The concept of so-called Special Regions on Mars—that is, any region “interpreted to have a high potential for the existence of extant martian life forms” or regions where the conditions permit the proliferation of organisms introduced from Earth1—presents an interesting case study in the evolution of planetary protection policies and associated requirements. This appendix presents a chronological discussion of this evolution with particular emphasis on the role played by the National Academies and its committees.2
LATE 1990s/EARLY 2000s
Observations conducted by NASA’s Mars Global Surveyor in the late-1990s and early-2000s led to the discovery of transient activity in martian gullies suggesting that liquid water may have flown on the surface of Mars in recent times.3 This discovery (see Figure B.1, step 2) had an important impact on planetary protection, demonstrating that some regions may be more suitable to life than others.4
In April 2002, the Committee on Space Research (COSPAR) and the International Astronomical Union convened a workshop in Williamsburg, Virginia, to discuss planetary protection policies.5 The workshop (Figure. B.1, step 3) resulted in a revision of COSPAR’s policies (Figure B.1, steps 4-7) and, in particular, established a new mission category—Category IVc—for spacecraft accessing a Special Region on Mars.6 COSPAR defined a Special
1 G. Kminek, C. Conley, V. Hipkin, and H. Yano, “COSPAR Planetary Protection Policy,” Space Research Today, No. 200, December 2017, p. 18.
2 Material in this appendix has been extracted and adapted from the report National Academies of Sciences, Engineering, and Medicine and European Science Foundation, Review of the MEPAG Report on Mars Special Regions, The National Academies Press, Washington, D.C., 2015
3 M.C. Malin and K.S. Edgett, Evidence for recent groundwater seepage and surface runoff on Mars, Science, 288, pp. 2330-2335, 2000.
4 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, pp. 381-383.
5 J.D. Rummel, “Report of the Workshop on Planetary Protection Held Under the Auspices of the Committee on Space Research and the International Astronomical Union of the International Council for Science at Williamsburg, Virginia, USA on 2-4 April 2002,” COSPAR, Paris, 2002.
6 COSPAR, Planetary Protection Policy, COSPAR Information Bulletin, No. 156., pp. 67-74, 2003.
Region as a zone “within which terrestrial organisms are likely to propagate, or a region which is interpreted to have a high potential for the existence of extant martian life forms. Given the current understanding, this is to apply to regions where liquid water is present or may occur. Specific examples include, but are not limited to: subsurface access in an area and to a depth where the presence of liquid water is probable, penetrations into the polar caps, [and] areas of hydrothermal activity.”7
In 2005, NASA adopted COSPAR’s concept of a Special Region within its planetary protection policy. In addition, NASA requested the National Research Council (NRC) to conduct (Figure B.1, step 3) a study to assess the body of policies, requirements, and techniques designed to protect Mars from Earth-originating organisms that could interfere with and compromise scientific investigations.8 The resulting NRC report, Preventing the Forward Contamination of Mars, concluded that there were insufficient data to distinguish between Special Regions on Mars and regions that are not special.9 The committee proposed a new classification system, which would replace COSPAR’s Categories IVa through IVc, with Category IVn for Non-Special Regions and Category IVs for Special Regions.10 In addition, the NRC committee commented: “Until measurements are made that permit distinguishing confidently between regions that are special on Mars and those that are not, NASA should treat all direct-contact missions (i.e., all Category IV missions) as Category IVs missions.”11 In other words, the NRC recommended that all of Mars be considered a Special Region until additional observational data with better resolution can be obtained.
7 COSPAR, Planetary Protection Policy, COSPAR Information Bulletin No. 156, p. 71, 2003.
8 National Research Council (NRC), Preventing the Forward Contamination of Mars, The National Academies Press, Washington, D.C. 2006, p. 1.
9 NRC, Preventing the Forward Contamination of Mars, The National Academies Press, Washington, D.C. 2006.
11 Ibid, pp. 118-119.
If implemented, this recommendation required that all Mars landers be subjected to the most stringent—so-called Viking-level—bioload reduction procedures.
The programmatic consequences of subjecting all Mars landers to Viking-level bioload reduction led NASA to request that NASA’s Mars Exploration Program Analysis Group (MEPAG) charter a so-called Science Analysis Group (SAG) to look at Special Regions (Figure B.1, step 3). In particular, the MEPAG group—SR-SAG—was asked “to develop a quantitative clarification of the definition of ‘special region’ that can be used to distinguish between regions that are ‘special’ and ‘non-special’” and to undertake “a preliminary analysis of specific environments that should be considered “special” and “non-special.”12 The SR-SAG found that COSPAR’s definition of Special Regions needed additional clarification; specifically, the uses of the words propagate and likely, which can have different meanings and interpretations.13 The SR-SAG also constrained physical variables that could be used to define a Special Region, such as the following: how long they exist (about 100 years), the maximum depth of penetration by a spacecraft (about 5 m into the crust), and the lower limit for the survival of terrestrial life in terms of temperature (–15°C or –20°C including margin) and water activity (0.62 or 0.5 including margin).14 The SR-SAG report concluded by proposing a new definition of Special Region that retained the original COSPAR definition and added to it a set a clarifications and implementation guidelines.15
In 2007, COSPAR held a Mars Special Regions Colloquium, with the goal of reviewing the conclusions and recommendations contained in both the 2006 NRC and MEPAG reports and devising a consolidated definition of Special Regions (Figure B.1, step 4).16 The report of the COSPAR Colloquium disagrees with the NRC 2006 report by stating that there is sufficient data to distinguish between Special and Non-Special Regions and it differs from SR-SAG report by reducing the lower temperature limit for the survival of terrestrial life from –20°C to –25°C.17 The colloquium report also recommended that the definition of a Special Region and the list of terrains classified as Special be reviewed every 2 years.18 COSPAR subsequently adopted (Figure B.1, steps 4-7) the recommendations of the colloquium report and planetary protection policy was updated (Figure B.1, step 1).
Following the recommendation of the COSPAR colloquium to review the standards every 2 years, MEPAG empaneled a new science analysis group (SR-SAG2) in the latter part of 2014 to revisit (Figure B.1, steps 2-3) the concept of Special Regions on Mars in light of the latest scientific findings.
The resulting SR-SAG2 report provided a comprehensive distillation of the current understanding of the limits of terrestrial life and relevant martian conditions and presented an analytical approach for considering Special Regions using current and future improvements in knowledge. The SR-SAG2 report also determined that the lower limit for temperature should be –18°C and water activity (aw) above 0.60 and updated the list of features on Mars that should be classified as Special, Non-Special, and Uncertain regions.19 In reference to human missions,
12 D. Beaty, K. Buxbaum, M. Meyer, N. Barlow, W. Boynton, B. Clark, J. Deming, et al., Findings of the Mars Special Regions Science Analysis Group, Astrobiology 6:677-732, 2006.
13 Ibid., p. 684.
14 Ibid., pp. 684-691.
15 Ibid., p. 719.
16 Ibid. pp. 677-732.
17 G. Kminek, J.D. Rummel, C.S. Cockell, R. Atlas, N. Barlow, D. Beaty, W. Boynton, M. Carr, et al., Report of the COSPAR Mars Special Regions Colloquium, Advances in Space Research 46:826, 2010.
19 J.D. Rummel, D.W. Beaty, M.A. Jones, C. Bakermans, N.G. Barlow, P.J. Boston, V.F. Chevrier, et al., A new analysis of Mars “Special Regions”: Findings of the Second MEPAG Special Regions Science Analysis Group (SR-SAG2), Astrobiology 14:894-898, 2014.
the SR-SAG2 found that although these locations would be preferable for potential in situ resources, human missions should not contaminate Special Regions, and precautions should be taken to avoid converting Non-Special Regions to Special Regions.20
In October 2014, following the completion of the SR-SAG2 report—but prior to its formal publication in the November 2014 issue of the journal Astrobiology—NASA’s asked (Figure B.1, step 3) the National Academies “to review the conclusions and recommendations contained in the SR-SAG2 report and assess their consistency with current understanding of both the martian environment and the physical and chemical limits for the survival and propagation of microbial and other life on Earth.” Since the European Space Agency (ESA) had already requested the European Science Foundation (ESF) conduct a very similar review of the SR-SAG2 report, the National Academies and ESF established a joint committee to address the needs of both space agencies.
The joint committee discussed findings of the SR-SAG2 report in light of additional information from scientific publications not addressed by the MEPAG group and new knowledge obtained by ongoing space missions, field studies, and laboratory experiments. The joint committee focused on the survivability of life forms singularly versus in communities and SR-SAG2’s approach to defining geographical areas as Special Regions. The major conclusions of the joint committee were as follows:
- The authors of the SR-SAG2 report were commended for their comprehensive review of the issues associated with Special Regions and the factors used to define them.
- The environmental parameters used to define Special Regions are appropriate.
- The reported detection of methane in the martian atmosphere, may indicate biogenic activity, and if confirmed, that may demand that the methane source region be designated as a Special Region.
- The identification of Mars Special Regions is problematic for several two reasons. First, detailed knowledge of the physical and chemical conditions of the surface and sub-surface of Mars at various scales is lacking, particularly the microscale. Second, current understanding of the ability of life to propagate is limited. It is not known if one, ten, or one million cells from a single species are required for propagation in an extraterrestrial environment or if replication in alien conditions is only possible in the context of diverse microbial communities.
- Supported the current practice of reassessing the concept of a Special Region and its definition every 2 years.
- Suggested that some of the specific terrains identified as Special Regions in both the COSPAR policy and in the SR-SAG2 report are best regarded as “Uncertain Regions” until proven otherwise.21,22
The reports of SR-SAG2 and joint National Academies-ESF review committee were formally presented at an international workshop, organized by COSPAR’s Panel on Planetary Protection, and held in Bern, Switzerland, on September 22-24, 2015. Each group had a half day to present their conclusions and recommendations. An additional half day was devoted to additional discussion of both reports and to reaching consensus on proposed revisions to COSPAR’s policies concerning Mars Special Regions.
21 National Academies of Sciences, Engineering, and Medicine and the European Science Foundation, Review of the MEPAG Report on Mars Special Regions, The National Academies Press, Washington, D.C., 2015.
22 See, also, P. Rettberg, A. Anesio, V.R. Baker, J.A. Baross, S.L. Cady, E. Detsis, C.M. Foreman, et al., Planetary protection and Mars Special Regions—A suggestion for updating the definition, Astrobiology 16:119-125, 2016.
Recommendations from the Bern Workshop were forwarded to the COSPAR Panel on Planetary Protection for presentation, discussion, and final approval (Figure B.1, steps 4-7) at the July 2016 COSPAR Scientific Assembly in Istanbul.23 Unfortunately, political unrest in Turkey caused the assembly’s cancellation and subsequent deliberations by the Panel on Planetary Protection (Figure B.1, step 5) were conducted remotely. Since the scheduled meetings of COSPAR’s leadership groups (Figure B.1, step 6) in Istanbul could not take place, subsequent discussion and approval (Figure B.1, step 7) of the Panel on Planetary Protection recommendations concerning Mars Special Regions were deferred until the next meeting of the COSPAR Bureau, scheduled for March 2017.
The COSPAR Bureau approved (Figure B.1, step 7) the Panel on Planetary Protection’s recommendations concerning the policy updates at its March 2017 meeting.24 However, the pace of scientific results concerning Mars continued unabated. Of particular note was the publication in the latter part of the year of new results concerning so called recurring slope lineae (RSL) by Colin Dundas and colleagues (Figure B.1, step 2). RSL are dark features found on canyon and crater wall which appear to extend downslope, darken and then fade on a seasonal cycle. Dundas and colleagues’ analysis indicated that “the terminal slopes of [RSL] match the stopping angle for granular flows of cohesionless sand in active martian aeolian dunes.”25 In other words, RSL may have a lot more to do with flowing sand than with running water.
At about the same time, the former chairs of NASA’s by then-defunct internal planetary protection and planetary sciences advisory committees initiated a dialogue on issues of common interest relating to Mars Special Regions (Figure B.1, step 3). The first result of this dialogue was the convening of a workshop in Washington, D.C., to discuss the consequences of creating an artificial special region if a spacecraft equipped with a radioisotope power system crashes on Mars.26 Planning is under way for a second workshop, to be held in 2018, on the exploration of Special Regions.
23 G. Kminek, V.J. Hipkin, A.M. Anesio, J. Barengoltz, P.J. Boston, B.C. Clark, et al. Meeting Report: COSPAR Panel on Planetary Protection Colloquium, Bern, Switzerland, September 2015, Space Research Today, No. 195, pp. 42-51.
24 G. Kminek, C. Conley, V. Hipkin, and H. Yano, COSPAR Planetary Protection Policy, Space Research Today, No. 200, December 2017, pp. 12-24.
25 C.M. Dundas, A.E. McEwen, M. Chojnacki, M.P. Milazzo, S. Byrne, J.N. McElwaine, and A. Urso, Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water, Nature Geosciences 10:903-908, 2017.
26 Personal communication from Clive Neal to committee staff, December 12, 2017.