This research provides the theoretical framework and tools needed to model and interpret the increasing evidence for the presence and actions of microbes in the deep biosphere in oceanic crust. It will also allow us to make predictions of microbial habitation and metabolic mechanisms which will ensure greater returns on the costly investments required to access the deep biosphere through seafloor exploration and drilling. This research uses existing data on diffuse fluids and altered rocks from subsurface basalt aquifers to quantify the supply of energy that can be used by microbes.

Work to codify the interactions between essential biomolecules and enzymes and geological materials will permit the prediction of mechanisms of microbial metabolism as function of temperature, pressure, fluid composition, and extent of rock alteration. Justification for the work comes from the fact that the deep biosphere in the oceanic crust is sustained by the disequilibrium between seawater and igneous rocks. Recent work provides estimates of the supply of energy that supports the deep biosphere derived from observations of the extent of oxidative alteration of basalts and other crustal igneous rocks that suggest the portion of the deep biosphere hosted in altering igneous rocks may rival that in seafloor sediments. As a result, the deep biosphere has become a major target for Earth exploration, but lack of knowledge of the signatures of and metabolic needs of microbes in the subsurface have prevented us from adequately investigating their presence and importance. This research attacks this issue.

Broader impacts of the work include development of a thermodynamic framework for microbiological processes that will be made publicly available on the Internet. Results of the work also cross over into biology and can be used by environmental scientists for the bioremediation of toxic waste and the downstream impacts of engineered nanoparticles. The work also supports the training of graduate and undergraduate students and the creation of a display for the Arizona State University Open House and Museum on the deep biosphere. Work will complement activities in both NSF's IODP and Ocean Observing Systems Programs.