Hydrogen-producing hydrothermal systems in the deep ocean are rare but critical to understanding Earth's internal processes and the conditions that may have fostered life's origins. Now scientists from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) have discovered a massive hydrogen-rich hydrothermal system beneath the western Pacific seafloor, offering a new glimpse into deep-sea serpentinization—a process in which iron- and magnesium-rich rocks chemically react with water to form serpentine minerals and release hydrogen.