URANUS' SATELLITES

157Uranus' satellites are known at the moment: Ariel, Belinda, Bianca, Caliban, Cordelia, Cressida, Desdemona, Juliet, Miranda, Oberon, Ophelia, Portia, Puck, Rosalind, Sycorax, Titania, and Umbriel. Their names come from characters of Shakespeare's and Pope's works. Titania and Oberon, the largest ones, were discovered by Herschel in 1787; then come Ariel, Umbriel and Miranda. All the remaining ones were unknown until a few years ago, and have been discovered by the Voyager 2 probe as late as 1986. All these satellites have nearly circular orbits, which lay on the equatorial plane of the planet. Thus, they are very inclined with respect to its orbital plane. In fact, the rotation axis of Uranus is inclined by just 8 degrees above its orbital plane.

           Distance    Radius    Mass
Satellite  (x1000 km)    (km)    (kg)   Discoverer   Date
---------  ----------  ------  -------  ----------  -----
Ariel             191     579  1.27e21  Lassell      1851
Belinda            75      34    ?      Voyager 2    1986
Bianca             59      22    ?      Voyager 2    1986
Caliban          7200      30    ?      Gladman      1997
Cordelia           50      13    ?      Voyager 2    1986
Cressida           62      33    ?      Voyager 2    1986
Desdemona          63      29    ?      Voyager 2    1986
Juliet             64      42    ?      Voyager 2    1986
Miranda           130     236  6.30e19  Kuiper       1948
Oberon            583     761  3.03e21  Herschel     1787
Ophelia            54      16    ?      Voyager 2    1986
Portia             66      55    ?      Voyager 2    1986
Puck               86      77    ?      Voyager 2    1985
Rosalind           70      27    ?      Voyager 2    1986
Sycorax         12200      60    ?      Gladman      1997
Titania           436     789  3.49e21  Herschel     1787
Umbriel           266     585  1.27e21  Lassell      1851

Ariel, the lightest-colored of Uranus' satellites, has craters, valleys and canyons. (NASA/JPL)

Miranda is the smallest and inner of the major Uranus' satellites. It has two types of ground: the one shown in this figure is old, cratered and irregular. The other one is younger and has rifts and slopes. (NASA/JPL)

Oberon, whose surface is frozen and full of craters. Near the left edge a mountain can be seen, 6 km high. (NASA/JPL)

Titania is the biggest satellite among those of Uranus. It has a few impact basins, craters and rifts. (NASA/JPL)

Umbriel  is the darkest-colored satellite. Its surface is old and cratered. (NASA/JPL)