August 25 th, 1989 Voyager 2 encounters with Uranus and Neptune January 24 th, 1986August 25 th, 1989

The English astronomer, William Herschel, discovered Uranus in 1781

McDonald Observatory image of Uranus and some of its moons

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Uranus is the only planet whose axis of rotation lies in its orbital plane (tilt of 98°), probably caused by a large impact.

Comparison of the densities and compositions of the Jovian planets

Interior Structure of Uranus and Neptune *

Approach of Viking 2 on July 15, 1985 of Uranus and 4 of its moons (composite).

False color (left) and true color images of Uranus, taken by Viking 2

The ring system of Uranus

Some of the rings of Uranus, discovered by the Viking spacecraft

Rings of the planet Uranus, with two shepherd moons which keep the ring particles in place, discovered by the Viking spacecraft

Continuous distribution of small particles throughout the ring system of Uranus. Picture taken while the Viking spacecraft was in the shadow of Uranus. These dust lanes were previously unknown. 96 second exposure, hence, background stars form streaks.

Epsilon ring of Uranus, and three of the moons discovered by the Viking spacecraft

Size comparison of the larger moons of Uranus

Miranda, ~468 km in diameter

5 km high scarp on Miranda – Miranda may have split apart and reassembled

50 km wide “chevron” on Miranda indicates complex history

Ariel – 1,160 km in diameter; shows many tectonic features

Umbriel - 1,168 km in diameter Resolution of this Viking image is ~ 10 km. Umbriel is highly cratered, particularly on its southern hemisphere (right). It is the darkest moon of Uranus, with an albedo of ~ 16 %, like our moon. It also is the moon with lowest internally- generated geologic activity. The bright spot at the top of the image (near the equator) may be frost.

Titania – 1,580 in diameter; heavily cratered but also has long scarps

Oberon – 1,520 km in diameter; bright surface markings, many impact craters