According to new mathematical modeling, some of those moons – at least, those with very specific conditions – could potentially harbor both atmospheres and liquid water, thanks to a combination of cosmic radiation and the tidal forces exerted on the moon by the gravitational interaction with its planet.

This heat is also what helps keep the water on Earth's surface liquid – a prerequisite for life as we know it.

So, a team of scientists led by astronomer Patricio Javier Ávila of the University of Concepción in Chile sought to model the possibility of such exomoons existing around rogue gas giant exoplanets.

Their findings suggest that a significant amount of water can be formed in the exomoon's atmosphere, and retained in liquid form.

This would produce 10,000 times less water than Earth's oceans, but 100 times more than the atmosphere – that, the researchers said, would be sufficient for life.