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Project Progress

Progress has been made with submodels and fieldwork toward supporting a coherent model of how detectable biosignatures may be produced on extrasolar planets:

Architecture of the coupling between the Life Modules and the geosphere and atmosphere (Kiang, Rye , Bolton , Armstrong, and other NAI teams). The Life Module components from cross-team collaborations have been completed (microbial mats, Archean ecosystem), and links have been forged with NASA Earth Sciences for simulating a planet at different stages of its history, and for validating the model compared to the modern Earth. Improvements to existing Earth land surface models have commenced to predict the currently prescribed albedoes of vegetation. The architecture for interfacing these Life Modules with the geosphere and atmosphere is now in intensive development.

Analysis of life in aquifers and springs associated with terrestrial serpentinizing bodies ( Rye and Johnson). We now have preliminary data on microbial community structure, and have begun to develop clone libraries. Detailed geochemical analysis has allowed us to develop better targeted media for culture work. Despite extremely dilute inorganic chemistry (<100 ppm total dissolved solids) and very simple mineralogy, we find that there is complex organic chemistry present in this system. This site is already serving as a model system for life at the surface of young terrestrial bodies and how it may be simulated.

Process-based, one-dimensional reactive transport models of the interactions between surface rocks, water, atmospheric gases and life ( Rye , Bolton , and Steefel) . The models developed thus far primarily simulate abiological processes, but we have shown that such models can reproduce weathering profiles on black shales, sediments that preserve ancient (dead) biological matter. Such weathering is likely a key part of the biologically driven portion of the carbon cycle as oxygen levels in atmospheres are strongly controlled by the imbalance between carbon fixation and carbon respiration/weathering.

Archean ecosystem model (Kasting and Kharecha) . The investigators have found that hydrogen fluxes and the carbon cycle of the Archean would have readily supported biogenic methane fluxes of the same magnitude as today’s. Previous results suggested that such a flux would allow methane levels to rise to ~350 ppmv, thereby averting massive glaciation. This is more evidence that life can profoundly, and potentially detectably, affect the climate and atmosphere of extrasolar planets, even in the absence of oxygenic photosynthesis.