72 Exploration of the Deep Biosphere

Monday, 10 October 2011
8:00 AM - 12:00 PM
Room 101A-C

FOLLOW THE WATER - A SEARCH STRATEGY FOR EXPLORATION OF THE EARTH'S DEEP BIOSPHERE

Paper number: 72-4
Program: Technical Sessions
Time: 9:05 AM – 9:35 AM

Authors

Abstract

The discovery of life at the hydrothermal vents sparked a revolution in our understanding of the range of possible mechanisms for sustaining life. Since that time, our understanding that life is not simply a thin veneer on the earth's surface but may permeate deep into the subsurface of this planet has evolved rapidly. Serpentinization of ultramafic rocks and alteration of basaltic ocean floor have been invoked as key mechanisms by which geochemical processes of water-rock interaction may provide energy and reducing power for chemoautotrophic microbial communities on the seafloor. A major gap remains in our understanding of life in the deep, but not so hot, biosphere. Investigations, particularly in the continental or terrestrial deep subsurface, are recognizing that chemosynthetic communities are not restricted to the high temperature hydrothermal vents and springs, but can be sustained under lower temperature regimes by similar types of water-rock reactions, albeit at slower rates. The implications of this conceptual evolution are profound, as it suggests much larger volumes of the Earth's subsurface may be habitable.

Via the Deep Carbon Observatory, a Network for Inner Space Observation (NISO) has brought together teams of researchers in geology, geochemistry, hydrogeology, microbiology and genomics to explore Earth’s “Inner Space” taking advantage of deep boreholes, subsurface mines and deep research laboratories worldwide. The presentation will highlight work at underground sites in 2-3 billion year old Precambrian Shield rocks in South Africa, Canada and Finland where isotope geochemistry has identified large accumulations of free H2 gas, methane and higher hydrocarbons dissolved in saline fracture waters with residence times on the order of millions of years. The integration of isotopic, geochemical and hydrogeological investigations with molecular and culture-based microbiology provides an exploration strategy to identify different zones of habitability in the deep biosphere and demonstrates that hydrogeologically-isolated fracture networks of geochemically distinct groundwaters exert a major control on the distribution and nature of microbial life and metabolic function in the deep surface.