Recurring wet-dry cycles driven by tidal stresses could enable chemical processes essential for the emergence of life, even without sunlight.

A new study from LMU Munich and the Max Planck Institute suggests moons around rogue, free-floating planets could sustain liquid water oceans for up to 4.3 billion years, powered by tidal heating and hydrogen-rich atmospheres.

In these cold, dark environments, hydrogen-driven warming outperforms CO2-based greenhouse effects because CO2 would condense, making hydrogen a more robust mechanism at very low temperatures.

If rogue planets with moons are common, the Milky Way could host many more habitable environments than previously imagined, effectively widening the habitable-zone concept into interstellar space.

Hydrogen atmospheres trap heat through collision-induced absorption, acting like an insulating blanket that sustains long-lived habitable conditions in extreme cold.

The research draws a parallel to early Earth, proposing hydrogen-rich environments and tidal activity could drive prebiotic chemistry and molecular cycles on rogue moons.

Tidal heating from a moon's gravitational flexing can keep surface oceans from freezing in the absence of starlight.

Rogue planets are ejected from their systems and roam interstellar space, often retaining moons on highly eccentric orbits that influence their thermal and chemical dynamics.