This cross-section of Saturn’s frigid moon Enceladus shows how it may be heated from the inside out. As cool water seeps into its porous rock core, the water is warmed by heat generated from tidal forces (caused by Saturn’s gravitational pull on Enceladus). This now-hot water then pushes its way through hydrothermal vents on the seafloor, ultimately melting certain areas of the ocean’s outer icy shell. In turn, this forms fissures in the shell, from which jets of water vapor and particles from the seafloor are ejected into space.