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6 Additional Recommendations RECOMMENDATIONS FOR RESEARCH Any future changes in recommendations made to ensure planetary protection, especially for piloted or sample return missions, will depend on the acquisition of new data. To this end, the task group believes that a sequence of unpiloted missions to Mars, undertaken well before a piloted mission, is imperative. One of the keys to deciphering the question of life on Mars lies in knowing where to look; the Viking landing sites were not optimum in this sense. They were selected primarily on the basis of considerations of spacecraft safety, rather than scientific potential. Because of this, we have a paucity of critical data needed to assess the possibility of contemporary or ancient life on Mars. Data should be gathered from a broad spectrum of sample sites with measurements focusing on data most likely to contribute to a better understanding of the probability of life on Mars. Among the classes of information needed are chemical (e.g., data on mineralogy, soil pH), physical (e.g., data on temperature, lightâqualitative and quantitative), and hydrological (i.e., data on the status of water availability, historical and current). Until such data are available, it will be impossible to make informed decisions concerning landing sites for in-depth biological study. Such data also will greatly affect the ability to make future decisions concerning the standards of rigor required for spacecraft cleanliness and possible sterilization. The term planetary protection encompasses two very distinct concepts: the forward contamination of Mars and the back contamination 51
of Earth. In this report, the task group specifies the planetary protection policy it believes appropriate with regard to forward contamination, i.e., (1) sterilization in missions with life-detection goals and (2) a general rigorous reduction of bioload in all others. Although these differ from the 1978 recommendations, the rationale is grounded in the scientific consideration of risk assessment (i.e., that the survival and/or growth of terrestrial organisms transported to Mars is highly unlikely) and aspects that threaten mission goals (i.e., that life-detection experiments may be compromised by spacecraft contaminants). However, the task group believes that there are areas in which the lack of current available data limits both the formulation of recommendations for planetary protection and the potential for mission success. To correct for this, the collection of certain data sets and the adoption of the overall approach outlined below are strongly recommended. These recommendations emphasize the need to firmly characterize the existing environmental conditions and the geochemical composition of Mars. This information will serve two purposes: (1) it will allow informed estimates of the potential for life (as we currently understand it) to exist on Mars and of the potential threat of contamination posed by backward transport of such life to Earth, and (2) it will identify those locations where life-detection missions should be sent. It is essential that these studies precede any lifedetection or piloted missions to the martian surface as well as any missions designed to return samples to Earth. Collection of Essential Data Viking provided us with pictures of a martian surface varying widely in its geomorphological features. Unfortunately, the Viking landers were located in relatively featureless, exposed areas of the planet chosen on the basis of landing safety. Therefore the data collected by these landers reflect only this harsh physical and chemical environment. To establish a policy to ensure planetary protection from back contamination, we need data from locations with a much greater potential to support life. Measurements taken from a variety of sites might allow specification of which martian environments might be least hostile to life; these will be very important sites for collection of relevant data regarding environmental variables (e.g., water, temperature, radiation) that might be used to predict the existence or survival of life forms. This approach would minimize any argument that the potential for life (and therefore for the back contamination of Earth) is underestimated by models incorporating data on only the harshest or least hospitable conditions. These same issues are significant in the placement of life-detection landers on the planet; sites with the greatest potential to support life now or in the past must be identified. 52
It was not the charge of this task group to identify locations or specific measurements or experiments for future missions; that is left to others. However, the recommendation to locate martian landers in sites with the maximal likelihood of fostering life might be further refined to suggest that these sites may be determined from our rudimentary understanding of Mars and our growing, but extensive, knowledge of the basic requirements of life. The existence of contemporary life on Mars has been presumed unlikely based on the lack of water, low temperatures, high UV flux, strongly oxidizing surface chemistry, and other parameters. If these factors are assumed to limit life, landers should be located in those areas where it is suspected that these conditions are least severe now or were so in the martian past. Given the consideration of water, a suitable site might lie in the polar regions, in one of the fluvial features associated with earlier hydrological activity, and/or in an area where geothermal vents are most likely to be found. In addition to selecting sites appropriate on a large scale, it is important to consider the subsurface of Mars. Temperature, UV attenuation, and other factors vary with depth and season and may offer a stable or transient refuge for life. Thus within a site it may prove to be important to design data collections that probe below the readily accessible surface, thus providing information on subsurface environments. The surface of Mars may well be highly heterogeneous, even more so than is now suspected. Microenvironmentsâwhether on the surface or in isolated vents, cracks, or layers of the subsurfaceâmay exist now or may have existed in the past. Properly designed experiments may be able to address the issue of spatial and (perhaps) temporal heterogeneity and its possible relationship to our ability to evaluate the biotic and abiotic status of a given site. Future sample return missions, piloted missions, and their associated quarantines will benefit from a planetary protection policy predicated on an approach that yields the least conservative estimates of existing martian life. Collection of the appropriate data should allow the scientific community to amend recommendations for a planetary protection policy for back contamination, perhaps resulting in recommendations similar to those that this task group has made for altering current policy on forward contamination. In addition, the determination of current or inferred past geophysical conditions on Mars may help in identifying locations where life-detection missions should be sent. This information would certainly increase the likelihood of success in meeting the goals of those missions. 53
Assessment of Spacecraft Bioload The task group's recommendation to "reduce" bioload on spacecraft in all missions and to sterilize those spacecraft used in life- detection missions assumes the use of Viking procedures. However, the task group recommends against the use of the Viking protocols for assessment of spacecraft bioloads after these cleaning procedures have been done. The 1980 guidelines for Viking bioload assessment1 are outdated and far less sensitive than the methods that will most likely be used to detect martian life. We now know that many organisms are undetected by standard culturing methods and that bioload estimates may, in fact, represent only 1 percent of the organisms actually present. The task group recommends that efforts be initiated immediately to adopt state-of-the-art methods for use in the determination of bioload. These methods should be the same as those most likely to be used in actual life-detection experiments conducted on Mars. They would, therefore, have the advantage of being sensitive enough to recognize low levels of biomarkers and of obviating the need to culture microorganisms. Since a major concern driving the task group recommendations is preventing the invalidation of life-detection missions by spacecraft-borne contaminants, it is critical that methods for assessing bioload be compatible with methods for detecting life: methods for both assessment and detection must reflect the same limits and sensitivity. Although it is not reasonable to demand that these methods be used for upcoming launches, it is imperative that they be used for missions involving life detection and that a program to implement them be established as soon as possible. Data on bioloads of Viking components and spacecraft are not relevant to current life-detection procedures. It is absolutely necessary that NASA investigate the bioload of component parts with state-of- the-art methods. Early funding of research designed to address the issue of detecting biomarkers after application of various cleaning procedures could lead to the use of less stringent means of reducing bioload. It would also allow NASA to customize procedures for specific life-detection methods. As there currently is no budget for this type of activity, the task group recommends that NASA's Office of Planetary Protection be given funds for the purpose of bioload research. RECOMMENDATIONS CONCERNING OTHER ISSUES Piloted Versus Unpiloted Missions Plans for future missions to Mars include bringing samples back to Earth as well as landing humans on Mars. Although humans may be effective, and perhaps even necessary, for the detection of past life (e.g., 54
by the collection and analysis of fossil-containing sediments and rocks), missions carrying humans will contaminate the planet, thereby making the search for extant life much more difficult. It is therefore critical that a major effort be made to determine whether there are places in local martian environments, such as active hydrothermal areas, where life might plausibly survive, and to more closely examine these areas robotically, before contamination by humans occurs. Relevant evidence could be obtained either by bringing back samples to Earth for examination or by making in situ measurements. Realistically, it is not likely that there will be near-term opportunities to bring samples back to Earth. If sample return is not possible, then every effort should be made to obtain chemical and physical measurements germane to the issue of life on Mars. Societal and Legal Issues The issues of forward and back contamination involved in missions to Mars have societal and legal implications at international levels. They are serious enough concerns in today's society to warrant discussion here. A dominant force in the 1980s was the powerful wave of public concern about environmental problems. The task group believes that these concerns are real and continuing and should be given serious attention by NASA. A substantial number of national and international organizations, active and well funded, are on the alert for environmental abuse. There is every reason to take seriously the concern (already expressed in some cases) about contamination of Mars and almost certainly about the issue of back contamination of Earth by martian samples. Although public concern over such issues is often sincere and useful, it at times becomes distorted and exaggerated in the media, sometimes in a sensationalist and nonproductive way, leading to public misunderstanding and opposition.2 In some cases, these concerns have led to lengthy court actions. To forestall such unnecessary confrontation, the task group recommends that NASA make every attempt to inform the public about current planetary protection plans and provide continuing updates concerning Mars exploration and sample return. The task group thinks that there is not likely to be great public concern over the question of outbound contamination, especially if the public understands the scientific objectives and is aware that the issue of contamination has been addressed (and that appropriate precautions are being taken). The better the effort at public education and the earlier it begins, the smaller the likelihood that there will be public concern and negative reaction. In the case of sample return missions, the task group believes that the potential for negative reaction is much greater and that the need for public education and involvement is therefore even greater. In addition to the scientific aspects of planetary protection that need to be considered, there are also legal issues that must be addressed, 55
involving international restrictions as well as federal, state, and local statutes that may come into play. A number of relevant statutes and regulations are written by agencies as diverse as the Department of Agriculture, the U.S. Public Health Service, the Department of Interior, and the Environmental Protection Agency, all of which deal with the exposure of American citizens to hazardous or toxic materials. International groups such as the United Nations, the World Health Organization, and the International Labor Organization have also attempted to address questions involving protection of Earth's environment and minimization of risk to populations from space exploration activity. In most cases, these documents lack specific details and contain almost no scientifically based discussion of risk of contamination, precautions needed, or procedures to follow in case of an accident. There are currently no binding international agreements concerning forward or back contamination.3 The task group believes it is essential (1) to assess the legal limits (and implied liabilities) in existing legislation that relates to martian exploration and (2) to pursue the establishment of international standards that will safeguard the scientific integrity of research on Mars, as well as provide protection for Earth and her inhabitants. NASA should make a strong effort to obtain international agreement for planetary protection issues. A strong international component will help assuage possible domestic concern. NASA should, even at this early date, acknowledge the problems outlined above and reestablish the kind of planetary protection program that existed through the Viking Program. Although a planetary protection officer exists, there is no budgeted program to implement needed planetary protection research, public education programs, and the like. The task group recommends that NASA correct this situation as soon as possible by redefining the responsibilities and authority or its planetary protection officer and by providing sufficient resources to carry out the recommendations made in this report. REFERENCES 1. National Aeronautics and Space Administration (NASA). 1980. NASA Standard Procedures for the Microbiological Examination of Space Hardware. NHB 5340.1B. NASA, Washington, D.C. 2. DeVincenzi, D.L., H.P. Klein, and J.R. Bagby. 1991. Planetary Protection Issues and Future Mars Missions. NASA conference publication. NASA Ames Research Center, Moffett Field, Calif. 3. Robinson, George S. 1991. "Exobiology and Planetary Protection-The Evolving Law," an unpublished paper presented to the Space Studies Board Planetary Protection Workshop, NAS Beckman Center, September 13. 56