The Moons of Uranus: Underrated Worlds
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| Modelling of possible interiors of the major moons of Uranus. Credit: NASA/JPL-Caltech |
Uranus is the butt of a lot of jokes, and along with being really far out, it could be why only one mission has ever been sent to it. Which is too bad, because Uranus is a fascinating world. However this article is not about Uranus, but about its moons. The moons of Uranus are much smaller than those around Jupiter or Saturn, but five of them are large enough to be roughly spherical. The moons orbit sideways along the lopsided equator of Uranus. These moons aren't named after mythological features (well some are), but after characters from Shakespeare and Alexander Pope.
The only mission to visit Uranus was Voyager 2 in 1986, and we haven't been there since. However in 2022, a Uranus flagship mission was announced as the one of the next big outer solar system planetary missions for NASA, on par with the Cassini-Huygens mission to Saturn. The mission would probably orbit Uranus, and send an atmospheric probe into the clouds like the one aboard the Galileo spacecraft. While it would primarily study Uranus, it would take hundreds of images of the surrounding moons, giving us unprecedented knowledge about the system. Unfortunately, the mission probably won't get to Uranus until the 2040s. Meanwhile, we'll have to do with the decades old Voyager 2 images for this article.
Miranda
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| Credit: NASA/JPL-Caltech |
- Date Discovered: February 16, 1948 by Gerard Kuiper
- Mass: 6.594141106x10^19 Kilograms
- Radius: 235.8 Kilometres
- Density: 1.178 g/cm^3
- Surface Gravity: 0.079 m/sec^2
- Rotational Period: 34 hours
- Orbital Period: 34 Hours
Gerard Kuiper discovered Miranda at the McDonald Observatory in Texas on February 16, 1948. This was the last discovery of a moon around Uranus until the Voyager 2 flyby in 1986. Miranda is the smallest of Uranus's major moons. However it has the best images, because Voyager 2 was able to approach Miranda closer than the other moons during its flyby. Miranda is highly unusual in its appearance, with scars and cliffs everywhere you look. The original theory for this absurd looking geology was that Miranda suffered a violent impact that tore it to pieces. These fragments then reformed the moon in a hodge-podge fashion. However newer theories suppose that Miranda could be suffering geological upheaval in parts of its surface due to tidal heating with Uranus and the other moons. Or perhaps meteor collisions warmed up some parts of the surface, causing the Frankenstien-esque surface. A unique suface feature that's only found on Miranda is known as a "corona." These coronae are lighter patches of the surface that possess less cratering. Miranda possesses the tallest cliff in the solar system: Verona Rupes, which can be seen at the bottom of this image. The cliffs are almost 10 kilometres high, and due to the low gravity, it would take 10 minutes for a rock to fall from the top to the bottom. The moon takes its name from the daughter of Prospero in Shakespeare's "The Tempest."
Ariel
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| Credit: NASA/JPL |
- Date Discovered: October 24, 1851
- Mass: 1.2948x10^21 Kilograms
- Radius: 578.9 Kilometres
- Density: 1.539 g/cm^3
- Surface Gravity: 0.258 m/sec^2
- Rotational Period: 2.52 Days
- Orbital Period: 2.52 Days
Umbriel
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| Credit: NASA/JPL |
- Date Discovered: October 24, 1851
- Mass: 1.2214x10^21 Kilograms
- Radius: 584.7 Kilometres
- Density: 1.523 g/cm^3
- Surface Gravity: 0.238 m/sec^2
- Rotational Period: 4.144 Days
- Orbital Period: 4.144 Days
Umbriel was discovered at the same time as Ariel by William Lassell. This is the darkest of Uranus's major moons, with most of the moon covered in dark material. At the top of this Voyager 2 image is a bright crater called Wunda, but scientists don't really know what gives it its bright appearence. Umbriel is a character from the works of Alexander Pope.
Titania
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| Credit: NASA/JPL |
Titania is Uranus's largest moon, and was discovered by William Herschel shortly after he discovered Uranus. Titania has a few large craters, and bright icy canyons that can be seen in the image. These canyons, trenches, and frosty areas are perhaps evidence that Titania used to be more geologically active in the past. Titania is named after the queen of the fairies in Shakespeare's "A Midsummer Night's Dream."
Oberon
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| Credit: NASA/JPL |
- Date Discovered: January 11, 1787
- Mass: 2.8834x10^21 Kilograms
- Radius: 761.4 Kilometres
- Density: 1.664 g/cm^3
- Surface Gravity: 0.331 m/sec^2
- Rotational Period: 13.463 Days
- Orbital Period: 13.463 Days
Along with Titania, Oberon was discovered by William Herschel on January 11, 1787. Oberon is the second largest moon of Uranus, and possess many craters. Oberon has a large mountain, that's around 6 kilometres high. The largest known crater is Hamlet, which is around 296 kilometres in diameter. Oberon is named after the king of the fairies in Shakespeare's "A Midsummer Night's Dream."
Puck
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| Voyager 2 image of Puck. Credit: NASA/JPL |
- Date Discovered: December 30, 1985
- Mass: 2.8939x10^18 Kilograms
- Radius: 81 Kilometres
- Density: 1.3 g/cm^3
- Surface Gravity: 0.029 m/sec^2
- Rotational Period: 18.24 Hours
- Orbital Period: 18.24 Hours
Puck was discovered by the Voyager 2 spacecraft in December on its way to Uranus, and was the only minor moon that got a decent image taken. However the image was almost lost. Puck was the largest of the minor moons of Uranus, and the Voyager team realised they could get a decent image of it at closest approach. The image was recieved on January 24 the next year, but was lost because of a problem with the antenna alignment at one of the Australian tracking stations. Fortunately the image was transmitted again, and recieved 2 days later. The image is still quite poor quality, and the only feature that can be made out is a large crater, which was named Lob after a British sprite. Puck itself takes its name from the mischievious sprite in Shakespeare's "A Midsummer Night's Dream."
Uranus has many other small moons, but they haven't been imaged at more than a few pixels, if at all. Until we get a new Uranus mission to study these moons, here is a list of the ones discovered so far. Be sure to check out a similar article I did on the moons of Neptune here.
In order of size are:
- Sycorax: Mother of Caliban in Shakespeare's "The Tempest"
- Portia: Heroine in Shakespeare's "The Merchant of Venice"
- Juliet: Lover of Romeo in Shakespeare's "Romeo and Juliet"
- Belinda: Had her lock of hair stolen in Pope's "Rape of the lock"
- Cressida: Main character in Shakespeare's "Troilus and Cressida"
- Rosalind: Daughter of a banished Duke in Shakespeare's "As You Like it"
- Caliban: Character in Shakespeare's "The Tempest"
- Desdemona: Wife of Othello in Shakespeare's "Othello, the Moor of Venice"
- Bianca: Sister of Kate in Shakespeare's "The Taming of the Shrew"
- Prospero: Sorcerer in Shakespeare's "The Tempest"
- Setebos: Patagonian deity featured in Shakespeare's "The Tempest"
- Ophelia: Daughter of Polonius in Shakespeare's "Hamlet"
- Cordelia: Youngest daughter of King Lear in Shakespeare's "King Lear"
- Stephano: King Alonso's butler in Shakespeare's "The Tempest"
- Perdita: Daughter of Leontes and Hermione in Shakespeare's "The Winter's Tale"
- Mab: Fairy queen in English folklore that was mentioned in Shakespeare's "Romeo and Juliet"
- Francisco: Nobleman in Shakespeare's "The Tempest"
- Margaret: Woman who serves Hero in Shakespeare's "Much Ado About Nothing"
- Ferdinand: Son of King Alonso in Shakespeare's "The Tempest"
- Cupid: Roman god of love who appeared in Shakespeare's "Timon if Athens"
- Trinculo: Jester in Shakespeare's "The Tempest"
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