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Toward More Interaction Between the NASA Astrobiology Institute and the Planetary and Astronomical Sciences Two space science activities, planetary science and the astronomical search for origins, have made and continue to make strong intellectual contributions to astrobiology. Yet both of these disciplines, especially the latter, are underrepresented in the Astrobiology program in general and in the NASA Astrobiology Institute (NAI) in particular. In this chapter the committee explores this imbalance and makes recommendations for its rectifica- tion. PLANETARY SCIENCES AND ASTROBIOLOGY Intellectually and programmatically balanced research programs within NASA have the greatest potential for successful scientific output. The planetary science community, working within the context of NASA's Solar System Exploration program, has achieved this balance after some decades of evolution. In the first decade of the existence of planetary science as a distinct discipline (through about 1970), planetary scientists focused largely on supporting the primary NASA effort in human exploration of the Moon. While other missions were conceived and executed (e.g., the Mariner missions to Mars and Venus), most of the resources were expended on the Ranger, Lunar Orbiter, and Surveyor spacecraft sent to the Moon. Much was learned about our nearest neighbor in space, with perhaps the most spectacular results being the development of the impact origin of the Moon and the realization that impact processes have played a fundamental role in planetary evolution.) However, the narrow intellectual focus of NASA's planetary science activities made them vulnerable to the rise and fall of the Apollo program, and lunar studies fell victim to the end of human lunar exploration. In planetary science's second decade (through 1980), the Solar System Exploration program broadened somewhat, but large resources were expended on the one goal of searching for life on Mars. While technologically successful, the Viking missions of the mid-1970s cast a scientific pall on the exploration of Mars until the mid- 1990s, and in the late 1970s the agency found itself with a few large missions modeled, in scale at least, after Viking.2 From 1980 through 1990, planetary science largely relied on these large missions, and consequent delays, failures, or cancellation damaged the intellectual vigor of the field. COEL argues that the situation today in planetary science is spectacularly different, and much healthier. NASA's Solar System Exploration program includes a mix of flight programs, which run from Discovery missions (e.g., Mars Pathfinder, Near-Earth Asteroid Rendezvous, and Stardust) through to flagship missions (e.g., Galileo 32

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NASA ASTROBIOLOGY INSTITUTE AND THE PLANETARY AND ASTRONOMICAL SCIENCES 33 and Cassini), and provides a varied tapestry of flight-preparation times, risks, and rewards. Notable among these has been the spectacular exploration of the outer solar system, commencing with the Pioneer 10 and 11 missions, through the Voyager discoveries about the satellite systems of the giant planets, and culminating in the Galileo discoveries about Europa and the promise of Cassini discoveries at Saturn. Laboratory studies have blossomed as well, because techniques developed to analyze the Apollo lunar samples have been applied to the large numbers of meteorite samples found, serendipitously, through Antarctic exploration. Among these samples are pieces of Mars and the Moon, and laboratory studies inspired the goal of directly collecting small-body samples that is being realized through the ongoing Stardust mission. These direct samplings of primitive and evolved material in the solar system, including organic phases, are being directly applied as well to the astronomical study of planetary origins. For over a decade, the astronomical studies have provided increasingly detailed information on planetary systems in formation (from space-based platforms such as the Hubble Space Telescope [MST] and ground-based systems such as the twin 10-m Keck telescopes). But perhaps most extraordinarily, the detection and now the characterization of extrasolar planets has created a new intellectual realm within planetary science, and also has produced profound synergies between observational planetary astronomy and its parental roots in large telescopic observations of the cosmos. Giant planets are being detected indirectly and, in a few cases, observed directly to allow analyses of their bulk and atmospheric properties. Flight opportunities ranging in scale from Explorer (microlensing) through Discovery (Kepler-transits) to flagship (the Space Interferometry Mission [SIM]) missions cannot truly be classified as astronomical or planetological because they are informed by both. Theoretical understanding of planets gleaned from flight missions within the solar system is being applied successfully to extrasolar planets, today in the realm of the giants, but eventually to terrestrial planets as well. Indeed, for these reasons the planetary science activities today are so intellectually robust that the sudden cancellation in 2002 of two outer planet missions (to Europa and Pluto) will cause much less disruption in the program than it would have in the 1980s or 1990s. Astrobiology has strong intellectual links with the planetary sciences that go well beyond the exploration of two objects (Mars and Europa) to the investigation of diverse environments within which organic evolution has transpired and extended to the origin of life itself. Several of the node principal investigators in the NAI are either planetary scientists or individuals with a strong interest in the planetary sciences. A number of planetary scientists are involved in other Astrobiology program elements, such as the Exobiology research and analysis program and the Astrobiology Science and Technology Instrument Development program. However, COEL believes that the relationship between astrobiology and the planetary sciences could be better. The recent effort to produce a decadal strategy for planetary sciences exhumed deep suspicions within a significant portion of the planetary community that astrobiology would dominate solar system exploration to the exclusion of a balanced flight program, and that it would displace scientific priorities in planetary exploration not having to do with the search for life. In part, this suspicion dates back to the 1970s with the strong Viking emphasis on finding life on Mars at the expense of potential geophysical and geochemical explorations of the red planet. Today, however, planetary science is so intellectually strong and broad that such concerns are unfounded, if NASA continues to recognize the value and strength of a broad planetary program. COEL believes that the broad planetology and astrobiology communities jointly have a responsibility to go beyond shallow and polarizing characterizations of the two research areas to a much more extensive intellectual and research relationship. This may require formal efforts to bring larger numbers of scientists together to explore the intellectual connections more deeply than they have been explored to date. COEL commends NASA for developing a strong and well-balanced Solar System Exploration program that forms an important foundation for much of the central endeavor of astrobiology. Recommendation The NASA Astrobiology Institute should initiate a much broader suite of focus group programs with planetary scientists, beyond those currently devoted to studies of Mars and Europa, to create a deeper level of mutual understanding and appreciation of the two research areas and to provide new perspectives for future solar system exploration.

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34 LIFE IN THE UNIVERSE ASTRONOMICAL SEARCH FOR ORIGINS AND ASTROBIOLOGY Astronomical Search for Origins, as a NASA program, comprises study of the formation and early evolution of galaxies, stars, and planets. It has also come to include the detection and characterization of extrasolar giant planets, leading eventually to the detection and characterization of extrasolar planets the size and nature of Earth. The advent of space telescopes and large ground-based telescopes have enabled fundamental advances in these areas. Key results include, for example, the following: Origin and evolution of galaxies, production of the biogenic elements, history of star formation rates, . . .. . . . . .. . ... .. . .. . . . . . .. - . . . . ~ . - temporal and spatial changes in stellar metallicity, relationships between metallicity and planet formation and habitability;4 The relationship between star formation and the frequency of planet-forming disks;s The frequency of formation of giant planets and terrestrial planets;6 Properties of extrasolar giant planets and their evolution via orbital migration;7 Stability of planetary orbits and spin states as affected by gravitational perturbations from other planets and from natural satellites over the history of planetary systems;8 Elucidation of practical techniques for the detection and characterization of extrasolar habitable planets;9 and Understanding the chemical composition of molecular clouds, protostellar disks, and comets.~ Research relating to the astronomical search for origins is incredibly fertile today, and one would be hard- pressed to decide whether the most exciting results are being obtained on the largest (cosmological) or smallest (planetary systems) scales. It is not an exaggeration to argue that the Copernican revolution is in fact being completed today in the elucidation of the structure and fate of the cosmos, and in the determination of the frequency with which planetary systems form and the nature of the worlds thus built. The astronomical search for origins is also a programmatically healthy research area in the sense that discoveries are accomplished with a mix of ground- and space-based facilities, which in turn involve projects both small (inexpensive) and large (expen- . . slve) In scope. Millimeter-wavelength telescopes of 10- to 12-m diameter or greater are crucial in establishing the chemical composition of comets, planetary atmospheres, and interstellar gas. Small ground-based optical telescopes 1 m or less in aperture accomplished the first discoveries of planets around other stars and then their first characteriza- tion by transits. These achievements required precise spectroscopic and photometric techniques developed in the laboratory. The iodine gas absorption cells serving as a reference for the stellar wavelength shifts induced by orbiting planets, and the precise photometry enabled by modern electronic detectors, transformed these modest telescopes into major planet-detection and -characterization facilities. Much larger optical telescopes, with a mirror aperture of 6 m or larger and equipped with advanced adaptive optics capabilities, are required to examine the broader class of extrasolar planets that are not in the unusual orbital orientation necessary to make studies of transit possible. Such facilities, supported outside NASA with other federal, private, or state funds, represent a substantial monetary contribution to the research area of astrobiology, on a level of hundreds of millions of dollars in infrastructure. At the same time, existing or approved large-scale projects such as HST, the James Webb Space Telescope (JWST), and SIM take such observations much farther in terms of precision and sensitivity. (The latter mission is one component of NASA's so-called Navigator program, focusing on the detection and characterization of extrasolar planets.) With HST, it has been possible not only to infer the size of an extrasolar giant planet by means of transit photometry, but also to measure the atmospheric composition of the object.~3 JWST will take the transit capability even farther. Moreover, SIM will enable detection and characterization of planets down to bodies a few times the mass and/or size of Earth. There are natural intellectual connections between studies in the general areas of the astronomical search for origins and astrobiology. First, life as we understand it is a planetary phenomenon, and we seek its existence on appropriate planets in orbit around other stars. Second, life is the culmination of chemical evolution that has

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NASA ASTROBIOLOGY INSTITUTE AND THE PLANETARY AND ASTRONOMICAL SCIENCES 35 transpired on cosmic time scales. Hence, the origin of the nonhydrogenic chemical elements including carbon in stellar and galactic evolutionary processes leads naturally to organic chemistry in a variety of astrophysical environments, and thence to the origin and evolution of carbon-based life in the free-energy-rich environment of planet Earth. Indeed, in the NASA Astrobiology Roadmap, the astronomical search for origins and the astronomi- cal techniques used to study them play strong roles. Paradoxically, this is not the case programmatically within the Astrobiology program. Little astronomically oriented research is conducted within the framework of the current Exobiology and Evolutionary Biology R&A programs. Rather, this research fits more naturally within the Origins of Solar Systems R&A program. The latter activity is comparable in size to the Exobiology program, and is administered under the Office of Space Science but not from within the Astrobiology program. The technological-development programs (ASTID and ASTEP) are devoted to techniques aimed at observing planets within the solar system or ecosystems on Earth, while the separate Astronomical Search for Origins program focuses on developing new techniques for characterizing extrasolar planets. The NAI itself has not been able to successfully centralize research teams devoted to the astronomical search for origins in a meaningful way, with the exception of the node led by the University of Washington, which was selected in the second round. Where NAI nodes have included astronomical studies related to the search for origins as part of their research, this could be better integrated into and be a more important part of the overall NAI effort. Part of the difficulty in doing so arises because little common ground exists between the techniques and facilities that astronomers use to detect and characterize extrasolar planets and those familiar to biologists. Further, there is a suspicion among a portion of the astronomical community that the usual difficulty of assembling a peer-review panel for NAI membership that truly spans discipline breadth among biology, geology, and astronomy may have served to rule out worthy proposals based on novel astronomical approaches to astrobio- logical issues in the last competition for NAI membership. ENHANCING INTERACTION BETWEEN ASTROBIOLOGY AND THE ASTRONOMICAL SEARCH FOR ORIGINS COEL sees a danger in attempting a forced realignment of the NAI toward the astronomical search for origins. The natural center of gravity of the research at the NAI and its 15 nodes is not in astronomical studies relating to origins, and it would be detrimental to the flow of research to do anything beyond collegial encouragement and free exchange of ideas between astronomers and other disciplines in the NAI. However, the fertility of current activities in the general area of the astronomical search for origins is exceedingly high. Moreover, public excite- ment has been high over the discovery of new planets and what this foretells for the eventual discovery of Earth- like planets. That research should not be forced into a different intellectual context simply for the sake of creating an appearance of completeness in NASA's Astrobiology program itself. COEL offers two suggestions for increasing the volume and value of interactions between scientists active in the general areas of the astronomical search for origins and astrobiology. The first is to encourage the NAI and major astronomical institutions to initiate joint study efforts, ranging from conferences to long-term focus groups, that will enable more researchers in both areas to talk, mutually educate themselves, and "cross over" between the disciplines. The Space Telescope Science Institute's conference Astrophysics of Life (May 2002) is an excellent start to such an endeavor. It could be continued by initiating formal discussions, along the NAI's Mars and Europa focus group models, exploring topics in, for example, "astrobiology and the astronomical search for origins." The NAI and major astronomical institutions, recognizing the parity in research efforts between the two and avoiding the impression that the NAI is trying to reinvent the astronomical wheel, should initiate such focus groups jointly. The second suggestion, which is longer term, devolves from the fact that the NAI itself was intended to be an experiment in the creation and operation of a virtual institute, whose outcome, if successful, would be the propagation of such a structure to other promising fields of scientific endeavor. Astronomical studies relating to the search for origins could be the next activity ripe for a consortium-based institution a NASA Origins Institute (NOI) promoting research of scale, which is informed by and informs the large-scale ground- and space-based programs now under way. The breadth of astronomical origins from the creation of galaxies to the formation and early evolution of planets is a strength in this regard. It would contribute to the potential intellectual scope of such

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36 LIFE IN THE UNIVERSE a new institute and to the level of competition that would be anticipated in the call for proposals for it. Arguing for this approach is the current lack of consortium-based research opportunities in astronomical studies related to origins on a scale larger than the individual R&A grants (typically $100,000 per year) and smaller than the flight missions (typically $100 million or larger in total development cost, spanning several years or more). Finally, the roadmap makes clear the intellectual and technical linkages among different problems and activities in the Astro- nom~cal Search for Ongins program. An NOI would allow NASA to reap the benefits of these linkages by encouraging and funding collaboration among multiple institutions with differing expertise in the full range of studies relating to the astronomical search for ongins. COEL recognizes the natural overlaps between the NAI and an NOI, particularly in the area of organic chemistry and the origin of life. In the main, the areas and techniques employed in NAI and NOI research would be complementary, not redundant. Creation of an NOI would be an acknowledgment of both the success of the NAI and the need to maximize the scientific opportunities inherent in the astronomical search for ongins. It would also extend the experiment of the virtual institute concept to address the important issue of interactions between institutes. Could the NAI and an NOI foster additional and more meaningful interactions between the correspond- ing fields? Recommendations NASA should foster more extensive links between the Astrobiology and the Astronomical Search for Ongins programs. In the short term, these linkages require cooperation between the NAI and major astro- nom~cal institutions, such as the Space Telescope Science Institute and universities with extensive astronom~- cal programs, in creating joint workshops and focus groups to educate researchers in both areas and to initiate more extensive and novel research endeavors. Panels evaluating NAI membership proposals must be broadly constituted to ensure expert evaluation of research programs that are intellectually strong but have a discipline balance very different from that found in the existing NAI nodes. NASA should study the feasibility and desirability of creating and funding an institute, akin to the NAI, dedicated to consortium-based science and technology (e.g., involving multi-institution teams) related to the astronomical search for origins on the full range of spatial and temporal scales. NOTES AND REFERENCES 1. K. Righter and R. Canup, Origin of the Earth and the Moon, University of Arizona Press, Tucson, 2000. 2. M.H. Carr and J.B. Garvin, "Mars Exploration," Nature 412: 250-253, 2001. 3. Space Studies Board, National Research Council, New Frontiers in the Solar System: An Integrated Exploration Strategy, National Academies Press, Washington, D.C., 2003 (in press). 4. G. Gonzalez, D. Brownlee, and P. Ward, "The Galactic Habitable Zone I. Galactic Chemical Evolution," Icarus 152: 185-200, 2001. 5. C. Briceno, A.K. Vivas, N. Calvet, L. Hartmann, R. Pacheco, D. Herrera, L. Romero, P. Berlind, G. Sanchez, J.A. Snyder, and P. Andrews, "The CIDA-QUEST Large-Scale Survey of Orion OB1: Evidence for Rapid Disk Dissipation in a Dispersed Stellar Population," Science 291: 93-96, 2001. 6. J.I. Lunine, "The Occurrence of Jovian Planets and the Habitability of Planetary Systems," Proceedings of the National Academy of Sciences 98: 809-814, 2001. 7. G.W. Marcy, W.D. Cochran, and M. Mayor, "Extrasolar Planets Around Main Sequence Stars," pp. 1285-1311 in Protostars and Planets IV, V. Mannings, S. Russel, and A.P. Boss, eds., University of Arizona Press, Tucson, 2000. 8. M.J. Duncan and T. Quinn, "The Long-term Dynamical Evolution and Stability of the Solar System," pp. 1371-1394 in Protostars and Planets III, E.H. Levy and J.I. Lunine, eds., University of Arizona Press, Tucson, 1993. 9. C. Beichman, N.J. Woolf, and C.A. Lindensmith, The Terrestrial Planet Finder, National Aeronautics and Space Administration, Washington, D.C., 1999. 10. A. Li and J.M. Greenberg, "A Comet Dust Model for the ~ Pictoris Disk," Astronomy and Astrophysics 331: 291-313, 1998. 11. E.F. van Dishoeck and G.A. Blake, "Chemical Evolution of Star-Forming Regions," Annual Reviews of Astronomy and Astrophysics 36: 317-368, 1998. 12. G.W. Marcy, W.D. Cochran, and M. Mayor, "Extrasolar Planets Around Main Sequence Stars," pp. 1285-1311 in Protostars and Planets IV, V. Mannings, S. Russel, and A.P. Boss, eds., University of Arizona Press, Tucson, 2000. 13. D. Charbonneau, T.M. Brown, R.W. Noyes, and R.L. Gilliland, "Detection of an Extrasolar Planet Atmosphere," The Astrophysical Journal 568: 377-384, 2002.