Hydrogen, Hydrocarbons, and Habitability Across the Solar System

The ingredients to make an environment habitable (e.g., liquid water, chemical disequilibria, and organic molecules) are found throughout the solar system. Liquid water has existed transiently on some bodies and persistently as oceans on others. Molecular hydrogen occurs in a plume on Saturn’s moon Enceladus. It can drive the reduction of CO2 to release energy. Methane has been observed in many places: from the dusty plains of Mars, to the great lakes of the Saturnian moon Titan, to the glacial wonderland that is Pluto. Organic molecules are common where volatile elements and reducing conditions prevail: these organic molecules can have diverse origins. Future space missions will attempt to illuminate the “organic solar system” and the role played by possible extraterrestrial life.