Over the last few decades, planetary scientists have been steadily adding to the list of moons in our solar system that may harbor interior oceans either currently or at some point in their past. For the most part, these moons (such as Europa or Enceladus) have been gravitationally bound to the gas giants Jupiter or Saturn. 

Recently, though, planetary scientists have been turning their attention further afield, towards the ice giant Uranus, the coldest planet in the solar system. And now, new research based on images taken by the Voyager 2 spacecraft has suggested that Miranda, a small Uranian icy moon, may have once possessed a deep liquid water ocean beneath its surface.