Umbriel (moon) that obliterated its older surface. Covered by numerous impact craters reaching in diameter, Umbriel is the second most heavily cratered satellite of Uranus after Oberon. The most prominent surface feature is a ring of bright material on the floor of Wunda crater. This moon, like all moons of Uranus, probably formed from an accretion disk that surrounded the planet just after its formation. The Uranian system has been studied up close only once, by the spacecraft "Voyager 2" in January 1986. It took several images of Umbriel, which allowed mapping of about 40% of the moon’s surface. Umbriel, along with
Dysnomia (moon) pronounces the same as his wife's nickname, Di. Because of this, Brown pronounces the full name , with a long "y". Dysnomia serves as the extraterrestrial origin of the alien antagonist in the independent horror/comedy short film, "Skinhead Junkies From Dysnomia". Dysnomia (moon) Dysnomia (Greek: "Δυσνομία")—officially (136199) Eris I Dysnomia—is the only known moon of the dwarf planet Eris (the most massive known dwarf planet in the Solar System). It was discovered in 2005 by Mike Brown and the laser guide star adaptive optics team at the W. M. Keck Observatory, and carried the provisional designation of until officially named