Exploration of the deep-subseafloor-biosphere frontiers: Achievements and perspectives

Abstract

Scientific ocean drilling over the past half-century has significantly expanded our knowledge of life, ocean, and Earth. The discovery of the spatially vast deep-subseafloor biosphere, a milestone scientific achievement, has extended the planetary habitability of life on Earth. To date, multiple lines of evidence form the core samples have demonstrated that a remarkable amount of physiologically unknown microbial life is present deep beneath the ocean floor where water supply and energy substrates are severely limited. Although subseafloor microbial ecosystems generally function extremely slowly, the consequence of long-term activity on geological timescales may play significant ecological roles in global biogeochemical carbon and other elemental cycles.