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Post-Viking Biological Investigations of Mars Committee on Planetary Biology and Chemical Evolution 'Space Science Board 'Assembly of Mathematical and Physical Sciences National Research Council NATIONAL ACADEMY OF SCIENCES Washington, D.C. 1977 NAS-NAE OCTe 1977, LIBRARY

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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the Councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the Committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to pro- cedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.

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FOREWORD As the Viking mission approached, the Space Science Board become increas- ingly aware that the problems associated with questions of possible biology and prebiotic chemistry on other planets in the solar system were different from those involved with the use of space to study problems of terrestrial biology and different from the medical and biological problems attending the presence of man in space. Accordingly, in 1973 the Board established an Ad Hoc Exobiology Panel under its Committee of Space Biology and Medicine. In 1975 the Panel became standing, and in 1976 it was constituted as a sepa- rate Committee of the Board and renamed the Committee on Planetary Bi- ology and Chemical Evolution. One major responsibility assigned by the Board to the Panel and then to the Committee has been to monitor the progress of the biologically relevant experiments on Viking, both before launch and after the landing, and to develop a recommended strategy for post-Viking biological investigation of Mars. This report constitutes their evaluation and their recommendations. The report has been reviewed in detail and in toto by the Board and was ap- proved unanimously on April 5, 1977. Therefore, both the findings and the recommendations in the report represent the views of the Space Science Board. A. G. w. CAMERON, Chairman Space Science Board III

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PREFACE The current Viking mission emphasizes the prominent position that has been accorded to Mars in the exploration of our solar system. One reason for this prominence, and for Viking, is that Mars, among all the extraterrestrial ob- jects orbiting the sun, is deemed the most likely to have, or to have had, living inhabitants. The discovery and characterization of present or prior life on Mars would, in the opinion of many, constitute a scientific finding of un- paralleled significance to biology, and it would constitute a finding of major importance to planetology, especially to an understanding of the evolution of differences among the planets Venus, Earth, and Mars. For these reasons Viking carried several experiments that were designed to yield information of direct and indirect biological significance. And it is for these reasons that the biological implications of the Viking findings must be weighed in formu- lating the strategy for the next stages of the exploration of the solar system. The Space Science Board charged our Committee with evaluating the bio- logical implications of the Viking mission, and it requested us to develop recommendations for post-Viking biological investigations of Mars. This report constitutes both our evaluation and our recommended strategy. As our report developed, its contents were made available to the Board's Committee on Planetary and Lunar Exploration (COMPLEX), which is cur- rently completing a report of its recommendations on science strategy in general for the inner solar system, including Mars. About two years ago, the Space Science Board decided that Board reports on strategy for future space science should state the high priority scientific questions that require resolution and the sequence in which they should be investigated and should give some indication as to what measurements need to be made, with what precision, and by what methods. Equally important, the Board decided that the strategy reports should avoid to the maximum extent possible describing strategies in terms of specific flight missions, spe- cific payloads, and specific tactics for missions. Our Committee's report was prepared to be consistent with that policy. As specific missions are conceived and developed by NASA, the strategy documents will be used by the Board (and hopefully by NASA, the Congress, and the public as well) to gauge the scientific importance and appropriateness of the specific missions and their experimental payloads.

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The Committee obtained the necessary background for its tasks in a variety of ways. First, it met five times in 1975 and 1976 with members of the Viking Biology Team (H. P. Klein, N. H. Horowitz, J. Lederberg, G. V. Levin, V. I. Oyama, A. Rich, and their colleagues) in Washington, D.C., and at Boston University, the Jet Propulsion Laboratory, and the Ames Research Center. The meetings before the Viking landings were devoted to the nature of the instruments and the design and methods of the biology and organic analysis experiments, to the results obtained when the experiments were con- ducted on terrestrial soil samples, and to the tactics that the Biology Team expected to apply to the diagnosis of data returned from the surface of Mars. The meetings after the landings were devoted to discussions of the findings from Mars and their interpretation and to discussions of ongoing Earth-based simulation experiments. Second, the Committee attended two and a half days of presentations at the Jet Propulsion Laboratory and the California Institute of Technology on the results of the other Viking experiments. Third, in the fall of 1976, members of the Committee participated in two meetings of COMPLEX, meetings that were concerned with the development of a strategy for the exploration of the entire inner solar system (Mercury, Venus, Earth, Mars, Moon, asteroids, and comets). Finally, we received information and contributions to our understanding of the facts and their interpretation from consultants invited to our meetings and from personal communications with Viking scientists and other colleagues. Specifically, in this regard, we would like to acknowledge the contributions of N. Anderson, K. Biemann, F. Brown, J. Buchanan, S. Chang, F. Cocks, D. DesMarais, D. DeVincenzi, C. Farmer, N. Horowitz, D. Hunten, R. Johnson, H. Kieffer, H. Klein, J. Lawless, J. Martin, E. Merek, T. Owen, R. Setlow, G. Soffen, P. Toulmin, T. Wydeven, and R. Young, as well as members of the Space Science Board. In addition, the Committee wishes to acknowledge the invaluable role played by its Executive Secretary, Mr. Milton Rosen, and his staff in orga- nizing and guiding our meetings and in the preparation of our report. This report represents the unanimous view of the Committee. We hope it conveys some sense of the excitement we have felt over the privilege of being accorded an intimate view of the Viking mission, and we hope that it conveys a sense of our enthusiasm for the biological questions that future missions to Mars will surely address over the next decade. PETER MAZUR, Chairman Committee on Planetary Biology and Chemical Evolution vi

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Space Science Board A. G. W. CAMERON, Chairman PETER L. BENDER RALPH BERNSTEIN FRANCIS P. BRETHERTON NEAL S. BRICKER STIRLING A. COLGATE HARLYN O. HALVORSON FRANCIS S. JOHNSON CHARLES F. KENNEL LYNN MARGULIS PETER MAZUR PETER MEYER EUGENE N. PARKER ROBERT PHINNEY VERA C. RUBIN FREDERICK L. SCARF RICHARD B. SETLOW IRWIN I. SHAPIRO HARLAN J. SMITH GERALD J. WASSERBURG SHELDON WOLFF NAS Staff MILTON W. ROSEN, Executive Secretary VII

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Committee on Planetary Biology and Chemical Evolution* PETER MAZUR, Chairman Oak Ridge National Laboratory ELSO S. BARGHOORN Harvard University CHARLES D. COX University of Massachusetts HARLYN O. HALVORSON Brandeis University THOMAS H. JUKES University of California, Berkeley ISSAC R. KAPLAN University of California, Los Angeles LYNN MARGULIS Boston University 'Formerly Exobiology Panel. viii

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CONTENTS INTRODUCTION I SUMMARY OF VIKING FINDINGS RELEVANT TO MARTIAN BIOLOGY II POST-VIKING BIOLOGY STRATEGY FOR MARS 12 III RECOMMENDATIONS ON POST-VIKING BIOLOGY STRATEGY FOR MARS 23 REFERENCES 25 IX