Starless moons could stay warm for billions as hydrogen atmospheres trap tidal heat

Researchers discovered that moons orbiting rogue planets ejected into interstellar space could remain warm enough for liquid water for up to 4.3 billion years through dense hydrogen atmospheres that trap internal tidal heat. These thick atmospheres, up to 100 times Earth's pressure, use collision-induced absorption to retain heat generated by gravitational stretching as moons orbit their host planets in elongated paths. The study suggests such environments could support early life processes through wet-dry cycles and ammonia chemistry, even without starlight.