Hydrogen‑rich moons of rogue planets stay habitable
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- David Dahlbüdding led a study (with Giulia Roccetti) that predicts hydrogen‑dominated atmospheres on moons of free‑floating exoplanets can retain tidal heat and stay habitable for billions of years after planetary ejection.
- Hydrogen in high‑pressure atmospheres can absorb infrared radiation via collision‑induced absorption, acting as a potent greenhouse gas comparable to CO₂ and methane.
- Moons with hydrogen atmospheres up to 100 times Earth’s surface pressure could keep surface temperatures high enough for liquid water for up to 4.3 billion years after their host planet’s ejection.
- Giulia Roccetti’s 2023 orbital‑circularization model was incorporated to estimate how tidal heating declines over time, allowing calculation of the maximum habitable duration.
- Detection of such exomoons may become feasible soon, but confirming atmospheric composition remains out of reach for the near future.
- Early Earth may have experienced similar hydrogen‑rich, high‑pressure conditions that enhanced collision‑induced absorption, potentially aiding the formation of RNA.
Why it matters: Astrobiologists gain a vastly larger pool of potentially habitable worlds, as moons of rogue planets could sustain liquid water for billions of years without stellar heating, while the study also offers a new perspective on early Earth’s chemistry, implying that hydrogen‑rich atmospheres may have been crucial for the origin of life.
