Earth System Analysis and the Determination of Habitable Zones

Werner von Bloh
Potsdam Institute for Climate Impact Research, Germany



A conceptual Earth system model is presented in order to investigate the long-term co-evolution of the geosphere-biosphere complex. This integrated system approach includes the basic geodynamic processes and focuses on the global carbon cycle mediated by life and driven by increasing solar luminosity and plate tectonics. The main CO2 sink, the weathering of silicates, as well as the main CO2 source, tectonic processes dominated by sea-floor spreading are calculated. This approach is used to determine the the life span of the biosphere on Earth and to revisit the habitable zone concept, revealing the band of orbital distances from the Sun warranting Earth-like conditions. Furthermore, the model is applied to the determination of habitability in extra-solar planetary systems. Finally, the number of habitable Earth-like planets in the Milky Way over cosmological time scales is investigated. We find that there was maximum number of habitable planets around the time of Earth's origin.



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