Some moons may have conditions suitable for the emergence of life Premium

In this week's Science for All newsletter, XX explains

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In an astonishing discovery in 2009, a mission to the moon chanced upon traces of water on the craggy celestial body 3,80,000 km from Earth. Now, scientists have said that distant moons, far away from planets and even the sun, may have conditions suitable for life.

In a new paper in the Monthly Notices of the Royal Astronomical Society, scientists have shown that these ‘exomoons’ around free-floating ‘rogue’ planets — those that have been flung out of their orbits by other planets, and with no parent star — can keep their water oceans liquid for 4.3 billion years, or for almost as long as the Earth has existed and life developed on it.

This is thanks to dense hydrogen atmospheres and tidal heating (or the process of being heated internally). The way the exomoon orbits these free-floating planets keeps changing: the orbit becomes so elliptical that there is a constant change in their distance from the planet, and with this change, the moon gets deformed as its interior is compressed. This push-pull of stresses begins to generate heat through friction.

And so, in this in the icy interstellar space, without a stellar energy source, the tidal heat can still be adequate to keep the liquid water, found the study.

This “definitely expands the possibilities for life to emerge in the universe, as free-floating planets are currently estimated to be at least as numerous as stars in our galaxy,” David Dahlbüdding, doctoral researcher at the University of Munich, and lead author of the study, told The Hindu. “While we could soon detect a first exomoon, detecting life and its biosignatures is another question. For this, one needs to observe the atmosphere and its composition, which is already hard for small rocky planets like the Earth, and likely even more challenging for exomoons,” he added.