Titania (moon) have a spatial resolution of about 3.4 km (only Miranda and Ariel were imaged with a better resolution). The images cover about 40% of the surface, but only 24% was photographed with the precision required for geological mapping. At the time of the flyby, the southern hemisphere of Titania (like those of the other moons) was pointed towards the Sun, so the northern (dark) hemisphere could not be studied. No other spacecraft has ever visited the Uranian system or Titania, and no mission is currently planned. One possibility, now discarded, was to send "Cassini" on from Saturn to Uranus in
Moons of Neptune formed "in situ". Triton and Nereid are unusual irregular satellites and are thus treated separately from the other five irregular Neptunian moons, which are more like the outer irregular satellites of the other outer planets. Firstly, they are the largest two known irregular moons in the Solar System, with Triton being almost an order of magnitude larger than all other known irregular moons. Secondly, they both have atypically small semi-major axes, with Triton's being over an order of magnitude smaller than those of all other known irregular moons. Thirdly, they both have unusual orbital eccentricities: Nereid has one of the