Unlike our Moon, they can keep water in oceans liquid for more than 4 billion years.

Add Yahoo as a preferred source to see more of our stories on Google. When you buy through links on our articles, Future and its syndication partners may earn a commission. This artist's concept of a ...

Add Yahoo as a preferred source to see more of our stories on Google. This artist’s concept depicts a potential volcanic exomoon between the exoplanet WASP-49Ab, left, and its parent star.

While all the ingredients are there, the moon's composition likely prevents them from coming together in any meaningful way. Reading time 3 minutes Saturn’s moon Titan is often pegged as one of the ...