Out of the five major moons of Uranus, it orbits the planet the second closest, with quite a fast orbiting time of just a few days. One side of this moon always faces Uranus at it orbits it, which we call a tidal lock. The North and South poles of Ariel are victim to this, as it takes Uranus 82 years to orbit the Sun. This means that each pole will see the Sun for 42 years, then get 42 years of darkness.