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THE SEARCH FOR LIFE'S ORIGINS Progress and Future Directions in Plan eta ry Biology and Chemical Evolution SPACE STUDIES BOARD Committee on Planetary Biology and Chemical Evolution Commission on Physical Sciences, Mathematics, and Applications National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1990
NATIONAL ACADEMY PRESS · 2101 Constitution Avenue, N.W. · Washington, D.C. 20418 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 compe- tences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures 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. Support for this project was provided by Contract NASW 4102 between the National Academy of Sciences and the National Aeronautics and Space Administration. Library of Congress Cataloging-in-Publication Data The Search for life's origins: progress and future directions in planetary biology and chemical evolution / Committee on Planetary Biology and Chemical Evolution. p. cm. Includes bibliographical references. Includes index. ISBN 0-309-04246-1 1. Life Origin. 2. Space biology. 3. Chemical evolution. I. National Research Council (U.S.). Committee on Planetary Biology and Chemical Evolution. QH325.S4 18 1990 577 dc20 Copyright @) 1990 by the National Academy of Sciences 90-36899 CIP No part of this book may be reproduced by any mechanical, photographic, or electronic process, or in the form of a phonographic recording, nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use, without written permission from the publisher, except for the purposes of official use by the U.S. government. Printed in the United States of America
COMMITTEE ON PLANETARY BIOLOGY AND CHEMICAL EVOLUTION HAROLD P. KLEIN, Santa Clara University, Chairman JOHN CRONIN, Arizona State University GEORGE FOX, University of Houston DIANA FRECKMAN, University of California at Riverside RICHARD HANSON, University of Minnesota HYMAN HARTMAN, University of California at Berkeley ERIC HERBST, Duke University WILLIAM IRVINE, University of Massachusetts JENNIFER KITCHELL, University of Michigan ANDREW KNOLL, Harvard University JOHN ORO, University of Houston TOBIAS OWEN, State University of New York at Stony Brook NORMAN PACE, Indiana University DAVID RAUP, University of Chicago WILLIAM REINERS, University of Wyoming NORMAN SLEEP, Stanford University JILL TARTER, University of California at Berkeley DAVID USHER, Cornell University ROBERT WOODMANSEE, Colorado State University Consultants SHERWOOD CHANG, NASA Ames Research Center BRUCE FEGLEY, JR., Massachusetts Institute of Technology MITCHELL SOGIN, National Jewish Center K. D. STEWART, Miami University XANDIER THIELENS, University of California at Berkeley CARL WOESE, University of Illinois MICHAEL YARUS, Colorado University Space Studies Board Stay JOYCE M. PURCELL, Executive Secretary MELANIE M. GREEN, Secretary . . .
SPACE STUDIES BOARD LOUIS J. LANZEROTTI, AT&T Bell Laboratories, Chairman PHILIP ABELSON, American Association for the Advancement of Science JOSEPH A. BURNS, Cornell University JOHN R. CARRUTHERS, INTEL ANDREA K. DUPREE, Center for Astrophysics JOHN A. DUTTON, Pennsylvania State University LARRY W. ESPOSITO, University of Colorado JAMES P. FERRIS, Renssalear Polytechnic Institute HERBERT FRIEDMAN, Naval Research Laboratory RICHARD L. GARWIN, IBM T. J. Watson Research Center RICCARDO GIACCONI, Space Telescope Science Institute NOEL W. HINNERS, Martin Marietta Corporation JAMES R. HOUCK, Cornell University DAVID A. LANDGREBE, Purdue University JOHN W. LEIBACHER, National Solar Observatory ELLIOTT C. LEVINTHAL, Stanford University MICHAEL MENDILLO, Boston University WILLIAM J. MERRELL, JR., Texas A&M University RICHARD K. MOORE, University of Kansas ROBERT H. MOSER, NutraSweet Corporation NORMAN F. NESS, Bartol Research Institute MARCIA NEUGEBAUER, Jet Propulsion Laboratory JOSEPH M. REYNOLDS, Louisiana State University SALLY K. RIDE, California Space Institute ROBERT F. SEKERKA, Carnegie-Mellon University MARK SETTLE, ARCO Oil and Gas Company L. DENNIS SMITH, University of California at Irvine BYRON D. TAPLEY, Center for Space Research IV
COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND APPLICATIONS* NORMAN HACKERMAN, Robert A. Welch Foundation, Chairman GEORGE F. CARRIER, Harvard University HERBERT D. DOAN, The Dow Chemical Company (retired) DEAN E. EASTMAN, IBM T. J. Watson Research Center MARYE ANNE FOX, University of Texas GERHART FRIEDLANDER, Brookhaven National Laboratory PHILLIP A. GRIFFITHS, Duke University. NEAL F. LANE, Rice University CHRISTOPHER F. MCKEE, University of California at Berkeley RICHARD S. NICHOLSON, American Association for the Advancement of Science JEREMIAH P. OSTRIKER, Princeton University Observatory ROY F. SCHWITTERS, Superconducting Super Collider Laboratory LARRY L. SMARR, University of Illinois at Urbana-Champaign NORMAN METZGER, Executive Director *The project that is the subject of this report was initiated under the predecessor group of the Commission on Physical Sciences, Mathematics, and Applications, which is the Commission on Physical Sciences, Mathematics, and Resources, whose members are listed in the appendix. v
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Frank Press is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Samuel O. Thier is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's pur- poses of furthering knowledge and advising the federal government. Functioning in accor- dance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engi- neering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council. Vl
Foreword One of the areas of interest to the Space Studies Board has long been the field of exobiology. This multidisciplinary endeavor seeks to understand the interactions between a developing and evolving biological system and the physical environments within which these evolutionary processes take place. Over the years, through its Committee on Planetary Biology and Chemical Evolution, the board has developed strategies for studies in this area, has evaluated the prospects for extant biology elsewhere in the solar system, and has provided guidelines for the protection, of both the Earth and other bodies, from the possible contamination resulting from space missions (Post-Viking Biological Investigations of Mars t19771; Recom- mendations on Quarantine Policy for Mars, Jupiter, Saturn, Uranus, Nep- tune, and Titan t19781; Origin and Evolution of LifeImplications for the Planets: A Scientific Strategy for the 1980s [198111. A decade has passed since the board last evaluated the status of this field a decade during which many exciting new observations and discov- eries have been made, both in space missions and in ground-based laborato- ries and observatories. Among these may be cited new information from the Comet Halley, Voyager, and Infrared Astronomy Satellite missions; from field studies indicating the possible influences of extraterrestrial fac- tors on biological evolution; and from laboratory studies on the replication of simple macromolecules. These and many other developments prompted the board to initiate a new study of planetary biology and chemical evolu- tion in order to identify opportunities for conducting such investigations in space. The current report is the result of deliberations that began with a summer study at Snowmass, Colorado, in August of 1986 and continued until the end of 1988. The resulting document includes discussions of the evolution . . V11
. ~ . Vlll FOREWORD of organic compounds in the interstellar medium and solar nebula; assess- ment of the information regarding prebiotic conditions on the early Earth and of the fossil record of early terrestrial organisms; assessment of our understanding of the surface and subsurface of Mars with a view toward paleontological investigations of that planet; evaluation of the status of laboratory investigations on the origin and early evolution of life on Earth; and discussion of techniques to find evidence of biological activity in other solar systems. These considerations are particularly important at this time as the nation approaches and plans for a period of increasingly vigorous scientific inves- tigations in space over the next decade and beyondon solar-system mis- sions and from orbiting observational platforms. LOUIS J. LANZEROTTI, Chairman Space Studies Board
Contents EXECUTIVE SUMMARY 1 OVERVIEW............ 2 THE COSMIC HISTORY OF THE BIOGENIC ELEMENTS AND COMPOUNDS ............................................ . . 3 EARLY PLANETARY ENVIRONMENTS: IMPLICATIONS FOR CHEMICAL EVOLUTION AND THE ORIGIN OF LIFE ......... 4 THE ORIGIN OF LIFE ................. 5 THE EVOLUTION OF CELLULAR AND MULTICELLULAR LIFE ............... 6 SEARCH FOR LIFE OUTSIDE THE SOLAR SYSTEM 7 MAJOR RESEARCH RECOMMENDATIONS 8 SPACE SCIENCE PROGRAM AND POLICY ISSUES REFERENCES . GLOSSARY . . APPENDIX . . INDEX 16 21 56 IX 78 91 105 123 130 133 135 139 141
THE SEARCH FOR LIFE' S ORIGINS