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2006 Annual Science Report

Virtual Planetary Laboratory (JPL/CalTech) Reporting  |  JUL 2005 – JUN 2006

The Generalized Terrestrial Planet Photochemical Model

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

We have completed the updates and interfacing to the KINETICS model for planetary atmospheric chemical composition. The updated KINTEICS is now a generalized model for terrestrial planet atmospheres ranging from CO2 to N2 dominated, which interfaces with the VPL database, so that it can be used in conjunction with models of other planetary components from within the VPL modeling suite. KINETICS can now be used to model the chemistry of planetary atmospheres not found in our Solar System. A master reaction and chemical species list has been compiled by consolidating individual reaction and species lists for present-day and Early Earth, Mars, Venus, Titan and Jupiter, a total of 616 species and 2247 reactions. The structure for input of photochemical data has been re-engineered to easily allow existing photochemical cross sections to be updated and for additional cross sections to be added to the model. To improve ease of use, KINETICS can now be run from the VPL model GUI interface. The new model is currently being used to explore the chemistry of sulfur and hydrocarbon species in the Martian atmosphere.

A paper using KINETICS, “Production of Oxidants in the Atmosphere of a Snowball Earth: Implication for the Origin of Oxygenic Photosynthesis” by Mao-Chang Liang, Hyman Hartman, Robert E. Kopp, Joseph L. Kirschvink and Yuk L. Yung has been submitted to PNAS. In that paper, the models indicate that, during ‘hard Snowball’ intervals, a weak hydrological cycle coupled with photochemical reactions involving water vapor would give rise to the sustained production and sequestration of hydrogen peroxide. This compound would be buried in the snow/ice and would accumulate over the lifetime of the Snowball. The accumulated oxidant would be released directly into the ocean and the atmosphere upon melting and could explain global oxidation events in the aftermath of the Snowball. Low levels of peroxides generated during Archean and earliest Proterozoic non-Snowball glacial intervals could have driven the evolution of oxygen-mediating enzymes and thereby paved the way for the eventual appearance of oxygenic photosynthesis.

    Mark Allen Mark Allen
    Project Investigator
    Jason Weibel
    Project Investigator
    Mao-Chang Liang

    Giovanna Tinetti

    Yuk Yung

    Objective 1.1
    Models of formation and evolution of habitable planets

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems