystems which are involved in the acquisition, delivery, and analysis of samples used for life detection must be sterilized to these levels, and a method of preventing recontamination of the sterilized subsystem and the containment of the material to be analyzed is in place.” Category IVc missions—i.e., those accessing special regions on Mars, even if not carrying life detection instrument—must meet Category IVa requirements plus: “if the landing site is within the special region, the entire landed system is restricted to a surface bioburden level of ≤30 spores (note 4)”; or “if the special region is accessed through horizontal or vertical mobility, either the entire landed system is restricted to a surface bioburden level of ≤30 spores (note 4), or the subsystems which directly contact the special region shall be sterilized to these levels, and a method of preventing their recontamination prior to accessing the special region shall be provided.”|
|Note 4||The 30 spore limit “takes into account the occurrence of hardy organisms with respect to the sterilization modality. This specification assumes attainment of Category IVa surface cleanliness, followed by at least a four order-of-magnitude reduction in viable organisms. Verification of bioburden level is based on pre-sterilization bioburden assessment and knowledge of reduction factor of the sterilization modality.”|
NOTE: The table also shows examples of the solar system bodies assigned to each category and the corresponding principal planetary protection requirements. Note that the table does not incorporate all of the nuances of current planetary protection policy for Category III and IV missions to Europa and Enceladus or Category V missions to Mars, Europa, Enceladus or small solar system bodies.
SOURCE: Data from G. Kminek, C. Conley, V. Hipkin, and H. Yano, “COSPAR Planetary Protection Policy,” Space Research Today, No. 200, December 2017, pp. 12-24.
The National Academies have been intimately involved in the development of planetary protection policies since the late 1950s, and the SSB has been NASA’s principal source of independent, multidisciplinary advice on planetary protection issues (see Figure 2.1).
The Early Years of the Space Age
On August 2, 1958, the NAS announced the establishment of the SSB in response to a joint request from the National Science Foundation (NSF), the National Advisory Committee for Aeronautics, and the Advanced Research Projects Agency. One of the tasks given to the SSB was to cooperate with ICSU and other international organizations on “the prevention of undesirable and unnecessary contamination of Moon and planet surfaces and atmospheres with alien particles of energy and matter introduced from Earth by space vehicles.”22 In the latter part of 1958, the SSB endorsed the activities and initial recommendations of CETEX and began the task of securing the support and cooperation of relevant federal agencies to implement contamination control protocols. SSB recommendations formed the basis of the NAS response to ICSU. At about the same time, the SSB established the East Coast group of the Panel on Extraterrestrial Life (EASTEX) as a forum for the discussion of issues concerning the detection of extraterrestrial life and the biological contamination of planetary environments. A parallel West Coast group (WESTEX), under the leadership of Joshua Lederberg, was subsequently established and concentrated its efforts on the requirements for spacecraft sterilization. WESTEX issued its first recommendations to NASA that “an immediate study program be initiated to determine sterilization requirements and to develop recommendations compatible with present design and assembly processes.”23
Lederberg and his much more junior WESTEX colleague Carl Sagan “advocated that a high priority be placed on preventing planetary probes from carrying terrestrial contamination into space, and nearly as high a priority on the prevention of back contamination from sample return missions.”24 Both argued that these priorities be official SSB policy and that they be adopted by COSPAR. However, at least one member of WESTEX argued strongly that concerns about back contamination were overblown. In fact, it was argued that the risks associated with the introduction of extraterrestrial pathogens into the terrestrial environment were minor compared to the “potential benefits to mankind of unhampered traffic with the planets.”25
The Lederberg-Sagan viewpoint prevailed, and the twin objectives of planetary protection—protecting extraterrestrial environments from biological contamination that might preclude future scientific activities and protecting Earth’s environment and its inhabitants from potentially harmful extraterrestrial contamination—eventually became enshrined in SSB, NASA, and COSPAR policies.
The Middle Years of Planetary Protection
In the period between the early 1960s and the late 1980s, the SSB and its various committees drafted some dozen reports for NASA on various aspects of planetary protection policy. Many of the reports issued in this period were concerned with the estimation of key numerical parameters—particularly Pg, the probability of growth—appearing in the probabilistic equations providing the requirements flowing from planetary protection policies
22 National Research Council (NRC), “National Academy of Sciences Establishes Space Science Board,” press release, August 3, 1958.
23 September 14, 1959.
24 Meltzer, p. 35.
25 Norman Horowitz letter to Joshua Lederberg, January 20, 1960, quoted in Meltzer, p. 36.
in vogue during that period.26,27,28 As NASA spacecraft ventured into new parts of the solar system and/or new information was received from ongoing missions, the SSB would propose new values for key numerical factors on the basis of the latest scientific understanding. Thus, the chronological listing of these reports (see Figure 2.1) reflects the penetration of NASA spacecraft beyond the Moon, to Mars and Venus, in support of the Mariner and Viking missions, and out into the outer solar system in preparation for the flights of Pioneers 10 and 11 and Voyagers 1 and 2.
SSB studies focusing on the estimation of numerical factors effectively ceased when the requirements flowing from contemporary planetary protection policies evolved from a quantitative to a qualitative standard based on target-body mission-type characteristics in 1984.29 Thereafter, the focus of the SSB’s planetary protection studies changed to providing advice to NASA on the appropriate characterization of specific missions. Only three such studies were conducted by the SSB in the 1980s: for the Mars Orbiter mission in 1985,30 the Comet Rendezvous–Asteroid Flyby (CRAF) in 1986,31 and CRAF and Cassini-Huygens in 1988,32 reflecting the post-Viking slowdown in the pace of solar system exploration activities.
The SSB’s Planetary Protection Activities in the Recent Past
The number of requests from NASA for input on planetary protection issues began to accelerate in the early 1990s and has continued unabated to the present time. In addition, the complexity of the requested study topics has followed a similar trajectory. The change in pace and scope can be attributed to the following five factors:
- The post-Viking doldrums were over. NASA’s planetary science budget began to rise virtually monotonically.
- New, more numerous, smaller, and lower-cost missions began to appear as part of NASA’s Discovery program adding a quantity of projects that had to fit planetary protection requirements into very tight cost caps.
- The nature of the missions planned became more complex. The era of flyby probes and simple orbiters was over. The new types of spacecraft—landers, rovers, and sample return missions—posed planetary protection challenges not previously addressed.
- Plans for missions to new planetary environments—asteroids, comets, the giant planets and their icy satellites—not covered by planetary protection guidelines, began to appear.
- International cooperation became more common. U.S.-provided payloads on foreign spacecraft and foreign instruments on NASA missions posed unique planetary protection issues.
- Planetary protection became more controversial. The implementation of requirements derived from longstanding planetary protection policies began to conflict, or appear to conflict, with the legitimate scientific aspirations of the scientific community.
26 C. Sagan and S. Coleman, Spacecraft sterilization standards and contamination of Mars, Journal of Astronautics and Aeronautics 3(5):22-27, 1965.
27 C. Sagan and S. Coleman, “Decontamination Standards for Martian Exploration Programs,” pp. 470-481 in NRC, Biology and the Exploration of Mars, National Academy Sciences, Washington, D.C., 1966.
28 S. Schalkowski and R.C. Kline, Jr., “Analytical Basis for Planetary Quarantine,” pp. 9-26 in Planetary Quarantine (L.B. Hall, ed.), Gordon and Breach, London, U.K., 1971.
29 D.L. DeVincenzi, P.D. Stabekis, and J. Barengoltz, Refinement of planetary protection policy for Mars missions, Advances in Space Research 18:314, 1994.
30 NRC, “On the Categorization of the Mars Orbiter Mission,” letter from Harold Klein, Chair, Committee on Planetary Biology and Chemical Evolution, to Arnauld Nicogossian, Director, NASA Life Sciences Division, June 6, 1985.
31 NRC, “On the Categorization of the Comet Rendezvous–Asteroid Flyby Mission,” letter from Harold Klein, Chair, Committee on Planetary Biology and Chemical Evolution, to Arnauld Nicogossian, Director, NASA Life Sciences Division, May 16, 1986.
32 NRC, “Recommendation on Planetary Protection Categorization of the Comet Rendezvous-Asteroid Flyby Mission and the Titan-Cassini Mission,” letter from Harold Klein, Chair, Committee on Planetary Biology and Chemical Evolution, to John Rummel, Chief, NASA Planetary Quarantine Program, July 6, 1988.
The key planetary protection issues addressed by the SSB during the last couple of decades are as follows:
- Mars forward contamination,
- Mars sample return and backward contamination,
- Sample return for small solar system bodies, and
- Exploration of the icy bodies of the outer solar system.
The subsequent sections briefly describe the relevant issues addressed and the SSB’s recommendations.
Mars Forward Contamination
In 1990, NASA commissioned the SSB to examine policy issues relating to the forward contamination of Mars in light of the most recent findings in the planetary and life sciences. The committee’s report recommended that Viking-level bioload-reduction procedures—that is, a 10−5 reduction in the spacecraft’s bioload beyond that achievable by standard cleaning techniques such as swabbing with alcohol—be used only on landed spacecraft carrying life detection experiments.33 Swabbing or other cleaning techniques would suffice for all other landers. The report’s recommendation was accepted by NASA and subsequently was incorporated into COSPAR policy: Specifically, Category IV missions (see Table 2.1) were divided into two subcategories—IVa (landers without life detection instruments) and IVb (landers with life detection instruments).
Issues relating to the forward contamination of Mars were revisited by the SSB more than a decade later when NASA requested that the 1992 report be updated in light of recent scientific advances and the introduction of the concept of Special Regions on Mars—that is, areas where terrestrial organisms might survive or where indigenous life might exist—by COSPAR. The SSB’s 2006 report recommended that because then current understanding of the martian environment was insufficient to distinguish Special and Non-Special Regions, all of Mars should be treated as a Special Region until proven otherwise.34
One potential outcome of the SSB 2006 recommendation on Special Regions was that its implementation would effectively undo the relaxation of planetary protection policies for Mars landers initiated by the 1992 report. Another potential outcome was that NASA and COSPAR needed to define a Special Region more explicitly than was the case in 2005 to 2006. The latter option was taken and resulted in a series of additional activities on the part of NASA, COSPAR, and a recent joint study by the SSB and the European Science Foundation.35 Details of the latter activities concerning Special Regions and their associated planetary protection concerns can be found in Appendix B. Spacecraft intending to enter Special Regions receive a mission categorization of IVc (see Table 2.1).
Mars Sample Return and Backward Contamination
As the exploration of Mars resumed in earnest in the latter half of the 1990s, planning began for executing the long-standing goal of returning samples collected on the surface of Mars to Earth for study. NASA commissioned the SSB to address the planetary protection implications of sample return in the context of the then-current scientific understanding of the prospects for indigenous life on Mars and its potential to cause harm to Earth’s biosphere. A 1997 report addressing these issues recommended that any samples returned to Earth be strictly contained and that any release from containment be contingent on the results of a biohazard assessment.36 The report’s recommendations were accepted by NASA and subsequently were incorporated into COSPAR policy.
33 NRC, Biological Contamination of Mars, National Academy Press, Washington, D.C., 1992.
34 NRC, Preventing the Forward Contamination of Mars, The National Academies Press, Washington, D.C., 2006.
35 NASEM and the European Science Foundation, Review of the MEPAG Report on Mars Special Regions, The National Academies Press, Washington, D.C., 2015.
36 NRC, Mars Sample Return Issues and Recommendations, National Academy Press, Washington, D.C., 1997.
Subsequently, the specifics of the biohazard assessment were addressed in a series of workshops sponsored by NASA.37 The details of the containment facility within which the initial studies of martian samples would be conducted were the subject of a 2002 SSB report.38 However, budgetary and technical issues precluded the launch of a Mars sample return mission in the early 2000s.
In 2008, as part of a developing trend to revisit policy recommendations on major planetary protection issues at least once per decade, NASA asked the SSB to revisit the 1997 sample return report. The resulting study, issued in 2009, gave a nuanced endorsement of the recommendations made a decade earlier.39
Sample Return for Small Solar System Bodies
Soon after the SSB’s 1997 report on back contamination from Mars, NASA requested that a new SSB study be initiated to “extend current advice on Mars to other small solar system bodies.”40 The study committee assessed the potential for living entities to be present in samples returned to Earth from a variety of different small bodies, including satellites, comets, and asteroids. They also compared the potential risk of returning samples via spacecraft to that inherent in the natural influx of similar materials to Earth in the form of, for example, meteorites. By considering how its assessment of the biological potential of different bodies varied according to their respective environmental conditions, the committee devised a novel approach to gauging concerns about back contamination. Environmental factors—such as the presence of organic matter, liquid water, or sterilizing radiation—pertaining to a specific body can be assembled in a decision tree to determine whether or not samples returned from it be classified as restricted Earth return (i.e., subject to strict containment).41 This approach was very well received, and it is now incorporated in both NASA and COSPAR policies.
Exploration of the Ocean Worlds of the Outer Solar System
The discovery in the mid-1990s of evidence that Jupiter’s moon Europa harbors an ocean of liquid water beneath its icy surface prompted the formulation of plans for robotic missions to study this unique aquatic environment and also how it might be protected from contamination by those selfsame spacecraft. NASA requested that the SSB initiate a study on forward contamination issues as they related to Europa. The study committee was unable to reach consensus on a scheme to extend to Europa the qualitative planetary protection approach used for Mars missions. The committee’s report recommended, with two dissenting opinions, that a quantitative approach be adopted for Europa.42 The recommended approach was retrograde in that it represented a return to a methodology that had already been abandoned for other solar system bodies. Nevertheless, NASA accepted the committee’s recommended approach, and it was subsequently incorporated into COSPAR policy. Indeed, the numerical methodology was subsequently extended to cover other icy solar system bodies.
In keeping with the policy of revisiting major planetary protection recommendations on a quasi-decennial timescale, NASA requested in 2011 that the SSB reassess the 2000 Europa report’s recommended methodology and its applicability to the other icy satellites of the outer solar system. Such a revisit was appropriate because of increased scientific understanding of Europa and related bodies and by lingering concern that the quantitative approach now incorporated in NASA and COSPAR policy was both cumbersome and arbitrary. The study committee rapidly agreed that the existing approach was not scientifically defensible. In its place, the committee
37 See, for example, J.D. Rummel, M.S. Race, D.L. DeVincenzi, P.J. Schad, P.D. Stabekis, M. Viso, and S.E. Acevedo, eds., A Draft Test Protocol for Detecting Possible Biohazards in Martian Samples Returned to Earth, NASA/CP-20-02-211842, NASA Ames Research Center, Moffett Field, Calif., 2002, and references therein, https://planetaryprotection.nasa.gov/summary/DraftTestProtocol.
38 NRC, The Curation and Certification of Martian Samples, The National Academies Press, Washington, D.C., 2002.
39 NRC, Assessment of Planetary Protection Requirements for Mars Sample Return Missions, The National Academies Press, Washington, D.C., 2009.
40 Letter to Claud Canizares, Chair, Space Studies Board, from Wesley T. Huntress, Jr., Associate Administrator for Space Science, NASA, May 5, 1997.
41 NRC, Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making, National Academy Press, Washington, D.C., 1998.
42 NRC, Preventing the Forward Contamination of Europa, National Academy Press, Washington, D.C., 2000.
recommended that a decision-tree methodology should be adopted.43 The suggested decision tree was conceptually similar to the one already incorporated in COSPAR policy for determining whether or not samples returned from small solar system bodies be categorized as restricted or unrestricted Earth return. Despite the simplicity of the decision-tree approach and its precedents in existing COSPAR policies, NASA and COSPAR did not adopt the methodology. NASA’s failure to provide a formal, written response to the SSB’s 2012 report precluded any definitive discussion of its perceived deficiencies.
Planetary Protection Policy Development Within NASA
NASA’s involvement in planetary protection began in earnest soon after it was established. In response to the SSB’s September 1959 recommendation to adhere to the ICSU policy and to sterilize U.S. space probes,44 NASA issued an initial planetary protection guideline to all NASA field centers on October 15, 1959.45
At that time, scientific opinion about the Moon harboring extraterrestrial life was divided. If ice or water was beneath the lunar surface, then microorganisms, insulated by the material above, might exist there. On that chance, NASA Headquarters officials included lunar spacecraft under the terms of the 1959 directive.
First in line for application of the NASA sterilization policy were the robotic Ranger lunar hard-lander spacecraft. The first two Rangers (in 1961) were test vehicles, primarily designed to test the flight system, and as such were not sterilized.46
Sterilization was implemented beginning with Ranger 3. All components, including the lunar capsule subsystem components, were subjected to heating at 125°C for 24 hours. When Rangers 3, 4, and 5 each experienced a series of failures in 1962, NASA established a board of inquiry that found problems with the quality and reliability assurance program. Recommendations of the board, including abandoning heat sterilization, were implemented for the last four Ranger flights in 1964 and 1965, all of which were successful. Although subsequent robotic missions to the Moon in the Surveyor and Lunar Orbiter programs were not subject to heat sterilization, they did provide important information about sources and mechanisms of contamination. Microbial assays conducted at various stages during spacecraft assembly and transportation to the launch site revealed, for example, that shipping containers and spacecraft shrouds were important sources of microbial contamination.47
NASA established the Office of Planetary Quarantine in 1963.48 In the same year, on the basis of extensive studies and the advice of the SSB, NASA adopted the following policy regarding the Moon, Mars, and Venus:
Lunar spacecraft will reduce their microbial load to a “minimum” through the use of assembly and check out in clean rooms and the application of surface sterilants after final assembly and check out; Mars flights will have less than 10−4 probability of hitting the planet, while landers would be sterilized after complete assembly and check out, using appropriate procedures and sealed units that would not be open; Venus flights will have less than 10−2 probability of hitting the planet.49
43 NRC, Assessment of Planetary Protection Requirements for Spacecraft Missions to the Icy Solar System Bodies, The National Academies Press, Washington, D.C., 2012.
44 NRC, “Space Probe Sterilization,” letter from Hugh Odishaw, Executive Director, Space Science Board, to T. Keith Glennan, Administrator, NASA, and Roy Johnson, Director, Advance Research Projects Agency, September 14, 1959.
45 Abe Silverstein, “Sterilization of Payloads,” memorandum for director, Goddard Space Flight Center, October 15, 1959, folder 006696, “Sterilization/Decontamination,” NASA Historical Reference Collection.
46 However, as part of the test program, the Ranger 1 battery was exposed to the planned heat sterilization temperature profile with disastrous results. A week later, with the battery installed in the spacecraft, the battery erupted, spewing electrolyte all over the entire inside of the spacecraft. The temperature profile was modified and a new heat-treated battery was installed with similar results. Following that, there were no more attempts in the Ranger program to heat-sterilize batteries.
47 M. Meltzer, When Biospheres Collide: A History of NASA’s Planetary Protection Programs, NASA SP-2011-4234, U.S. Government Printing Office, Washington, D.C., 2011, p. 98.
48 The office’s name was changed to Planetary Protection in 1976.
49 NASA, Unmanned Spacecraft Decontamination Policy, NMI-4-4-1, NASA, Washington, D.C., September 9, 1963, https://archive.org/stream/nasa_techdoc_19700073941/19700073941_djvu.txt.
Following the experience with the Rangers and in preparation for the Viking missions to Mars, NASA conducted a comprehensive research program to develop a dry-heat process that could effectively sterilize spacecraft systems. Additionally, the Viking project successfully executed a component selection and qualification process along with a comprehensive testing program to implement safely dry-heat system sterilization, and Viking subsequently landed on Mars in 1976.50
In 1982, NASA, acting on advice by the SSB, completed an effort to change planetary protection policy drastically. The current policy places substantive planetary protection controls only on missions to bodies where there is evidence of indigenous water or other unique chemistry that could support the evolution of life.51 For the near-term future, this means only Mars, Europa, or Enceladus.
Institutional Developments Within NASA
Planetary protection responsibilities were located within various organizational niches within NASA throughout the period 1963 to 1991. However, in 1992 NASA created the Office of Planetary Protection (OPP) within what was then called the Solar System Exploration Division, and this arrangement effectively survived until 2018. However, unlike many of NASA’s other scientific activities, planetary protection did not have an internal advisory process (equivalent to other standing committees of the NASA Advisory Council) until the late 1990s.
In 1997, the SSB recommended that NASA create an external advisory committee for planetary protection to integrate the latest scientific knowledge and to involve a broader set of federal agency and international stakeholders. The report noted the following:
Although NASA is the lead agency on matters pertaining to the exploration of space and extraterrestrial bodies, other federal agencies, such as the U.S. Department of Agriculture, may have a regulatory interest in the return of samples from Mars or other solar system objects. To coordinate regulatory and other oversight responsibilities, NASA should establish a panel analogous to the Interagency Committee on Back Contamination that coordinated regulatory and oversight activities during the lunar sample-return missions. To be effective, planetary protection measures should be integrated into the engineering and design of any sample-return mission, and, for an oversight panel to be in a position to coordinate the implementation of planetary protection requirements, it should be established as soon as serious planning for a Mars sample-return mission has begun.52
After a NASA task force reiterated the need for this type of committee, the Planetary Protection Advisory Committee (PPAC) was formed in 2000 under the aegis of the NASA Advisory Council (NAC). The PPAC’s membership included scientists, representatives from other federal agencies (e.g., Department of Agriculture, Department of Health and Human Services, Environmental Protection Agency, and Federal Aviation Administration), and international representatives (e.g., from the European Space Agency and the Japan Aerospace Exploration Agency). The committee did not include representatives from the commercial space industry, because at that time private-sector entities were not conducting space activities with planetary protection implications.
PPAC’s charge was to advise the OPP, review proposed missions at an early stage, and assign a planetary protection category to them. The OPP then informed the mission team as to the necessary planetary protection requirements to be met. In 2006, the NAC was reorganized and the scientists then serving on the Council, including the chair of PPAC, were removed. The PPAC became a subcommittee under the NAC’s Science Committee. This change caused concern among the PPAC members because, by being subordinated under a committee that focused on the science missions, the new planetary protection subcommittee lacked the level of independence necessary for effective planetary protection. During this period, neither the PPAC nor the Planetary Protection Subcommittee received the attention needed for renewing and refreshing the membership. This problem was particularly evident
51 G. Kminek, C. Conley, V. Hipkin, and H. Yano, COSPAR Planetary Protection Policy, Space Research Today, No. 200, December 2017, pp. 12-24.
52 NRC, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington, D.C., 1997, p. 6.
in the reduced participation of federal agencies and other national space agencies. By 2016, the committee had become completely moribund, and it was formally disbanded in late 2017.
The Apollo Experience
When the Apollo program began, discussions on forward and backward contamination were already beginning to formalize at NASA and other organizations. In the late 1950s, the NAS, NSF, and the American Institute of Biological Sciences began discussions on spacecraft sterilization for forward contamination, while WESTEX was addressing how to protect the exploration of and preservation of planetary surfaces.53
The “National Security Action Memo (NSAM235): Large Scale Scientific or Technological Experiments with Possible Adverse Environmental Effects” was signed and went into effect on April 17, 1963. The policy required that
The head of any agency that proposes to undertake a large-scale scientific or technological experiment that might have significant or protracted effects on the physical or biological environment will call such proposals to the attention of the Special Assistant to the President for Science and Technology. Notification of such experiments will be given sufficiently in advance that they may be modified, postponed, or cancelled, if such action is judged necessary in the national interest.54
NSAM No. 235 ensured that relevant agencies were following an approval process that would provide for the safety of the United States. The process generally includes the following three steps:55
- The sponsoring agency notifies the Special Assistant to the President for Science and Technology with a “detailed evaluation of the importance of the particular experiment and the possible direct or indirect effects that might be associated with it”;
- The Special Assistant reviews the material provided by the sponsoring agency and makes a recommendation to the President; and
- Based on the recommendation, if there is not enough information available to make a decision, then the Special Assistant may request additional studies be conducted from organizations such as the NAS, international scientific bodies, and intergovernmental organizations.
53 B. Pugel. “Restricted by Whom? A Historical Review of Strategies and Organization for Restricted Earth Return of Samples from NASA Planetary Missions,” presentation to the Committee on Planetary Protection Policy Development Processes, Space Studies Board, National Academy of Sciences, July 2017, Slide 29.
54 J.F. Kennedy, “National Security Action Memoranda (NSAM 235): Large-Scale Scientific or Technological Experiments with Possible Adverse Environmental Effects,” Papers of John F. Kennedy, Presidential Papers, National Security Files, Meetings and Memoranda, JFKNSF-340-023, John F. Kennedy Presidential Library and Museum, https://www.jfklibrary.org/Asset-Viewer/Archives/JFKNSF-340-023.aspx.
55 J.F. Kennedy, “National Security Action Memoranda (NSAM 235): Large-Scale Scientific or Technological Experiments with Possible Adverse Environmental Effects,” Papers of John F. Kennedy, Presidential Papers, National Security Files, Meetings and Memoranda, JFKNSF-340-023, John F. Kennedy Presidential Library and Museum, https://www.jfklibrary.org/Asset-Viewer/Archives/JFKNSF-340-023.aspx; B. Pugel, “Restricted by Whom? A Historical Review of Strategies and Organization for Restricted Earth Return of Samples from NASA Planetary Missions,” presentation to the Committee on Planetary Protection Policy Development Processes, Space Studies Board, National Academy of Sciences, July 2017, Slide 14.
57 See, for example, J.R. Bagby, Jr., Back Contamination: Lessons Learned During the Apollo Lunar Quarantine Program, prepared for the Jet Propulsion Laboratory under Contract #560226, July 1, 1975.
- To protect the public’s health, agriculture, and other living resources;
- To protect the integrity of the lunar samples and the scientific experiments; and
- To ensure that the operational aspects of the program were least compromised.
The ICBC was comprised of 12 members from six government agencies and other organizations, including the following: NASA (six members), Public Health Service (two members), Department of Agriculture (one member), Department of Commerce (one member), Department of the Interior (one member), and NAS (one member).58
The formalization of lunar quarantine protocols developed during the 1960s and began when the NAS advised NASA to create an interagency committee to handle the fast-paced emergence of interplanetary exploration in 1960. Five years later, the SSB had already convened the first meeting between government agencies on backward contamination, and NASA was establishing interagency liaison tools to facilitate the establishment of rules and procedures for back-contamination control. In 1966, the ICBC began meeting and 1 year later produced “MSCI 8030.1—Management Instruction: Assignment of Responsibility for Prevention of Contamination of Biosphere by Extraterrestrial Life.”59
Planetary protection protocols distinguish between restricted and unrestricted Earth return. Restricted Earth return applied to Apollo missions 11 (1969), 12 (1969), and 14 (1971), where astronauts, laboratory team members, and other relevant staff were quarantined (see Figure 2.2). Although these missions occurred before Biosafety Levels (BSLs) were standardized,60 the Lunar Receiving Facility treated them as BSL-3/BSL-4. Unrestricted Earth return occurred for all missions after Apollo 14. During the lunar quarantine process, out of the total mass of lunar samples returned by the Apollo missions, 25 percent were returned under quarantine protocols.61
After the completion of Apollo 11 and Apollo 12, the ICBC reviewed the quarantine procedures in January 1970. The primary concern was whether quarantine procedures be continued for crewmembers, while biological examination of the returned lunar samples would continue to assure integrity of the sample. The following month, the SSB advised that the quarantine policy continue to be followed. After the Apollo 14 mission in January 1971, lunar quarantine was discontinued.62
Early Soviet Mars Missions
The former Soviet Union conducted many unsuccessful Mars missions during the 1960s and 1970s. The missions of Mars 1 (1962) and Mars 2 and 3 (1971) are of particular interest to understanding the implementation of planetary protection policies. Soviet planetary protection protocols were believed to have largely differed from then-applicable U.S. procedure and included a combination of heat, radiation, and gaseous techniques, depending on the nature of the materials being sterilized.63
Mars 1 was a flyby mission, while Mars 2 and 3 were orbiter-lander combinations. The Mars 1 mission was set to take photographs of the martian surface and successfully collected data in interplanetary space while in transit but lost contact with the spacecraft prior to its Mars flyby. The lander portion of Mars 2 was equally unsuccessful, and it crashed onto the martian surface in late-November 2017. However, the lander of its twin, Mars 3 (see Figure 2.3), did succeed in landing on the Red Planet early the following month. Unfortunately, radio contact with the lander was lost 20 seconds after touchdown. According to Soviet scientists, life detection instruments were
58 B. Pugel. “Restricted by Whom? A Historical Review of Strategies and Organization for Restricted Earth Return of Samples from NASA Planetary Missions,” presentation to the Committee on Planetary Protection Policy Development Processes, Space Studies Board, National Academy of Sciences, July 2017, Slide 5.
59 Ibid., Slide 13.
60 BSLs are a set of precautions for containment of dangerous biological agents in enclosed laboratories. The levels range from 1 (least strenuous) to 4 (most demanding).
61 B. Pugel. “Restricted by Whom? A Historical Review of Strategies and Organization for Restricted Earth Return of Samples from NASA Planetary Missions,” presentation to the Committee on Planetary Protection Policy Development Processes, Space Studies Board, National Academy of Sciences, July 2017, Slide 9.
62 Ibid., Slide 14.
63 B.C. Murray, M.E. Davies, and P.K. Eckman, Planetary contamination II: Soviet and U.S. practices and policies, Science 155:1505-1511, 1967.
not included on the Mars 2 and 3 landers. The Mars 2 and 3 orbiters were somewhat more successful but returned little or no useful scientific data.64
Soviet sources claimed that the planetary protection protocols applied to the Mars 1, 2, and 3 missions were on par with then-applicable COSPAR standards, but evidential data were not made readily available at the time.65,66 According to V.T. Vashkov, a member of the USSR space program, the methods used for sterilizing Mars 1, 2, and 3 primarily included a combination of the following:67,68
- A combination of heat or radiation sterilization of individual components depending on their nature;
- Assembly of sterile components in laminar-flow cleanrooms;
64 A.S. Siddiqi, Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, NASA-SP-2002-4524, NASA, Washington, D.C., 2002, pp. 86-88.
65 B.C. Murray, M.E. Davies, and P.K. Eckman, “Planetary contamination II: Soviet and U.S. practices and policies, Science 155:1507, 1967.
66 L.B. Hall, ed., Planetary Quarantine: Principles, Methods, and Problems, Gordon and Breach, New York, 1971, p. 35.
67 Memos from NASA Planetary Quarantine Officer Lawrence B. Hall Memo to Associate Administrator for Space Science and others, “Soviet Planetary Quarantine Sterilization of Mars 1 and 2,” June 1, 1972, and “Analysis of the Planetary Quarantine Effort in the U.S.S.R.,” no date.
68 M. Meltzer, When Biosphere’s Collide: A History of NASA’s Planetary Protection Programs, NASA SP-2011-4234, 2011, pp. 65-66.
- Surface cleaning of the assembled spacecraft with hydrogen peroxide followed by ultraviolet irradiation; and
- Prior to launch, the entire spacecraft was exposed to “OB mixture”—a gas consisting of one part of ethylene oxide to 1.44 parts of methyl bromide—at 50°C for 6 hours.
To ensure that their planetary protection procedures were effective, bioassays were conducted on a model of the spacecraft using a “mopping” technique that is believed to be similar to the swabbing procedure NASA uses for Mars missions. The spacecraft was further protected in the confines of a plastic bag until it exited Earth’s atmosphere.69
Besides the lack of hard information about the detailed implementation of prelaunch planetary protection protocols employed on early Soviet planetary missions, a postlaunch practice is worth mentioning. Tracking of early Soviet spacecraft clearly indicated that their interplanetary trajectories were not intentionally biased away from their intended destinations.70 Rather, the Soviet practice was to deflect unwanted, Earth-escape and/or cruise stage away from the intended destination via a terminal manoeuver. Thus, a spacecraft failure prior to the terminal course correction left the target body open to contamination by uncleaned hardware.
The Viking Missions
NASA’s Viking missions in the 1970s first explored the possibility that Mars might harbor, or once sustained, life.71 By any standard, Viking stands out as one of the most ambitious and expensive robotic projects NASA has ever implemented. Launched in 1975, Viking’s two orbiters and two landers carried out high-resolution, remote-sensing measurements at Mars, successfully executed soft landings, and conducted the first in situ life detection experiments on another solar system body.
The goals and objectives of the Viking project meant that both planetary protection and science integrity were concerns. NASA and COSPAR had previously discussed planetary protection in connection with Mars, but the Viking missions were the first time planetary protection measures were applied in connection with in situ, life detection experiments. The Viking project fully embraced planetary protection objectives and incorporated requirements established by NASA and guidance from COSPAR into the design of the spacecraft and the scientific instruments. One prime contractor built all the scientific instruments for Viking, which facilitated the effective implementation of planetary protection measures.
To meet planetary protection objectives, the Viking team developed new approaches, including the construction of a unique facility to sterilize spacecraft (see Figure 2.4) and use of a special metal-tape data recorder. Implementing planetary protection measures also affected the selection of components, the design of subsystems, and the choice of propellant for the spacecraft. Despite the demanding nature of the planetary protection requirements, implementation of the requirements remained “stable since day-one.”72
Even though Viking’s life detection experiments produced null or, at best, inconclusive results, the planetary protection program was a success. In today’s dollars, Viking cost about $6.8 billion,73 making it still the most expensive planetary science mission ever launched. Of that, about $4.4 billion can be attributed to the landers where the dominant share of the planetary protection effort was expended. An independent analysis by the Aerospace Corporation estimates that Viking spent about 10 percent of its lander budget on meeting planetary protection
69 Ibid., p. 66.
70 B.C. Murray, M.E. Davies, and P.K. Eckman, “Planetary contamination II: Soviet and U.S. practices and policies, Science 155:1507-1510, 1967.
71 The Viking planetary protection narrative provided in this document is taken from the presentation to the committee by A.T. Young, who was the NASA Mission Director for the Viking Landers.
72 T. Young, Lockheed Martin (retired), presentation to committee, May 24, 2017.
73 See, for example, NASEM, Powering Science: NASA’s Large Strategic Science Missions, The National Academies Press, Washington, D.C., 2017, p. 11.
requirements (~$400 million).74 As noted above, Viking was defined and developed during the Mercury/Gemini/Apollo era when very expensive, so-called “flagship” missions were the norm. In addition, biology was less advanced in the 1970s, and whole spacecraft sterilization was a reasonable approach in light of existing knowledge.
The conditions that explain the Viking approach to planetary protection and that made Viking a success in planetary protection terms no longer exist. NASA space science projects routinely have budget constraints, require the use of heritage hardware developed for other programs, and have instruments built by many contractors all over the world. These factors often limit the flexibility in how a project may be able to implement planetary protection policies. In addition, microbiology has developed significantly since the 1970s, especially in the area of genomics. This new knowledge opens up possibilities for new approaches to planetary protection in connection with space exploration.
74 D. Bearden and E. Mahr, “Cost of Planetary Protection Implementation,” presentation to the committee, June 28, 2017, http://sites.nationalacademies.org/cs/groups/ssbsite/documents/webpage/ssb_180771.pdf.
NASA Mars Missions: 1976 to 2001
After the Viking mission failed to produce convincing results from its life detection experiments, Mars projects went into a long hiatus. The Mars science community began to think in terms of the detection of “habitable environments” rather than life itself. At the same time, very expensive multi-billion dollar missions (e.g., Galileo, Cassini), which in NASA’s reduced budget environment could only be launched once per decade, began to fall into disfavor and alternatives were sought.
Seventeen years after Viking, NASA launched Mars Observer (MO), an experiment in cost reduction as well as a return to basic science. This experiment failed in two ways. First, by the time all the necessary deep space modifications (thermal control, communications, propulsion, etc.) had been made to allow spacecraft designed for Earth orbit to operate at Mars, the cost was approaching that of a purpose-built mission. Second, MO failed to reach Mars, probably as the result of an explosion in the propulsion system.
Subsequent to MO, NASA entered the “faster-better-cheaper” era of missions for which there was a heavy emphasis in shortening development time and reducing development costs, all while encouraging innovative approaches to mission architecture. That period yielded some early notable successes (Mars Pathfinder and Mars Global Surveyor), but then some very spectacular and public failures in 1999 (Mars Climate Orbiter and Mars Polar Lander). An independent review found that the failures resulted from an indiscriminate application of the concept of faster-better-cheaper.75
After the twin failures, the Mars Exploration Program underwent a thorough restructuring that, among other actions, reinstituted the rigorous systems engineering that is required of complex space missions.76
The European Space Agency’s (ESA’s) Mars Express mission was launched in 2003. It carried a small lander, Beagle 2, which was designed and built in the United Kingdom (see Figure 2.5). The primary goal of Beagle 2 was to search for evidence of past life within the martian soil using instruments designed to detect the following:
- Presence of water;
- Existence of minerals deposited in aqueous environments;
- Occurrence of residual organic or carbonaceous species;
- Complexity of organic structure; and
- Identification of isotope fractionation between organic and inorganic phases.
Beagle 2 was classified as a Category IVa mission (see Table 2.1) under COSPAR guidelines and was required to meet the bioburden levels of the hardware, at launch, and for exposed surfaces. Beagle 2 utilized a variety of bioload-reduction techniques tailored to the requirements of specific components. These methods included dry heating, alcohol wipes, exposure to hydrogen peroxide gas, and irradiation by gamma rays. In addition, the mission complied with all requisite clean room procedures, and bioload reduction was confirmed by microbiological analyses. Unfortunately, the mission was not a success, because all communications with the spacecraft were lost as it was scheduled to land on the martian surface.
NASA Mars Missions: 2001 to 2013
From the launch of Mars Odyssey in 2001 through that of the Mars Science Laboratory (MSL) Curiosity launched in 2011, NASA’s Mars Exploration Program has been fully successful, with some missions operating
76 S. Hubbard, Exploring Mars, Chronicles from a Decade of Discovery, University of Arizona Press, Tucson, Ariz., 2012.
many years past their prime mission.77 During this period leading up to launch of MSL in 2011, planetary protection was always a requirement for project implementation. However, the requirements were relatively straightforward, because the missions were focused on planetary geology rather than on life detection. Consequently, Mars Pathfinder (launched in 1996) and the two Mars Exploration Rovers (MERs)—Spirit and Opportunity (launched in 2003)—were classified as IVa (see Table 2.1), because their primary missions did not include searches for evidence of extant life.
The pace and scientific focus of the missions prior to MSL was not accidental. Rather, there was a strategic approach to deploy an orbiter to characterize the planet, then a lander to examine ground truth in areas identified by the orbiters. The top-level scientific objective was to locate ancient habitable environments and then characterize the local geology. However, up through the 2004 twin MERs and 2008 Phoenix lander, there was no landed scientific payload that was specifically designed to test for complex organic compounds. Because Phoenix was targeted to test for water ice at the martian north pole, it was categorized IVc (see Table 2.1).78 A bioshield “cocoon” surrounding the digging and sample acquisition arm was designed and implemented without substantial difficulty. Phoenix was a smaller class of mission (a so-called Mars Scout) with fewer instruments and objectives than a flagship mission like MSL.
77 Missions during this period were Mars Odyssey (Orbiter), Mars Exploration Rovers Spirit and Opportunity (Landers), Mars Reconnaissance Orbiter (Orbiter), Phoenix (Lander), and MAVEN (Orbiter).
78 Category IVc is for missions investigating regions that are likely to be able to support terrestrial organisms or where there is high potential for martian life, i.e., “Special Regions,” see Appendix B. Category IVa is for spacecraft carrying instruments not designed to search for extant life.
The lack of instruments seeking complex organics was deliberately changed with the formulation of MSL. It was thought that by a launch originally scheduled for 2009, the progression of scientific knowledge would be sufficient that landed areas that might contain organics could be located. At the time of the level-1 science requirements definition, the Planetary Protection Officer (PPO) was engaged and asked to provide the mission categorization and the planetary protection requirements for the mission.
At the time of launch in 2011, MSL was 2 years late and $900 million over budget, and some notable planetary protection issues had erupted into the public sphere. Specifically, MSL carried a set of drill bits that were to be housed in a sterile box until landing on Mars and that would then be used to examine samples of rocks on Mars. However, the box was opened before launch to remove one of the bits to be installed in the drill. The bits were re-cleaned, but the protocol approved by the PPO for ensuring sterility of the drill bit system was broken. Consequently MSL’s planetary protection categorization was downgraded from IVc to IVa, thus requiring that the landing site would not be likely to be able to harbor life (i.e., not a Special Region).
As a result of these issues, in 2013, the NASA Planetary Science Division commissioned a MSL lessons learned study.79 Among other responsibilities, the study was to delve into the planetary protection practices and procedures. The report, which was presented to the Planetary Protection Subcommittee of NASA Advisory Council, says, in part, that “Planetary Protection, as a discipline, does not follow effective systems engineering and management practices,”80 that the process of transmitting planetary protection requirements for MSL were not sufficiently clear, concise, and verifiable, and that various formal documents relating to planetary protection requirements for MSL had ambiguities.
The thrust of the lessons learned report’s planetary protection conclusion was that even if prior, less structured approaches for issuing requirements had worked in the past, those approaches were no longer satisfactory for increasingly complex new missions. It would appear that as the instrumentation came ever closer to being able to detect the “fingerprints of life,” standard practices of the PPO began to collide with the constraints of major mission implementation. Thus, as the committee will explain below, it is no surprise that Mars 2020, which would be the de facto start of a campaign to return samples from a body of astrobiological interest, would encounter even more difficult and contentious planetary protection issues.
The Russian space agency, Roscosmos, space mission,81 Phobos-Grunt, attempted to explore the martian moon and return samples of Phobos to Earth for analysis. The Phobos spacecraft consisted of the Russian sample return package and a small Chinese Mars orbiter, Yinghuo-1. Also included was a small capsule, the Living Interplanetary Flight Experiment (LIFE), funded by the U.S.-based Planetary Society. The presence of an experiment provided by a private U.S. organization on a Russian spacecraft raised interesting questions as to the respective responsibilities of the United States and Russia under articles VI and IX of the OST.
The Phobos-Grunt mission was intended to return not only a sample from Phobos but also the terrestrial microorganisms confined in the LIFE capsule for the duration of the round trip. Phobos-Grunt was launched in November 2011 and was scheduled to arrive back to Earth in the summer of 2014 after 34 months in space. However, after being launched into Earth’s orbit, the spacecraft failed to respond to commands from the ground. In January 2012, the spacecraft fell to Earth in an uncontrolled descent and crashed in the South Pacific Ocean.82
The Phobos-Grunt mission was one of the first complex missions involving planetary protection, due to its risk of both forward and backward contamination. According to one Russian scholar, “this [imposed] on us a huge responsibility and [involved] a thorough compliance with all requirements of planetary protection in both
79 M. Saunders, “MSL Lessons Learned Study,” presentation to Planetary Protection Subcommittee of the NASA Advisory Council, April 29, 2013, https://smd-prod.s3.amazonaws.com/science-red/s3fs-public/atoms/files/MSL_LL_to_NAC.pdf.
80 M. Saunders, “MSL Lessons Learned Study,” presentation to Planetary Protection Subcommittee of the NASA Advisory Council, May 20, 2014, Finding 6, Slide 10, https://smd-prod.s3.amazonaws.com/science-red/s3fs-public/atoms/files/MSL_LL_-_2.pdf.
82 D. Clery, Russia Explores New Phobos-Grunt Mission to Mars, Science, February 2, 2012, http://www.sciencemag.org/news/2012/02/russia-explores-new-phobos-grunt-mission-mars
major areas: the protection of Mars from terrestrial microorganisms (necessary for further studies of the planet) and protection of Earth from potential extraterrestrial contamination.”83 The LIFE capsule was a unique test to see if terrestrial life could survive exposure to the space environment during a round-trip between Earth and Mars.84 However, the risks involving the LIFE capsule posed a threat to the contamination of Mars.
Because of the complexity of execution and involvement from international partners, the Phobos-Grunt mission had to pass a variety of planetary protection requirements. The design of the capsule involved multiple sealing techniques, including an outer titanium shield, an inner ceramic carrier that is easily sterilized, 30 polymer containers holding the microorganisms, and a polymer container holding a permafrost sample. There was an indium wire crushed for sealing the top and bottom units and three integral locking lugs that are safety wired in place to prevent the top from coming undone.85 Overall, LIFE was designed as a passive experiment with no active control or actuators with placement inside the space volume between the aero shell heat shield and internal avionics.86 Moreover, “LIFE aimed to be ‘simple, compact, and rugged,’” while “strictly following COSPAR planetary protection guidelines to responsibly reduce any possibility that this experiment could contaminate Mars with its life signature.”87
This was a controversial case. In fact, the NASA and ESA planetary protection officers met with officials from Roscosmos and the Space Research Institute (IKI) of the Russian Academy of Sciences about Phobos-Grunt twice, prior to its launch. In addition, they reviewed the spacecraft’s proposed trajectory and hardware reliability data. During the second meeting, the NASA and ESA officials signed a formal set of documents agreeing that Roscosmos’s proposed approach—that is, treating Phobos-Grunt as if it were a restricted Earth return mission—was consistent with COSPAR guidelines.88
Non-NASA Sample Return Missions
As new national and international space agencies began to develop their own plans for planetary exploration missions, they were often able to build upon planetary protection policies and implementations used by prior U.S. and/or Soviet spacecraft. However, when plans called for undertaking activities not previously attempted, the new players, by necessity, became involved in the planetary protection policy development arena.
Following ESA’s very successful Giotto flyby of the nucleus of Comet Halley in 1986, interest in both NASA and ESA turned to follow-on studies of comets. The NASA project was the CRAF mission, and ESA began consideration of a follow-on Comet Nucleus Sample Return (CNSR) mission.89 While CRAF posed no significant planetary protection issues, CNSR did potentially. ESA began work needed to define and implement the requirements for such a mission. Legal issues such as the ownership of the samples returned by CNSR and questions relating to the landing site, if not located in the territory of a participating nation, had to be addressed.
Unfortunately, all of this preparatory work came to naught. In 1992, NASA cancelled CRAF due to budgetary constraints, and the following year, ESA abandoned the ambitious CNSR plans, opting instead to develop a CRAF-style project. ESA’s multi-asteroid flyby and comet-rendezvous spacecraft, Rosetta, was launched in 2004, and it went on to conduct a highly successful mission to comet 67P/Cheryumov-Gerasimenko. Although Rosetta’s Philae module completed the first soft-landing on a comet nucleus and ultimately hard-landed itself on September 30, 2016, it broke no new ground from a planetary protection perspective.
83 N.M. Khamidullina, Realization of the COSPAR Planetary Protection Policy in the Phobos-Grunt Mission, Solar System Research 46(7):498-501, 2012.
84 D. Warmflash et al., “Living Interplanetary Flight Experiment (LIFE): An Experiment on the Survivability of Microorganisms During Interplanetary Transfer,” presentation at the First International Conference on the Exploration of Phobos and Deimos, Moffett Field, Calif., November 5-7, 2007, http://www.lpi.usra.edu/lpi/contribution_docs/LPI-001377.pdf.
87 R. Fraze, T. Svitek, B. Betts, and L. Friedman, “Phobos-LIFE: Preliminary Experiment Design,” presentation at the First International Conference on the Exploration of Phobos and Deimos, NASA Ames Research Center, Moffett Field, Calif., November 5-7, 2007, LPI Contribution No. 1377, https://www.lpi.usra.edu/lpi/contribution_docs/LPI-001377.pdf.
88 Protocol, Phobos-Grunt Technical Meeting, held in Moscow on November 6, 2009.
89 G.H. Schwehm, Rosetta-comet nucleus sample return, Advances in Space Research 9:185-190, 1989.
The Japanese Hayabusa 1 mission is interesting from the planetary protection policy implementation perspective because it involved activities on the part of Japan, the United States, Australia, and COSPAR. Hayabusa 1, formerly known as MUSES-C (Mu Space Engineering Spacecraft-C), was developed by JAXA to return samples from a small near-Earth asteroid named 1998 SF36 (later given the formal designation of 25143 Itokawa) to Earth for further analysis. JAXA and the Japanese Institute for Space and Astronautical Science (ISAS) performed an assessment of the mission’s planetary protection categorization, based on the framework presented in the SSB’s 1998 report on sample returns from small solar system bodies, and concluded that Hayabusa 1 is a Category V, unrestricted Earth return mission.90 Since NASA was providing communications and navigation support for the mission, ISAS requested that NASA’s PPAC review the JAXA/ISAS findings. The PPAC reviewed the findings, evaluated the mission for the purpose of its categorization, and recommended that
No special containment for samples returned from 1998 SF36 is required for the purposes of planetary protection, provided that subsequent information obtained prior to sample return remain consistent with the classification of that body as an undifferentiated metamorphosed asteroid. As such, we recommend that for NASA purposes, the mission be designated Planetary Protection Category V, “unrestricted Earth return.”91
Because Hayabusa’s samples were scheduled to return to Earth in the Woomera Prohibited Area in South Australia, ISAS and Environment Australia requested that COSPAR review the planetary protection aspects of the Hayabusa mission. Following presentations from ISAS and NASA on the deliberations of NASA’s PPAC about the mission and its target body, and consideration with respect to the COSPAR policy, the workshop agreed to the following statement: “The COSPAR Workshop on Planetary Protection considered the categorization of the MUSES-C mission, and concurred with the recommendations of the NASA Planetary Protection Advisory Committee on the Muses-C mission, agreeing that its asteroid target (1998 SF36) meets the SSB classification for a body from which a Category V mission with ‘unrestricted Earth-return’ is warranted.”92
The actions by PPAC and COSPAR led to Environment Australia issuing a one-page decision instrument that the action by the Japan’s ISAS to return a sample from 1998 SF36 is “not controlled.” Soon afterward, Biosecurity Australia issued a 38-page document for public comment on the action,93 and after receiving comments, issued a 2-page policy memorandum permitting the sample return.
Hayabusa was launched on May 9, 2003, and after several near-death experiences, returned trace samples of 25143 Itokawa to Earth on June 13, 2010, 3 years later than originally planned.
NASA Missions to the Outer Planets
Pioneers 10 and 11 and Voyagers 1 and 2 were the first spacecraft to explore the outer planets, contributing valuable information and paving the way for subsequent, more detailed investigations. In particular, the Voyager spacecraft revealed intriguing information about Europa, suggesting that this moon of Jupiter might “have a thin crust (less than 18 miles or 30 kilometers thick) of water ice, possibly floating on a 30-mile-deep (50-kilometer-deep) ocean.” The Voyager spacecraft provided evidence that “the most active surface of any moon seen in the Saturn system was that of Enceladus. The bright surface of this moon, marked by faults and valleys, showed evidence of tectonically induced change.”94
90 NRC, Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies: Framework for Decision Making, National Academy Press, Washington, D.C., 1998.
91 Minutes of the NASA Planetary Protection Advisory Committee, March 19, 2002.
92 Report of the Workshop on Planetary Protection, held under the auspices of the Committee on Space Research (COSPAR) and the International Astronomical Union (IAU) of the International Council for Science (ICSU) at Williamsburg, Virginia, April 2-4 2002. Report Prepared by the COSPAR Panel on Planetary Protection, John D. Rummel, Chair, COSPAR, Paris, 2002.
93 Biosecurity Australia, “Quarantine Review of the MUSES-C Project: Surface Sample Returned from Asteroid 1998 SF36,” Commonwealth Department of Agriculture, Fisheries and Forestry, Australia, July 2002, http://www.agriculture.gov.au/SiteCollectionDocuments/ba/memos/2002/animal/2002-35a.doc.
94 NASA, Voyager to the Outer Planets and Into Interstellar Space, NASA Facts, JPL 400-1538, Jet Propulsion Laboratory, Pasadena, Calif., September 2013, https://www.jpl.nasa.gov/news/fact_sheets/voyager.pdf.
Following the Pioneers and Voyagers, NASA’s Galileo mission was launched to Jupiter in October 1989 and arrived at Jupiter in December 1995. The spacecraft spent nearly 8 years collecting vast amounts of scientific data on the planet and its moons. The Galileo mission was classified as a Category II (see Table 2.1) mission for planetary protection purposes, requiring only documentation on probabilities of impact, contamination control procedures used during assembly, and disposition of all launched hardware at completion of the mission. Microbiological assays were not required. However, because of the Voyager discoveries, the Galileo planetary protection plan contained the following disposition requirement:
In addition, the Project will supply data obtained bearing on the biological interest of the Jovian satellites to the Planetary Protection Officer in a timely manner. This information will be provided by letter before the end of mission and while the spacecraft is controllable. If the Planetary Protection Officer finds that a satellite requires protection beyond that called for in Category II requirements, the Project will negotiate options that will preclude an impact of that satellite by the Orbiter.95
One of the most significant discoveries from Galileo was the detection of the magnetic signature of a global ocean of salty water below the icy surface of Europa. The thickness of the ice crust is still a subject of scientific debate. As a result, on September 21, 2003, the Galileo spacecraft made a controlled entry into the atmosphere
95 J. Barengoltz, “Project Galileo Planetary Protection Plan (draft),” NASA/JPL PD 625-14, March 28, 1984.
of Jupiter, thereby preventing any possibility of collision with and possible contamination of one of Jupiter’s icy moons.96
The Cassini mission was launched in October 1997 and entered orbit around Saturn in July 2004. It spent 13 years studying the planet, its rings, moons, and magnetosphere. Like Galileo, the Cassini mission was classified as Category II (see Table 2.1) for planetary protection purposes, with the same disposition requirement proviso.
During close flybys of Saturn’s Enceladus in January and February of 2005, NASA’s Cassini spacecraft imaged plumes emanating from the moon’s southern polar regions (see Figure 2.6).97 After many flybys of Enceladus, including flying through the water plumes, three lines of evidence—that is, direct detection of salt-laced ice grains, a combination of gravity and topographic mapping, and oscillation in the moon’s rotation state—led to the conclusion that Enceladus contains a salty, liquid ocean underneath the ice surface. Multiple lines of evidence, including measurements of electric fields and tidal distortions, led researchers to conclude that Titan also possesses a global ocean.
Looking back over the history of planetary protection policy and practice, notable themes emerge. First, the emphasis to date has been almost entirely on science and the protection of scientific exploration. Policies have generally been based on well-established scientific understanding, and for forward contamination, they have been directed on preserving the ability to undertake future scientific studies of solar system bodies. Indeed, with the exception of the Apollo program in the 1960s and 1970s, the principal focus of solar system exploration has been on research carried out on or near other bodies, and so the focus of planetary protection has been on forward contamination rather than backward contamination. As a result, efforts have concentrated on avoiding biological and organic contamination as a requirement to support scientific searches for evidence of life and the origin of life beyond Earth.
A second important theme has been adjustment of planetary protection policies in response to growing scientific knowledge about solar system bodies. In the early 1960s, when no data about any solar system body’s capacity to support terrestrial or indigenous life existed, all bodies were treated with caution. However, as researchers learned more about which bodies are likely or unlikely to support life, the number of bodies for which planetary protection remains an issue has been significantly reduced.
The international dimensions of planetary protection policy comprise a third theme. International cooperation and coordination have been integral components of the policy development process. The OST, which has been ratified by 105 countries, including all of the spacefaring nations, and signed by 25 more, has been a remarkably successful and non-contentious basis for international cooperation on planetary protection policies. Similarly, COSPAR has proved an effective forum for the development of international consensus on planetary protection guidance for science exploration missions.
Fourth, the United States has demonstrated sustained international leadership on planetary protection as part of space exploration activities. Scientific advice developed by the SSB, most of which has been incorporated, and policies designed by NASA have been the driving and determining factors in the formulation and implementation of COSPAR guidance on planetary protection. However, NASA has experienced difficulty in achieving an effective institutional design for planetary protection policy development, as evidenced by problems with the placement of the OPP within the agency and with the provision of external advice to the OPP (see Chapter 3).
Fifth, only a small number of countries have engaged in space exploration activities that have planetary protection implications. The limited number of spacefaring nations has contributed to the success of international cooperation under the OST and through COSPAR.
96 See, for example, NRC, “Scientific Assessment of Options for the Disposal of the Galileo Spacecraft,” letter from Claude Canizares, Chair, Space Studies Board, and John Wood, Chair, Committee on Planetary and Lunar Exploration, to John Rummel, Planetary Protection Officer, NASA, June 28, 2000.
97 C.C. Porco, P. Helfenstein, P.C. Thomas, A.P. Ingersoll, J. Wisdom, R. West, G. Neukum, et al., Cassini observes the active South Pole of Enceladus, Science 311:1393-1401, 2006.
Sixth, during this historical period through the present day, private-sector enterprises have not conducted space activities that required the implementation of planetary protection measures. Companies have supplied components to government-sponsored missions, and planetary protection policies applied to the integration of these components into spacecraft. However, no company has undertaken space missions on its own that generated significant planetary protection issues.
Finally, since 1972, human space exploration by the leading government agencies has been limited to low Earth orbit. The space shuttle program and development of the International Space Station have not presented planetary protection issues.
As the next four chapters explain, changes in space exploration and the science informing planetary protection create challenges that are likely to transform how countries and international cooperation mechanisms approach planetary protection and develop policy for it.