“Planetary Biology, Evolution and Intelligence”
We ask 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? We 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, and 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. This research, sponsored by the NASA Astrobiology Institute, 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 will be exploring two new investigations into the oxidation of early Earths environment. While the biological aspects of this ‘oxygen transition’ have been recently emphasized, both mechanisms to be explored here (peroxy in rocks and aerosol formation in the atmosphere, building on an analogy to processes now occurring in the atmosphere of Saturns 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 photosynthetic organisms possible. We will test 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.
SETI Institute NAI
NASA Astrobiology Institute (NAI)