SETI Institute/NASA Astrobiology Institute Team

Executive Summary

The Astrobiology Roadmap asks three fundamental questions: (1) How does life begin and evolve; (2) Does life exist elsewhere in the universe? and (3) What is the future of life on Earth and beyond? The SETI Institute will conduct a set of coupled research projects in the co-evolution of life and its planetary environment, beginning with fundamental ancient transitions that ultimately made complex life possible on Earth. We conclude with a project that brings together many of these investigations into an examination of the suitability of planets orbiting M stars for either single-celled or more complex life. Results will help the next generation scientific Search for Extraterrestrial Intelligence (SETI) choose the 10⁵ to 10⁶ target stars that it will survey for signs of technical civilizations using the new Allen Telescope Array (ATA) being built by the SETI Institute in partnership with the University of California, Berkeley.

SETI is a natural part of the continuum of research that comprises astrobiology. This is recognized explicitly in the Astrobiology Roadmap, which calls for a strategy "for recognizing novel biosignatures" that "ultimately should accommodate a diversity of habitable conditions, biota and technologies in the universe that probably exceeds the diversity observed on Earth." From the life detection point of view, the Roadmap notes that "although technology is probably much more rare than life in the universe, its associated biosignatures perhaps enjoy a much higher 'signal-to-noise' ratio. Accordingly, current methods should be further developed and novel methods should be identified for detecting electromagnetic radiation or other diagnostic artifacts that indicate remote technological civilizations."

Overview of Proposed Research

The research in the Institute's proposal intends to elucidate the co-evolution of life and its planetary environment, typically investigating global-scale processes that have shaped, and been shaped by, both. Throughout, we recognize the importance of pursuing the planetary evolution aspects of this research in the context of comparative planetology: since laboratory experiments are impossible over some of the time and spatial scales relevant to early Earth, we must supplement laboratory data with the insight as we can gain by exploring extraterrestrial environments that may provide partial analogs to the early Earth environment and its processes.

We begin by proposing two new investigations into the oxidation of early Earth's environment. While the biological aspects of this "oxygen transition" have been recently emphasized, both mechanisms to be explored here (peroxy in rocks [Drs. Friedemann Freund and Lynn Rothschild] and aerosol formation in the atmosphere [Dr. Emma Bakes], building on an analogy to processes now occurring in the atmosphere of Saturn's moon Titan) are non-biological. If such mechanisms were to be shown to be quantitatively significant, it would suggest that the oxygen transition on an Earth-like world could take place independently of the invention of any particular metabolic pathways (such as photosynthesis or methanogenesis) that have been proposed as driving this transition. Since Earth's oxygen transition ultimately set the stage for the oxygen-based metabolism evidently essential for metazoa, understanding this transition is crucial to elucidating both Earth's evolution and the evolution of complex (including intelligent) life. Our geological investigations are tightly coupled with microbiological experiments to understand the extent to which the proposed mechanism might have led to the evolutionary invention of oxidant protective strategies and even aerobic metabolism.

One of the major sinks for oxygen on early Earth would have been reduced iron. At the same time iron could have provided shielding against ultraviolet (UV) light that would have been reaching Earth's surface in the absence of the ozone shield generated by atmospheric oxygen. Nanophase ferric oxide minerals in solution could provide a sunscreen against UV while allowing the transmission of visible light, in turn making the evolution of at least some photosynthesic organisms possible. We will test [Drs. Janice Bishop and Lynn Rothschild] this hypothesis through coupled mineralogical and microbiological work in both the lab and the field, and examine its implications not only for Earth but for Mars as well--with an emphasis on implications for upcoming spacecraft observations.

The survival of microorganisms in very high UV environments can also be tested empirically through the exploration of Earth's highest altitude lakes and ponds, in Bolivia and Chile. We propose [Drs. Nathalie Cabrol and Edmond Grin] a series of investigations of these lakes to examine the strategies employed by these microorganisms.

Just as global-scale changes in oxygen (or iron) were critical for the early biosphere, so too would have been global processes involving other key "biogenic" elements such as carbon [Dr. Bakes] or nitrogen [Drs. Rocco Mancinelli, Amos Banin, David Summers, and Bishun Khare]. We propose coupled laboratory and field research to understand the partitioning of nitrogen on early Earth--and on Mars--between different possible reservoirs, and the abiotic to biotic transition in this cycling.

The work described so far examines the evolution of planetary surface habitability. With the recognition that a subsurface ocean likely exists on Jupiter's moon Europa, we know that habitability in possibly entirely subsurface environments must also be explored. We propose spacecraft data analysis and modeling to examine the geology of Europa and its implications for the free energy sources that would be needed to power a europan biosphere [Drs. Cynthia Phillips and Christopher Chyba]. We will then couple these results with terrestrial analog work [Chyba] and direct low-temperature laboratory experiments [Dr. Max Bernstein] to make predictions about the possible abundance and survivability of any oceanic biomarkers that might reach Europa's surface through active geology. These results will have implications for astrobiological exploration of Europa from either an orbiter or a surface lander.

Finally, we suggest research (Drs. Peter Backus, Jill Tarter, and Chyba) to examine the prospects of planets orbiting dwarf M stars being habitable for either microscopic or complex life. The results of this work will directly influence the strategy employed in the next generation SETI search program to begin in 2005.

The SETI Institute

The SETI Institute was founded in 1984 as a nonprofit scientific research institution. From its beginning, its mission has been to explore the origin, nature and prevalence of life in the universe, and to explain this science to the public. The Institute may be best known for its ongoing Search for Extraterrestrial Intelligence (SETI) programs, but the study of virtually all other aspects of astrobiology has been part of our mandate from the beginning.

The Institute employs nearly 120 individuals. Sixty-four of these are employed through the Center for the Study of Life in the Universe, directed by Dr. Frank Drake. Another twenty-six scientists and engineers are employed within the Center for SETI Studies, directed by Dr. Jill Tarter, who is a Co-Investigator on this grant. The remainder are in administration and education. The Institute has a public/private partnership with the University of California Berkeley, with which it is currently building the Allen Telescope Array to conduct the next generation of SETI searches. Funding for the Institute's SETI projects is almost entirely through private funds, whereas research within the Center for the Study of Life in the Universe is nearly entirely funded through peer-reviewed grants. Several of the projects proposed here have so far been funded at the pilot project level through private resources made available by the Institute. This proposal therefore represents a private/public partnership with the opportunity for peer-reviewed funding to leverage previous substantial initial private investments into major research accomplishments.

Strengthening the Community

The SETI Institute's EPO programs have a long and successful history of engaging our scientists and educators with teachers and the general public. The Institute's proposed NAI-EPO program [Ms. Edna DeVore] will comprise four major activities: (1) conduct professional development for high school science teachers implementing Voyages Through Time (VTT), an integrated astrobiology curriculum developed by the SETI Institute, and make VTT a resource available to the entire NAI by inviting other NAI teams to participate in the professional development program; (2) collaborate with the California Academy of Sciences to plan and develop new exhibits and to support and participate in education and outreach programs with CAS throughout the NAI membership period; (3) facilitate education outreach, media opportunities, and public event appearances for Institute NAI scientists; and (4) participate in the NAI EPO network and NASA OSS and Education Activities.

For much of the public, one of the topics of greatest interest in astrobiology is the scientific search for intelligent life. While our research and EPO activities span the range of astrobiology, the SETI Institute is unique in being able to bring forefront scientific research on this issue to the NASA Astrobiology Institute.

Strategic Planning and Management

Professor Christopher Chyba is the Principal Investigator for this proposal. Chyba holds the Carl Sagan Chair for the Study of Life in the Universe at the SETI Institute. Chyba is also an associate professor (research) in the Department of Geological and Environmental Sciences at Stanford University. He teaches undergraduate and graduate courses in astrobiology at Stanford, and is currently the PhD thesis advisor for Mr. Kevin Hand.

Chyba has extensive service as chair or member of numerous NASA and other federal committees, and as a leader and integrator of diverse research projects at the SETI Institute. In 1996 he received a Presidential Early Career Award and in October 2001 was awarded a MacArthur Fellowship for his work in both astrobiology and international security.

Chyba, Mancinelli and DeVore will constitute an ongoing strategic planning and management "troika" for this proposal.

Over the past two years, the Center for the Study of Life in the Universe at the SETI Institute has carried out, using private funding, a strategic planning process that demonstrates its ability to bring together research scientists in interdisciplinary and successful ways. Co-chaired by Chyba and USC geomicrobiologist Ken Nealson, this Strategic Planning Group (SPG) brought together some two dozen scientists and engineers to range across the field of astrobiology and identify new areas of innovative research ripe for pursuit by the SETI Institute.