This grant provides two years of continued administrative and research support to the Deep Life Community of the Deep Carbon Observatory (DCO). One of four scientific communities within the DCO, the Deep Life community is a multi-national consortium of scientists working to revolutionize our understanding of the quantities, movements, forms, and origins of deep life. Subsurface microbial ecosystems may extend to 20,000 feet beneath the seafloor and continental surface, and studies of these deep, dark biological reservoirs suggest their total carbon content may rival all surface life. Instead of tapping into solar power, deep microbial communities harvest energy from fuels such as methane and hydrogen sulfide or buried detrital matter to drive synthesis of macromolecules and reproduce. Led by microbial biologist Mitch Sogin of the Marine Biological Laboratory, the Deep Life Community will use grant funds to extend molecular studies to a greater number of samples from high-value marine and continental sites and describe the diversity, distribution, and functional adaptations of deep life. Experiments will explore life’s interplay with geological processes in the deep subsurface, including studies of microbial activities and distributions in hydrogen-rich habitats which favor abiogenic synthesis of methane and higher hydrocarbons. In addition, deep life researchers will explore the limits of deep life using improved life detection capabilities and develop and apply tracer approaches to track the flow of carbon into biomolecules and cells.