Rogue Planets Can Have Underground Oceans

Rogue planets—worlds that got kicked out of their solar systems—should be frozen, lifeless rocks. No Sun means no heat, right? Not always. Some of them, especially rocky planets about 3.5 times Earth’s mass, may have deep, subsurface oceans heated by their own interior. Imagine an Earth-like planet, lost in the dark, but still with a vast ocean buried under miles of ice. No sunlight, no seasons, but geothermal vents keeping everything liquid. Could life survive there? Maybe. Some scientists think rogue planets could be common, meaning the universe might be full of hidden ocean worlds, drifting forever in the void.