Moons of Uranus
Moons of Uranus
Here a Solar System trivia question for you:
What world has a canyon 12 times deeper than the Grand Canyon with gravity so low that a rock dropped from the top would take 10 minutes to reach the bottom?
If you guessed Mars, nice try. But, you're incorrect.
The world is called Miranda, which is one of the 27 moons of Uranus. The planet has a fascinating collection of satellites, most of which were discovered only recently.
Uranus is so far from Earth – nearly 3 billion miles – that it was not until 1781 that William Herschel discovered the planet. It took the British astronomer another six years to find the two largest of Uranus' moons, which were named Oberon and Titania. In the two centuries that followed, astronomers found only three other moons – Ariel, Umbriel and Miranda.
That changed when Voyager 2 swept past Uranus in 1986. The NASA spacecraft, the first and only probe to explore the planet, discovered 10 new moons around Uranus and revealed some startling details about the known ones.
Miranda is the most bizarre moon in our Solar System. Measuring a mere 500 km in diameter, the strange world is made up of varied types of terrain that seem to have been assembled, Frankenstein-style, from other worlds. The moon has massive fault canyons as well as "coronae," which are lightly cratered collections of relatively new ridges and valleys separated by sharp boundaries from older, more heavily cratered areas.
Cratered Surface of Miranda
No one is sure what forces are responsible for Miranda's odd appearance. Some scientists believe that the coronae resulted from large meteorite strikes that melted subsurface ice, which then refroze. Others suspect that Miranda re-assembled itself after being torn apart by a large collision with another object.
Voyager 2 also revealed some fascinating things about the other moons of Uranus. Ariel, composed of water ice and silicate rock, is the brightest of the 27 satellites. It also has one of the youngest surfaces, with many smaller craters that appear to have wiped away larger ones created earlier in the moon's history. The moon also features fault-bound valleys known as grabens.
Umbriel is one of the oldest and darkest of Uranus' moons, reflecting only 16 percent of the light that strikes it. Precisely why the world is so dark is uncertain. However, Umbriel has a very bright ring that measures about 140 km (90 miles) across, which could be frost deposits around the outer edges of an impact crater.
Two satellites, Cordelia and Ophelia, are shepherd moons that keep the materials in Uranus' outer "epsilon" ring in place. Similar moons perform the same function for Saturn's rings.
Uranus' moons are not named for figures from Greek and Roman mythology like many worlds but rather characters from the plays of William Shakespeare and Alexander Pope. Oberon, Titania and Puck honor fairies in "A Midsummer Night's Dream."
"Sweet Moon," Shakespeare wrote in that play. "I thank thee for thy sunny beams; I thank thee, Moon, for shining now so bright." Although he was writing of Earth's moon, the sentiment seems appropriate for the moons of Uranus.
Learn More about Uranus' Moons
Uranus: Moons Solar System Explorer