Planetary protection issues in advance of human exploration of Mars.

Current planetary quarantine considerations focus on robotic missions and attempt a policy of no biological contamination. The presence of humans on Mars, however, will inevitably result in biological contamination and physical alteration of the local environment. The focus of planetary quarantine must therefore shift toward defining and minimizing the inevitable contamination associated with humans. This will involve first determining those areas that will be affected by the presence of a human base, then verifying that these environments do not harbor indigenous life nor provide sites for Earth bacteria to grow. Precursor missions can provide salient information that can make more efficient the planning and design of human exploration missions. In particular, a robotic sample return mission can help to eliminate the concern about returning samples with humans or the return of humans themselves from a planetary quarantine perspective. Without a robotic return the cost of quarantine that would have to be added to a human mission may well exceed the cost of a robotic return mission. Even if the preponderance of scientific evidence argues against the presence of indigenous life, it must be considered as part of any serious planetary quarantine analysis for missions to Mars. If there is life on Mars, the question of human exploration assumes an ethical dimension.     

Annual solar UV exposure and biological effective dose rates on the Martian surface.

The ultraviolet (UV) environment of Mars has been investigated to gain an understanding of the variation of exposure throughout a Martian year, and link this flux to biological effects and possible survival of organisms at the Martian surface. To gain an idea of how the solar UV radiation varies between different regions, including planned landing sites of two future Mars surface missions, we modelled the total solar UV surface flux throughout one Martian year for two different dust scenarios. To understand the degree of solar UV stress on micro-organisms and/or molecules essential for life on the surface of Mars, we also calculated the biologically effective dose (BED) for T7 and Uracil in relevant wavelength regions at the Martian surface as a function of season and latitude, and discuss the biological survival rates in the presence of Martian solar UV radiation. High T7/Uracil BED ratios indicate that even at high latitudes where the UV flux is significantly reduced, the radiation environment is still hostile for life due to the persisting UV-C component of the flux.     

Planetary protection and the search for life beneath the surface of Mars.

The search for traces of extinct and extant life on Mars will be extended to beneath the surface of the planet. Current data from Mars missions suggesting the presence of liquid water early in Mars' history and mathematical modeling of the fate of water on Mars imply that liquid water may exist deep beneath the surface of Mars. This leads to the hypothesis that life may exist deep beneath the Martian surface. One possible scenario to look for life on Mars involves a series of unmanned missions culminating with a manned mission drilling deep into the Martian subsurface (approximately 3Km), collecting samples, and conducting preliminary analyses to select samples for return to earth. This mission must address both forward and back contamination issues, and falls under planetary protection category V. Planetary protection issues to be addressed include provisions stating that the inevitable deposition of earth microbes by humans should be minimized and localized, and that earth microbes and organic material must not contaminate the Martian subsurface. This requires that the drilling equipment be sterilized prior to use. Further, the collection, containment and retrieval of the sample must be conducted such that the crew is protected and that any materials returning to earth are contained (i.e., physically and biologically isolated) and the chain of connection with Mars is broken.     

太阳电池电路深空探测服役环境与关键技术分析

针对月球、火星、木星等不同的深空探测任务，本文通过在轨服役环境分析，说明了火星探测火星表面光谱计算方法、火星光谱太阳电池设计思路、火星表面除尘技术路线及木星探测低温低光强技术风险。结合工程技术经验，给出了特殊任务应用条件下单片太阳电池推算整板输出功率的计算方法，解决了我国尚无特殊条件的瞬态大太阳模拟器作为整板输出功率测试地面模拟光源的工程难题，为相关科研人员提供参考。     

Selection of sterilization methods for planetary return missions.

Two tasks must be accomplished to provide planetary protection for Mars return missions: (1) sterilization of the scientific module to be landed on Mars and (2) reliable sterilization of all material returned to Earth, while ensuring the scientific integrity of martian samples. This paper examines similarity and differences between these two tasks, and includes a discussion of technological implementation conditions and the nature of terrestrial and hypothesized martian microflora. The feasibility of a number of chemical and physical (ultraviolet and ionizing radiation and heating) methods of sterilization for use on the ground and onboard are discussed and compared. A combination of different methods will probably be selected as the most appropriate for ensuring planetary protection on the return mission.     

Improved environment radiation models

The two components of the space radiation environment, galactic cosmic rays and solar energetic particles, are of special importance for the planning of space missions and designing space vehicles for flights in the inner heliosphere. There is a constant need for developing and updating the models for calculating the fluxes of these particles for purposes of forecasting radiation conditions anticipated for future flights, including missions to the Moon and Mars.     

Science strategy for human exploration of Mars.

The scientific objectives of Mars exploration can be framed within the overarching theme of exploring Mars as another home for life, both for evidence of past or present life on Mars, and as a potential future home for human life. The two major areas of research within this theme are: 1) determining the relationship between planetary evolution, climate change, and life, and 2) determining the habitability of Mars. Within this framework, this paper discusses the exploration objectives for exobiology, climatology and atmospheric science, geology, and martian resource assessment. Human exploration will proceed in four major phases: 1) Precursor missions which will obtain environmental knowledge necessary for human exploration, 2) Emplacement phase which includes the first few human landings where crews will explore the local area of the landing site; 3) Consolidation phase missions where a permanent base will be constructed and crews will be capable of detailed exploration over regional scales; 4) Utilization phase, in which a continuously occupied permanent Mars base exists and humans will be capable of detailed global exploration of the martian surface. The phases of exploration differ primarily in the range and capabilities of human mobility. In the emplacement phase, an unpressurized rover, similar to the Apollo lunar rover, will be used and will have a range of a few tens of kilometers. In the Consolidation phase, mobility will be via a pressurized all-terrain vehicle capable of expeditions from the base site of several weeks duration. In the Utilization phase, humans will be capable of several months long expeditions to any point on the surface of Mars using a suborbital rocket equipped with habitat, lab, and return vehicle. Because of human mobility limitations, it is important to extend the range and duration of exploration in all phases by using teleoperated rover vehicles. Site selection for human missions to Mars must consider the multi-decade time frame of these four phases. We suggest that operations in the first two phases be focused in the regional area containing the Coprates Quadrangle and adjacent areas.     

MEP (Mars Environment Package): toward a package for studying environmental conditions at the surface of Mars from future lander/rover missions.

In view to prepare Mars human exploration, it is necessary to promote and lead, at the international level, a highly interdisciplinary program, involving specialists of geochemistry, geophysics, atmospheric science, space weather, and biology. The goal of this program will be to elaborate concepts of individual instruments, then of integrated instrumental packages, able to collect exhaustive data sets of environmental parameters from future landers and rovers of Mars, and to favour the conditions of their implementation. Such a program is one of the most urgent need for preparing human exploration, in order to develop mitigation strategies aimed at ensuring the safety of human explorers, and minimizing risk for surface operations. A few main areas of investigation may be listed: particle and radiation environment, chemical composition of atmosphere, meteorology, chemical composition of dust, surface and subsurface material, water in the subsurface, physical properties of the soil, search for an hypothesized microbial activity, characterization of radio-electric properties of the Martian ionosphere. Scientists at the origin of the present paper, already involved at a high degree of responsibility in several Mars missions, and actively preparing in situ instrumentation for future landed platforms (Netlander--now cancelled, MSL-09), express their readiness to participate in both ESA/AURORA and NASA programs of Mars human exploration. They think that the formation of a Mars Environment working group at ESA, in the course of the AURORA definition phase, could act positively in favour of the program, by increasing its scientific cross-section and making it still more focused on human exploration.     

Planetary protection issues and the future exploration of Mars.

A primary scientific theme for the Space Exploration Initiative (SEI) is the search for life, extant or extinct, on Mars. Because of this, concerns about Planetary Protection (PP), the prevention of biological cross-contamination between Earth and other planets during solar system exploration missions, have arisen. A recent workshop assessed the necessity for, and impact of, PP requirements on the unmanned and human missions to Mars comprising the SEI. The following ground-rules were adopted: 1) information needed for assessing PP issues must be obtained during the unmanned precursor mission phase prior to human landings; 2) returned Mars samples will be considered biologically hazardous until proven otherwise; 3) deposition of microbes on Mars and exposure of the crew to Martian materials are inevitable when humans land; and, 4) human landings are unlikely until it is demonstrated that there is no harmful effect of Martian materials on terrestrial life forms. These ground-rules dictated the development of a conservative PP strategy for precursor missions. Key features of the proposed strategy include: 1) for prevention of forward contamination, all orbiters will follow Mars Observer PP procedures for assembly, trajectory, and lifetime. All landers will follow Viking PP procedures for assembly, microbial load reduction, and bioshield; and, 2) for prevention of back contamination, all sample return missions will have PP requirements which include fail-safe sample sealing, breaking contact chain with the Martian surface, and containment and quarantine analysis in an Earth-based lab. In addition to deliberating on scientific and technical issues, the workshop made several recommendations for dealing with forward and back contamination concerns from non-scientific perspectives.     

Implementing planetary protection requirements for sample return missions.

NASA is committed to exploring space while avoiding the biological contamination of other solar system bodies and protecting the Earth against potential harm from materials returned from space. NASA's planetary protection program evaluates missions (with external advice from the US National Research Council and others) and imposes particular constraints on individual missions to achieve these objectives. In 1997 the National Research Council's Space Studies Board published the report, Mars Sample Return: Issues and Recommendations, which reported advice to NASA on Mars sample return missions, complementing their 1992 report, The Biological Contamination of Mars Issues and Recommendations. Meanwhile, NASA has requested a new Space Studies Board study to address sample returns from bodies other than Mars. This study recognizes the variety of worlds that have been opened up to NASA and its partners by small, relatively inexpensive, missions of the Discovery class, as well as the reshaping of our ideas about life in the solar system that have been occasioned by the Galileo spacecraft's discovery that an ocean under the ice on Jupiter's moon Europa might, indeed, exist. This paper will report on NASA's planned implementation of planetary protection provisions based on these recent National Research Council recommendations, and will suggest measures for incorporation in the planetary protection policy of COSPAR.     

Planetary protection issues related to human missions to Mars

In accordance with the United Nations Outer Space Treaties [United Nations, Agreement Governing the Activities of States on the Moon and Other Celestial Bodies, UN doc A/RES/34/68, resolution 38/68 of December 1979], currently maintained and promulgated by the Committee on Space Research [COSPAR Planetary Protection Panel, Planetary Protection Policy accepted by the COSPAR Council and Bureau, 20 October 2002, amended 24 March 2005, http://www.cosparhq.org/scistr/PPPolicy.htm], missions exploring the Solar system must meet planetary protection requirements. Planetary protection aims to protect celestial bodies from terrestrial contamination and to protect the Earth environment from potential biological contamination carried by returned samples or space systems that have been in contact with an extraterrestrial environment. From an exobiology perspective, Mars is one of the major targets, and several missions are currently in operation, in transit, or scheduled for its exploration. Some of them include payloads dedicated to the detection of life or traces of life. The next step, over the coming years, will be to return samples from Mars to Earth, with a view to increasing our knowledge in preparation for the first manned mission that is likely to take place within the next few decades. Robotic missions to Mars shall meet planetary protection specifications, currently well documented, and planetary protection programs are implemented in a very reliable manner given that experience in the field spans some 40 years. With regards to sample return missions, a set of stringent requirements has been approved by COSPAR [COSPAR Planetary Protection Panel, Planetary Protection Policy accepted by the COSPAR Council and Bureau, 20 October 2002, amended 24 March 2005, http://www.cosparhq.org/scistr/PPPolicy.htm], and technical challenges must now be overcome in order to preserve the Earth’s biosphere from any eventual contamination risk. In addition to the human dimension of the mission, sending astronauts to Mars will entail meeting all these constraints. Astronauts present huge sources of contamination for Mars and are also potential carriers of biohazardous material on their return to Earth. If they were to have the misfortune of being contaminated, they themselves would become a biohazard, and, as a consequence, in addition to the technical constraints, human and ethical considerations must also be taken into account.     

Overview of current capabilities and research and technology developments for planetary protection

The pace of scientific exploration of our solar system provides ever-increasing insights into potentially habitable environments, and associated concerns for their contamination by Earth organisms. Biological and organic-chemical contamination has been extensively considered by the COSPAR Panel on Planetary Protection (PPP) and has resulted in the internationally recognized regulations to which spacefaring nations adhere, and which have been in place for 40 years. The only successful Mars lander missions with system-level “sterilization” were the Viking landers in the 1970s. Since then different cleanliness requirements have been applied to spacecraft based on their destination, mission type, and scientific objectives. The Planetary Protection Subcommittee of the NASA Advisory Council has noted that a strategic Research & Technology Development (R&TD) roadmap would be very beneficial to encourage the timely availability of effective tools and methodologies to implement planetary protection requirements. New research avenues in planetary protection for ambitious future exploration missions can best be served by developing an over-arching program that integrates capability-driven developments with mission-driven implementation efforts. This paper analyzes the current status concerning microbial reduction and cleaning methods, recontamination control and bio-barriers, operational analysis methods, and addresses concepts for human exploration. Crosscutting research and support activities are discussed and a rationale for a Strategic Planetary Protection R&TD Roadmap is outlined. Such a roadmap for planetary protection provides a forum for strategic planning and will help to enable the next phases of solar system exploration.     

Modern aspects of planetary protection and requirements to sterilization of space hardware.

The viewpoint of working group of Russian experts on the problem of planetary protection for future manned and unmanned Mars mission is presented. Recent data of Martian environment and on survival of terrestrial microorganisms in extreme conditions were used for detailed analysis and overview of planetary protection measures in regard to all possible flight situations including accidental landing. The special emphasis on "Mars-94" mission was done. This analysis resulted in revised formulation of spacecraft sterilization requirements and possible measures for their best implementation. New general combined approach to spacecraft sterilization was proposed. It includes penetrating radiation and heat treatment of spacecraft parts and components which is to be carried out before the final assembly of spacecraft and gaseous radiation sterilization of the whole spacecraft during the flight to Mars (or from Mars for return missions).     

载人火星探测的行星保护

行星保护是影响载人火星探索任务的重要问题之一。载人探测的行星保护包括3个方面,即防止来源于地球的微生物污染目标星球的正向污染防护、防止外来生物对地球的潜在危害的逆向污染防护,以及确保航天员的健康和安全。国际宇航界已经开始针对载人火星探测的行星保护制定政策法规和开展技术研讨。本文介绍了行星保护的定义和法理依据,简要回顾了美国国家航空航天局在“阿波罗登月”中的行星保护措施,并对未来载人火星探测中的主要污染物、污染途径以及污染防护策略进行了初步探讨。     

Biological space experiments for the simulation of Martian conditions: UV radiation and Martian soil analogues.

The survivability of resistant terrestrial microbes, bacterial spores of Bacillus subtilis, was investigated in the BIOPAN facility of the European Space Agency onboard of Russian Earth-orbiting FOTON satellites (BIOPAN I -III missions). The spores were exposed to different subsets of the extreme environmental parameters in space (vacuum, extraterrestrial solar UV, shielding by protecting materials like artificial meteorites). The results of the three space experiments confirmed the deleterious effects of extraterrestrial solar UV radiation which, in contrast to the UV radiation reaching the surface of the Earth, also contains the very energy-rich, short wavelength UVB and UVC radiation. Thin layers of clay, rock or meteorite material were shown to be only successful in UV-shielding, if they are in direct contact with the spores. On Mars the UV radiation climate is similar to that of the early Earth before the development of a protective ozone layer in the atmosphere by the appearance of the first aerobic photosynthetic bacteria. The interference of Martian soil components and the intense and nearly unfiltered Martian solar UV radiation with spores of B. subtilis will be tested with a new BIOPAN experiment, MARSTOX. Different types of Mars soil analogues will be used to determine on one hand their potential toxicity alone or in combination with solar UV (phototoxicity) and on the other hand their UV protection capability. Two sets of samples will be placed under different cut-off filters used to simulate the UV radiation climate of Mars and Earth. After exposure in space the survival of and mutation induction in the spores will be analyzed at the DLR, together with parallel samples from the corresponding ground control experiment performed in the laboratory. This experiment will provide new insights into the principal limits of life and its adaptation to environmental extremes on Earth or other planets which and will also have implications for the potential for the evolution and distribution of life.     

Estimation and assessment of Mars contamination.

Since the beginning of the exploration of Mars, more than fourty years ago, thirty-six missions have been launched, including fifty-nine different space systems such as fly-by spacecraft, orbiters, cruise modules, landing or penetrating systems. Taking into account failures at launch, about three missions out of four have been successfully sent toward the Red Planet. The fact today is that Mars orbital environment includes orbiters and perhaps debris, and that its atmosphere and its surface include terrestrial compounds and dormant microorganisms. Coming from the UN Outer Space Treaty [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 (the "Outer Space Treaty") referenced 610 UNTS 205 - resolution 2222(XXI) of December 1966] and according to the COSPAR planetary protection policy recommendations [COSPAR Planetary Protection Policy (20 October 2002), accepted by the Council and Bureau, as moved for adoption by SC F and PPP, prepared by the COSPAR/IAU Workshop on Planetary Protection, 4/02 with updates 10/0, 2002], Mars environment has to be preserved so as not to jeopardize the scientific investigations, and the level of terrestrial material brought on and around Mars theoretically has to comply with this policy. It is useful to evaluate what and how many materials, compounds and microorganisms are on Mars, to list what is in orbit and to identify where all these items are. Considering assumptions about materials, spores and gas location and dispersion on Mars, average contamination levels can be estimated. It is clear now that as long as missions are sent to other extraterrestrial bodies, it is not possible to keep them perfectly clean. Mars is one of the most concerned body, and the large number of missions achieved, on-going and planned now raise the question about its possible contamination, not necessarily from a biological point of view, but with respect to all types of contamination. Answering this question, will help to assess the potential effects of such contamination on scientific results and will address concerns relative to any ethical considerations about the contamination of other planets.     

Regenerative life support systems--why do we need them?

Human exploration of the solar system will include missions lasting years at a time. Such missions mandate extensive regeneration of life support consumables with efficient utilization of local planetary resources. As mission durations extend beyond one or two years, regenerable human life support systems which supply food and recycle air, water, and wastes become feasible; resupply of large volumes and masses of food, water, and atmospheric gases become unrealistic. Additionally, reduced dependency on resupply or self sufficiency can be an added benefit to human crews in hostile environments far from the security of Earth. Comparisons of resupply and regeneration will be discussed along with possible scenarios for developing and implementing human life support systems on the Moon and Mars.     

Planetary protection issues for sample return missions.

Sample return missions from a comet nucleus and the Mars surface are currently under study in the US, USSR, and by ESA. Guidance on Planetary Protection (PP) issues is needed by mission scientists and engineers for incorporation into various elements of mission design studies. Although COSPAR has promulgated international policy on PP for various classes of solar system exploration missions, the applicability of this policy to sample return missions, in particular, remains vague. In this paper, we propose a set of implementing procedures to maintain the scientific integrity of these samples. We also propose that these same procedures will automatically assure that COSPAR-derived PP guidelines are achieved. The recommendations discussed here are the first step toward development of official COSPAR implementation requirements for sample return missions.     

美国2020火星车着陆区遴选进展及对2020中国火星任务着陆探测部分的一些思考

总结了近20年来火星探测的重要发现以及生命、气候和地质3个方面尚未解决的关键科学问题;介绍了美国国家航空航天局(NASA)2020火星探测任务的科学目标、科学载荷和着陆区选择的工程条件限制,并重点分析了经过3次着陆区选择研讨会,上百位行星科学家投票选取的排名前3的预选着陆区的地质情况。在此基础上,提出了对我国2020年火星任务的着陆探测部分的一些思考,并根据不同的任务目标(聚焦生命、气候和地质问题;支持载人火星探测的资源勘察;工程技术验证)提出了3个候选着陆区。     

Use of lunar regolith as a substrate for plant growth.

Regenerative Life Support Systems (RLSS) will be required to regenerate air, water, and wastes, and to produce food for human consumption during long-duration missions to the Moon and Mars. It may be possible to supplement some of the materials needed for a lunar RLSS from resources on the Moon. Natural materials at the lunar surface may be used for a variety of lunar RLSS needs, including (i) soils or solid-support substrates for plant growth, (ii) sources for extraction of essential, plant-growth nutrients, (iii) substrates for microbial populations in the degradation of wastes, (iv) sources of O2 and H2, which may be used to manufacture water, (v) feed stock materials for the synthesis of useful minerals (e.g., molecular sieves), and (vi) shielding materials surrounding the outpost structure to protect humans, plants, and microorganisms from harmful radiation. Use of indigenous lunar regolith as a terrestrial-like soil for plant growth could offer a solid support substrate, buffering capacity, nutrient source/storage/retention capabilities, and should be relatively easy to maintain. The lunar regolith could, with a suitable microbial population, play a role in waste renovation; much like terrestrial waste application directly on soils. Issues associated with potentially toxic elements, pH, nutrient availability, air and fluid movement parameters, and cation exchange capacity of lunar regolith need to be addressed before lunar materials can be used effectively as soils for plant growth.