ROLE OF GEOBIOLOGY IN THE ASTROBIOLOGICAL EXPLORATION OF THE SOLAR SYSTEM

Discoveries in geobiology have dramatically shaped our understanding of the nature, distribution and evolutionary potential of terrestrial life, while paving the way for new exploration strategies to search for life elsewhere in our Solar System, and beyond. Terrestrial life has adapted to an astounding array of environmental extremes, being limited primarily by the distribution and abundance of liquid water, nutrients and energy sources. While life's origin remains uncertain, molecular studies suggest that the last common ancestor of life on Earth may have lived in hydrothermal environments where it utilized hydrogen and sulfur as sources of chemical energy. These and related discoveries have contributed extensively to the view that life could be much more widely distributed in the Solar System than once thought. For example, the discovery of a subsurface biosphere on Earth, fueled by inorganic chemical energy, distributed over a broad range of environmental extremes, has opened up exciting new horizons for the astrobiological exploration, with targeted missions to Mars, as well as icy satellites of the outer Solar System. We now believe it possible that life could have arisen in surface environments on Mars earlier in the planet's history, when liquid water was widespread there. Furthermore, a subsurface hydrosphere, suggested by both models and geomorphic evidence, could have sustained continuously habitable zones on Mars that might still support a deep subsurface biosphere today. Ongoing efforts to systematically explore for potentially habitable environments and life elsewhere in our Solar System have helped to catalyze the development of astrobiology, an emerging interdisciplinary science that seeks to understand the origin, evolution, distribution and future of life in the cosmos. Geobiology, which examines the varied interactions of biological and physical/chemical systems and how they have evolved over the history of our planet, is a core discipline of astrobiology, that provides fertile ground for Earth-based analogue studies, as well as the development of exploration strategies and novel technologies for implementing the search for life beyond Earth.