Uranus has 27 moons, but the researchers focused on the five largest, which are Ariel, Umbriel, Titania, Oberon and Miranda. Of these, Ariel is the smallest at 720 miles (1,160 kilometers) across, while Titania is the largest at 980 miles (1,580 km) across.
Previously, scientists thought only Tatiana was likely to generate any internal heat via radioactive decay — the process by which unstable atoms lose energy through radiation — believing the other moons to be too small.
However, modeling the other moons' porosity suggested that all but Miranda are insulated enough to retain internal heat created by radioactive decay.
The researchers also found that any potential oceans beneath the icy crusts of these moons would be rich in chlorides, ammonia and salts, both of which would lower the freezing point of the water. The combination of a low freezing point and enough internal heat could mean that Ariel, Umbrial, Titania and Oberon all have oceans dozens of miles deep within their interiors, the researchers reported.