Since
the first discovery of chemolithotrophic “rock-eating” microbial life at the
hydrothermal vents, 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. Geochemical processes of water-rock interaction are the
key to providing energy and reducing power for subsurface chemoautotrophic
microbial communities.
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 H
2
gas, methane and higher hydrocarbons
dissolved in saline fracture waters with residence times on the order of
millions to billions 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 Earth’s
deep biosphere, and
is informing exploration strategies for the search
for life on Mars, Enceladus and Europa.