2005 Annual Science Report

Virtual Planetary Laboratory (JPL/CalTech) Reporting  |  JUL 2004 – JUN 2005

The Virtual Planetary Laboratory - The Life Modules

Project Summary

Coupled model of the anaerobic, early Archean biosphere, prior to the origin of oxygenic photosynthesis (Kharecha, Kasting, and Siefert). This model includes organisms that metabolize using H2, H2S, and Fe++ as reductants. A primary goal was to estimate the production rate of methane.

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

Coupled model of the anaerobic, early Archean biosphere, prior to the origin of oxygenic photosynthesis (Kharecha, Kasting, and Siefert). This model includes organisms that metabolize using H2, H2S, and Fe++ as reductants. A primary goal was to estimate the production rate of methane. For reasonable assumptions about hydrogen outgassing and escape rates, CH4 production should have been within a factor of 3 of the modern value, ~500 Tg CH4/yr. In the low-O2 Archean atmosphere, this would have been enough to produce CH4 concentrations of 1000 ppmv, or higher. Such CH4 concentrations could have helped to keep the climate warm despite reduced solar luminosity at that time.

Horizontal gene transfer (HGT) and its effect on genome coalescence (Siefert). The effect of HGT on cyanobacterial genomes and the Bacilliaceae lineage has been examined using a bioinformatics approach. It is found that genes can be defined that are both unique and less likely to be transferred in each lineage of bacteria.

Analysis of life in aquifers and hyperalkaline (pH > 11) dilute (<100 ppm total dissolved solids) springs associated with terrestrial serpentinizing bodies ( Rye, Johnson). We are characterizing the microbial community structure at the Cedars site, California. Analysis of data from DGGE experiments has yielded a preliminary tree of roughly 20 novel organisms. Media development has now allowed us to isolate a number of pure cultures, all of which map within the Betaproteobacteria. This site continues to serve as a model system for the simulation of life at the surface of young terrestrial bodies.

Photosynthetically active radiation and light-harvesting photosynthetic pigments on Earth-like planets around F, K, and M stars (Kiang, Segura, Siefert, Tinetti, Cohen, Meadows). A paper is soon to be submitted on our extensive survey of Earth’s photosynthetic organisms, comparing their metabolisms, pigments, reflectance spectra, and environmental niches. We have identified strong candidate wavelengths of photosynthetic pigment light absorption for organisms evolved on Earth-like planets orbiting F, K, and M stars with different atmospheric compositions (Figure 1), thus defining potential alternative biosignatures for remote detection.

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  • PROJECT INVESTIGATORS:
    Nancy Kiang Nancy Kiang
    Project Investigator
    Robert Rye Robert Rye
    Project Investigator
  • PROJECT MEMBERS:
    Brad Bebout
    Co-Investigator

    James Kasting
    Co-Investigator

    Janet Siefert
    Co-Investigator

    Martin Cohen
    Collaborator

    David Des Marais
    Collaborator

    Victoria Meadows
    Collaborator

    Antigona Segura-Peralta
    Collaborator

    Giovanna Tinetti
    Collaborator

    Orion Johnson
    Doctoral Student

    Pushker Kharecha
    Doctoral Student

  • RELATED OBJECTIVES:
    Objective 3.2
    Origins and evolution of functional biomolecules

    Objective 3.3
    Origins of energy transduction

    Objective 4.1
    Earth's early biosphere

    Objective 4.2
    Foundations of complex life

    Objective 5.3
    Biochemical adaptation to extreme environments

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

    Objective 6.2
    Adaptation and evolution of life beyond Earth

    Objective 7.1
    Biosignatures to be sought in Solar System materials

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems