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2003 Annual Science Report

NASA Ames Research Center Reporting  |  JUL 2002 – JUN 2003

Biogeochemistry of Earth's Greenhouse Leading to the Rise of Oxygen

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

The second complete year of this module work has accomplished the technical objective: production of a respectable modern atmospheric chemistry model, which has been incarnated as GAIA, Global Atmospheric Integrator for Astrobiology. GAIA is capable of extending full diel variability of emissions and photochemical concentrations to estimate the composition of a planetary atmosphere on a geologic timescale. GAIA incorporates fully modern descriptions of atmospheric photolysis and ultraviolet (UV) shielding, photochemical reactions, thermal reactions, a simple water cycle, and lower and upper driving fluxes, i.e., biogeochemical interchange and hydrogen escape. It is driven by data tables where possible, making it easy to accomplish parameter studies and to share with other research groups. GAIA performs stably as fluxes of O2 and reduced (CH4, H2) gases are increased, thus allowing a full study of composition accompanying the rise of aerobic life. Interactions with the radiative consequences of composition must be iterated offline, at this point. Previously, there was a “forbidden zone” of parameters using prior models where convergence was not possible, and separate “low-productivity” and “nearly modern” regimes were required. The difficulties of the “forbidden zone” are of course promising that there might be purely chemical instabilities in Earth’s oxic transition. We have found none, yet. Simulations of atmospheric concentrations of greenhouse gases can be achieved for a larger spectrum of plausible O2 and reduced-gas emissions fluxes. The significance of this technology is that we may simulate conditions for the full rise of O2 in the Earth’s atmosphere, including periods associated with “Snowball Earth” and other interesting episodes. The model has been adopted by University of Washington for use by Dr. David Catling’s group. Mr. Mark Claire, a member of Dr. Catling’s group, has received a Graduate Student Research Program grant that will enable him to apply the simulation technique.

    Robert Chatfield
    Project Investigator
    David Catling

    Kevin Zahnle

    Mark Claire
    Doctoral Student

    Objective 1.1
    Models of formation and evolution of habitable planets

    Objective 1.2
    Indirect and direct astronomical observations of extrasolar habitable planets

    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 4.1
    Earth's early biosphere

    Objective 6.1
    Environmental changes and the cycling of elements by the biota, communities, and ecosystems

    Objective 7.1
    Biosignatures to be sought in Solar System materials

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems