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Astrobiology, the transcendent science: the promise of as an integrative approach for science and engineering education and research James T Staley

Astrobiology is rapidly gaining the worldwide attention of exobiology, a term which, by definition, refers to the scientists, engineers and the public. Astrobiology’s captivation is study of life outside . Excluding Earth and earthl- due to its inherently interesting focus on life, its origins and ings seems inappropriate for at least three reasons. First, it distribution in the Universe. Because of its remarkable breadth as is ironic to disregard Earth, because it is the only place so a scientific field, astrobiology touches on virtually all disciplines in far known in the Universe where life actually exists. the physical, biological and social sciences as well as Second, exobiology implies that there is something very engineering. The multidisciplinary nature and the appeal of its different and strange about creatures from other planetary subject matter make astrobiology ideal for integrating the bodies. Why shouldn’t all living matter in the Universe teaching of science at all levels in educational curricula. The share common properties in the same sense as other rationale for implementing novel educational programs in matter? Third, the study of life on Earth, including its astrobiology is presented along with specific research and evolution and diversity, provides valuable clues and les- educational policy recommendations. sons for the exploration of other worlds that may harbor life. After all, if we cannot understand life, its origins and Addresses its limits on Earth, how can we possibly begin to identify Department of , NSF Astrobiology IGERT Program, life and efficiently study it elsewhere? University of Washington, Box 357242, Seattle, WA 98195, USA e-mail: [email protected] The perception of scientists and lay people has changed since NASA introduced the term astrobiology, because Current Opinion in 2003, 14:347–354 it optimistically embraces the study of all life in the Universe, including life on Earth. The introduction of This review comes from a themed issue on the term astrobiology coincided with NASA’s establish- Science policy Edited by Rita R Colwell ment in 1998 of the NASA Astrobiology Institute (NAI), which now encompasses about a dozen universities and 0958-1669/03/$ – see front matter research centers at NASA and elsewhere (http://www.nai. ß 2003 Science Ltd. All rights reserved. arc..gov). In the five years since the NAI began as DOI 10.1016/S0958-1669(03)00073-9 a virtual institute, an international effort has linked its astrobiology program to those of several other countries. These include Spain (Centro de Astrobiologia), the United Abbreviations NAI NASA Astrobiology Institute Kingdom (UK Astrobiology Forum and Network), France NASA National Aeronautics and Space Administration (Groupement de Recherche en Exobiologie), Europe NSF National Science Foundation (The European Exo/Astrobiology Network Association) SETI search for extraterrestrial intelligence and Australia (Australian Centre for Astrobiology).

Why is astrobiology so appealing? Introduction How is it that astrobiology has captured the curiosity, This article introduces the multidisciplinary field of astro- fascination and admiration of so many? Surely much of its biology, which bridges the gap between the biological and appeal has to do with the great metaphysical questions of physical sciences and engineering. In addition, recom- astrobiology. Where did we come from? How does life mendations are made for astrobiology to serve as an begin and evolve? What is life’s future? Does life occur alternative model for teaching science and engineering elsewhere in the universe? at all levels of education including primary, secondary, undergraduate and graduate students. I am writing this This young and vigorous field holds great expectations article largely based upon the experience that my collea- that these questions can and will be answered. Herein lies gues and I have had in developing a PhD program in the appeal of astrobiology. Not only is the subject matter astrobiology at the University of Washington. of broad interest to virtually all of us, it is basic to our perception of the world in which we live. Furthermore, What a difference a word makes scientists are sanguine about our ability to answer at least For four decades the National Aeronautics and Space some of these questions in the foreseeable future. So, it is Administration (NASA) sponsored a science program on not surprising that the air bristles with excitement and www.current-opinion.com Current Opinion in Biotechnology 2003, 14:347–354 348 Science policy

anticipation at astrobiology meetings as scientists report Box 1 Example topic areas in astrobiology. how they are unraveling the mysteries of life, its tenacity, Star birth, death and recycling of elements fragility, distribution and origins. Formation of planetary systems Origin and evolution of life The transcendent nature of astrobiology Search for extraterrestrial biosignatures Astrobiology is remarkable in its extreme breadth and Habitable planets and satellites within and beyond our solar system therefore its potential for multidisciplinary education Earth’s early geosphere, hydrosphere and atmosphere Earth’s early biosphere and research. It touches on virtually all fields of science Mass extinctions and diversity of life and engineering. As a result it is perhaps unique among all Fossil and geochemical evidence of early life disciplines. Astrobiology is unlike, for instance, biology Life in extreme environments which is exclusively centred on the study of all aspects of Planetary protection life on Earth. Astrobiology, by contrast, considers ques- tions that transcend our planetary boundary. When biol- microorganisms are intimately involved in rock weath- ogists ask the question ‘What is life?’ they are constrained ering processes. From an astrobiological perspective, by the range of life forms on Earth. However, when the biological weathering processes leave ‘signatures of life’ astrobiologist asks the same question, all boundaries are such as specific biological compounds or microbial fossils removed. The astrobiologist is no longer confined to life thatcouldbeusedtoidentifylifeonrocksfromother on Earth, but is forced to conjure possibilities beyond the planetary bodies such as Mars. The traditional training of requirements of water and the DNA! RNA! protein geologists and microbiologists does not prepare PhD dogma. Indeed, imagination is the only limitation to the graduates to study these geobiological activities by them- astrobiologist’s thinking, although it is a severe one. To selves; however, in astrobiology, scientists work together test your own imagination, contemplate the question in designing and testing hypotheses and thereby expand- ‘What is life?’ and propose one or two truly alternative ing our understanding of fundamental but poorly studied life styles to that which we know so well. processes.

A special multidisciplinary challenge for astrobiology In our astrobiology PhD program at the University of relates to the dating of early events on Earth and provides Washington, we have seen examples of interdisciplinary another example of its transcendent nature. Geologists work that have resulted in unique perspectives. It is working with paleontologists provided us with the noteworthy in this regard that it is not always the faculty Geological Timetable during the last half of the 20th who have made these breakthroughs, but it is often our century. From this effort, much was learned about the PhD students. One example of this is work carried out by past 600 million years of animal and plant evolution. an astronomy student, John Armstrong, and a biology However, little is known about early evolution, that is, student, Llyd Wells, who have worked with an astron- from the Precambrian Eon after Earth’s formation about omy faculty member, Guillermo Gonzalez. They pro- 4.5 billion years ago until 600 million years ago. Our only posed that the Moon, as ‘Earth’sattic’, probably contains hope to uncover this information is through the mutual rocks with microbial fossils and other signatures of life efforts of geologists, micropaleontologists, microbiolo- from Earth that were ejected to the Moon as it drifted gists and phylogeneticists. Fossils alone cannot answer away from Earth after its formation. These fossils would the important questions about the order in which pro- be well preserved, because they have not been exposed cesses such as methanogenesis and sulfate reduction to weathering and tectonic processes on Earth. These occurred, because microbial fossils are too simple. Che- rocks are therefore likely to contain geochemical and mical biomarkers for processes and specific microbial fossil evidence that may tell us much about early Earth groups are needed in conjunction with phylogenetic history [1]. In a second paper, they suggest that, had a analyses. Already astrobiologists from the various disci- major sterilizing impact occurred on Earth following the plines are talking with one another about resolving this evolution of life, rocks subsequently ejected from the issue through multidisciplinary efforts. Moon by an impact event could have been brought back to Earth to re-seed it [2]. These papers are having a So, not only does astrobiology provide genuine appeal to major influence on NASA’s thinking concerning the all, but it is perhaps unique in its transcendence of possibility of launching a mission to the Moon to retrieve science. It encompasses aspects of biology, astronomy, early Earth rocks. physics, planetary sciences, chemistry and geology as well as the social sciences. Example topic areas in astrobiology Another example of interdisciplinary collaboration in- are given in Box 1. volves two of our faculty members. Peter Ward and Don Brownlee, a paleontologist and an astronomer, respec- Interdisciplinary astrobiology research tively, have collaborated in writing two recent provocative Much of the exciting research in astrobiology lies at the books on astrobiology, ‘Rare Earth’ and ‘The Life and Death interface between two or more disciplines. For example, of Planet Earth’ (Box 2).

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Box 2 Astrobiology book and journal list (since 2000). Astrobiology as an exciting new field for research Textbooks Bennett J, Shostak S, Jakosky B: Life in the Universe. Boston: In this brief article, it is not possible to provide detailed Addison Wesley; 2003. information about ongoing astrobiology research that is For introductory college courses for nonscience majors; stronger changing our views of our world and the possibility of life on the physical sciences than biology Goldsmith D, Owen T: The Search for Life in the Universe, 3rd Edn. elsewhere. What I have done is to ask my colleagues to San Francisco: Benjamin Cummings; 2002. submit references of recent articles that they believe For introductory college courses for nonscience majors; stronger have made major contributions in their fields. I have on the physical sciences than biology grouped these below under various astrobiology subject Prather E, Offerdahl E, Slater T: Life in The Universe Activities Manual. Boston: Addison-Wesley; 2003. headings along with brief descriptions of their content Student activities to accompany the textbook by Bennett et al. and significance. This is not meant to be a complete Zubay G: Origins of Life on the Earth and in the Cosmos, 2nd Edn. listing, but should provide an indication of the vitality London: Harcourt; 2000. Tutorial approach to the biochemistry of how life works and its origin and breadth of the field. An excellent general reference on astrobiology has been written by Des Marais and Popular books Clark S: Life on Other Worlds and How to Find It. New York: Walter [3 ]. Springer-Praxis: 2000. Darling D: Life Everywhere: the Maverick Science of Astrobiology. Extreme environments and extremophiles New York: Basic Books; 2001. Several groups have looked at extreme environments on Well-written; includes personalities of researchers Darling D: The Extraterrestrial Encyclopedia: an Alphabetical Earth, protracting their findings to possible conditions on Reference to All Life in the Universe. Three Rivers; 2001. other planetary bodies. For example, Doran and collea- deDuve C: Life Evolving: Molecules, Mind, and Meaning. Oxford UK: gues [4] report on Lake Vida, one of the largest lakes in Oxford University Press; 2002. Nobelist argues for the inevitability of the emergence of life the McMurdo Dry Valleys of Antarctica, which was pre- Dick S: Life on Other Worlds: the 20th Century Extraterrestrial Life viously believed to be frozen solid. However, it now turns Debate. Cambridge UK: Cambridge University Press; 2001. out to contain a briny liquid (seven times seawater sali- Shorter, popular version of ‘The Biological Universe’ listed below nity, temperature below 108C) beneath a 19 m thick ice Fry I: The Emergence of Life on Earth: a Historical and Scientific Overview. New Jersey: Rutgers University Press; 2000. cover that has effectively isolated the brine for about 2800 Excellent overview of past and current ideas on the origin of life years. The ice cover contains microbial populations that Grady M: Astrobiology. Washington: Smithsonian Institution Press; 2001. are metabolically active upon thawing. The physical Nice slim volume Koerner D, Levay S: Here be Dragons: the Scientific Quest for features and geological history of the lake suggest it Extraterrestrial Life. Oxford UK: Oxford University Press; 2000. may be an analog of the last vestige of an ancient Martian Ward P: Rivers in Time: the Search for Clues to Earth’s Mass aquatic ecosystem. Extinctions. Columbia: Columbia University Press; 2000. Ward P, Brownlee D: Rare Earth: Why Complex Life is Uncommon in the Universe. Copernicus, 2000. Similarly, Kelley and coworkers [5 ] describe a new class Pioneering synthesis; astronomer and paleontologist argue that planets of marine hydrothermal system hosted on peridotites. with conditions for life more complex than single cells are The field hosts at least 30 active and inactive 30–60 m rare in the Universe Ward P, Brownlee D: The Life and Death of Planet Earth: How the tall carbonate chimneys that vent fluids at 40–758Cwith New Science of Astrobiology Charts the Ultimate Fate of Our pH values of 9–10. The chimneys harbor dense and World. New York: Henry Holt; 2003. diverse microbial communities. Because this system is Wills C, Bada J: The Spark of Life: Darwin and the Primeval Soup. Cambridge MA: Perseus; 2000. hosted in peridotites, it is very reducing and associated with high pH fluids. It may be the best current analog Scholarly publications Dick S: The Biological Universe: the Twentieth-Century to hydrothermal systems that operated on early Earth Extraterrestrial Life Debate and the Limits of Science. (Figure 1). Cambridge UK: Cambridge University Press; 2000. The definitive historical study of the development over the 20th Other groups have investigated various environments, century of ideas (both scientific and more popular, e.g. UFOs) on extraterrestrial life, origin of life, exobiology and astrobiology including winter sea-ice [6 ] (Figure 2), active sulfide Horneck G, Baumstark-Khan C (Eds): Astrobiology: The Quest for the chimneys [7,8 ], and the acidic, iron-rich red river, Rio Conditions of Life. New York: Springer; 2002. Tinto, in Southern Spain [9]. Together, these types of Most chapters (by separate authors) are an outgrowth of a workshop on astrobiology held in Germany; uneven coverage studies have highlighted the harsh environments in which Lemarchand G, Meech K (Eds): Bioastronomy ‘99: A New Era in life can exist and have helped scientists understand the Bioastronomy. Proceedings of the Astronomical Society of the range of environments outside Earth that may harbor Pacific Conference; Hawaii, USA, 2–6 August 1999. Vol. 213. microbial life. ASP, 2000. Proceedings of a wide-ranging conference; strongest on the astronomy Geological sciences Journals Astrobiology. New York: Mary Ann Liebert, Inc.; (2001–). Sudbury in Ontario is the largest known and most impor- International Journal of Astrobiology. Cambridge UK: Cambridge tant bolide impact structure (astrobleme) on Earth, being University Press; (2002–). one of the first to be recognized and debated. Its many geological features are exposed at the Earth’s surface, and www.current-opinion.com Current Opinion in Biotechnology 2003, 14:347–354 350 Science policy

Figure 1

Several groups have looked at extreme environments on Earth, protracting their findings to possible conditions on other planetary bodies. Kelley and coworkers [5] described a new class of marine hydrothermal system from the mid-Atlantic Ridge that is hosted on peridotites, which may be the best current analog to hydrothermal systems that operated on early Earth. The figure shows a hydrothermal vent off the coast of Washington State. The structures at this site vent at temperatures up to 3008C. Detailed analyses of one of the sulfide structures shows that they host dense and diverse microbial communities. (The photograph is reproduced with kind permission from D Kelley.)

it is one of the world’s largest sources of nickel ore. The in the past may have thawed frozen subsurface water Fe-Ni-Cu-S ore was not derived from the bolide, but leading to temporary episodes of rain and flash floods [15]. formed by processes induced by the impact. Naldrett [10] has reviewed our current understanding of this site in an Earth may have actually frozen over completely in its article that illustrates the contribution of the geological past, a phenomenon referred to as ‘Snowball Earth’. sciences to astrobiology. Hoffman and Schrag [16] have recently reviewed this field and Warren et al. [17] discuss where surface life may Planetary and atmospheric science have survived during one of these remarkable events. Astronomers are beginning to discover planets beyond Earth’s solar system and new models are being proposed Until recently, atmospheric scientists explained how early for their formation [11]. Data from the Hubble Space Earth could remain unfrozen even when the sun was 30% Telescope provided the first direct detection of the atmo- less luminous because they believed the atmosphere had spheric composition of a planet orbiting a star outside our high levels of the greenhouse gas, carbon dioxide. This solar system [12]. Sodium was found in the atmosphere view has now changed as Pavlov et al. [18] showed how of a planet orbiting a yellow, Sun-like star called HD biogenic methane in an early anoxic atmosphere could 209458, located 150 light-years away in the constellation have served as the key greenhouse gas. Catling et al. [19] Pegasus. Although this particular planet is a gas giant like showed that the high methane concentration in the early Jupiter and unlikely to harbor life, the study demon- atmosphere could also explain the oxidation of the atmo- strated that it is feasible to measure the chemical makeup sphere: ultraviolet light’s decomposition of methane to of extrasolar planetary atmospheres and to potentially hydrogen and its escape to space would have left Earth search for the chemical markers of life (such as O2) more oxidized before biogenic oxygen production. beyond our solar system [13]. Early evolution Recent evidence strongly supports the view that Mars has As surprising as it may seem microbiologists are still water that has flowed in the recent past, supporting the discovering on Earth entirely new kingdoms of microbial notion that subsurface brinesmay exist [14]. Bolide impacts life including representatives from each of the three

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Figure 2

Sea-ice on Earth has become a model system in which to study planetary bodies such as Jupiter’s moon , which has a frozen ocean that is shown in close-up view. The texture of the ocean supports the view that there are large blocks of ice floating on a liquid ocean that may support microbial life. (Figure reproduced with courtesy of the Jet Propulsion Laboratory at NASA/Caltech.)

domains, the Bacteria, Archaea and Eucarya. One exam- trophic metabolism in which organic matter is oxidized ple is described in the recent paper of Huber et al. [20] anaerobically with sulfate, it implies that microbial eco- who reported an unexpected group of the Archaea, systems were already quite diverse with complex trophic known species of which parasitize other members of webs and biogeochemical cycles. As sulfate reduction the Archaea. requires sophisticated biochemical control, it further implies that soon after the end of heavy meteorite bom- Much confusion still exists about the evolution of the first bardment of the Earth, life was already quite advanced in organisms. Woese [21] considers the importance of hor- its cellular functions. izontal gene transfer on the evolution of early cellular life. He proposed the ‘Darwinian Threshold’ as a seminal Considerable doubt has been cast on the claim that there period that separates early evolution in which horizontal is carbon-isotopic evidence for life on Earth older than gene transfer dominated evolutionary processes from the 3.85 Ga [24,25]. If correct, this claim would imply that subsequent period in which evolution followed the ver- autotrophic organisms inhabited the Earth at the time of tical inheritance of life as we now know it. the heavy meteorite bombardment and therefore that life could have been widespread in the early solar system. Van Although evidence indicates that many of the traits of the Zuilen et al. [24] argue that the observed carbon-isotope Eucarya can be traced to the Bacteria and Archaea, until fractionation is not biotic, but is instead the result of recently tubulin genes have only been found in the metamorphic carbonate reduction to graphite. Fedo and Eucarya, all species of which have them. However, this Whitehouse [25] argue that the host rock for this graphite too is no longer true; a bacterium that contains a- and is an altered igneous rock and not a sedimentary banded b-tubulin homologs has now been discovered [22]. iron formation, so it should not be expected to host biological remains. Paleontology Shen et al. [23] demonstrate the existence of microbial Planetary protection and the search for sulfate reduction as early as 3.45 billion years ago, pro- extraterrestrial intelligence viding the first evidence of a specific metabolism in Astrobiologists are concerned about the biological con- Earth’s evolutionary record. As this is typically a hetero- tamination of planetary bodies by life from elsewhere. www.current-opinion.com Current Opinion in Biotechnology 2003, 14:347–354 352 Science policy

Rummel [26] has written an accessible review of the taught to all educational levels and it serves as an engag- history and state of planetary protection policy and imple- ing outreach program to the public. mentation. More specific issues, such as the handling and quarantine of samples returned from elsewhere (e.g. Because of the interest in astrobiology courses, several Mars), have been considered in some detail [27]. books have recently been published, some of which could serve as textbooks for courses at the undergraduate and In part 1 of a comprehensive treatment of biological graduate levels (Box 2). transfer, Mileikowsky et al. [28] discuss the potential for the natural transfer of microbes between solar system Policy recommendations for astrobiology bodies. This is based on knowledge that large impact science education and research events (from comets or asteroids) occurring on one body PhD traineeship programs can propel significant quantities of material off a planetary Evidence from our University of Washington National surface and into solar orbits that may intersect the orbits Science Foundation (NSF) Integrative Graduate Educa- of other bodies. tion and Research Traineeship (IGERT) astrobiology program (http://depts.washington.edu/astrobio/) indicates The search for extraterrestrial intelligence (SETI) con- that astrobiology can serve as an excellent subject area for tinues as one of the earliest endeavors that has attempted interdisciplinary PhD education in science and engineer- to discover advanced life on other planetary bodies [29]. ing. Because astrobiology is such a broad and exciting field of study in science, it should be promoted as a NASA’s astrobiology website contains links to the NAI curriculum in science education and research at the projects as well as an Astrobiology Roadmap that doctoral level. describes research goals. Perhaps what is most remarkable is that, during the past decade, this field has grown from a We recommend that NASA, NSF and other appropriate small core of dedicated scientists to a large and impressive federal agencies should provide support for the imple- group with many young scientists. With the emergence of mentation of PhD traineeship programs in science and new technologies, such as genome sequencing and extra- engineering education in astrobiology. This will develop solar system planetary discovery techniques, our under- a unique group of scientists and engineers who will be standing in all areas from molecular evolution to planetary able to effectively communicate and collaborate with one habitability is rapidly transforming our comprehension another. Furthermore, they will be able to subsequently of astrobiology. train university students in astrobiology and interdisci- plinary research. Astrobiology’s promise for multidisciplinary science education and research Astrobiology students who receive PhD degrees will be Most educators agree there is a need to rethink science ideal candidates for the instruction of courses for doctoral and engineering education. Many of the traditional dis- students interested in astrobiology. At this time there are ciplines seem to lack context in our modern world, at least very few students. Even when more students graduate, to many young scholars. By incorporating astrobiology however, it should be recognized that they will not have into a curriculum, the treatment of subject matter the in-depth experience to supervise students in PhD changes. For example, consider the biology instructor courses and research in areas outside their own disciplin- who is interested in teaching about the diversity of life. ary expertise, so a co-mentoring approach appears more A typical approach would be to discuss the different appropriate. Astrobiology students trained in our program species from each of the numerous animal groups and complete all of the necessary requirements in their major how some are being threatened with extinction due to department and, in addition, complete the requirements habitat loss. In an astrobiology course the diversity issue for the astrobiology program. Therefore, they can com- could be addressed in the context of mass extinctions, pete effectively for post-graduate opportunities with such as, ‘What happened to the dinosaurs?’ The answer to others in their own area, but have the added experience this question entails a discussion of biology, paleontology, of working in a multidisciplinary training environment, astronomy, physics (for dating fossils), evolution and which, we believe, makes them better prepared for their could be followed up by a discussion of the human-driven future careers. mass extinction that is occurring now. Therefore, astro- biology can provide a compelling way of integrating the Astrobiology PhD programs are likely to remain inter- sciences in the classroom. departmental for the foreseeable future. Although they may eventually be accepted as departmental programs, Also, from a pragmatic standpoint, the subject matter in this seems premature now as it may actually detract from astrobiology is very flexible. It can be taught within the the true vision of a cross-disciplinary field. Nonetheless, if structure of an entire science curriculum at one extreme, life is discovered elsewhere in our solar system or in or as a single course. Furthermore, astrobiology can be another planetary system, it could certainly lead to a need

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to train additional astrobiologists through university websites, etc) that could be used for teaching primary, departmental programs. In this sense, an astrobiology secondary and undergraduate students interested in training program could serve as a forerunner for the cadre science and engineering. of scientists and engineers eventually needed. Conclusions The current NSF IGERT program is an excellent model Recent advances in scientific knowledge from such dis- to use for development of a joint NASA-NSF or other parate areas as microbiology, astronomy, geochemistry, agency program, because of the importance it places on paleontology, genomics, and molecular integrative student training and support for development evolution have culminated in the formation of the new of novel educational ideas. field of astrobiology. Astrobiology, which transcends vir- tually all of the sciences, aims to answer the great ques- Undergraduate university level tions about the origin of life and its distribution and Astrobiology is currently amenable for the instruction of evolution in the Universe. Astrobiology has quickly undergraduate students in single courses. Textbooks are ascended to international prominence as a novel multi- available that may be used for that purpose if institutions disciplinary and integrated scientific research area. have faculty members who can teach in the various Because of its innately interesting subject material, astro- subject areas. biology is ideally suited for teaching science from kin- dergarten to the graduate level. Now is the time to Because astrobiology covers such a vast area, most instruc- implement astrobiology into educational programs in tors will find it difficult to teach an entire course; however, the form of new courses and new curricula. In order to it could be team-taught by faculty from biology and the accomplish this goal, governmental resources will be physical sciences. Ultimately, as PhD scientists and engi- needed to train teachers and develop appropriate instruc- neers are trained in astrobiology, they would become tional guidelines and materials. ideal candidates to teach an entire course at the under- graduate level. Acknowledgements I want to thank my colleagues at the University of Washington who have made suggestions and provided some of the references mentioned, Our recommendation for teaching astrobiology at the especially Roger Buick, David Catling, Eric Cheney, Jody Deming, undergraduate level is to provide support for training of Deborah Kelley, Marsha Landolt, Thomas Quinn, Steve Warren and Llyd existing faculty at institutions that wish to develop astro- Wells. In addition, I wish to thank David Morrison who provided the book listing and Woodruff Sullivan III who provided book annotations. Also biology courses or a curriculum. This could be handled by thanks to Rosalind Grymes and John Rummel for their excellent supporting faculty study leaves to a university in which a suggestions, most of which I have adopted. I am also grateful to the NSF graduate level program in astrobiology is in place, as well IGERT and NASA NAI programs for providing support for my laboratory’s research in astrobiology. as at the various non-academic NAI institutions. References and recommended reading Primary and secondary education Papers of particular interest, published within the annual period of Astrobiology is an exciting field that is ideal for teaching review, have been highlighted as: science to students in secondary education. Some materi- of special interest als are currently available for this such as Astro-Venture of outstanding interest for grades 5–8, at the NAI site mentioned previously, and 1. Armstrong J, Wells L, Gonzalez G: Rummaging through Earth’s the SETI Institute high school curriculum (www.seti.org/ attic for remains of ancient life. Icarus 2002, 160:183-196. This paper suggests that the moon may contain fossils of early Earth Welcome.html). However, there is a need to train tea- organisms in rocks that were ejected to the moon by impacts. chers and develop additional instructional materials. This 2. Wells L, Armstrong J, Gonzalez G: Reseeding Earth by impacts of could be initiated with a trial period at primary and returning ejecta during the late heavy bombardment. Icarus: in secondary schools that wish to pursue this subject matter press. Since the moon probably received ejecta from early Earth, returning in their science curriculum. Once this trial period is over, ejecta from the moon could have re-inoculated the Earth, which might say after five years, the concept could be evaluated and, if have been sterilized by large impacts. appropriate, implemented. 3. Des Marais D, Walter M: Astrobiology: exploring the origins, evolution, and distribution of life in the Universe. Annu Rev Ecol Systems 1999, 30:397-420. To teach astrobiology at this level we recommend that Comprehensive review article with 100 citations of technical articles. support is provided for workshops and course planning 4. Doran P, Fritsen C, McKay C, Priscu J, Adams E: Formation and sessions for scientists from universities with astrobiology character of an ancient 19-m ice cover and underlying trapped brine in an ‘ice-sealed’ east Antarctic lake. Proc Natl Acad Sci programs and science teachers of primary and secondary USA 2003, 100:26-31. school students. The goal of these workshops is to 5. Kelley D, Karson I, Blackman D, Fruh-Green D, Gee J, Butterfield D, develop trial curricula for teaching astrobiology at the Lilley M, Olson E, Schrenk M, Roe K: An off-axis hydrothermal primary and secondary levels. It would also be necessary field discovered near the Mid-Atlantic Ridge at 308N. Nature 2001, 412:145-149. to support the development of astrobiology courses and This paper announces the discovery and describes the nature of the novel appropriate educational materials (textbooks, videos, ‘Lost City’ hydrothermal vent system near the mid-Atlantic ridge. www.current-opinion.com Current Opinion in Biotechnology 2003, 14:347–354 354 Science policy

6. Krembs C, Deming J, Junge K, Eicken H: High concentrations of This article models the ice thickness on the ocean of Snowball Earth, with exopolymeric substances in wintertime sea ice: implications the aim of identifying locations where surface life could have survived. for the polar ocean carbon cycle and cryoprotection of diatoms. Deep-Sea Res 2002, 49:2163-2181. 18. Pavlov A, Kasting J, Brown L, Rages K, Freedman R: Greenhouse This study of winter sea-ice cores shows that the ice is filled throughout warming by CH4 in the atmosphere of early Earth. J Geophys with high concentrations of exopolymeric substances (EPS). At winter-ice Res 2000, 105:11981-11990. temperatures to as low as –208C, EPS were observed to protect organ- Physics indicates that the Sun was about 30% less luminous 4 billion isms within the ice against physical damage by encroaching ice crystals. years ago, so Earth’s ancient atmosphere must have had higher con- centrations of greenhouse gases so that the Earth was not permanently 7. Schrenk M, Kelley D, Delaney J, Baross J: Incidence and diversity frozen. During the 1980s and 1990s it was widely hypothesized that of microorganisms within the walls of an active deep-sea Earth’s early atmosphere had very large levels of carbon dioxide. This sulfide chimney. Appl Environ Microbiol: in press. view has now been largely abandoned; Pavlov and colleagues show how A comprehensive, up-to-date treatment of the diversity of life within biogenic methane would build up in an early anoxic atmosphere and active sulfide chimneys. Fluorescence in situ hybridisation, 16S rDNA operate as the key greenhouse gas. sequences and cell count data are provided in several transects/zones across the wall of a 3008C chimney from the Mothra Hydrothermal Field. 19. Catling D, McKay C, Zahnle K: Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth. 8. Kelley D, Baross J, Delaney J: Volcanoes, fluids, and life in Science 2001, 293:839-843. submarine environments. Annu Rev Earth Planetary Sci 2002, 30:385-491. 20. Huber H, Hohn M, Rachel R, Fuchs T, Wimmer V, Stetter K: A new This major review paper looks at processes in the mantle to the hydro- phylum of Archaea represented by a nanosized sphere in the context of impacts on microbial communities. Much of the hyperthermophilic symbiont. Nature 2002, 417:63-67. information is directly relevant to astrobiological questions concerning Some microbiologists have said jokingly that it is simpler to describe a the flux of volatiles, heat sources and linkages to microbial processes. new ‘kingdom’ or ‘phylum’ of the Bacteria and Archaea than a new This paper is being used by numerous upper undergraduate and graduate species. Clearly, however, new kingdoms are very important and this classes in a textbook fashion. article describes an unexpected phylum of the Archaea. 9. Zettler L, Gomez F, Zettler E, Keenan B, Amils R, Sogin M: 21. Woese C: On the evolution of cells. Proc Natl Acad Sci USA 2002, Eukaryotic diversity in Spain’s river of fire. Nature 2002, 417:137. 99:8742-8747. 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