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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, light—qualitative 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
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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.
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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. Microenvironments—whether on the surface or
in isolated vents, cracks, or layers of the subsurface—may 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.
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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.,
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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,
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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.
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Appendixes
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58
