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Volume 18, Number 2, 2018 ª Mary Ann Liebert, Inc. DOI: 10.1089/ast.2017.1785

Inadvertently Finding Contamination on Should Not Be a Priority for Anyone

John D. Rummel1 and Catharine A. Conley2

aire´n et al. (2018, in this issue) identify ‘‘the most out in An Exobiological Strategy for Mars Exploration from Fimportant scientific question driving Mars exploration; 1995 (Exobiology Program Office, 1995). One of the points that is, has life occurred on Mars, in the past or at present, and emphasized in this strategy is that it doesn’t make sense to how can we best answer this question with future Mars go to Mars trying to search for extant life without having missions?’’ It should be stated up front that both of us also a specific, qualified target for such a search. Further, upon believe that a search for life, extinct and/or extant, is finding such a target, it’s necessary to control against false- among the highest priorities for Mars science. Accepting that positive indications of life caused by Earth-sourced con- this objective is not up for debate, we further contend that tamination (Space Studies Board, Task Group on Planetary such a high-priority search should be protected at a level Protection, 1992; Exobiology Program Office, 1995). consistent with its importance—that is, not be conducted in a Specifically the Strategy states, way that could obscure evidence of martian life while care- . It is evident that several hypothetical alternative niches lessly introducing our own to the most hospitable places for for have been suggested in the exobiological Earth life on Mars—Special Regions. literature. As of this writing, however, these remain to be This is in contrast to the specifics proposed by Faire´n located and characterized. Thus, the initial thrust of the et al. (2017), which involve searching for martian life using strategy for extant life on Mars must be to determine whether spacecraft that carry Earth contamination at levels likely to or not these environments actually exist. Only with the ac- confound the desired result—and potentially other future quisition of this fundamental information will it be reason- human objectives at Mars. Despite what Faire´n et al. (2018) able, from the point of view of extant biology, to probe such seem to believe, current policies are not putative environments with landed instrumentation (Exo- to blame for the priorities of the NASA Mars Exploration biology Program Office, 1995). Program—or other space agencies’ exploration programs— Until a likely place on Mars that may currently support nor do arguments in favor of continued adherence to plan- life has been identified, searching for extant martian life is etary protection policies, as they have been developed over premature. If life was once widespread on Mars, and is not decades by the international scientific community, ‘‘illus- now, there should be much evidence for ancient martian life trate why we are not searching for life on Mars today and spread around the , and in less contaminable places why we haven’t done so during the last decades.’’ than those that qualify as modern Special Regions. Hence, Rather than revisiting the contentions of previous articles ‘‘searching for life on Mars’’ currently prioritizes looking point-by-point, we here consider three decisions that need to for conditions that would preserve biomarkers expected to be made when addressing the question, posed by Faire´n et al., reflect ancient Mars, rather than present-day Mars, because of how to detect martian life with future missions. These are we think we know where to look for them. In fact, one of the authors of the Faire´n et al. papers is a (1) Where should we look for martian life? Downloaded by Guangxi University for Nationalities from online.liebertpub.com at 02/18/18. For personal use only. coauthor of a recent paper entitled ‘‘Critical Assessment (2) What are the concerns associated with Earth of Analytical Techniques in the Search for Biomarkers on contamination? Mars: A Mummified Microbial Mat from Antarctica as a (3) Which missions should be sent, and when? Best-Case Scenario’’ (Blanco et al., 2017). We agree with In reviewing how the Mars exploration community has this approach. Detecting biomarkers of ancient (and possibly evaluated these options over time, we illustrate the thought extinct, microbial-mat) life may, indeed, be the best way to processes that have contributed to their development—which find martian life. follow a train of logic that applies equally well to future missions. Despite this, Faire´n et al. (2018) seem to feel that the Space Studies Board advice to target locations with high preservation potential runs counter to ‘‘the actual priorities, 1. Where Should We Look for Martian Life? goals, and desires of the Mars community’’—but they do not The NASA , post-Viking, has cite references that identify even one specific location on not been actively searching for extant life on Mars because Mars where a search for extant life is advocated as the the program has effectively been following the roadmap laid primary mission goal. To justify this ‘‘community’’

1SETI Institute, Mountain View, California. 2NASA Headquarters, Washington, DC.

108 FINDING MARTIAN LIFE ON MARS 109

statement, Faire´n et al. (2018) listed the following refer- missions has run into several billions of dollars, so the ences: McKay et al. (2013), Grossman (2013), Heldmann fractional cost of planetary protection measures could be et al. (2014), Vago et al. (2015), King (2015), Levin and under 10%. Again, it becomes a question of priorities—if Straat (2016), Gordon and Sephton (2016), et al. one really wanted to study a Mars Special Region, this (2017), Xie et al. (2017), Niles et al. (2017), Ehlmann et al. would be an acceptable cost. However, because access to (2017). These references generally relate to the concept of Special Regions was not identified as a high priority in life detection on Mars, but the advocacy of these references Decadal Surveys, the investments neces- for the assertion that a search for extant life is the highest sary to reestablish those capabilities (linking back to the priority for Mars exploration is decidedly weak. In contrast, Viking experience) have not been made. one of the strongest reasons given for doing that search is This does not mean that it is suddenly sensible to allow related to ensuring the safety of future human explorers access to Special Regions by spacecraft that carry viable against a possible biological threat—exactly what planetary Earth organisms, as Faire´n et al. propose, at least not without protection is intended to accomplish and what COSPAR evaluating the potential consequences, and as a global policy specifies. community—not just the Mars community—deciding that For a summary of how each of these references maps to a we’re willing to accept them. search for extant life on Mars, see Table 1. In the context of introducing Earth contamination to Our previous statement that ‘‘the Mars community is not Mars, Faire´n et al. make the following three-point claim: convinced that a mission to attempt detection of extant . the current robotic will have little (if martian life is a high priority’’ is well-supported by the any) impact on potential martian biospheres or on our efforts recommendations of the most recent Planetary Science for searching for active life on Mars, because (i) the micro- Decadal Survey (Space Studies Board, Committee on the bial burden carried by unmanned robots is minimal and not Planetary Science Decadal Survey, 2012) on Planetary renewable and, most importantly, known and identifiable; (ii) Science priorities through 2022. A mission to go to a Special the is bactericidal in nature; and (iii) we Region and search for extant martian life, although espoused know how to distinguish an Earth from po- by Faire´n et al. (2017, 2018), was not among the missions tential . prioritized by the Space Studies Board in 2012. Note that, in As it turns out, the first two of these claims are already the eyes of NASA and the US Congress, the Planetary incorporated into the COSPAR Planetary Protection Science Decadal Survey documents ‘‘the actual priorities, Policy—and the third is not supported by any available data. goals, and desires of the Mars community.’’ It may be true, as Faire´n et al. stated, that ‘‘the Mars community, including NASA, always points to life detection 2.1. Microbial burden on as a number-one priority in Mars exploration,’’ but it is It is thanks to planetary protection cleanliness require- important to note that ‘‘life detection’’ does not necessarily ments that the microbial burden on Mars robotic spacecraft is mean going to Special Regions to try to culture or sequence ‘‘minimal’’—andalso‘‘notrenewable’’solongasthemicrobial microbes. In fact, although we consider this evident lack of passengers are not introduced into places where they can grow interest unfortunate, it would be even more unfortunate to (the definition of Special Regions). However, current technolo- permit access to Special Regions in the absence of appro- gies to identify microbial populations carried on spacecraft are priate planetary protection precautions. inadequate and would be even less well-developed if not re- quired for planetary protection. A reasonable genetic inventory 2. What Are the Concerns Associated of microbial contaminants in the extremely oligotrophic envi- with Earth Contamination? ronments of spacecraft assembly clean rooms may be achievable by using technologies developed for other fields but will re- The current definition of Special Regions is based on the quire further advances in sample collection and analysis— characteristics of possible contaminating Earth organisms, only developments that are currently being pursued by planetary (Rummel et al., 2014). But even granting that the best places to protection researchers.

Downloaded by Guangxi University for Nationalities from online.liebertpub.com at 02/18/18. For personal use only. find signs of extant life on Mars may also be in Special Re- In contrast, the stringent control of diversity and quantity gions, the logic of introducing Earth organisms into the places of microbial populations in spacecraft assembly clean rooms where they are most likely to grow—and potentially obscure is not something other communities do—and is not some- signals of martian life as a result—evades us. thing space agencies can do, or will ever do, without re- Issues that are of most concern to mission planners in- quirements being enforced by someone. This control is clude cost and technical capability—yet the exactly what the COSPAR Planetary Protection Category was successful in sending nearly sterile life-detection mis- IVc specifies to allow access to a Mars Special Region sions to Mars when that had never been done before. The (Kminek and Rummel, 2015). Flying such a mission right development of technical capability certainly incurs costs— away is fine with us—and we agree with Faire´n et al. that and estimates of the costs associated with performing full- Mars community advocacy, including appropriate invest- system dry heat microbial reduction of a Mars have ments in the necessary cleaning capabilities, is what is remained essentially constant at the equivalent of one large needed to get this sort of mission sent to that sort of place. science instrument, as we cited previously (Rummel and Conley, 2017). On the one hand, it is not possible to say that 2.2. Biocidal factors on Mars this is inexpensive, given that recent large instruments (e.g., mass spectrometers) sent to Mars have cost over 100 million Information we have gained about the martian sur- dollars. On the other hand, the total cost of recent Mars face environment does include evidence of challenging Downloaded by Guangxi University for Nationalities from online.liebertpub.com at 02/18/18. For personal use only.

Table 1. Astrobiology Community Papers Cited by Faire´n et al. (2018) as Giving Direct Support for a Search for Extant Life as the Highest Priority for Mars Exploration

Paper cited by Cat IVb extant Faire´n et al. life-detection (2018, in this issue) mission required? Relation to extant life detection? Summary from paper Additional notes McKay et al., 2013 No Not required. Organic analysis ‘‘(1) Search for specific that would Assessment of habitability is as planned. be conclusive evidence of life. (2) Perform a close to extant life detection general search for organic molecules in the as this payload actually gets. ground . (3) Determine the processes of Secondary objectives are ground ice formation and the role of liquid ‘‘Climate history and crust . (4) Understand the mechanical evolution.’’ properties of the martian polar ice-cemented soil. (5) Assess the recent habitability of the environment with respect to required elements to support life, energy sources, and possible toxic elements. (6) Compare the elemental composition of the northern plains with midlatitude sites.’’ Grossman, 2013 N/A Not a science paper; News Journalist’s description of some potential Scientists mentioned: , Carr, article. life-detection science instruments. Schulze-Makuch, Levin, Anbar. Heldmann et al., 2014 No Identify sites for possible ‘‘Systematically analyzed remote-sensing data A possible in situ resource for

110 analytical examination. sets to determine whether a viable landing human exploration. site exists in the northern midlatitudes to enable a robotic mission that conducts in situ characterization and searches for evidence of life in the ice.’’ Vago et al., 2015 Yes, subsystem Adaptive strategy focused on ‘‘On the Earth, microbial life quickly became Effective chemical identification approach extinct life. a global phenomenon. If a similar explosive of requires access process occurred in the early history of Mars, to well-preserved organic then the chances of finding evidence of past molecules. life may be good. Even more interesting would be the discovery and study of life forms that have successfully adapted to modern Mars. However, this presupposes the prior identification of geologically suitable, life friendly locations where it can be demonstrated that liquid water still exists—at least episodically throughout the year. None have been identified so far. For these reasons, the science advisory team recommended that ESA focus mainly on the detection of extinct life; but also, build enough flexibility into the mission design to allow identifying present life.’’ (continued) Downloaded by Guangxi University for Nationalities from online.liebertpub.com at 02/18/18. For personal use only.

Table 1. (Continued) Paper cited by Cat IVb extant Faire´n et al. life-detection (2018, in this issue) mission required? Relation to extant life detection? Summary from paper Additional notes King, 2015 N/A. Analogue Potential forward contamination ‘‘Results presented here show that carbon Environmental models. suspects identified. monoxide, which is abundant in Mars’ (Earth). atmosphere, could be used at local scales under conditions that occur at RSL, including moderate temperatures, low pressure, high CO2, low oxygen concentrations, and extreme water potentials. Halophilic CO-oxidizing Proteobacteria, and recently discovered extremely halophilic CO-oxidizing Euryarchaeota described in this study, represent ideal models for understanding the capacity of Mars’ atmosphere to support microbial communities.’’ Levin and Straat, 2016 Yes, to validate Let’s go! ‘‘It is concluded that extant life is a strong Russian crashes before Viking Viking results. possibility, that abiotic interpretations of the didn’t contaminate Mars, but now LR data are not conclusive, and that, even Mars is contaminated by more setting our conclusion aside, biology should recent spacecraft. still be considered as an explanation for the LR experiment. Because of possible 111 contamination of Mars by terrestrial microbes after Viking, we note that the LR data are the only data we will ever have on biologically pristine martian samples.’’ Gordon and Sephton, 2016 No A major goal of astrobiology, ‘‘For a rapid assessment of past habitability with MSR in situ operations would but no specific in situ mission multiple samples, a pyrolysis-FTIR method attempt to identify and cache advocated to search for that can provide high sensitivity and samples that exhibit high extant life. diagnostic information is desired.’’ scientific potential, rather than seeking maximum scientific return while on the martian surface. Smith et al., 2017 No Technique paper focused on ‘‘To our knowledge, this is the first report of ‘‘We have therefore provided extinct or extant life. multivariate analysis methods, namely an analytical methodology useful MCR-ALS, with Raman microspectroscopic for the search for extant or past mapping being employed to differentiate life on the surface of Mars.’’ carbonaceous material from hematite. We have therefore provided an analytical methodology useful for the search for extant or past life on the surface of Mars.’’ Xie et al., 2017 No Technique paper focused on ‘‘Detection of b-carotene suggests the presence This analogue mission found a recently extinct or extant life. of endolithic communities within the rock.’’ dinosaur fossil and some petrified wood, too. Other involved investigators may focus on extant life. (continued) Downloaded by Guangxi University for Nationalities from online.liebertpub.com at 02/18/18. For personal use only.

Table 1. (Continued) Paper cited by Cat IVb extant Faire´n et al. life-detection (2018, in this issue) mission required? Relation to extant life detection? Summary from paper Additional notes Niles et al., 2017 No Find the water, first. ‘‘Past habitable environments with high ‘‘Discovering evidence for existing preservation potential for ancient life on Mars would be an biosignatures are the primary target for extraordinary discovery and our understanding of the history of would allow us to study the habitability of the Planet.’’ biology that is likely to be completely alien from our own. Locations on Mars that allow for the presence of liquid water would be the primary target for this search which would have to be conducted carefully under strict planetary protection protocols.’’

112 Ehlmann et al., 2017 Yes, for planetary Essential as part of planetary ‘‘For instance, key knowledge gaps for both ‘‘Synergistic measurement protection protection for human NASA-sponsored and commercial human opportunities include: . iv) considerations commercial and exploration exploration include . d) evidence that extant continued characterization of missions [see COSPAR life is not widespread in martian surface martian surface materials to Planetary Protection Policy, materials.’’ determine whether extant life as well]. is present as well as identify potential chemical hazards to .’’ ‘‘Critically, robotic sample return could ‘‘The 2020s could focus on an facilitate uncontaminated return of samples orbital mapping effort for from Mars special regions, where the chance localized exposures of current for extant life is highest—in contrast to other and past volatiles (and resources) terrains for which collection by a human is as well as astrobiological less likely to interfere with scientific investigations for extant life, measurement.’’ which should be pursued vigorously before humans begin in situ exploration.’’

Note that only 3 of the 11 papers (10 science papers and 1 news article) specifically support that goal, including support for the ExoMars mission, which is a Category IVb mission (sample train cleaned to the Viking standard), advocacy for a repeat of the Viking Labeled Release experiment by the principal investigator and coinvestigator of that experiment, and advocacy for an attempt to detect extant life as part of due diligence before humans have uncontrolled exposure to martian surface materials that could contain life. FINDING MARTIAN LIFE ON MARS 113

environmental factors, such as , peroxides, and about martian life, it is permissible (and even advisable) to UV radiation that are biocidal to many Earth microbes. consider alternative scenarios as well as the preferred one. However, there is no justification for Faire´n et al. to con- In line with our general skepticism about relying on clude, regarding a robotic rover, that ‘‘after the interplan- martian life to use DNA, we are also concerned by scenarios etary trip and just one single on the surface of Mars in which identifying a DNA-bearing martian organism receiving direct ’’ a spacecraft ‘‘will be as biologi- would not be simple—for example, the continuing discovery cally clean (and maybe even more) as the Viking probes of Earth organisms that root near the base of the 16/18S were when they left Earth.’’ RNA tree, and also the potential for lateral gene transfer to This statement is invalidated both by the fact that some alter the anticipated placement of putative martian organ- microbes will ride inside a nonsterilized rover and by data isms on a general relatedness tree of life. from earlier Mars missions and experimental studies. Faire´n et al. did go on to cite other strategies for detecting In fact, what we currently know about Earth microbes martian life that do not involve detecting nucleic acids—but suggests that some microbes that are relatively common in many of the biosignatures proposed for use in these other spacecraft assembly clean rooms (e.g., SAFR-032) are also methods would be even more easily confused or obscured resistant to the biocidal factors that have been identified on by Earth microbial contamination than is DNA. In this Mars (cf. Schuerger et al., 2006, Nicholson et al., 2012). context, the suggestion of Faire´n et al. that ‘‘Relaxing the Further, even susceptible Earth microbes will not be af- forward contamination rules and allowing a dedicated fected if they are not exposed to the relevant biocidal search for life on Mars now’’ would almost guarantee that factors—for example, not every external surface on a Mars we do find life on Mars—but not necessarily martian life. lander is exposed to sunlight, but all may be covered by a Their further suggestion that this ‘‘would actually assist in UV-protective dust layer. understanding the actual risks of returning samples from As stated by Schuerger et al. (2006) ‘‘the presence of UV Mars in the future, as we will have a better idea whether resistant microbes on spacecraft surfaces rapidly covered in there is life on Mars or not’’ is entirely incorrect. It could be dust during landing operations, and non--exposed sur- damaging to future Mars exploration, if we do detect faces of spacecraft remain concerns that must continue to be indications of life on Mars but can’t be confident that these addressed through adequate spacecraft sanitizing procedures are not martian life, because the noise of Earth contamina- prior to launch.’’ tion is so high. In the context of bringing martian material to This potential for survival is something that needs to be Earth, a false-negative result is a much greater risk to the appreciated, especially if a search for martian life can have safety of Earth than a false positive—for this reason, if some any hope of success. For example, in Box 1 of Faire´n et al. sort of life has been detected on Mars, we have to assume (2018), the authors state that planetary protection maintains that martian life is present until it can be demonstrated ‘‘some accepted popular concepts [that] are either outdated otherwise. This would not be an easy task. or simply wrong,’’ although those concepts are basic points Faire´n and his coauthors contend that ‘‘using one argu- related to biological cross contamination and to the capa- ment on one side of the issue and then the opposite argu- cities of adventitious pathogens. We were entertained by the ment on other side of the same issue, however it fits, is not mental image of jungle parrots flying around on Mars, but acceptable in a scientific debate.’’ We are not primarily parrots are no more poorly suited to survive there than in engaging in a ‘‘debate,’’—our objective is to establish ap- some microbe-supporting Earth environments, such as propriate parameters for ensuring the effectiveness of a Yellowstone’s Grand Prismatic Spring. search for martian life, and associated questions of Earth In the context of understanding the possible advent and safety assurance. As such, some arguments do cut both survival of more hardy Earth organisms on Mars, it is cu- ways. rious that Faire´n et al. (2018) ignored another of their co- Early consideration of alternative scenarios that could con- author’s papers (Goordial et al., 2016), which states found interpretation of results is what contingency planning is all about. Dry permafrost as observed in University Valley is rare on Earth, likely only occurring in the McMurdo Dry Valleys, Downloaded by Guangxi University for Nationalities from online.liebertpub.com at 02/18/18. For personal use only. but is commonplace in the northern polar regions of Mars at 3. Which Missions Should Be Sent, and When? the landing site (Levy et al., 2009). Thus, our results have implications for our understanding of the cold limits of We do genuinely agree with the position of Faire´n et al. life in terrestrial environments, with potential implications ‘‘that we need to resume a dedicated robotic search for life for habitability models of Mars near surface permafrost and on Mars as soon as possible, before manned missions reach other icy worlds. the planet and it becomes too late.’’ We dispute, however, their contention that planetary protection cleanliness re- quirements are somehow to blame for the delay in sending 2.3. Distinguishing Earth and martian microbes life-detection missions to Mars. We also disagree with the Faire´n et al. (2018) stated that ‘‘We are clever enough to proposal that cleanliness requirements should be relaxed on recognize martians, if they exist.’’ This demonstrates im- near-term robotic missions—rather, improvements in our pressive confidence, given that the basic composition of understanding of environments on Mars and the capabilities martian life remains totally unknown. They go on to note of Earth organisms highlight the continued need to ensure that much of what they say about identifying martian life that planetary protection precautions are effective. based on DNA sequences is valid ‘‘if (a big if) martian life As noted by Faire´n et al., robotic missions will carry with is genetically similar to Earth’s.’’ True! But in the absence them only the bioburden that they have when they leave of evidence for each specific characteristic we might predict Earth, but some will survive the trip. For a mission not going 114 RUMMEL AND CONLEY

to a Special Region and not searching for extant life, many essential to the health and safety of future humans on Mars will remain alive inside spacecraft components for decades and that this effort needs to be conducted in the most ef- or more. The surface of Mars will kill many, but not all of fective possible way, without sacrificing its essential credi- them, and depending on the final resting place of the robot bility in the name of expediency. (in an old impact crater, rolled down a slope, sitting in the We strongly encourage continued discussion of these is- shadow of a large rock), some may have a chance to escape sues, both within the Mars exploration community and also captivity and find a better . A handful could in an expanded global community of citizens who both pay survive, and if lodged near martian ice, they might one day for and could be affected by such efforts. do even better than that. Note that the spread of Earth contamination on Mars is not dependent on the original amount introduced. Taking a Acknowledgments dirty spacecraft to a location specifically defined as a place The work described here was supported by the NASA where Earth organisms can survive could likely lead to the Planetary Sciences Division and the Office of Planetary ‘‘discovery’’ of a contaminating Earth organism, and the Protection. Thanks, too, to Sherry Cady and the staff of potential mis-identification of it as a martian . by others . Astrobiology for their assistance with this paper and for the who could then claim that NASA is hiding the discovery of Forum of which it is a part. life on Mars. Such a mission should not be flown—because such a ‘‘detection’’ would make the possibility of a bio- logical threat to human explorers of more concern than it References needs to be. Blanco, Y., Gallardo-Carren˜o, I., Ruiz-Bermejo, M., Puente- By the time human missions are sent, the goal should be Sa´nchez, F., Cavalcante-Silva, E., Quesada, A., Prieto- that additional information about both Earth microbes and Ballesteros, O., and Parro, V. (2017) Critical assessment of martian environments will be made available from robotic analytical techniques in the search for biomarkers on Mars: missions to facilitate human mission goals and provide for the a mummified microbial mat from Antarctica as a best-case appropriate tailoring of planetary protection requirements. scenario. Astrobiology 17:984–996. Human missions, by design, will keep associated mi- Conley, C.A. and Rummel, J.D. (2010) Planetary protection crobes alive as long as habitats are powered, and many will for human exploration of Mars. Acta Astronautica 66:792– reproduce in great profusion. The humans, however, will 797. need to contain and constrain microbial growth and repro- Ehlmann, B.L., Johnson, S.S., Horgan, B., Niles, P.B., Amador, duction, both to ensure proper operation of life support E.S., Archer, P.D., Jr, Byrne, S., Edwards, C.S., Fraeman, A.A., Glavin, D.P., Glotch, T.D., Hardgrove, C., Hayne, P.O., Kite, systems and because the humans and the microbes will be E.S., Lanza, N.L., Lapotre, M.G.A., Michalski, J., Rice, M., and competing for water. It is true that ‘‘some degree of forward Rogers, A.D. (2017) Mars Exploration Science in 2050 [abstract contamination associated with human explorers is 8236]. In Planetary Science Vision 2050 Workshop, Lunar and inevitable’’ (Conley and Rummel, 2010), but for human Planetary Institute, Houston, LPI Contribution 1989. exploration missions, the spread of those microbes into Exobiology Program Office. (1995) An Exobiological Strategy for Mars Special Regions can be minimized, if not avoided Mars Exploration, NASA SP-530, NASA, Washington, DC. completely, by appropriate operational and technological Faire´n, A.G., Parro, V., Schulze-Makuch, D., and Whyte, L. precautions. We do not dwell on the possibility of human (2017) Searching for life on Mars before it is too late. As- missions arriving on the surface of Mars prior to an op- trobiology 17:962–970. portunity to conduct an appropriately clean mission to some Faire´n, A.G., Parro, V., Schulze-Makuch, D., and Whyte, L. Special Region on that planet, because we judge the likeli- (2018) Is searching for martian life a priority for the Mars hood of that event to be small. community? Astrobiology 18, doi:10.1089/ast.2017.1772. The short paper by Ehlmann et al. (2017) noted the need Goordial, J., Davila, A., Lacelle, D., Pollard, W., Marinova, for ‘‘evidence that extant life is not widespread in martian M.M., Greer, C.W., DiRuggiero, J., McKay, C.P., and Whyte, surface materials’’ and the opportunity for the ‘‘continued L.G. (2016) Nearing the cold-arid limits of microbial life in permafrost of an upper dry valley, Antarctica. ISME J 10: Downloaded by Guangxi University for Nationalities from online.liebertpub.com at 02/18/18. For personal use only. characterization of martian surface materials to determine whether extant life is present’’ as important opportunities to 1613–1624. address critical knowledge gaps about Mars. We contend Gordon, P.R. and Sephton, M.A. (2016) detec- that it would be ethically incorrect to send a human mission tion on Mars by pyrolysis-FTIR: an analysis of sensitivity and without understanding the resultant potential for exposing matrix effects. Astrobiology 16:831–845. people (tourists?) to martian materials that may contain Grossman, L. (2013, July 20) NASA urged to seek live martians with 2020 rover. New Sci 219:9. living organisms. Regulatory frameworks for licensing Heldmann, J.L., Schurmeier, L., McKay, C., Davila, A., Stoker, space missions exist, and treaty obligations apply even to C., Marinova, M., and Wilhelm, M.B. (2014) Midlatitude countries that may not have implemented the appropriate ice-rich ground on Mars as a target in the search for evidence national laws. It would be surprising if human missions to of life and for in situ resource utilization on human missions. Mars were authorized to launch, prior to consideration of Astrobiology 14:102–118. these sorts of concerns. King, G.M. (2015) Carbon monoxide as a metabolic energy For multiple reasons, we reject the proposal by Faire´n source for extremely halophilic microbes: implications for et al. that we should cut corners and attempt to fly ro- microbial activity in Mars . Proc Natl Acad Sci USA botic missions that could only equivocally resolve questions 112:4465–4470. about martian life, before humans arrive on the planet. Kminek, G. and Rummel, J.D. (2015) COSPAR’s Planetary Nonetheless, we believe that a Mars life-detection mission is Protection Policy. Today 193:7–19. FINDING MARTIAN LIFE ON MARS 115

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