Biogeochemical Cycles and the Search for Life Beyond the Solar System.

NASA and ESA are currently supporting the development of missions to directly detect and characterize Earth-sized planets around other stars. These missions, slated for launch in the 2015 time frame, will provide our first opportunity to spectroscopically study the global characteristics of Earth-like planets beyond our solar system, and to search for the first clues as to whether these planets are currently habitable, or support life. Concepts for subsequent missions will build upon these initial discoveries, but provide higher spectral resolution for improved characterization of the worlds that we find. To inform this mission development, it is important that we understand the global characteristics of planets that support life, at each stage in their evolutionary development. Consequently improvements in our understanding of the evolution of Earth's biogeochemical cycles and the effect that life has on planetary characteristics on a global scale, has direct relevance to the search for life beyond the solar system. This talk will describe current work by the Virtual Planetary Laboratory of the NASA Astrobiology Institute to provide the framework for understanding the links between biogeochemical cycles and detectable global parameters over the course of the Earth's history, and for a range of plausible extrasolar terrestrial planet types. Specifically, we will describe two complementary modeling efforts: 1) ongoing efforts to characterize the cycles of S, C and O globally on early Earth using zero dimensional ecological models as well as 2) the initial development of a mosaic of regional models that will characterize the cycles of a series of biologically relevant elements in several different sorts of environments. The ecological modeling, which is essentially zero dimensional, builds on a heritage of models that have been used to estimate the range of plausible conditions in early Earth systems that lack strong empirical constraints. These models will be used to explore how highly parameterized versions of biogeochemical systems respond to perturbations. Such exploration will help to determine the conditions used in testing the full model. Ultimately, we will replace the simpler ecological models with a mosaic of modules that will describe the biogeochemical and physical behavior of elements as they cycle in environments ranging from the highest mountains to the abyssal ocean plains. These modules will synthesize the state-of-the-art in reactive transport modeling of biogeochemical systems.