Ariel, Uranus' second-closest moon, shows bright, fractured terrain that may have formed above a vast ocean deep beneath its surface, new study suggests. Ariel, one of Uranus' icy moons, may once have concealed a vast ocean more than 100 miles (170 kilometers) deep beneath its frozen crust, according to new research. The findings add to growing evidence that Uranus' moons could have been ocean worlds in the distant past. To do this, the team modeled how Uranus' gravity would have stretched and squeezed Ariel over time, fracturing and reshaping the moon's icy crust. Either Ariel harbored a massive ocean covered by a relatively thin ice shell, or a smaller ocean paired with stronger orbital stresses.