At the frozen edge of our solar system, a world long assumed to be geologically dead has revealed signs of restless inner life. Data from NASA's New Horizons mission shows that liquid nitrogen has erupted from beneath Pluto's vast Sputnik Planitia glacier within the past million years — perhaps far more recently — leaving dark, unmistakable traces across the ice. This discovery invites us to reconsider what we mean by 'active' and 'alive' when applied to worlds so remote and cold that our intuitions about planetary behavior no longer serve as reliable guides.