LExEn: Stochastic Photochemistry and Stochastic Photobiology in the Galactic Environment

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ABSTRACTP.I.: Wheeler, J. Craig Proposal Number: AST-9907582"LExEn: Stochastic Photochemistry and Photobiology in the Galactic Environment"This project seeks to understand the importance and implications of a new type of extreme environmental influence that should affect the development of microbial life in most planetary and satellite systems: frequent short-lived jolts of high-energy photons and particles that are an inevitable consequence of the Galactic environment. These events include various phenomena associated with supernovae, novae, gamma ray bursts, and supernova remnant shocks. The project will demonstrate, by comparing the estimated source fluxes with the solar background and minimum levels for biological activity, whether these events can drive non-equilibrium photochemistry in the atmospheres of planets and satellites. They may also be a potent intermittent source of biological alteration for microorganisms on planets with or without ultraviolet shields like ozone. Specific problems that are being addressed include: (1) the probability that these various sources of high energy radiation exceed the background flux received from the Sun; (2) hydrodynamics and radiative transfer in the astronomical sources, especially in the early shock breakout stage of supernovae; (3) transformation of the emitted spectral energy distributions as they propagate through the model prebiotic, Archean, and post-ozone atmospheres; (4) non-equilibrium photochemistry in outer Solar system bodies like Titan; and (5) biological effect of both the calculated surface fluxes and the variation in stellar flux due to changes in atmospheric chemistry on microorganisms.This project is part of the NSF Life in Extreme Environments (LExEn) program.Funding is provided by the NSF Division of Astronomical Sciences StellarAstronomy & Astrophysics (SAA) program and the NSF Division of Molecular& Cellular Biosciences (MCB).