EVOLUTION OF HYDROTHERMAL ECOSYSTEMS ON EARTH (AND MARS?) The Ciba Foundation is an international scientific and educational charity (Registered Charity No. 313574). It was established in 1947 by the Swiss chemical and pharmaceutical company of CIBA Limited-now Ciba-Geigy Limited. The Foundation operates independently in London under English trust law. The Ciba Foundation exists to promote international cooperation in biological, medical and chemical research. It organizes about eight international multidisciplinary symposia each year on topics that seem ready for discussion by a small group of research workers. The papers and discussions are published in the Ciba Foundation symposium series. The Foundation also holds many shorter meetings (not published), organized by the Foundation itself or by outside scientific organizations. The staff always welcome suggestions for future meetings. 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Goode. p. cm. -+Ciba Foundation Symposium; 202) “Symposium on Evolution of Hydrothermal Ecosystems on Earth (and Mars?), held at the Ciba kundation, London, January 3GFebruary 1, 1996”-P. Includes bibliographical references and indexes. ISBN 0 471 96509 X (alk. paper) 1. Lifdrigin4ngresses. 2. Hot spring ecology- Congresses. 3. Exobiology-Congresses. I. Bock, Gregory. 11. Goode, Jamie. 111. Symposium on Evolution of Hydrothermal Ecosystems on Earth (and Mars?) (1996: Ciba Foundation) IV Series. QH3253963 1996 96-31351 574.5‘263-dc20 CIP British Ljbmry Cak&g&g in Publication Da& A catalogue record for this book is available from the British Library ISBN 0 471 96509 X Typeset in 10/12pt Garamond by DobbieTypesetting Limited,Tavistock, Devon. Printed and bound in Great Britain by Biddles Ltd, Guildford. This book is printed on acid-freep aper responsibly manufactured from sustainable forestation, for which at least two trees are planted for each one used for paper production. ATMOSPHERE 4.2 Ga 510 bars of CO, ,‘,,‘$,, H2 /’,’/.$,’ co - - - - - - - - f -b 1 rnrn Molecular phylogenetic studies show that the deepest branches of the ‘universal tree of life’ are occupied by hyperthermophiles. Either life arose at high temperatures (one possible model for this is shown above), or only the hyperthermophiles survived the ‘late heavy bombardment’ during the final stages of accretion of the Earth. Thermal springs were abundant on the early Earth and their deposits are well known to mineral explorers because of the contained gold, copper and other valuable metals; they are a source of palaeobiological information that has yet to be tapped. All the indications are that such springs also would have been abundant on Mars early in its history; their deposits are a prime target for the exploration for former life on that planet. Thefgure irmodij5edfrom M.J , XurreNandA .J . Hall ( 1996) The emergence of Iqefrom iron monorulphidt bubbler at 1 snbmarine lydrothermal redox andpHfront. Journal ofthe Geological Society of London (in prerr) . V Contents Symposium on Euolution ~lydmthemalecosyskmso n Earth @ndM ars?))h eldatthe Ciba Foundation, London)J anuary PcFebnrary 1 1996 Editors: Gregoy R. Bock (Organkeer)a nd Jamie A. Goode This symposium was basedon aproposal made & Malcolm Walter, David Des Marais, Jack firmerand Nan9 Hinman K. 0. Stetter Hyperthermophiles in the history of life 1 Discussion 11 General discussion I Beehive diffusers 19 How much oxygen was there in the Archaean atmosphere? 20 S. M. Barns, C. F. Delwiche, J. D. Palmer, S. C. Dawson, K. L. Hershberger and N. R. Pace Phylogenetic perspectives on microbial life in hydrothermal ecosystems, past and present 24 Distusion 32 E. L. Shock Hydrothermal systems as environments for the emergence of life 40 Discursion 52 R.W. Henley Chemical and physical context for life in terrestrial hydrothermal systems: chemical reactors for the early development of life and hydrothermal ecosystems 61 Dircwsion 76 D. J. Des Marais Stable light isotope biogeochemistry of hydrothermal systems 83 Ducmion 94 A. Pentecost High temperature ecosystems and their chemical interactions with their environment 99 Discmion 108 M. R. Walter Ancient hydrothermal ecosystems on Earth: a new palaeobiological frontier 112 Discwsion 127 vii ... Vlll CONTENTS N. H. Trewin The Rhynie cherts: an early Devonian ecosystem preserved by hydrothermal activity 131 Dicmion 145 S. L. Cady and J. D. Farmer Fossilization processes in siliceous thermal springs: trends in preservation along the thermal gradient 150 Discussion 170 R. E. Summons, L. L. Jahnke and B. R. T. Simoneit Lipid biomarkers for bacterial ecosystems: studies of cultured organisms, hydrothermal environments and ancient sediments 174 Dicmion 193 General discussion I1 Marine hydrothermal systems 195 A. H. Knoll and M. R.Walter The limits of palaeontological information: finding the gold among the dross 198 Discussion 210 J. F. Huntington The role of remote sensing in finding hydrothermal mineral deposits on Earth 214 Discusion 231 R. A. Horn Exploration strategies for hydrothermal deposits 236 Discmion 246 M. H. Cam Water on early Mars 249 Discussion 265 General discussion 111 Catastrophic fluvial systems and potential hydrothermal systems in the ancient history of Mars 268 J. D. Farmer Hydrothermal systems on Mars: an assessment of present evidence 273 Discmion 295 General discussion IV Martian stable isotopes: volatile evolution, climate change and exobiological implications 300 P. C.W. Davies The transfer of viable microorganisms between planets 304 Di.rcmion 314 M. R.Walter Summing-up 318 Index of contributors 321 Subject index 325 Participants S. M. Barns Environmental Molecular Biology, M888, Life Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA S. L. Cady NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035-1000, USA M. H. Carr US Geological Survey, MS-975,345 Middlefield Road, Menlo Park, CA 94025, USA D. Cowan Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WClE 6BT, UK P. C. W! Davies Department of Physics and Mathematical Physics,The University of Adelaide, Adelaide, SA 5005, Australia D. J. Des Marais Space Science Division, NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035-1000, USA J. D. Farmer NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035- 1000, USA W. F. Giggenbach Institute of Geological and Nuclear Sciences, PO Box 31312, Lower Hutt, New Zealand R.W. Henley Etheridge Henley Williams, PO Box 250, Deakin West, ACT 2600, Australia R. A. Horn INCO Limited, 2060 Flavelle Boulevard, Missisauga, Ontario, Canada L5K 129 J. F. Huntington CSIRO Exploration and Mining, Mineral Mapping Technologies Group, PO Box 136, North Ryde, NSW 2113, Australia B. M. Jakosky Laboratory for Atmospheric and Space Physics and Department of Geological Science, University of Colorado, Boulder, CO 80309-0392, USA iX x PARTICIPANTS A. H. Knoll Botanical Museum, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA R. Kuzmin Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Kosygin Sneet 19, Moscow 177975, Russia E. G. Nisbet Department of Geology, Royal Holloway, University of London, Egham, Surrey,TW20 OEX, UK R. J. Parkes Department of Geology, University of Bristol, Bristol, BS8 IRJ, UK A. Pentecost Division of Life Sciences, King's College London, Campden Hill Road, LondonW8 7AH, UK C. L. Powell Department of Geology and Petroleum Geology, Meston Building, Kings College, Aberdeen, AB9 ZUE, UK M. J. Russell Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ UK H. Sakai 1-4-7-1508 Seishim-cho, Edogawa-ku, Tokyo, Japan E. L. Shock Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences,Washington University, St Louis, MO 63130, USA B. R.T. Simoneit College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-5503, USA K. 0. Stetter Lehrstuhl fur Mikrobiologie, Universitat Regensburg, Universitatstrasse3 1, D-93053 Regensburg, Germany R. E. Summons Australian Geological Survey Organisation, GPO Box 378, Canberra, ACT 2601, Australia N. H. Trewin Department of Geology and Petroleum Geology, Meston Building, Kings College, University of Aberdeen, Aberdeen AB24 3UE, UK M. R.Walter School of Earth Sciences, Macquarie University, North Ryde, NSW 2109 and Rix & Walter Pty Ltd, 265 Murramarang Road, Bawley Point, NSW 2539, Australia Preface The purpose of the meeting which lead to the production of this book was to bring together a diverse group of specialists who have complementary skills in the search for the earliest life on Earth, for its equivalents on Mars, and ultimately for the origin of life. Biologists write about ‘the universal tree of life’, and believe that they can recognise the deepest roots of that tree, and that these are thermophilic microorganisms. Many geochemists think that this makes sense in terms of what geologists know about the abundance of hydrothermal systems on the early Earth and in terms of the potent chemical reactions possible in such systems. Geologists have the opportunity and the techniques to test these hypotheses. Despite what is sometimes thought by biologists, there are ways for geologists to find a fossil record of the different domains or super- kingdoms of life thought to lie near the base of the universal tree, and thus both to test the phylogenetic hypotheses and to calibrate them against time. Well preserved rock successions 3.5 Ga old have yielded the oldest evidence of life on Earth, and even older successions are now known. The search for evidence of life in these successions has barely begun, and essentially no attention has yet been paid to the hydrothermal sys- tems that were the focus of the meeting. Going beyond the Earth, one of the greatest exploration efforts of modern times is the search for life elsewhere in the Universe. The SETI program, of searching for radio signals from other civilizations, has to contend with enormous odds, given the vast- ness of the Universe and the uncertainties of recognizing biogenic signals. The odds may well be more in favour of discovering whether there once was, and maybe still is, life on Mars. The discovery of evidence of former life on Mars could be interpreted in one of two ways: the first is that life arose on Mars independently of that on Earth. That to me seems every bit as significant as the discovery of life in the more distant realms of the Universe. The second possibility, in some ways even more startling, would be that early life on Mars could be found to be indistinguishable from that on Earth, That would re-ignite interest in the Panspermia hypothesis of Hoyle and Wikramisinge, or give a great boost to research on self-organizing systems (which might drive evolution in particular directions). In a petition published in Science in 1982, Carl Sagan wrote, interuiiu, ‘We are unan- imous in our conviction that the only significant test of the existence of extraterrestrial intelligence is an experimental one. No a priori arguments on this subject can be com- pelling or should be used as a substitute for an observational program’. That was a petition in support of the SETI program, but it has equal force in the search for former xi