Planetary Protection Issues and Future Mars Missions
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NASA Conference Publication 10086 Planetary Protection Issues and Future Mars Missions Edited by D. L. DeVincenzi Ames Research Center Moffett Field, California H. P. Klein Santa Clara University Santa Clara, Cafifomia J. R. Bagby Missouri State Dept. of Health Jefferson City, Missouri Proceedings of a workshop held at NASA Ames Research Center, Moffett Field, Cafifornia March 7-9, 1990 NASA NationalAeronauticsand SpaceAdministration Ames Research Center MoffettField,California94035-1000 1991 \ PREFACE This is the final report of a Workshop on "Planetary Protection Issues and the Human Exploration of Mars" conducted by NASA's Ames Research Center on March 7-9, 1990. It was jointly sponsored by the Office of Exploration and the Life Science Division both at NASA HQ. A preliminary report was presented at the 1990 meeting of the Commission on Space Research (COSPAR) in The Hague, and a paper on the subject is in press in Advances in Space Research. Following the announcement of the Space Exploration Initiative (SEI) by the President, NASA embarked on a series of mission design studies to develop various options for the achievement of the goals of future robotic and human exploration of the Moon and Mars. During the course of these studies, it became clear that useful guidelines did not exist for mission planners and designers to evaluate the impact of existing Planetary Protection policy on mission architectures for either robotic precursor or manned missions to Mars. Therefore, this Workshop was conceived to develop an interim set of strawman guidelines for use by mission planners until official policy for the various missions under consideration could be established. In order to achieve this goal, the Workshop considered both the possibility of forward contamination of Mars by terrestrial microbes carded on Mars-bound vehicles as well as the possibility of back contamination of Earth by species present in returned Mars samples. In addition to the scientific issues, the Workshop also attempted to assess the impact of non-scientific factors (including public, legal, international, societal, etc.) surrounding Planetary Protection on the implementation of exploration missions. This report contains strawman guidelines for Planetary Protection requirements for exploration missions, and also a series of recommendations for future research and development activities which may lead to a definitive settlement of the Planetary Protection issue. The guidelines and considerations presented herein are not to be taken as official NASA policy but rather as interim strawman guidelines, to be used for mission design and other programmatic studies until official policy is established. Official policy for Planetary Protection for SEI missions will be set by NASA in consultation with the National Academy of Sciences and with the concurrence of the international scientific community under the auspices of COSPAR. i TABLE OF CONTENTS Page Preface ..... ..................................................... 1 Executive Summary .................................................. i_ Introduction ....................................................... 1 Background ....................................................... 6 Scientific Issues .................................................... 16 Societal and Legal Issues .............................................. 29 Summary Recomn_ndations ........................................... 36 Acknowledgements ................................................. 39 Appendices B_Jbgraphy .................................................. 40 ParticipantList ................................................. 50 Workshop Agenda .............................................. 52 Glossary of Acronyms .............. ............................... 54 ii EXECUTIVE SUMMARY This report describes the results from the Workshop on "Planetary Protection Issues and the Human Exploration of Mars." Mars is a prime target in the continuing exobiological exploration of the solar system lor clues concerning the origin, evolution, and distribution of life and life-related molecules. Although the Viking missions greatly expanded our knowledge of the planet, they were limited, in their search for organic chemicals and extant life, to examining surface samples from two fixed sites chosen more for spacecraft safety than scientific interest. In addition, extrapolation of Viking data from the two landing sites to the planet as a whole is not possible. Therefore, questions about the nature and extent of prebiotic chemical evolution, possible odgin of life during a more clement era, and even the existence of extant life still remain open. Although the existence of life on present-day Mars is improbable, it cannot be ruled out with certainty. Therefore, Planetary Protection (PP), which is concerned with prevention of harmful cross-contamination of planets during space exploration, must be addressed in the planning of future missions to Mars. There are two primary issues that must be considered: 1) forward contamination, which refers to upsetting a natural ecosystem that may exist on Mars by terrestrial microbes carried to the planet on spacecraft; and, 2) back contamination, which refers to upsetting the Earth's ecosystems by life-forms that may be present in a returned Mars sample. Insufficient and incomplete knowledge about Mars prevents an accurate assessment of exact risks in either case. As a result, and until additional data about Mars is obtained, a conservative approach is recommended in planning future missions. This is an important point because implementation of PP requirements can affect mission design, hardware, and costs. PP requirements for Space Exploration Initiative (SEI) missions or Mission From Planet Earth (MFPE) were studied during a NASA-sponsored workshop. The purposes of the workshop were to identify key PP issues for SEI and to propose strawman guidelines for use in development of mission architectures. These guidelines would be preparatory to the development of official PP policy for SEI by NASA and the National Academy of Sciences, with the concurrence of the international scientific community through the Commission on Space Research (COSPAR). iii The U.S. is signatory to a 1967 international treaty, monitored by COSPAR, which establishes the requirement to avoid harmful contamination of planets during space exploration. The PP policy revision of 1984 by NASA and COSPAR established the framework for developing PP guidelines for each of the individual missions that make up the SEI precursor mission set. This revised policy allows for tailoring of the implementing procedures to the type of mission design (lander, orbiter, sample return) being contemplated. Interim strawman guidelines for the SEI mission set were developed at the workshop on the basis of that framework. In arriving at a set of strawman guidelines, it was assumed that PP issues will need to be dealt with in the precursor phase because deposition of microbes on Mars and exposure of the crew to Mars surface material will be inevitable once humans land. For the purposes of this workshop, the precursor mission set and sequence was assumed to be: Mars Observer, Global Network, Local Rover/Sample Return, High Resolution Orbiter, and Long-Range Rovers, as specitied in the Report of the 90-day Study on Human Exploration of the Moon and Mars. However, it should be noted that this mission set has already undergone change and probably will continue to do so. For planning purposes, it was also assumed that Mars samples were hazardous until shown by testing to be safe, and that human landings would be unlikely until sample safety was demonstrated. Based upon these assumptions, the following interim PP strawman guidelines are recommended for the various types of precursor missions: 1) To prevent forward contamination, all orbiters should be assembled under clean-room conditions, their trajectories should be biased to avoid unplanned impact, and they should meet certain orbital lifetime requirements. Additionally, all landers (including rovers, penetrators, surface stations, etc.) should be assembled under clean-room conditions, enclosed in a bio-shield, and treated to reduce microbial loads to acceptable limits. For landers, there might be other requirements imposed by biology or chemistry investigations that might be part of the payload. These are, in fact, the same guidelines that were used for the Mars Observer and Viking missions. 2) To prevent back contamination, all sample return missions should have landers that are encapsulated in a bio-shield and treated to reduce the microbial load to acceptable limits. The sample should be placed in a hermetically sealed container, preserved under Mars ambient conditions, and the contact chain with Mars' surface should be broken in order to prevent the transfer of un-contained surface material to the Earth on the exterior of the return vehicle. In addition, the sample should be returned to a high-containment facility on the Earth and subjected to a comprehensive quarantine protocol to investigate whether or not harmful constituents are iv i present. These guidelines have not been reviewed by the National Academy of Sciences, but have been discussed in the international forum of the 1988 COSPAR meeting. In addition to adopting these strawman guidelines, several other issues relevant to PP and the SEI were discussed at the workshop and require further analysis and evaluation. Some examples of the discussion are summarized