Barbara Ercolano

Astronomers investigated the possibility of submoons—small moons orbiting other moons. It turns out Earth could host an asteroid-sized submoon, while giant planets might have entire Earth-like worlds. But for life to emerge, a submoon needs about half of Earth's mass, and at that very mass its orbit

Scientists have found: moons around rogue planets can stay warm and wet for billions of years. A dense hydrogen atmosphere traps heat, and tidal forces warm the interior. These conditions are suitable for the emergence of life, including the formation of RNA.