Miranda (moon)

Last updated
PIA18185 Miranda's Icy Face.jpg
Discovered by Gerard P. Kuiper
Discovery dateFebruary 16, 1948
Pronunciation /mɪˈrændə/ mi-RAN-də
Uranus V
Adjectives Mirandan, Mirandian
Orbital characteristics
129390 km
Eccentricity 0.0013
1.413479 d
Average orbital speed
6.66 km/s (calculated)
Inclination 4.232° (to Uranus's equator)
Satellite of Uranus
Physical characteristics
Dimensions480×468.4×465.8 km
Mean radius
235.8±0.7 km (0.03697 Earths) [1]
700000 km2
Volume 54835000 km3
Mass (6.59±0.75)×1019 kg [2] (1.103×10−5 Earths)
Mean density
1.20±0.15 g/cm3 [2]
0.079 m/s2
0.193 km/s
Albedo 0.32
Surface temp. minmeanmax
solstice [3] ?60 K 84±1 K
15.8 [4]

Miranda, also designated Uranus V, is the smallest and innermost of Uranus's five round satellites. It was discovered by Gerard Kuiper on 16 February 1948 at McDonald Observatory, and named after Miranda from William Shakespeare's play The Tempest . [5] Like the other large moons of Uranus, Miranda orbits close to its planet's equatorial plane. Because Uranus orbits the Sun on its side, Miranda's orbit is perpendicular to the ecliptic and shares Uranus's extreme seasonal cycle.

Uranus Seventh planet from the Sun in the Solar System

Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have bulk chemical compositions which differ from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus' atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K, and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is mainly composed of ices and rock.

Natural satellite astronomical body that orbits a planet

A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet.

Gerard Kuiper Netherlands-born American astronomer

Gerard Peter Kuiper was a Dutch–American astronomer, planetary scientist, selenographer, author and professor. He is the eponymous namesake of the Kuiper belt. Kuiper is considered by many to be the father of modern planetary science. As professor at the University of Chicago, he was dissertation advisor to Carl Sagan. In 1958, the two worked on the classified military Project A119, the secret Air Force plan to detonate a nuclear warhead on the Moon.


At just 470 km in diameter, Miranda is one of the smallest closely observed objects in the Solar System that might be in hydrostatic equilibrium (spherical under its own gravity). The only close-up images of Miranda are from the Voyager 2 probe, which made observations of Miranda during its Uranus flyby in January 1986. During the flyby, Miranda's southern hemisphere pointed towards the Sun, so only that part was studied.

Solar System planetary system of the Sun

The Solar System is the gravitationally bound planetary system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury.

In fluid mechanics, a fluid is said to be in hydrostatic equilibrium or hydrostatic balance when it is at rest, or when the flow velocity at each point is constant over time. This occurs when external forces such as gravity are balanced by a pressure-gradient force. For instance, the pressure-gradient force prevents gravity from collapsing Earth's atmosphere into a thin, dense shell, whereas gravity prevents the pressure gradient force from diffusing the atmosphere into space.

<i>Voyager 2</i> Space probe and the second-farthest man-made object from Earth

Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets.

Miranda probably formed from an accretion disc that surrounded the planet shortly after its formation, and, like other large moons, it is likely differentiated, with an inner core of rock surrounded by a mantle of ice. Miranda has one of the most extreme and varied topographies of any object in the Solar System, including Verona Rupes, a 20-kilometer-high scarp that is the highest cliff in the Solar System, [6] [7] and chevron-shaped tectonic features called coronae . The origin and evolution of this varied geology, the most of any Uranian satellite, are still not fully understood, and multiple hypotheses exist regarding Miranda's evolution.

Planetary differentiation

In planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical behavior, where the body develops into compositionally distinct layers; the denser materials of a planet sink to the center, while less dense materials rise to the surface, generally in a magma ocean. Such a process tends to create a core and mantle. Sometimes a chemically distinct crust forms on top of the mantle. The process of planetary differentiation has occurred on planets, dwarf planets, the asteroid 4 Vesta, and natural satellites.

A mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by density. All terrestrial planets, a number of asteroids, and some planetary moons have mantles.

Verona Rupes rupes on Miranda

Verona Rupes is a cliff on Miranda, a moon of Uranus. The cliff face, previously thought to be from 5 to 10 km high, as of 2016 is estimated to be 20 km (12 mi) high, which makes it the tallest known cliff in the Solar System.

Discovery and name

Miranda was discovered on 16 February 1948 by planetary astronomer Gerard Kuiper using the McDonald Observatory's 82-inch (2,080 mm) Otto Struve Telescope. [5] [8] Its motion around Uranus was confirmed on 1 March 1948. [5] It was the first satellite of Uranus discovered in nearly 100 years. Kuiper elected to name the object "Miranda" after the character in Shakespeare's The Tempest , because the four previously discovered moons of Uranus, Ariel, Umbriel, Titania and Oberon, had all been named after characters of Shakespeare or Alexander Pope. However, the previous moons had been named specifically after fairies, [9] whereas Miranda was a human. Subsequently, discovered satellites of Uranus were named after characters from Shakespeare and Pope, whether fairies or not. The moon is also designated Uranus V.

Otto Struve Telescope

The Otto Struve Telescope was the first major telescope to be built at McDonald Observatory. Located in the Davis Mountains in West Texas, the Otto Struve Telescope was designed by Warner & Swasey Company and constructed between 1933 and 1939 by the Paterson-Leitch Company. Its 82-inch (2.1 m) mirror was the second largest in the world at the time. It was named after the Russian-American astronomer Otto Struve in 1966, three years after his death.

<i>The Tempest</i> Play by William Shakespeare

The Tempest is a play by William Shakespeare, probably written in 1610–1611, and thought to be one of the last plays that Shakespeare wrote alone. After the first scene, which takes place on a ship at sea during a tempest, the rest of the story is set on a remote island, where the sorcerer Prospero, a complex and contradictory character, lives with his daughter Miranda, and his two servants — Caliban, a savage monster figure, and Ariel, an airy spirit. The play contains music and songs that evoke the spirit of enchantment on the island. It explores many themes including magic, betrayal, revenge, and family. In act four, a wedding masque serves as a play-within-the play, and contributes spectacle, allegory, and elevated language. Though The Tempest is listed in the First Folio as the first of Shakespeare’s comedies, it deals with both tragic and comic themes, and modern criticism has created a category of romance for this and others of Shakespeare’s late plays. The Tempest has been subjected to varied interpretations—from those that see it as a fable of art and creation, with Prospero representing Shakespeare, and Prospero’s renunciation of magic signaling Shakespeare's farewell to the stage, to interpretations that consider it an allegory of Europeans colonizing foreign lands.

Ariel (moon) fourth-largest moon of Uranus

Ariel is the fourth-largest of the 27 known moons of Uranus. Ariel orbits and rotates in the equatorial plane of Uranus, which is almost perpendicular to the orbit of Uranus and so has an extreme seasonal cycle.


Of Uranus's five round satellites, Miranda orbits closest to it, at roughly 129,000 km from the surface; about a quarter again as far as its most distant ring. Its orbital period is 34 hours, and, like that of the Moon, is synchronous with its rotation period, which means it always shows the same face to Uranus, a condition known as tidal locking. Miranda's orbital inclination (4.34°) is unusually high for a body so close to its planet, and roughly ten times that of the other major Uranian satellites. The reason for this is still uncertain; there are no mean-motion resonances between the moons that could explain it, leading to the hypothesis that the moons occasionally pass through secondary resonances, which at some point in the past led to Miranda being locked for a time into a 3:1 resonance with Umbriel, before chaotic behaviour induced by the secondary resonances moved it out of it again. [10] In the Uranian system, due to the planet's lesser degree of oblateness, and the larger relative size of its satellites, escape from a mean-motion resonance is much easier than for satellites of Jupiter or Saturn. [11] [12] Miranda's orbit is the most inclined of any of Uranus's large satellites, at 4.232°, it is 10-20 times that of Titania, Ariel and Umbriel and 73 times that of Oberon. [13]

Rings of Uranus Planetary ring system

The rings of Uranus are a system of rings around the planet Uranus, intermediate in complexity between the more extensive set around Saturn and the simpler systems around Jupiter and Neptune. The rings of Uranus were discovered on March 10, 1977, by James L. Elliot, Edward W. Dunham, and Jessica Mink. William Herschel had also reported observing rings in 1789; modern astronomers are divided on whether he could have seen them, as they are very dark and faint.

The orbital period is the time a given astronomical object takes to complete one orbit around another object, and applies in astronomy usually to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars.

Moon Earths natural satellite

The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits. The Moon is after Jupiter's satellite Io the second-densest satellite in the Solar System among those whose densities are known.

Composition and internal structure

Voyager 2 image of Miranda's broken terrain. Verona Rupes is located at the bottom right of Miranda. Miranda - January 24 1986 (30906319004).jpg
Voyager 2 image of Miranda's broken terrain. Verona Rupes is located at the bottom right of Miranda.

At 1.2 g/cm3, Miranda is the least dense of Uranus's round satellites. That density suggests a composition of more than 60% water ice. [14] Miranda's surface may be mostly water ice, though it is far rockier than its corresponding satellites in the Saturn system, indicating that heat from radioactive decay may have led to internal differentiation, allowing silicate rock and organic compounds to settle in its interior. [15] [16] Miranda is too small for any internal heat to have been retained over the age of the Solar System. [17] Miranda is the least spherical of Uranus's satellites, with an equatorial diameter 3% wider than its polar diameter. Only water has been detected so far on Miranda's surface, though it has been speculated that methane, ammonia, carbon monoxide or nitrogen may also exist at 3% concentrations. [16] [18] These bulk properties are similar to Saturn's moon Mimas, though Mimas is smaller, less dense, and more oblate. [18]

Radioactive decay Process by which an unstable atom emits radiation

Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation, such as an alpha particle, beta particle with neutrino or only a neutrino in the case of electron capture, or a gamma ray or electron in the case of internal conversion. A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, proton emission.

Silicate class of chemical compounds, salts and esters of silicic acids

In chemistry, a silicate is any member of a family of anions consisting of silicon and oxygen, usually with the general formula [SiO(4−2x)−
, where 0 ≤ x < 2. The family includes orthosilicate SiO4−
, metasilicate SiO2−
, and pyrosilicate Si
. The name is also used for any salt of such anions, such as sodium metasilicate; or any ester containing the corresponding chemical group, such as tetramethyl orthosilicate.

Organic compound chemical compound that contains carbon (except for a several compounds traditionally classified as inorganic compounds)

In chemistry, an organic compound is generally any chemical compound that contains carbon. Due to carbon's ability to catenate, millions of organic compounds are known. Study of the properties and synthesis of organic compounds is the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds, along with a handful of other exceptions, are not classified as organic compounds and are considered inorganic. No consensus exists among chemists on precisely which carbon-containing compounds are excluded, making the definition of an organic compound elusive.

Precisely how a body as small as Miranda could have enough internal energy to produce the myriad geological features seen on its surface is not established with certainty, [17] though the currently favoured hypothesis is that it was driven by tidal heating during a past time when it was in 3:1 orbital resonance with Umbriel. [19] The resonance would have increased Miranda's orbital eccentricity to 0.1, and generated tidal friction due to the varying tidal forces from Uranus. [20] As Miranda approached Uranus, tidal force increased; as it retreated, tidal force decreased, causing flexing that would have warmed Miranda's interior by 20 K, enough to trigger melting. [20] [11] [12] The period of tidal flexing could have lasted for up to 100 million years. [20] Also, if clathrate existed within Miranda, as has been hypothesised for the satellites of Uranus, it may have acted as an insulator, since it has a lower conductivity than water, increasing Miranda's temperature still further. [20] Miranda may have also once been in a 5:3 orbital resonance with Ariel, which would have also contributed to its internal heating. However, the maximum heating attributable to the resonance with Umbriel was likely about three times greater. [19]

Surface features

Close-up of Verona Rupes, a large fault scarp on Miranda possibly 20 km (12 mi) high, taken by Voyager 2 in January 1986 Miranda scarp.jpg
Close-up of Verona Rupes, a large fault scarp on Miranda possibly 20 km (12 mi) high, taken by Voyager 2 in January 1986
Close-up of the ring of concentric fault scarps around Elsinore Corona. Miranda ridges.jpg
Close-up of the ring of concentric fault scarps around Elsinore Corona.
The three coronae imaged on Miranda by Voyager 2 Mirandaanicy.jpg
The three coronae imaged on Miranda by Voyager 2
The fault scarps around Elsinore (top right) and the chevrons of Inverness Corona (bottom left) Miranda elsinorinverness.jpg
The fault scarps around Elsinore (top right) and the chevrons of Inverness Corona (bottom left)

Due to Uranus's near-sideways orientation, only Miranda's southern hemisphere was visible to Voyager 2 when it arrived. The observed surface has patchwork regions of broken terrain, indicating intense geological activity in Miranda's past, and is criss-crossed by huge canyons, believed to be the result of extensional tectonics; as liquid water froze beneath the surface, it expanded, causing the surface ice to split, creating graben. The canyons are hundreds of kilometers long and tens of kilometers wide. [17] Miranda also has the largest known cliff in the Solar System, Verona Rupes, which has a height of 20 km (12 mi). [7] Some of Miranda's terrain is possibly less than 100 million years old based on crater counts, while sizeable regions possess crater counts that indicate ancient terrain. [17] [23]

While crater counts suggest that the majority of Miranda's surface is old, with a similar geological history to the other Uranian satellites, [17] [24] few of those craters are particularly large, indicating that most must have formed after a major resurfacing event in its distant past. [15] Craters on Miranda also appear to possess softened edges, which could be the result either of ejecta or of cryovolcanism. [24] The temperature at Miranda's south pole is roughly 85 K, a temperature at which pure water ice adopts the properties of rock. Also, the cryovolcanic material responsible for the surfacing is too viscous to have been pure liquid water, but too fluid to have been solid water. [20] [25] Rather, it is believed to have been a viscous, lava-like mixture of water and ammonia, which freezes at 176 K (-97 °C), or perhaps ethanol. [17]

Miranda's observed hemisphere contains three giant 'racetrack'-like grooved structures called coronae, each at least 200 km (120 mi) wide and up to 20 km (12 mi) deep, named Arden, Elsinore and Inverness after locations in Shakespeare's plays. Inverness is lower in altitude than the surrounding terrain (though domes and ridges are of comparable elevation), while Elsinore is higher, [16] The relative sparsity of craters on their surfaces means they overlay the earlier cratered terrain. [17] The coronae, which are unique to Miranda, initially defied easy explanation; one early hypothesis was that Miranda, at some time in its distant past, (prior to any of the current cratering) [16] had been completely torn to pieces, perhaps by a massive impact, and then reassembled in a random jumble. [26] [16] [22] The heavier core material fell through the crust, and the coronae formed as the water re-froze. [16]

However, the current favoured hypothesis is that they formed formed via extensional processes at the tops of diapirs, or upwellings of warm ice from within Miranda itself. [22] [27] [26] [28] The coronae are surrounded by rings of concentric faults with a similar low-crater count, suggesting they played a role in their formation. [25] If the coronae formed through downwelling from a catastrophic disruption, then the concentric faults would present as compressed. If they formed through upwelling, such as by diapirism, then they would be extensional tilt blocks, and present extensional features, as current evidence suggests they do. [27] The concentric rings would have formed as ice moved away from the heat source. [29] The diapirs may have changed the density distribution within Miranda, which could have caused Miranda to reorient itself, [30] similar to a process believed to have occurred at Saturn's geologically active moon Enceladus. Evidence suggests the reorientation would have been as extreme as 60 degrees from the sub-Uranian point. [29] The positions of all the coronae require a tidal heating pattern consistent with Miranda being solid, and lacking an internal liquid ocean. [29] It is believed through computer modelling that Miranda may have an additional corona on the unimaged hemisphere. [31]

Observation and exploration

Approaching the 7 December 2007 equinox Miranda produced brief solar eclipses over the center of Uranus. Miranda eclipse.jpg
Approaching the 7 December 2007 equinox Miranda produced brief solar eclipses over the center of Uranus.
A computer-simulated flight over Miranda

Miranda's apparent magnitude is +16.6, making it invisible to many amateur telescopes. [32] Virtually all known information regarding its geology and geography was obtained during the flyby of Uranus made by Voyager 2 on Jan 25 1986, [15] The closest approach of Voyager 2 to Miranda was 29,000 km (18,000 mi)—significantly less than the distances to all other Uranian moons. [33] Of all the Uranian satellites, Miranda had the most visible surface. [18] The discovery team had expected Miranda to resemble Mimas, and found themselves at a loss to explain the moon's unique geography in the 24-hour window before releasing the images to the press. [24] In 2017, as part of its Planetary Science Decadal Survey, NASA evaluated the possibility of an orbiter to return to Uranus some time in the 2020s. [34] Uranus was the preferred destination over Neptune due to favourable planetary alignments meaning shorter flight times. [35]

See also

Related Research Articles

Orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of two small integers

In celestial mechanics, an orbital resonance occurs when orbiting bodies exert a regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly this relationship is found for a pair of objects. The physical principle behind orbital resonance is similar in concept to pushing a child on a swing, where the orbit and the swing both have a natural frequency, and the other body doing the "pushing" will act in periodic repetition to have a cumulative effect on the motion. Orbital resonances greatly enhance the mutual gravitational influence of the bodies, i.e., their ability to alter or constrain each other's orbits. In most cases, this results in an unstable interaction, in which the bodies exchange momentum and shift orbits until the resonance no longer exists. Under some circumstances, a resonant system can be stable and self-correcting, so that the bodies remain in resonance. Examples are the 1:2:4 resonance of Jupiter's moons Ganymede, Europa and Io, and the 2:3 resonance between Pluto and Neptune. Unstable resonances with Saturn's inner moons give rise to gaps in the rings of Saturn. The special case of 1:1 resonance between bodies with similar orbital radii causes large Solar System bodies to eject most other bodies sharing their orbits; this is part of the much more extensive process of clearing the neighbourhood, an effect that is used in the current definition of a planet.

Umbriel (moon) moon of Uranus

Umbriel is a moon of Uranus discovered on October 24, 1851, by William Lassell. It was discovered at the same time as Ariel and named after a character in Alexander Pope's poem The Rape of the Lock. Umbriel consists mainly of ice with a substantial fraction of rock, and may be differentiated into a rocky core and an icy mantle. The surface is the darkest among Uranian moons, and appears to have been shaped primarily by impacts. However, the presence of canyons suggests early endogenic processes, and the moon may have undergone an early endogenically driven resurfacing event that obliterated its older surface.

Triton (moon) largest moon of Neptune

Triton is the largest natural satellite of the planet Neptune, and the first Neptunian moon to be discovered. The discovery was made on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the direction opposite to its planet's rotation. At 2,710 kilometres (1,680 mi) in diameter, it is the seventh-largest moon in the Solar System, the only satellite of Neptune massive enough to be in hydrostatic equilibrium and the second-largest planetary moon in relation to its primary, after Earth's Moon. Because of its retrograde orbit and composition similar to Pluto's, Triton is thought to have been a dwarf planet captured from the Kuiper belt.

Puck (moon) moon of Uranus

Puck is an inner moon of Uranus. It was discovered in December 1985 by the Voyager 2 spacecraft. The name Puck follows the convention of naming Uranus's moons after characters from Shakespeare. The orbit of Puck lies between the rings of Uranus and the first of Uranus's large moons, Miranda. Puck is approximately spherical in shape and has diameter of about 162 km. It has a dark, heavily cratered surface, which shows spectral signs of water ice.

Oberon (moon) moon of Uranus

Oberon, also designated Uranus IV, is the outermost major moon of the planet Uranus. It is the second-largest and second most massive of the Uranian moons, and the ninth most massive moon in the Solar System. Discovered by William Herschel in 1787, Oberon is named after the mythical king of the fairies who appears as a character in Shakespeare's A Midsummer Night's Dream. Its orbit lies partially outside Uranus's magnetosphere.

Cordelia (moon) moon of Uranus

Cordelia is the innermost known moon of Uranus. It was discovered from the images taken by Voyager 2 on January 20, 1986, and was given the temporary designation S/1986 U 7. It was not detected again until the Hubble Space Telescope observed it in 1997. Cordelia takes its name from the youngest daughter of Lear in William Shakespeare's King Lear. It is also designated Uranus VI.

Cressida (moon) moon of Uranus

Cressida is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 9 January 1986, and was given the temporary designation S/1986 U 3. It was named after Cressida, the Trojan daughter of Calchas, a tragic heroine who appears in William Shakespeare's play Troilus and Cressida. It is also designated Uranus IX.

Rosalind (moon) moon of Uranus

Rosalind is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 13 January 1986, and was given the temporary designation S/1986 U 4. It was named after the daughter of the banished Duke in William Shakespeare's play As You Like It. It is also designated Uranus XIII.

Belinda (moon) moon of Uranus

Belinda is an inner satellite of the planet Uranus. Belinda was discovered from the images taken by Voyager 2 on 13 January 1986 and was given the temporary designation S/1986 U 5. It is named after the heroine of Alexander Pope's The Rape of the Lock. It is also designated Uranus XIV.

Proteus (moon) moon of Neptune

Proteus, also known as Neptune VIII, is the second-largest Neptunian moon, and Neptune's largest inner satellite. Discovered by Voyager 2 spacecraft in 1989, it is named after Proteus, the shape-changing sea god of Greek mythology. Proteus orbits Neptune in a nearly equatorial orbit at the distance of about 4.75 times the radius of Neptune's equator.

Titania (moon) The largest moon of Uranus

Titania is the largest of the moons of Uranus and the eighth largest moon in the Solar System at a diameter of 1,578 kilometres (981 mi). Discovered by William Herschel in 1787, Titania is named after the queen of the fairies in Shakespeare's A Midsummer Night's Dream. Its orbit lies inside Uranus's magnetosphere.

Wunda (crater) crater on the surface of Uranus moon Umbriel

Wunda is a large crater on the surface of Uranus' moon Umbriel. It is 131 km in diameter and is located near the equator of Umbriel. The crater is named after Wunda, a dark spirit of Australian aboriginal mythology.

Moons of Uranus The natural satellites of the planet Uranus

Uranus, the seventh planet of the Solar System, has 27 known moons, most of which are named after characters that appear in - or are mentioned in - the works of William Shakespeare and Alexander Pope. Uranus's moons are divided into three groups: thirteen inner moons, five major moons, and nine irregular moons. The inner moons are small dark bodies that share common properties and origins with Uranus's rings. The five major moons are massive enough to have reached hydrostatic equilibrium, and four of them show signs of internally driven processes such as canyon formation and volcanism on their surfaces. The largest of these five, Titania, is 1,578 km in diameter and the eighth-largest moon in the Solar System, and about one-twentieth the mass the Earth's Moon. The orbits of the regular moons are nearly coplanar with Uranus's equator, which is tilted 97.77° to its orbit. Uranus's irregular moons have elliptical and strongly inclined orbits at large distances from the planet.

Exploration of Uranus

The exploration of Uranus has, to date, been solely through telescopes and NASA's Voyager 2 spacecraft, which made its closest approach to Uranus on January 24, 1986. Voyager 2 discovered 10 moons, studied the planet's cold atmosphere, and examined its ring system, discovering two new rings. It also imaged Uranus' five large moons, revealing that their surfaces are covered with impact craters and canyons.

Mommur Chasma chasma on Oberon

Mommur Chasma is the largest 'canyon' on the known part of the surface of Uranus' moon Oberon. This feature probably formed during crustal extension at the early stages of moon's evolution, when the interior of Oberon expanded and its ice crust cracked as a result. The canyon is an example of graben or scarp produced by normal fault(s). The chasma was first imaged by Voyager 2 spacecraft in January 1986.

Messina Chasmata chasma on Titania

The Messina Chasmata are the largest canyon or system of canyons on the surface of the Uranian moon Titania, named after a location in William Shakespeare's comedy Much Ado About Nothing. The 1492 km long feature includes two normal faults running NW–SE, which bound a down-dropped crustal block forming a structure called a graben. The graben cuts impact craters, which probably means that it was formed at a relatively late stage of the moon's evolution, when the interior of Titania expanded and its ice crust cracked as a result. The Messina Chasmata have only a few superimposed craters, which also implies being relatively young. The feature was first imaged by Voyager 2 in January 1986.

Rousillon Rupes rupes on Titania

Rousillon Rupes is a scarp on the surface of the Uranian moon Titania named after "Bertram, count of Rousillon" in William Shakespeare's comedy All's Well That Ends Well. The 402 km long feature is a normal fault situated near the equator and running perpendicular to it. The scarp cuts impact craters, which probably means that it was formed at a relatively late stage of moon's evolution, when the interior of Titania expanded and its ice crust cracked as a result. Rousillon Rupes has only few crater superimposed on it, which also implies its relatively young age. The scarp was first imaged by Voyager 2 spacecraft in January 1986.

Kachina Chasmata chasma on Ariel

The Kachina Chasmata are the longest canyon or system of canyons on the surface of the Uranian moon Ariel. The name comes from a spirit in Hopi mythology. The 622 km long and 50 km wide chasmata arise from a system of normal faults running from the north-west to south-east. The faults bound down-dropped crustal blocks forming structures called graben. The canyons cut the cratered terrain, which means that they were formed at a relatively late stage of the moon's evolution, when the interior of Ariel expanded and its ice crust cracked as a result. The floor of the canyons is not visible on the images obtained by the Voyager 2 spacecraft in January 1986; thus, whether it is covered by smooth plains like the floors of other Arielian graben is currently unknown.


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