1
Introduction

The past decade has seen a dramatic increase in knowledge of the history, geology, mineralogy, geochemistry, and physical properties of the martian surface. This increase in scientific knowledge has been enabled by a string of ambitious and highly successful orbital, lander, and rover missions over the past decade that continue to revolutionize understanding of the red planet. These missions and their major investigations are summarized in Table 1.1.

Recent successes in Mars exploration are attributable, in part, to the careful implementation of a well-coordinated, international effort initially articulated in NASA’s 1995 report An Exobiology Strategy for Mars Exploration.1 That document recommended a phased approach to Mars exploration that would alternate orbital and surface missions, with data acquired at each new opportunity advancing a discovery-driven program that would progressively focus and refine the selection of sites for surface exploration and, eventually, sample return. Spectral mapping from orbit has seen progressive increases in spatial resolution, over an expanded range of wavelengths, including probing of the subsurface by radar. Such observations have provided an increasingly detailed framework for identifying the best sites for landed missions, which have, in turn, provided ground-truth observations for interpreting the data from previous missions and refining the next generation of orbital investigations. This iterative strategy has allowed Mars exploration activities to become progressively more focused on a smaller number of high-priority sites for addressing fundamental questions about Mars, including the following:

  • Past and present habitability,2

  • The potential for life,

  • Strategies for Mars sample return,

  • Approaches to the containment and biohazard testing of martian samples, and

  • The availability of resources and potential hazards for planning human missions.

IMPORTANCE OF MARS SAMPLE RETURN

A Mars sample return mission is acknowledged to be a major next step in the exploration of Mars.3,4,5,6,7,8,9,10 Indeed, such a mission would provide essential support for answering many of the highest-priority scientific questions that have been identified by the international scientific community.11 The NRC’s 2003 solar system exploration decadal survey highlighted three areas where unambiguous answers to key science issues are unlikely without a sample-return mission:12



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1 Introduction The past decade has seen a dramatic increase in knowledge of the history, geology, mineralogy, geochemistry, and physical properties of the martian surface. This increase in scientific knowledge has been enabled by a string of ambitious and highly successful orbital, lander, and rover missions over the past decade that continue to revolution- ize understanding of the red planet. These missions and their major investigations are summarized in Table 1.1. Recent successes in Mars exploration are attributable, in part, to the careful implementation of a well-coordi- nated, international effort initially articulated in NASA’s 1995 report An Exobiology Strategy for Mars Exploration.1 That document recommended a phased approach to Mars exploration that would alternate orbital and surface mis- sions, with data acquired at each new opportunity advancing a discovery-driven program that would progressively focus and refine the selection of sites for surface exploration and, eventually, sample return. Spectral mapping from orbit has seen progressive increases in spatial resolution, over an expanded range of wavelengths, including probing of the subsurface by radar. Such observations have provided an increasingly detailed framework for identifying the best sites for landed missions, which have, in turn, provided ground-truth observations for interpreting the data from previous missions and refining the next generation of orbital investigations. This iterative strategy has allowed Mars exploration activities to become progressively more focused on a smaller number of high-priority sites for addressing fundamental questions about Mars, including the following: • Past and present habitability,2 • The potential for life, • Strategies for Mars sample return, • Approaches to the containment and biohazard testing of martian samples, and • The availability of resources and potential hazards for planning human missions. IMPORTANCE OF MARS SAMPLE RETuRN A Mars sample return mission is acknowledged to be a major next step in the exploration of Mars. 3,4,5,6,7,8,9,10 Indeed, such a mission would provide essential support for answering many of the highest-priority scientific questions that have been identified by the international scientific community.11 The NRC’s 2003 solar system exploration decadal survey highlighted three areas where unambiguous answers to key science issues are unlikely without a sample-return mission:12 

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0 ASSESSMENT OF PLANETARY PROTECTION REQUIREMENTS FOR MARS SAMPLE RETURN MISSIONS TABLE 1.1 Mars Spacecraft Missions and Investigations, 1965-2016 Operational at Spacecraft Name Mars (Mission Type) Agency Science Investigations Missions Operating Before Publication of Mars Sample Return: Issues and Recommendationsa 1965 Mariner 4 (Flyby) NASA Imaging system, cosmic dust detector, cosmic ray telescope, ionization chamber, magnetometer, trapped radiation detector, solar plasma probe, occultation experiment 1969 Mariner 6 (Flyby) NASA Imaging system, infrared spectrometer, ultraviolet spectrometer, infrared radiometer, celestial mechanics experiment, S-band occultation experiment 1969 Mariner 7 (Flyby) NASA Same as Mariner 6 1971-1972 Mariner 9 (Orbiter) NASA Imaging system, infrared spectrometer, ultraviolet spectrometer, infrared radiometer, celestial mechanics experiment, S-band occultation experiment 1976-1980 Viking 1 (Orbiter and Lander) NASA Orbiter: Imaging system, atmospheric water detector, infrared (Orbiter) thermal mapper 1976-1983 Aeroshell: Retarding potential analyzer, upper-atmosphere mass (Lander) spectrometer Lander: Same as Viking 2 1976-1978 Viking 2 (Orbiter and Lander) NASA Orbiter and Aeroshell: Same as Viking 1 (Orbiter) Lander: Imaging system, gas chromatograph mass spectrometer, 1976-1980 seismometer, x-ray fluorescence, biological laboratory, weather (Lander) instrument package, remote sampler arm Missions Operating After Publication of Mars Sample Return: Issues and Recommendationsa 1997-2006 Mars Global Surveyor (Orbiter) NASA High-/medium-/low-resolution imager, thermal-emission spectrometer, laser altimeter, radio science experiment, magnetometer and electron reflectometer 1997 Mars Pathfinder and Sojourner NASA Panoramic imager, alpha proton x-ray spectrometer, atmospheric (Lander and Microrover) structure/meteorology package, magnetic properties of dust experiment 2001-Current Mars Odyssey (Orbiter) NASA Thermal-emission imaging system, gamma ray spectrometer, neutron spectrometer, high-energy neutron detector, environmental radiation experiment 2003-Current Mars Express (Orbiter) European High-resolution stereo imager, subsurface and ionosphere sounding Space radar, infrared mineralogical mapping spectrometer, atmospheric Agency Fourier spectrometer, ultraviolet/infrared atmospheric spectrometer, plasma and energetic atom analyser, radio science experiment 2003-Current Mars Exploration Rovers Spirit NASA Panoramic stereo imager, thermal-emission imaging system, alpha and Opportunity particle x-ray spectrometer, Mössbauer spectrometer, microscopic imager, rock abrasion tool, magnetic properties of dust experiment 2005-Current Mars Reconnaissance Orbiter NASA Visible/near-infrared imaging spectrometer, high-resolution imager, medium-resolution imager, low-resolution imager, infrared radiometer, shallow subsurface sounding radar 2008 Phoenix (Lander) NASA Panoramic stereo imager, soil electrochemistry and conductivity experiment (with atomic-force microscope), thermal and evolved gas analyzer, robotic arm, robotic-arm camera, lidar and meteorological package

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 INTRODUCTION TABLE 1.1 Continued Operational at Spacecraft Name Mars (Mission Type) Agency Science Investigations Planned Future Missions To launch in Mars Science Laboratory NASA Panoramic stereo imager, laser-induced breakdown spectrometer, 2011 (Rover) alpha particle x-ray spectrometer, microscopic imager, x-ray diffraction/x-ray fluorescence instrument, gas chromatograph mass spectrometer, environmental radiation experiment, meteorological/ environmental monitoring package, pulsed neutron generator/ detector, descent imager To launch in Mars Atmosphere and Volatiles NASA Solar-wind electron and ion analyzers, suprathermal and thermal 2013 Evolution (Orbiter) ion composition experiment, solar energetic particles, Langmuir probe and waves experiment, magnetometer, imaging ultraviolet spectrometer, neutral gas and ion mass spectrometer To launch in ExoMars (Lander and Rover) European On rover: Panoramic color camera, infrared mapper, ground- 2016 Space penetrating radar, close-up imager, Mössbauer spectrometer, Agency laser Raman spectrometer, subsurface coring drill, multispectral microscopic imager for subsurface borehole studies, infrared microscope for characterization of drill cores and cuttings, x-ray diffractometer, gas chromatograph mass spectrometer and mass spectrometer for organic analysis, amino acid and chirality analyser On lander: Atmospheric radiation and electricity sensor, meteorological/environmental monitoring package, bistatic ground- penetrating radar, heat-flow sensor, radio science experiment, dust analyser, humidity sensor, magnetometer, seismometer, ultraviolet/ visible spectrometer for atmospheric studies aNational Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington, D.C., 1997. • The search for life. As the most Earth-like planet in the solar system, Mars has historically provided a major focus for exploration to determine whether or not life exists, or has existed, elsewhere in the solar system. The Viking experience suggests that addressing questions of past or present martian life via in situ life-detection experi- ments is likely to lead to ambiguous results. Life detection can be addressed more thoroughly and systematically using returned samples collected from well-targeted locations, rather than with in situ robotic investigations. • Geochemical studies and age dating. The history and evolution of Mars are encoded on a microscopic scale in the chemical and isotopic makeup of martian rocks. Study of a rock’s constituent minerals, inclusions, and alteration products can reveal information on its age, its origins, the dates of thermal and aqueous alteration events, and a history of magmatic processes. Key to unlocking the rock record are careful sample selection and preparation. • Climate and coupled atmosphere-surface-interior processes. Understanding the evolution of the martian climate over the past 4.5 billion years requires an understanding of the loss of atmospheric gases both to space and to surface reservoirs. Losses to the surface and to space leave characteristic isotopic signatures. Thus, com- positional and isotopic analysis of surface minerals, weathering rinds, and sedimentary deposits can establish the climatic roles played by liquid water and processes such as weathering. Similar measurements of the volatiles released from near-surface minerals may provide fossils of past atmospheric and chemical conditions that allow past climate to be better understood. Again, careful sample selection and preparation are essential. Although some progress toward addressing these three key areas can be achieved via in situ studies, return- ing samples to Earth is desirable for a number of reasons identified in reports issued by NASA and other major national and international space agencies. As noted in, for example, the recent report of the International Mars

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 ASSESSMENT OF PLANETARY PROTECTION REQUIREMENTS FOR MARS SAMPLE RETURN MISSIONS Architecture for the Return of Samples (iMARS) Working Group,13 returning samples to Earth is desirable for the following reasons: • Complex sample preparation. Many high-priority science investigations will require sample preparation procedures that are too complex for in situ robotic missions (e.g., separation of minerals; extraction and concentra- tion of trace elements and organic compounds using specialized solvents; chemical analysis using high-sensitivity instrumentation, or multiple analyses of samples; analyses at elevated temperatures; preparation and analysis of rock, or biological thin sections; high-magnification light and electron microscopy; and x-ray tomography). • Instrumentation not amenable to spacecraft application. Certain kinds of instruments are simply too large, require too much power, or are otherwise unsuitable for flight missions. • Instrument diversity. While the type and the diversity of instruments suitable for inclusion on a robotic Mars mission are limited, no such restriction applies to the instrumentation in terrestrial laboratories. Indeed, instruments and techniques unavailable at the time a mission is launched may be employed to full advantage for returned samples, allowing application of the most up-to-date, cutting-edge techniques. In summary, although much has been accomplished through in situ robotic analysis and/or Earth-based laboratory studies of martian meteorites, returned samples from targeted locations on Mars will provide the best pathway for obtaining definitive answers to questions about the origin and evolution of Mars, including its climatic history, habitability, and life. Obviously, the most valuable returned samples will be those that come with detailed contextual information (e.g., precise spatial locations, geological settings, and so on) to directly link samples to past and present environmental frameworks. With the advantages of Mars sample return comes an obligation to protect and preserve our home planet and all of its inhabitants against potential negative consequences of martian life forms returned to Earth. The purpose of this report is to provide an interim view of ongoing efforts to develop and implement plans for planetary protec- tion for Mars sample return. In other words, it is the understanding of the Committee on the Review of Planetary Protection Requirements for Mars Sample Return Missions that its findings and recommendations will be applied at the tactical level by subsequent groups specifically charged with the development of implementable protocols for the collection, handling, transfer, quarantine, and release of Mars samples. That is the approach that was taken by NASA after its receipt of the National Research Council’s (NRC’s) 1997 report Mars Sample Return: Issues and Recommendations.14 Indeed, the development of broad strategic guidelines by Space Studies Board commit- tees and the subsequent development of tactical plans for their implementation by NASA committees is a general approach that has served the space-science community well for most of the past 50 years. SAMPLE RETuRN AND PLANETARY PROTECTION In accordance with international treaty obligations,15 NASA maintains a planetary protection policy to avoid biological contamination of other worlds, as well as to avoid the potential for harmful effects on Earth due to the return of extraterrestrial materials by spaceflight missions. NASA’s implementation of the internationally accepted planetary protection guidelines—as promulgated by the Committee on Space Research (COSPAR) of the International Council for Science16—is based on advice and recommendations it receives from internal (e.g., the Planetary Protection Subcommittee of the NASA Advisory Council) and external (e.g., the NRC’s Space Studies Board) advisory groups. Planetary protection concerns can be divided into two components: • Forward contamination, the inadvertent transfer of terrestrial organisms or biological contaminants to extraterrestrial bodies via spacecraft missions; and • Back contamination, the transfer of putative biological materials and organisms to Earth via a sample return mission.

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 INTRODUCTION Although a 2006 NRC report dealt explicitly with forward-contamination issues relating to Mars missions, 17 it has been more than 10 years since back-contamination issues were examined. Within COSPAR’s guidelines, the planetary protection requirements levied on a particular spacecraft depend on the nature of its mission (e.g., flyby, orbiter, lander, or sample return) and the relevance of its destination to studies of chemical evolution and/or the origin of life. Each combination of mission type and destination is assigned a planetary protection category, with Category I being the least restrictive and Category V being the most restrictive. Each category has its own requirements for spacecraft cleanliness and bioload reduction before launch. Because Mars is of particular interest to astrobiology, it is subject to the strictest categories of planetary protection require- ments. Missions such as flybys or orbiters that have no direct contact with the planet are designated as Category III, whereas landers, or probes that have direct contact at the surface, are designated as Category IV. Category IV missions are subject to a variety of planetary protection requirements that depend on science objectives. Missions searching for extant martian life (e.g., the Viking landers) fall into Category IVb. Missions going to a place where liquid water is present, or where the presence of the spacecraft could cause liquid water to be present—so-called Special Regions—are Category IVc. Other missions to the surface (generally not investigat- ing life; e.g., the Mars Exploration Rovers) fall into Category IVa. All sample return missions, irrespective of their target, are designated as Category V. Target bodies like Mars, which are of direct interest to the search for extraterrestrial life, are further categorized as “restricted Earth return.” This COSPAR categorization mandates that the following precautions be implemented: 18 • “An absolute prohibition of destructive impact upon return” to Earth; • The need for containment, during every phase of the return trip to Earth, of all returned hardware that directly contacts the targeted body, or any unsterilized materials from the body; • A need to conduct timely analyses of any unsterilized samples collected and returned to Earth, under strict containment, and using the most sensitive techniques; and • “The need for containment of any unsterilized samples collected and returned to Earth; if any sign of the existence of a non-terrestrial replicating entity is found, the returned sample must remain contained unless treated by an effective sterilizing procedure.” Of course, the COSPAR guidelines are not absolute and have evolved over time as new scientific information has become available. As already mentioned, the SSB last considered back-contamination issues associated with Mars sample return missions more than a decade ago. The resulting NRC report—Mars Sample Return: Issues and Recommendations19—provided specific recommendations for the handling of samples returned to Earth from Mars (Box 1.1). Those recommendations, combined with inputs from a series of workshops, resulted in the publication by NASA in 2002 of a draft protocol describing how martian samples should be studied to establish whether or not they pose a biological hazard to Earth.20 However, at about the same time as the draft protocol was issued, a combination of budgetary and technical factors caused NASA to curtail its planning for a Mars sample return mission. Renewed interest in Mars sample return by both NASA and the international space exploration community has urged a systematic review of the findings of the NRC’s 1997 Mars report to update its recommendations based on current understanding of the biological potential of Mars, and in light of ongoing improvements in biological, chemical, and physical sample analysis capabilities and technologies. Although a detailed study is beyond the scope of the present activity, it is intended that the findings and recommendations that follow will provide useful interim advice for future NASA and international planning groups that will define a final protocol for handling and testing martian materials. MARS EXPLORATION STRATEGY The strategy for the astrobiological exploration of Mars responds to two major discoveries: first, that surface water environments were widespread on Mars early in the planet’s history, and second, that potentially habitable

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 ASSESSMENT OF PLANETARY PROTECTION REQUIREMENTS FOR MARS SAMPLE RETURN MISSIONS BOX 1.1 Recommendations from Mars Sample Return: Issues and Recommendations (1997) Seven of the nine recommendations made in Mars Sample Return1 concern the handling of samples returned from Mars. • Samples returned from Mars by spacecraft should be contained and treated as though potentially hazardous until proven otherwise. No uncontained martian materials, including spacecraft surfaces that have been exposed to the martian environment, should be returned to Earth unless sterilized. • Controlled distribution of unsterilized materials returned from Mars should occur only if rigorous analyses determine that the materials do not contain a biological hazard. If any portion of the sample is removed from containment prior to completion of these analyses, it should first be sterilized. • The planetary protection measures adopted for the first Mars sample return missions should not be relaxed for subsequent missions without thorough scientific review and concurrence by an appropriate independent [oversight] body. • A research facility for receiving, containing, and processing returned samples should be established as soon as possible after serious planning for a Mars sample return mission has begun. At a minimum, the facility should be operational at least 2 years prior to launch [of a Mars sample return mission]. The facility should be staffed by a multidisciplinary team of scientists responsible for the development and validation of procedures for detection, preliminary characterization, and containment of organisms (living, dead, or fossil) in returned samples and for sample sterilization. An advisory panel of scientists should be constituted with oversight responsibilities for the facility. • A panel of experts, including representatives of relevant governmental and scientific bodies, should be established as soon as possible once serious planning for a Mars sample return mission has begun, to coordinate regulatory responsibilities and to advise NASA on the implementation of planetary protection measures for sample-return missions. The panel should be in place at least 1 year prior to the establish- ment of the sample-receiving facility ([i.e.,] at least 3 years prior to launch). • An administrative structure should be established within NASA to verify and certify adherence to planetary protection requirements at each critical stage of a sample-return mission, including launch, reentry, and sample distribution. • Throughout any sample-return program, the public should be openly informed of plans, activities, results, and associated issues. 1National Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington, D.C., 1997. environments may have existed at least locally in the near subsurface throughout the planet’s history. Accordingly, exploration follows two basic paths:21,22 • Exopaleontology. The search for ancient aqueous sedimentary deposits and habitable environments that may have preserved fossil biosignatures of past life; and • Exobiology. The search for present habitable environments that could sustain extant life, with a focus on subsurface environments where liquid water could be present today, or the near-surface cryosphere, where remains of extant life forms may be preserved in ground ice or permafrost.

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 INTRODUCTION While surface water environments appear to have been widespread on Mars early in the planet’s history, 23 liquid water has probably been present in the deep subsurface throughout the planet’s history. 24,25 The oldest features identified on Mars, the cratered highlands, preserve a record of ancient habitable surface environments based on the widespread detection of sulfates and phyllosilicates from orbit by the OMEGA and CRISM imaging spectrometers on Mars Express and Mars Reconnaissance Orbiter, respectively. 26 Similarly, aqueously deposited carbonate minerals found in martian meteorite ALH 84001 suggest that potentially habitable environments were also present in the subsurface as early as 3.9 billion years ago.27 (See also Chapter 2.) Evidence for out-floods of subsurface water during the Hesperian (i.e., the middle era of martian history) is preserved as large channels, such as Ares Vallis and Tui Vallis.28 Similarly, the Eberswalde Crater provides evidence for standing bodies of water. Recent outflows of subsurface water have been suggested for volcanic sites, like Cerberus Rupes on the southern plains of Elysium (Figure 1.1),29 and very recent gully features (Figure 1.2) carved by fluid seeps and springs have been identified at a large number of high-latitude sites on Mars. 30,31,32 These examples suggest that surface/near-surface liquid water environments have been present throughout the history of Mars and may still exist in the shallow subsurface. While the discovery of potentially habitable environments on Mars (based on the inferred presence of water, bioessential elements, and energy sources) enhances the possibility that life could have originated there, it is understood that simply demonstrating the presence of factors considered necessary for life on Mars is inadequate assurance that life actually originated there. This is why we explore! Although there are important planetary protection implications associated with returning samples from any location on Mars, the greatest risk will be incurred by missions that return samples from so-called Special Regions,33 where habitable conditions may sustain viable organisms. The Viking lander mission established that present surface conditions on Mars are unfavorable for life as we understand it,34 and although favorable conditions may exist in the deep subsurface today, robotic technologies for deep drilling on Mars remain a distant prospect. Thus, the current path for the surface exploration of Mars places an emphasis on the search for fossil biosignatures preserved in ancient, water-formed sedimentary deposits. 35 The “build on your successes” approach followed during the past decade of Mars exploration has been enabled by the Mars community’s concerted effort to rapidly disseminate new data. As a result, NASA’s Mars Exploration Program has remained highly responsive to new discoveries, feeding new results into planning efforts for future mis- sions. For example, discoveries of Mars Global Surveyor directly supported NASA and community-based efforts to prioritize and select landing sites for the highly successful Mars Exploration Rover mission, 36,37 by providing planning insights up until 6 months before launch. Discoveries of the Mars Odyssey and Mars Reconnaissance Orbiter (MRO) missions also played a major role in the selection of the landing site for Phoenix. 38 The combined efforts of Odyssey, MRO, and the European Space Agency’s Mars Express missions are likewise providing new high-resolution data for selecting the best landing sites for the Mars Science Laboratory rover, currently scheduled for launch in 2011. Given the past successes of the phased strategy for exploration outlined above, it seems clear that data from current orbital and landed missions will continue to play crucial roles in the targeting of a site or sites for future Mars sample return(s). REPORT ORGANIZATION Since the purpose of this document is to revise, update, and replace the NRC’s 1997 report Mars Sample Return: Issues and Recommendations, it is most logical to organize it around the basic question, What has changed since the release of the 1997 report? Changes that have an impact on planetary protection requirements can be divided into two categories: changes in scientific understanding and changes in the technical and/or policy envi- ronment. Changes is scientific understanding have been organized as follows: • New insights on the roles played by surface and subsurface water throughout martian history and the potential for habitable environments on Mars. Chapter 2 provides a brief review of major discoveries in Mars exploration over the past decade that have shaped current understanding of the potential for past and present

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 ASSESSMENT OF PLANETARY PROTECTION REQUIREMENTS FOR MARS SAMPLE RETURN MISSIONS habitability. At the heart of this exploration effort has been a guiding principle, “follow the water,” based on the rationale that water in its liquid state provides a useful proxy for habitability. Pursuit of this principle for Mars has sustained remarkable successes, with new evidence for liquid water, both at the surface in the past and in the shallow subsurface of Mars, throughout much of the planet’s history. The discovery of a diverse subsurface bio- sphere on Earth has opened up possibilities for habitable zones of liquid water in the martian subsurface, where chemotrophic microbial life forms may survive by exploiting simple chemical sources of energy, such as carbon dioxide, hydrogen, or methane. This understanding has driven the development of radar instruments to explore for a subsurface hydrosphere on Mars from orbit (e.g., Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) and Shallow Radar (SHARAD) experiments onboard Mars Express and MRO, respectively). Chapter 2 also examines progress toward understanding the potential for past habitability on Mars, based on studies of martian meteorites. Over the past decade, advances in laboratory instrumentation and new analytical capabilities, applied to studies of martian meteorites, have provided new insights into the nature of past martian environments and the role that water has played in the alteration of crustal rocks on Mars. • Advances in microbial ecology that illuminate the limits of adaptability of life on Earth. Chapter 3 reviews recent discoveries that have shaped a new understanding of the basic requirements for living systems on Earth, including an expanded awareness of the environmental extremes occupied by microbial life and the diverse array of energy sources life utilizes. Again, one of the most significant discoveries is the ability of deep-subsurface life to survive on simple forms of chemical energy, which on Earth supports a vast subsurface biosphere. 39,40 Such discoveries require a focusing of the “follow the water” strategythat is, the institution of a strategy encompassing a nested set of requirements, with the availability of past/present water as the first step. Subsequent steps would be prioritized according to the inferred availability of the elemental building blocks and energy sources required for life. This focusing of the search strategy is evident in the enhanced payload capabilities of the Phoenix lander, which analyzed the chemistry of frozen regolith, and the Mars Science Laboratory and ExoMars missions, which are scheduled to deliver sophisticated biogeochemistry and organic chemistry experiments, respectively, to sites where orbital data provide strong evidence for past water. These efforts represent a renewal of Viking’s initial search in 1976 for organic matter preserved in rocks and ices on Mars, and they provide logical next steps toward in situ life detection experiments that should precede Mars sample return. • New understanding of the physical and chemical mechanisms by which evidence of life might be preserved on Mars and how that life might be detected in martian samples. Chapter 4 discusses developments in the field of geomicrobiology that have significantly advanced understanding of the varied roles that microorganisms play in sedimentary processes and have helped define new approaches for the astrobiological exploration of Mars. It provides a look at the role that terrestrial analog studies have played in advancing the understanding of habitabil- ity and in refining strategies for Mars exploration. In particular, studies of environmental molecular biology and processes of microbial fossilization in Mars analog environments on Earth have helped to refine approaches to in situ and laboratory-based biosignature detection, while studies of the fossilized remains in ancient Precambrian sediments have provided insights into the nature of preservational biases and the effects of post-burial alteration on the long-term retention of fossil biosignatures under different post-burial histories. Such studies continue to lay important groundwork for future in situ missions and Mars sample return. • New understanding of pathogenesis and the nature of biological epidemics. Chapter 5 briefly reviews how new developments in the biomedical community have affected understanding of the possibility that putative martian organisms may be pathogenic. • Additional insights as to the possibility that viable martian organisms might be transported to Earth by meteorites. Chapter 5 also discusses the natural interchange of materials between planets and the possibility that hypothetical martian organisms might survive ejection from Mars and transport to Earth. The changes in the technical and/or policy environment can be organized as follows: • A significant expansion of the size of the Mars exploration community and broadening of the scope of mission activities by both traditional and new space powers. Chapter 2 explores how a decade’s worth of highly successful Mars missions has resulted in significant growth in the size of the Mars exploration community inside

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 INTRODUCTION FIGURE 1.1 A colored image mosaic taken by the Thermal Emission Imaging System onboard the Odyssey spacecraft. This 240-km by 320-km image covers portions of the Cerberus Fossae (volcanic fissures) and the upper reaches of the Athabasca Valles channel system believed to have been formed by repeated outbursts of subsurface water, perhaps within the past 2 mil- lion years. Note the streamlining of deposits around impact craters located at the heads of some streamlined islands. Athabasca Valles lies ~1,000 kilometers southeast of the large martian volcano, Elysium Mons. SOURCE: Courtesy of NASA/Jet Propul- sion Laboratory and Arizona State University.

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 ASSESSMENT OF PLANETARY PROTECTION REQUIREMENTS FOR MARS SAMPLE RETURN MISSIONS FIGURE 1.2 Mars Orbiter Camera image (E11-04033) showing the north wall of a small (7-km-diameter) impact crater (39.1°S, 166.1°W) located within Newton Crater. The image shows numerous small gullies hypothesized to have been formed by water and sediment-laden debris flows, which formed lobe-shaped deposits at the base of the crater wall. The image shows an area approximately 3 km across. SOURCE: Courtesy of NASA/Jet Propulsion Laboratory and Malin Space Science Systems.

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 INTRODUCTION and outside the United States. Other factors of significance include the democratization of priority-setting exer- cises and the internationalization of mission activities. The combined effect of all these developments has been a significant acceleration in the pace of acquisition of new information about Mars. • Greater societal awareness of the potential for technical activities to cause harmful changes in the global environment. Chapter 5 briefly examines the potential for large-scale negative effects resulting from the inadver- tent release of pristine martian materials and possible extraterrestrial life forms into Earth’s environments. It also provides an update of the concept of panspermia and the potential for natural transfers of putative martian organ- isms to Earth by meteorites. Advances in modeling have helped to clarify the potential for exchanges of crustal materials between Earth and Mars by impact ejection. In addition, studies of the prolonged survival of microorgan- isms under extreme conditions have also shed new light on the potential for life forms to survive impact ejection, interplanetary transport, and landing on another planetary surface. • The de facto internationalization of a Mars sample return mission and subsequent sample-handling, sample- processing, sample-analysis, and sample-archiving policies. Chapter 6 raises complications that might arise for Mars sample return given that the execution of such a mission is likely to be beyond the resources of NASA or any other single agency. An international Mars sample return mission might suffer if differences in national poli- cies and legal frameworks significantly complicate issues relating to sample quarantine policies and biohazard certification. • The drafting and publication by NASA, with the assistance of international partners, of initial Mars sample- handling and biohazard-testing protocols based on the recommendations in the NRC’s  Mars Sample Return report. Chapter 6 compares and contrasts the policies for biohazard testing and criteria for releasing samples from containment included in NASA’s draft protocols and other recent reports. • The development of nondestructive methods of analysis that can be used to map the microscale spatial dis- tribution of minerals and biological elements in samples. Chapter 6 also discusses an issue arising from biohazard tests that will require the selection of small, representative subsamples from larger samples of martian materials. Advances in geomicrobiology (Chapter 4) have indicated that the distribution of biosignatures in rocks, soils, and ices is typically highly heterogeneous at the microscopic scale. This distributed heterogeneity raises concerns about how best to obtain representative samples that will yield reliable results during testing for potential biohazards. The application of new analytical techniques that can be used to map the microscale spatial distribution of minerals and biological elements in samples might provide a solution. • The proliferation of biocontainment facilities driven by biosecurity concerns and associated changes in public policy and in the public acceptance of such facilities. Chapter 7 examines the unique characteristics of a Mars sample-receiving facility and discusses previous recommendations for such containment facilities, including broader issues related to Mars sample return program oversight and public communication. • Lessons learned about the practical and logistical aspects of Mars sample return from experience with the Genesis and Stardust missions as well as experience gained from the planning for and commissioning of new bio- containment facilities. Chapter 7 summarizes the lessons learned from recent sample return missions, particularly as they relate to the landing, transport, and testing of extraterrestrial materials on Earth. Each chapter ends with conclusions and/or recommendations that suggest actions that should be considered during future science and technology planning efforts for Mars sample return. NOTES 1 . National Aeronautics and Space Administration (NASA), An Exobiological Strategy for Mars Exploration, NASA SP-530, NASA, Washington, D.C., 1995. 2 . Habitability is a concept used by astrobiologists to denote the potential of a particular environment (past or present) to be such that life could exist, grow, and proliferate. Its usage does not imply that life has or does exist. For a more complete discussion of the concept see National Research Council, An Astrobiology Strategy for the Exploration of Mars, The National Academies Press, Washington, D.C., 2007, p. 14. 3 . National Research Council, Strategy for the Exploration of the Inner Planets: -, National Academy of Sci- ences, Washington, D.C., 1978.

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0 ASSESSMENT OF PLANETARY PROTECTION REQUIREMENTS FOR MARS SAMPLE RETURN MISSIONS 4 . National Research Council, 0 Update to Strategy for Exploration of the Inner Planets, National Academy Press, Washington, D.C., 1990. 5 . National Research Council, International Cooperation for Mars Exploration and Sample Return, National Academy Press, Washington, D.C., 1990, pp. 1, 3, and 25. 6 . National Research Council, An Integrated Strategy for the Planetary Sciences: -00, National Academy Press, Washington, D.C., 1994. 7 . National Research Council, Review of NASA’s Planned Mars Program, National Academy Press, Washington, D.C., 1996, pp. 3, 26, and 29. 8 . National Research Council, Assessment of Mars Science and Mission Priorities, The National Academies Press, Washington, D.C., 2003, pp. 3, 83-88, and 99-102. 9 . National Research Council, An Astrobiology Strategy for the Exploration of Mars, The National Academies Press, Washington, D.C., 2007, pp. 8-9 and 106. 10 . Mars Exploration Program Analysis Group, “Scientific Goals, Objectives, Investigations, and Priorities: 2006,” J. Grant, ed., white paper, February 2006, available at http://mepag.jpl.nasa.gov/report/index.html. 11 . See, for example, Next Decade Science Action Group, Mars Exploration Program Analysis Group (MEPAG), “Sci- ence Priorities for Mars Sample Return,” unpublished white paper, posted March 2008 by MEPAG at http://mepag.jpl.nasa. gov/reports/ndsag.html. 12 . National Research Council, New Frontiers in the Solar System: An Integrated Exploration Strategy, The National Academies Press, Washington, D.C., 2003, pp. 198-199. 13 . The iMARS Working Group, Preliminary Planning for an International Mars Sample Return Mission: Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group, National Aeronautics and Space Admin- istration, Washington, D.C., and European Space Agency, Paris, France, 2008. 14 . National Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washing- ton, D.C., 1997. 15 . United Nations, Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies, U.N. Document No. 6347, January 1967. 16 . COSPAR, “COSPAR Planetary Protection Policy, 20 October 2002, as amended March 24, 2005, and July 20, 2008,” available at http://cosparhq.cnes.fr/Scistr/PPPolicy(20-July-08).pdf. 17 . National Research Council, Preventing the Forward Contamination of Mars, The National Academies Press, Wash- ington, D.C., 2006. 18 . COSPAR, “COSPAR Planetary Protection Policy, 20 October 2002, as amended March 24, 2005, and July 20, 2008,” available at http://cosparhq.cnes.fr/Scistr/PPPolicy(20-July-08).pdf. 19 . National Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washing- ton, D.C., 1997. 20 . 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. 21 . J.D. Farmer and D.J. Des Marais, “Exploring for a Record of Ancient Martian Life,” Journal of Geophysical Research 104:26977-26995, 1999. 22 . J.D. Farmer, “Exploring for a Fossil Record of Extraterrestrial Life,” pp. 10-15 in Palaeobiology II (D. Briggs and P. Crowther, eds.), Blackwell Science Publishers, Oxford, U.K., 2000. 23 . D.W. Beaty, S.M. Clifford, L.E. Borg, D. Catling, R.A. Craddock, D.J. Des Marais, J.D. Farmer, H.V. Frey, R.M. Haberle, C.P. McKay, H.E. Newsom, T.J. Parker, T. Segura, and K.L. Tanaka, “Key Science Questions from the Second Con- ference on Early Mars: Geologic, Hydrologic, and Climatic Evolution and the Implications for Life,” Astrobiology 5:663-689, 2005. 24 . S.M. Clifford, “A Model for the Hydrologic and Climatic Behavior of Water on Mars,” Journal of Geophysical Research 98:10973-11016, 1993. 25 . M.H. Carr, Water on Mars, Oxford University Press, Oxford, U.K., 1996. 26 . F. Poulet, J.-P. Bibring, J.F. Mustard, A. Gendrin, N. Mangold, Y. Langevin, R.E. Arvidson, B. Gondet, and C. Gomez, “Phyllosilicates on Mars and Implications for Early Martian Climate,” Nature 438:623-627, 2005. 27 . L.E. Borg, J.N. Connelly, L.E. Nyquist, C.-Y. Shih, H. Wiesmann, and Y. Reece, “The Age of the Carbonates in Martian Meteorite ALH 84001,” Science 286:90-94, 1999. 28 . F. Costard and V.R. Baker, “Thermokarst Landforms and Processes in Ares Vallis, Mars,” Geomorphology 37:289- 301, 2001.

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 INTRODUCTION 29 . D.M. Burr, J.A. Grier, A.S. McEwen, and L.P. Keszthelyi, “Repeated Aqueous Flooding from Cerberus Fossae: Evidence for Very Recently Extant, Deep Groundwater on Mars,” Icarus 159:53-73, 2002. 30 . M.C. Malin and K.S. Edgett, “Evidence for Recent Groundwater Seepage and Surface Runoff on Mars,” Science 288:2330-2335, 2000. 31 . W.K. Hartman, “Martian Seeps and Their Relation to Youthful Geothermal Activity,” Space Science Reviews 96:405- 410, 2001. 32 . P.R. Christensen, “Formation of Recent Martian Gullies Through Melting of Extensive Water-rich Snow Deposits,” Nature 42:45-48, 2003. 33 . COSPAR, “COSPAR Planetary Protection Policy, 20 October 2002, as amended March 24, 2005, and July 20, 2008,” available at http://cosparhq.cnes.fr/Scistr/PPPolicy(20-July-08).pdf. 34 . H.P. Klein, “Did Viking Discover Life on Mars?” Origins of Life and Evolution of the Biosphere 29:625-631, 1999. 35 . Mars Science Program Synthesis Group 2002-2003, Mars Exploration Strategy: 00-00 (D.J. McCleese, ed.), JPL 400-1131, Jet Propulsion Laboratory, Pasadena, Calif., 2003, available at http://mepag.jpl.nasa.gov/reports/MSPSG.pdf. 36 . P.R. Christensen, J.L. Bandfield, R.N. Clark, K.S. Edgett, V.E. Hamilton, T. Hoefen, H.H. Kieffer, R.O. Kuzmin, M.D. Lane, M.C. Malin, R.V. Morris, J.C. Pearl, R. Pearson, T.L. Roush, S.W. Ruff, and M.D. Smith, “Detection of Crystal- line Hematite Mineralization on Mars by the Thermal Emission Spectrometer: Evidence for Near-surface Water,” Journal of Geophysical Research 105:9623-9642, 2000. 37 . N.A. Cabrol, E.A. Grin, M.H. Carr, B. Sutter, J.M. Moore, J.D. Farmer, R. Greeley, R.O. Kuzmin, D.J. DesMarais, M.G. Kramer, H. Newsom, C. Barber, I. Thorsos, K.L. Tanaka, N.G. Barlow, D.A. Fike, M.L. Urquhart, B. Grigsby, F.D. Grant, and O. de Goursac, “Exploring Gusev Crater with Spirit: Review of Science Objectives and Testable Hypotheses,” Journal of Geophysical Research 108(E12):8076, doi:10.1029/202JE002026, 2003. 38 . R. Arvidson, D. Adams, G. Bonfiglio, P. Christensen, S. Cull, M. Golombek, J. Guinn, E. Guinness, T. Heet, R. Kirk, A. Knudson, M. Malin, M. Mellon, A. McEwen, A. Mushkin, T. Parker, F. Seelos IV, K. Seelos, P. Smith, D. Spencer, T. Stein, and L. Tamppari, “Mars Exploration Program 2007 Phoenix Landing Site Selection and Characteristics,” Journal of Geophysical Research 113:E00A03, doi:10.1029/2007JE003021, 2008. 39 . T. Gold, “The Deep, Hot Biosphere,” Proceedings of the National Academy of Sciences of the United States of America 89:6045-6049, 1992. 40 . D.J. Thomas, “Deep Microbes,” Ecology 80:2131-2132, 1999.