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Subsurface Biospheres Team

A better understanding of the Earth’s deep biosphere is essential because it can serve as a model for life on other planets, and it is a critical component of the Earth’s biogeochemical cycles. The University of Rhode Island (URI) Team works to gain a fundamental understanding of the life in deeply buried marine sediments.

Interdisciplinary sets of projects are carried out to take advantage of the considerable URI expertise in marine sedimentary microbiology, sedimentary biogeochemistry and deep ocean drilling. URI objectives are to understand the subsurface microbial ecosystems of marine sediments, their role in Earth’s biogeochemical cycles, and their relevance to the search for life on other planets.

Major Research Projects

• Explore the taxonomic composition, metabolic activity and geochemical consequences of buried microbial ecosystems in marine sediments with widely different physical and chemical characteristics
  Research environments include: (1) hot, deeply buried anoxic sediments where life may exist independently of the photosynthesis-based ecosystem at Earth’s surface and (2) old, deeply buried sediments where life may be limited by the availability of electron donors or key nutrients. The ecosystems of these subsurface habitats are potentially representative of the ecosystems that may exist on other planets.
• Document the nature, extent and perturbation-sensitivity of microbial activity in marine sediments and the effect of that activity on Earth’s biogeochemical cycles of various chemical species, particularly sulfate and methane.
  Sulfate, the second most abundant anion in seawater, is the dominant terminal electron acceptor in marine sediments. Methane is climatically active, and marine methane deposits comprise the largest untapped hydrocarbon reservoir on Earth. Biogeochemical cycles of these and other chemical species are potentially sensitive to time changes (centennial to millenial time periods) in Earth’s surface temperatures, nutrient fluxes to the ocean, and the structure of marine ecosystems.
• Identify signatures of present and past microbial processes in Earth’s subsurface as a guide to predicting such signatures in extraterrestrial subsurface environments
  Molecular-isotopic data generated as part of this project complements the objectives of the first two projects. For example, the study of biomarkers produced by deeply buried methanotrophic microbes will give us an indication of both past and present activity of this specific taxonomic group.

Research: Samples and Analysis Tools

• Deep Pacific drill-hole sample sets
• Procedures to identify sample contamination
• Set up instruments in a microbiology laboratory on the Ocean Drilling Program (ODP) drill-ship JOIDES Resolution
• Compile relevant global geochemical and physical databases
• Participation in the first ODP Leg (Leg 201) dedicated to Subsurface Biosphere research scheduled for 2002

These and other developments provide the framework for collecting, analyzing, and interpreting microbiological, biogeochemical, and physical data from a wide range of deep subsurface samples. This framework leaves us poised to advance Subsurface Biosphere objectives significantly.

Our approach is fundamentally interdisciplinary, and we will use advanced techniques from various fields, including microbiology, molecular biology, organic and inorganic biogeochemistry, isotope geochemistry, large data set integration and computational modeling. The work will be field-, laboratory-, and model-based. In order to effectively accomplish the program’s goals, we build teams of investigators, post-doctoral researchers, graduate students, and select undergraduate students with diverse skills. We are fully committed to implementing the collaborative and networking concepts of the NASA Astrobiology Institute.