Pluto is thought to possess a subsurface ocean beneath its thick ice shell. It has generally been assumed that the dwarf planet formed out of cold material and then later developed its ocean due to warming from radioactive decay. By combining numerical simulations with geological observations by NASA’s New Horizons mission, a team of researchers from the University of California Santa Cruz and the Southwest Research Institute demonstrated that Pluto was instead relatively hot when it formed, with an early subsurface ocean.