Thursday, 28 July 2016
Astrobiology, the search for the origin and distribution of life in the universe, demands a bold, interdisciplinary research strategy. To explore such a history requires the integration of forefront research in astronomy, chemistry, planetary sciences, and biology. Here, we propose such a far-reaching effort. Life’s origin remains a mystery, but all life as we know it requires an environment with three key ingredients: energy, water, and access to the critical elements from which biochemistry is assembled. Our proposal outlines a narrative that traces the evolutionary path starting with Solar System formation, planetary accretion and migration, moving on to planetary evolution, prebiotic molecular synthesis and ultimately the organization to cellular evolution and diversification. We propose to begin our study of life’s origin with investigations of the chemical evolution of circumstellar disks – environments in which simple organic molecules first are introduced to the nascent Solar System. We also propose to consider the fate of this organic matter during planetary formation through observations of extrasolar planets and through modeling of planetary system formation. These studies will be informed by our ongoing analytical research on organic matter in extraterrestrial samples, including meteorites, interplanetary dust particles, and comets. We propose to study the formation and early evolution of terrestrial planets, placing specific focus on the delivery and retention of volatiles on and within the terrestrial planets and the role of plate tectonics in sustaining deep carbon cycling in the mantle.
Life’s narrative continues via prebiotic molecular evolution on Earth, a subject that has inspired a half-century of chemical research. We propose to expand our investigations into the role that transition-metal minerals may have played in promoting key prebiotic organic reactions. Additionally, we will evaluate processes by which specific prebiotic organic species (such as chiral molecules) were selected, concentrated, and organized into macromolecular systems, through selective adsorption on mineral surfaces.
Complementary to these bottom-up investigations of life’s origin, we will continue our topdown efforts to document the nature of microbial life at extreme temperatures and pressures, including field studies of hydrothermal environments at deep-sea hydrothermal vents as well volcanic associated vent systems. Fieldwork will be complemented by laboratory studies of high-pressure microbial survival and adaptation. We will place specific focus on the studies of the isotopic signatures of microbial metabolism – as both a means of tracking metabolic evolution in the rock record as well as validating the use of isotopic abundance as a biosignature for life.
Astronomical observation, i.e. remote sensing of the existence, composition, and dynamics of planetary systems, remains a central astrobiological enterprise. The study of exosolar planetary systems simultaneously informs our thinking about the formation and evolution of our own Solar System and reveals the myriad paths the natural processes of star and planet formation take. Habitable environments depend on how the raw materials of the interstellar medium are processed to create planets.