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Assessment of Solar System Exploration Programs 1991 (Chapter 6) Assessment of Solar System Exploration Programs 1991 6 Exobiology Programs SCIENCE OBJECTIVES As noted in the Introduction, COMPLEX received formal advisory oversight for exobiology issues only in 1989, following the reorganization of the Space Science Board into the Space Studies Board and the dissolution of the Committee on Planetary Biology and Chemical Evolution (CPBCE). As a result, COMPLEX now has the responsibility for monitoring NASA's progress in the implementation of its exobiology program in relation to the existing CPBCE science strategy, and to revise that strategy as it becomes implemented or superseded by advances in scientific understanding. The recent CPBCE report The Search for Life's Origins: Progress and REPORT MENU Future Directions in Planetary Biology and Chemical Evolution (SSB, 1990c), lists NOTICE the following scientific goals and objectives for exobiology research: MEMBERSHIP FOREWORD The Cosmic History of the Biogenic Elements and Compounds SUMMARY CHAPTER 1 CHAPTER 2 Understand the history of physical and chemical transformations CHAPTER 3 undergone by the biogenic elements and compounds from nucleosynthesis to CHAPTER 4 their incorporation and subsequent modification in preplanetary bodies. CHAPTER 5 CHAPTER 6 Early Planetary Environments: Implications for Chemical Evolution and the Origin CHAPTER 7 of Life CHAPTER 8 CHAPTER 9 REFERENCES Understand the processes responsible for the chemical evolution of organic matter in the outer solar system. Understand how the conditions for chemical evolution and the origin of life were influenced by the physical and chemical development of the terrestrial planets. file:///C|/SSB_old_web/ssep91ch6.htm (1 of 4) [6/18/2004 1:58:18 PM]

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Assessment of Solar System Exploration Programs 1991 (Chapter 6) Origin of Life Understand the origin and evolution of metabolism in primitive life forms. Understand the origin and evolution of replication. Understand the origin and evolution of gene expression. Determine evolutionary events leading to the accretion of complex genomes. The Evolution of Cellular and Multicellular Life Develop a universal understanding of the temporal sequence and evolutionary relationships of life on Earth. Determine the properties of the universal ancestor of extant organisms. Understand what factors drive the biosphere. Generalize our understanding of environmental and early cellular evolution on Earth by comparative studies of Mars. Search for Life Outside the Solar System Understand the nature and distribution of life in the universe. CURRENT STATUS OF NASA'S EXOBIOLOGY PROGRAMS Although NASA has not yet had an opportunity to implement the new recommendations of the 1990 CPBCE report, many of the recommendations are carried over from an earlier report by that committee, Origin and Evolution of Life—Implications for the Planets: A Scientific Strategy for the 1980's (SSB, 1981). COMPLEX has received the agency's existing program and plans, and can provide the following brief assessment of its status on the basis of earlier recommendations. The 1990 CPBCE report listed major research recommendations, which were divided into two categories: flight opportunities and ground-based research. Studies of materials associated with hydrological activity on Mars were identified file:///C|/SSB_old_web/ssep91ch6.htm (2 of 4) [6/18/2004 1:58:18 PM]

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Assessment of Solar System Exploration Programs 1991 (Chapter 6) as the highest priority in the flight category. Currently planned robotic missions and proposed human exploration missions for investigation of Mars, if properly executed, promise to make significant contributions to the goals listed in the CPBCE report. Also discussed in the 1990 report were flight opportunities to comets and asteroids, and missions to Titan and the giant outer planets. The CRAF and Cassini missions are respectively expected to rendezvous with a comet and send a probe to Titan with an orbiter around Saturn. These missions and the Galileo mission to Jupiter will address many existing exobiology goals dealing with chemical evolution. Besides flybys on the Galileo, CRAF, and Cassini missions, there are no firm plans to investigate asteroids as discussed in the previous chapter. Recommendations for flight opportunities include use of Earth-orbital facilities for astronomical observations related to exobiology (e.g., extrasolar planetary detection), and Earth-orbital collection of interplanetary dust particles. Studies of these opportunities are now underway. In the main, however, exobiological considerations are largely incidental to currently planned missions. Intensive study of the Martian surface should include exobiological investigations as an important part of the scientific goals. COMPLEX notes that any excursion to the surface of Mars and the return of samples to Earth pose significant planetary quarantine issues. The 1990 report also recommends a program of ground-based research to support these flight opportunities. Important among these are studies of the origin and evolution of life. Currently, these programs are supported in the NASA (Code SB) Exobiology Research and Analysis program, Some progress has been made in these areas in recent years, partly as a result of NASA support. The NASA Exobiology Branch has played a leading role in organizing the loosely-knit community of biologists and chemists with interests in exobiology, through sponsorship of conferences and workshops. Unfortunately, many of the recommendations of the 1981 and 1990 CPBCE reports, although embraced by the NASA Exobiology Branch, await implementation because of severe funding limitations. file:///C|/SSB_old_web/ssep91ch6.htm (3 of 4) [6/18/2004 1:58:18 PM]