Titania (moon)

Titania (moon)

Overview
Titania is the largest of the moons of Uranus and the eighth largest moon in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 at a diameter of 1578 km. Discovered by William Herschel
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...

 in 1787, Titania is named after the queen of the fairies in Shakespeare's A Midsummer Night's Dream
A Midsummer Night's Dream
A Midsummer Night's Dream is a play that was written by William Shakespeare. It is believed to have been written between 1590 and 1596. It portrays the events surrounding the marriage of the Duke of Athens, Theseus, and the Queen of the Amazons, Hippolyta...

. Its orbit lies inside Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

' magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...

.

Titania consists of approximately equal amounts of ice and rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

, and is likely differentiated into a rocky core and an icy mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....

.
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Encyclopedia
Titania is the largest of the moons of Uranus and the eighth largest moon in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 at a diameter of 1578 km. Discovered by William Herschel
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...

 in 1787, Titania is named after the queen of the fairies in Shakespeare's A Midsummer Night's Dream
A Midsummer Night's Dream
A Midsummer Night's Dream is a play that was written by William Shakespeare. It is believed to have been written between 1590 and 1596. It portrays the events surrounding the marriage of the Duke of Athens, Theseus, and the Queen of the Amazons, Hippolyta...

. Its orbit lies inside Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

' magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...

.

Titania consists of approximately equal amounts of ice and rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

, and is likely differentiated into a rocky core and an icy mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....

. A layer of liquid water may be present at the core–mantle boundary
Core–mantle boundary
The core–mantle boundary lies between the Earth's silicate mantle and its liquid iron-nickel outer core. This boundary is located at approximately 2900 km of depth beneath the Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth...

. The surface of Titania, which is relatively dark and slightly red in color, appears to have been shaped by both impacts and endogenic processes. It is covered by numerous impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

s reaching 326 km in diameter, but is less heavily cratered than the surface of Uranus' outermost moon, Oberon
Oberon (moon)
Oberon , also designated ', 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...

. Titania probably underwent an early endogenic resurfacing event that obliterated its older, heavily cratered surface. Titania's surface is cut by a system of enormous canyon
Canyon
A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...

s and scarps
Fault scarp
A fault scarp is the topographic expression of faulting attributed to the displacement of the land surface by movement along faults. They are exhibited either by differential movement and subsequent erosion along an old inactive geologic fault , or by a movement on a recent active fault...

; the result of the expansion of its interior during its later evolution. Like all major moons of Uranus, Titania probably formed from an accretion disk that surrounded the planet just after its formation.

Infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 spectroscopy conducted from 2001 to 2005 revealed the presence of water ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 as well as carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 on the surface of Titania, which in turn suggested that the moon may possess a tenuous carbon dioxide atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

 with a surface pressure of about one 10 trillionth of a bar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...

. Measurements during Titania's occultation of a star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 put an upper limit on the surface pressure of any possible atmosphere at 10–20 nbar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...

.

As of 2011, the Uranian system has been studied up close only once: by the spacecraft Voyager 2
Voyager 2
The Voyager 2 spacecraft is a 722-kilogram space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space...

in January 1986. It took several images of Titania, which allowed mapping of about 40% of the moon’s surface.

Discovery and naming


Titania was discovered by William Herschel
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...

 on January 11, 1787, the same day he discovered Uranus' second largest moon, Oberon
Oberon (moon)
Oberon , also designated ', 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...

. He later reported the discoveries of four more satellites, although they were subsequently revealed as spurious. For nearly fifty years following their discovery, Titania and Oberon would not be observed by any instrument other than William Herschel's, although the moon can be seen from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 with a present-day high-end amateur telescope.

All of Uranus' moons are named after characters created by William Shakespeare
William Shakespeare
William Shakespeare was an English poet and playwright, widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's national poet and the "Bard of Avon"...

 or Alexander Pope
Alexander Pope
Alexander Pope was an 18th-century English poet, best known for his satirical verse and for his translation of Homer. He is the third-most frequently quoted writer in The Oxford Dictionary of Quotations, after Shakespeare and Tennyson...

. The name Titania was taken from the Queen of the Fairies in A Midsummer Night's Dream
A Midsummer Night's Dream
A Midsummer Night's Dream is a play that was written by William Shakespeare. It is believed to have been written between 1590 and 1596. It portrays the events surrounding the marriage of the Duke of Athens, Theseus, and the Queen of the Amazons, Hippolyta...

. The names of all four satellites of Uranus then known were suggested by Herschel's son John
John Herschel
Sir John Frederick William Herschel, 1st Baronet KH, FRS ,was an English mathematician, astronomer, chemist, and experimental photographer/inventor, who in some years also did valuable botanical work...

 in 1852, at the request of William Lassell
William Lassell
William Lassell FRS was an English merchant and astronomer.Born in Bolton and educated in Rochdale after the death of his father, he was apprenticed from 1814 to 1821 to a merchant in Liverpool. He then made his fortune as a beer brewer, which enabled him to indulge his interest in astronomy...

, who had discovered the other two moons, Ariel
Ariel (moon)
Ariel is the brightest and 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....

 and Umbriel
Umbriel (moon)
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...

, the year before.

Titania was initially referred to as "the first satellite of Uranus", and in 1848 was given the designation by William Lassell, although he sometimes used William Herschel's numbering (where Titania and Oberon are II and IV). In 1851 Lassell eventually numbered all four known satellites in order of their distance from the planet by Roman numerals
Roman numerals
The numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...

, and since then Titania has been designated .

Shakespeare's character's name is pronounced t, but the moon is often pronounced t, by analogy with the familiar chemical element titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....

. The adjectival form, Titanian, is homonymous with that of Saturn's moon Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....

.

Orbit


Titania orbits Uranus at the distance of about 436,000 km, being the second farthest from the planet among its five major moons. Titania's orbit has a small eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...

 and is inclined very little relative to the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

 of Uranus. Its orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...

 is around 8.7 days, coincident with its rotational period. In other words, Titania is a synchronous
Synchronous orbit
A synchronous orbit is an orbit in which an orbiting body has a period equal to the average rotational period of the body being orbited , and in the same direction of rotation as that body.-Properties:...

 or tidally locked satellite, with one face always pointing toward the planet.

Titania's orbit lies completely inside the Uranian magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...

. This is important, because the trailing hemispheres of satellites orbiting inside a magnetosphere are struck by magnetospheric plasma, which co-rotates with the planet. This bombardment may lead to the darkening of the trailing hemispheres, which is actually observed for all Uranian moons except Oberon (see below).

Because Uranus orbits the Sun almost on its side, and its moons orbit in the planet's equatorial plane, they (including Titania) are subject to an extreme seasonal cycle. Both northern and southern poles spend 42 years in a complete darkness, and another 42 years in continuous sunlight, with the sun rising close to the zenith
Zenith
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e...

 over one of the poles at each solstice
Solstice
A solstice is an astronomical event that happens twice each year when the Sun's apparent position in the sky, as viewed from Earth, reaches its northernmost or southernmost extremes...

. The Voyager 2 flyby coincided with the southern hemisphere's 1986 summer solstice, when nearly the entire northern hemisphere was unilluminated. Once every 42 years, when Uranus has an equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

 and its equatorial plane intersects the Earth, mutual occultation
Occultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...

s of Uranus' moons become possible. In 2007–2008 a number of such events were observed including two occultations of Titania by Umbriel on August 15 and December 8, 2007.

Composition and internal structure


Titania is the largest and most massive Uranian moon, and the eighth most massive moon in the Solar System. Its density of 1.71 g/cm³, which is much higher than the typical density of Saturn's satellites, indicates that it consists of roughly equal proportions of water ice and dense non-ice components; the latter could be made of rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 and carbonaceous
Carbonaceous
Carbonaceous is the defining attribute of a substance rich in carbon. Particularly, carbonaceous hydrocarbons are very unsaturated, high-molecular-weight hydrocarbons, having an elevated carbon:hydrogen ratio....

 material including heavy organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

s. The presence of water ice is supported by infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 spectroscopic observations made in 2001–2005, which have revealed crystalline water ice on the surface of the moon. Water ice absorption band
Absorption band
An absorption band is a range of wavelengths, frequencies or energies in the electromagnetic spectrum which are able to excite a particular transition in a substance...

s are slightly stronger on Titania's leading hemisphere than on the trailing hemisphere. This is the opposite of what is observed on Oberon, where the trailing hemisphere exhibits stronger water ice signatures. The cause of this asymmetry is not known, but it may be related to the bombardment by charged particles from the magnetosphere of Uranus, which is stronger on the trailing hemisphere (due to the plasma's co-rotation). The energetic particles tend to sputter
Sputtering
Sputtering is a process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic particles. It is commonly used for thin-film deposition, etching and analytical techniques .-Physics of sputtering:...

 water ice, decompose methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 trapped in ice as clathrate hydrate
Clathrate hydrate
Clathrate hydrates are crystalline water-based solids physically resembling ice, in which small non-polar molecules or polar molecules with large hydrophobic moieties are trapped inside "cages" of hydrogen bonded water molecules...

 and darken other organics, leaving a dark, carbon-rich residue
Residue (chemistry)
In chemistry, residue is the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction....

 behind.

Except for water, the only other compound identified on the surface of Titania by infrared spectroscopy is carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, which is concentrated mainly on the trailing hemisphere. The origin of the carbon dioxide is not completely clear. It might be produced locally from carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....

s or organic materials under the influence of the solar ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 radiation or energetic charged particles coming from the magnetosphere of Uranus. The latter process would explain the asymmetry in its distribution, because the trailing hemisphere is subject to a more intense magnetospheric influence than the leading hemisphere. Another possible source is the outgassing
Outgassing
Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...

 of the primordial CO2 trapped by water ice in the Titania's interior. The escape of CO2 from the interior may be related to the past geological activity on this moon.

Titania may be differentiated into a rocky core surrounded by an icy mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....

. If this is the case, the radius of the core (520 km) is about 66% of the radius of the moon, and its mass is around 58% of the moon’s mass—the parameters are dictated by moon's composition. The pressure in the center of Titania is about 0.58 GPa (5.8 kbar
KBAR
KBAR may refer to:* KBAR-FM, a radio station licensed to Victoria, Texas, United States* KBAR , a radio station licensed to Burley, Idaho, United States...

). The current state of the icy mantle is unclear. If the ice contains enough ammonia or other antifreeze
Antifreeze
Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....

, Titania may possess a liquid ocean layer at the core-mantle boundary. The thickness of this ocean, if it exists, is up to 50 km and its temperature is around 190 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

. However the present internal structure of Titania depends heavily on its thermal history, which is poorly known.

Surface features


Among Uranus' moons, Titania is intermediate in brightness between the dark Oberon and Umbriel and the bright Ariel and Miranda
Miranda (moon)
-External links:* at * at The Nine8 Planets* at Views of the Solar System* * from the...

. Its surface shows a strong opposition surge
Opposition surge
The opposition surge is the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer...

: its reflectivity decreases from 35% at a phase angle of 0° (geometrical albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

) to 25% at an angle of about 1°. Titania has a relatively low Bond albedo
Bond albedo
The Bond albedo, named after the American astronomer George Phillips Bond , who originally proposed it, is the fraction of power in the total electromagnetic radiation incident on an astronomical body that is scattered back out into space...

 of about 17%. Its surface is generally slightly red in color, but less red than that of Oberon
Oberon (moon)
Oberon , also designated ', 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...

. However, fresh impact deposits are bluer, while the smooth plains situated on the leading hemisphere near Ursula crater
Ursula (crater)
Ursula is a large crater on Uranus's moon Titania. It is about 135 km across, and is cut by Belmont Chasma. It is named after attendant on Hero in William Shakespeare's comedy Much Ado About Nothing....

 and along some grabens are somewhat redder. There may be an asymmetry between the leading and trailing hemispheres; the former appears to be redder than the latter by 8%. However, this difference is related to the smooth plains and may be accidental. The reddening of the surfaces probably results from space weathering
Space weathering
Space weathering is a blanket term used for a number of processes that act on any body exposed to the harsh space environment. Airless bodies incur many weathering processes:* collisions of galactic cosmic rays and solar cosmic rays,* irradiation, implantation, and sputtering from solar wind...

 caused by bombardment by charged particles and micrometeorites over the age of the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

. However, the color asymmetry of Titania is more likely related to accretion of a reddish material coming from outer parts of the Uranian system, possibly, from irregular satellite
Irregular satellite
In astronomy, an irregular moon is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They are believed to have been captured by their parent planet, unlike regular satellites, which form in situ....

s, which would be deposited predominately on the leading hemisphere.

Scientists have recognized three classes of geological feature on Titania: craters
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

, chasmata (canyon
Canyon
A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...

s) and rupes
Rupes
Rupes is the Latin word for 'cliff'. It is used in planetary geology to refer to escarpments on other planets, such as Mercury, and moons, such as Luna, Earth's natural satellite.How rupes are formed is, as of 2008, a matter of speculation...

 (scarps
Escarpment
An escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...

). The surface of Titania is less heavily cratered than the surfaces of either Oberon or Umbriel, which means that it is much younger. The crater diameters range from a few kilometers at the low end to 326 kilometers for the largest known crater, Gertrude
Gertrude (crater)
Gertrude is the largest known crater on Uranus's moon Titania. It is about 326 km across, 1/5 of Titania's diameter. It is named after the mother of Hamlet in William Shakespeare's play Hamlet. Features on Titania are named after female Shakespearean characters.The crater rim of Gertrude is...

. Some craters (for instance, Ursula
Ursula (crater)
Ursula is a large crater on Uranus's moon Titania. It is about 135 km across, and is cut by Belmont Chasma. It is named after attendant on Hero in William Shakespeare's comedy Much Ado About Nothing....

 and Jessica) are surrounded by bright impact ejecta (rays) consisting of relatively fresh ice. All large craters on Titania have flat floors and central peaks. The only exception is Ursula, which has a pit in the center. To the west of Gertrude there is an area with irregular topography, the so-called "unnamed basin", which may be another highly degraded impact basin with the diameter of about 330 km.

Titania's surface is intersected by a system of enormous faults, or scarps. In some places, two parallel scarps mark depressions in the satellite's crust, forming graben
Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....

s, which are sometimes called canyons. The most prominent among Titania's canyons is Messina Chasma
Messina Chasma
Messina Chasma is the largest canyon 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 chasma is made of two normal faults running NW–SE, which bound a down-dropped crustal block forming a structure...

, which runs for about 1500 km from the equator almost to the south pole. The grabens on Titania are 20–50 km wide and have a relief of about 2–5 km. The scarps that are not related to canyons are called rupes, such as Rousillon Rupes
Rousillon Rupes
Rousillon Rupes is a scarp on the surface of the Uranian moon Titania named after a location 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...

 near Ursula crater. The regions along some scarps and near Ursula appear smooth at Voyager's image resolution. These smooth plains were probably resurfaced later in Titania's geological history, after the majority of craters formed. The resurfacing may have been either endogenic in nature, involving the eruption of fluid material from the interior (cryovolcanism), or, alternatively it may be due to blanking by the impact ejecta from nearby large craters. The grabens are probably the youngest geological features on Titania—they cut all craters and even smooth plains.

The geology of Titania was influenced by two competing forces: impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 formation and endogenic resurfacing. The former acted over the moon's entire history and influenced all surfaces. The latter processes were also global in nature, but active mainly for a period following the moon's formation. They obliterated the original heavily cratered terrain, explaining the relatively low number of impact craters on the moon's present-day surface. Additional episodes of resurfacing may have occurred later and led to the formation of smooth plains. Alternatively smooth plains may be ejecta blankets of the nearby impact craters. The most recent endogenous processes were mainly tectonic in nature and caused the formation of the canyons, which are actually giant cracks in the ice crust. The cracking of the crust was caused by the global expansion of Titania by about 0.7%.

Named surface features on Titania
Feature Named after Type Length (diameter), km Coordinates
Belmont Chasma Belmont
Belmonte Calabro
Belmonte Calabro, known simply as Belmonte prior to the proclamation of the Kingdom of Italy, is a town and comune in the province of Cosenza, in Calabria...

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 (The Merchant of Venice
The Merchant of Venice
The Merchant of Venice is a tragic comedy by William Shakespeare, believed to have been written between 1596 and 1598. Though classified as a comedy in the First Folio and sharing certain aspects with Shakespeare's other romantic comedies, the play is perhaps most remembered for its dramatic...

)
Chasma
Chasma
Chasma is a term used in astrogeology to refer to "a deep, elongated, steep-sided depression". The plural is chasmata. An example is Eos Chasma on Mars. Below are images of some of the major chasmata of Mars...

238 8.5°N 32.6°W
Messina Chasma
Messina Chasma
Messina Chasma is the largest canyon 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 chasma is made of two normal faults running NW–SE, which bound a down-dropped crustal block forming a structure...

Messina
Messina, Italy
Messina is the third largest city on the island of Sicily, Italy and the capital of the province of Messina. It has a population of about 250,000 inhabitants in the city proper and about 650,000 in the province...

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 (Much Ado About Nothing
Much Ado About Nothing
Much Ado About Nothing is a comedy written by William Shakespeare about two pairs of lovers, Benedick and Beatrice, and Claudio and Hero....

)
1,492 33.3°N 335°W
Rousillon Rupes
Rousillon Rupes
Rousillon Rupes is a scarp on the surface of the Uranian moon Titania named after a location 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...

Roussillon
Roussillon
Roussillon is one of the historical counties of the former Principality of Catalonia, corresponding roughly to the present-day southern French département of Pyrénées-Orientales...

, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 (All's Well That Ends Well
All's Well That Ends Well
All's Well That Ends Well is a play by William Shakespeare. It is believed to have been written between 1604 and 1605, and was originally published in the First Folio in 1623....

)
Rupes
Rupes
Rupes is the Latin word for 'cliff'. It is used in planetary geology to refer to escarpments on other planets, such as Mercury, and moons, such as Luna, Earth's natural satellite.How rupes are formed is, as of 2008, a matter of speculation...

402 14.7°N 23.5°W
Adriana Adriana (The Comedy of Errors
The Comedy of Errors
The Comedy of Errors is one of William Shakespeare's earliest plays. It is his shortest and one of his most farcical comedies, with a major part of the humour coming from slapstick and mistaken identity, in addition to puns and word play. The Comedy of Errors is one of only two of Shakespeare's...

)
Crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

50 20.1°N 3.9°W
Bona Bona (Henry VI, Part 3
Henry VI, part 3
Henry VI, Part 3 or The Third Part of Henry the Sixt is a history play by William Shakespeare believed to have been written in 1591, and set during the lifetime of King Henry VI of England...

)
51 55.8°N 351.2°W
Calphurnia Calpurnia Pisonis
Calpurnia Pisonis
Calpurnia Pisonis , daughter of Lucius Calpurnius Piso Caesoninus, sister of Lucius Calpurnius Piso, "the Pontifex", was a Roman woman and the third and last wife of Julius Caesar. Calpurnia was the great-granddaughter of a lieutenant of Lucius Cassius Longinus, whose name was Lucius Piso...

 (Julius Caesar
Julius Caesar (play)
The Tragedy of Julius Caesar, also known simply as Julius Caesar, is a tragedy by William Shakespeare, believed to have been written in 1599. It portrays the 44 BC conspiracy against...

)
100 42.4°N 291.4 °W
Elinor Eleanor of Aquitaine
Eleanor of Aquitaine
Eleanor of Aquitaine was one of the wealthiest and most powerful women in Western Europe during the High Middle Ages. As well as being Duchess of Aquitaine in her own right, she was queen consort of France and of England...

 (The Life and Death of King John)
74 44.8°N 333.6°W
Gertrude
Gertrude (crater)
Gertrude is the largest known crater on Uranus's moon Titania. It is about 326 km across, 1/5 of Titania's diameter. It is named after the mother of Hamlet in William Shakespeare's play Hamlet. Features on Titania are named after female Shakespearean characters.The crater rim of Gertrude is...

Gertrude
Gertrude (Hamlet)
In William Shakespeare's play Hamlet, Gertrude is Hamlet's mother and Queen of Denmark. Her relationship with Hamlet is somewhat turbulent, since he resents her for marrying her husband's brother Claudius after he murdered the King...

 (Hamlet
Hamlet
The Tragical History of Hamlet, Prince of Denmark, or more simply Hamlet, is a tragedy by William Shakespeare, believed to have been written between 1599 and 1601...

)
326 15.8°N 287.1°W
Imogen Imogen (Cymbeline
Cymbeline
Cymbeline , also known as Cymbeline, King of Britain or The Tragedy of Cymbeline, is a play by William Shakespeare, based on legends concerning the early Celtic British King Cunobelinus. Although listed as a tragedy in the First Folio, modern critics often classify Cymbeline as a romance...

)
28 23.8°N 321.2°W
Iras Iras (Antony and Cleopatra
Antony and Cleopatra
Antony and Cleopatra is a tragedy by William Shakespeare, believed to have been written sometime between 1603 and 1607. It was first printed in the First Folio of 1623. The plot is based on Thomas North's translation of Plutarch's Lives and follows the relationship between Cleopatra and Mark Antony...

)
33 19.2°N 338.8°W
Jessica Jessica (The Merchant of Venice
The Merchant of Venice
The Merchant of Venice is a tragic comedy by William Shakespeare, believed to have been written between 1596 and 1598. Though classified as a comedy in the First Folio and sharing certain aspects with Shakespeare's other romantic comedies, the play is perhaps most remembered for its dramatic...

)
64 55.3°N 285.9°W
Katherine Katherine (Henry VIII
Henry VIII (play)
The Famous History of the Life of King Henry the Eight is a history play by William Shakespeare and John Fletcher, based on the life of Henry VIII of England. An alternative title, All is True, is recorded in contemporary documents, the title Henry VIII not appearing until the play's publication...

)
75 51.2°N 331.9°W
Lucetta Lucetta (The Two Gentlemen of Verona
The Two Gentlemen of Verona
The Two Gentlemen of Verona is a comedy by William Shakespeare, believed to have been written in 1590 or 1591. It is considered by some to be Shakespeare's first play, and is often seen as his first tentative steps in laying out some of the themes and tropes with which he would later deal in more...

)
58 14.7°N 277.1°W
Marina Marina (Pericles, Prince of Tyre
Pericles, Prince of Tyre
Pericles, Prince of Tyre is a Jacobean play written at least in part by William Shakespeare and included in modern editions of his collected works despite questions over its authorship, as it was not included in the First Folio...

)
40 15.5°N 316°W
Mopsa Mopsa (The Winter's Tale
The Winter's Tale
The Winter's Tale is a play by William Shakespeare, originally published in the First Folio of 1623. Although it was grouped among the comedies, some modern editors have relabelled the play as one of Shakespeare's late romances. Some critics, among them W. W...

)
101 11.9°N 302.2°W
Phrynia Phrynia (Timon of Athens
Timon of Athens
The Life of Timon of Athens is a play by William Shakespeare about the fortunes of an Athenian named Timon , generally regarded as one of his most obscure and difficult works...

)
35 24.3°N 309.2°W
Ursula
Ursula (crater)
Ursula is a large crater on Uranus's moon Titania. It is about 135 km across, and is cut by Belmont Chasma. It is named after attendant on Hero in William Shakespeare's comedy Much Ado About Nothing....

Ursula (Much Ado About Nothing
Much Ado About Nothing
Much Ado About Nothing is a comedy written by William Shakespeare about two pairs of lovers, Benedick and Beatrice, and Claudio and Hero....

)
135 12.4°N 45.2°W
Valeria Valeria (Coriolanus
Coriolanus
Gaius Marcius Coriolanus was a Roman general who is said to have lived in the 5th century BC. He received his toponymic cognomen "Coriolanus" because of his exceptional valor in a Roman siege of the Volscian city of Corioli. He was then promoted to a general...

)
59 34.5°N 4.2°W
Surface features on Titania are named for characters from Shakespeare's works.

Atmosphere


The presence of carbon dioxide on the surface suggests that Titania may have a tenuous seasonal atmosphere of CO2, much like that of the Jovian moon Callisto. Other gases like nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 or methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 are unlikely to be present, because the moon's weak gravity could not prevent them escaping into the space. At the maximum temperature attainable during Titania's summer solstice
Summer solstice
The summer solstice occurs exactly when the axial tilt of a planet's semi-axis in a given hemisphere is most inclined towards the star that it orbits. Earth's maximum axial tilt to our star, the Sun, during a solstice is 23° 26'. Though the summer solstice is an instant in time, the term is also...

 (89 K), the vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

 of carbon dioxide is about 3 nbar.

On September 8, 2001, Titania occulted
Occultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...

 a bright star (HIP106829) with a visible magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 of 7.2; this was an opportunity to both refine the moon's diameter and ephemeris
Ephemeris
An ephemeris is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds of ephemerides are used for astronomy and astrology...

, and to detect any extant atmosphere. The data revealed no atmosphere to a surface pressure of 10–20 nanobars; if it exists, it would have to be far thinner than that of Triton
Triton (moon)
Triton is the largest moon of the planet Neptune, discovered on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, which is an orbit in the opposite direction to its planet's rotation. At 2,700 km in diameter, it is...

 or Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...

. This upper limit is still several times higher than the maximum possible surface pressure of the carbon dioxide, meaning that the measurements place essentially no constraints on parameters of the atmosphere.

The peculiar geometry of the Uranian system causes the moons' poles to receive more solar energy than their equatorial regions. Since the vapor pressure of CO2 is a steep function of temperature, this may lead to the accumulation of carbon dioxide in the low-latitude regions of Titania, where it can stably exist on high albedo patches and shaded regions of the surface in the form of ice. During the summer, when the polar temperatures reach as high as 85–90 K, carbon dioxide sublimates and migrates to the opposite pole and to the equatorial regions, giving rise to a type of carbon cycle
Carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth...

. The accumulated carbon dioxide ice can be removed from cold traps by magnetospheric particles, which sputter it from the surface. Titania is thought to have lost a significant amount of carbon dioxide since its formation 4.6 billion years ago.

Origin and evolution


Titania is thought to have formed from an accretion disc
Accretion disc
An accretion disc is a structure formed by diffuse material in orbital motion around a central body. The central body is typically a star. Gravity causes material in the disc to spiral inward towards the central body. Gravitational forces compress the material causing the emission of...

 or subnebula; a disc of gas and dust that either existed around Uranus for some time after its formation or was created by the giant impact that most likely gave Uranus its large obliquity. The precise composition of the subnebula is not known; however, the relatively high density of Titania and other Uranian moons compared to the moons of Saturn indicates that it may have been relatively water-poor. Significant amounts of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 and carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 may have been present in the form of carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 and N2 instead of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 and methane. The moons that formed in such a subnebula would contain less water ice (with CO and N2 trapped as a clathrate) and more rock, explaining the higher density.

Titania's accretion probably lasted for several thousand years. The impacts that accompanied accretion caused heating of the moon's outer layer. The maximum temperature of around 250 K was reached at the depth of about 60 km. After the end of formation, the subsurface layer cooled, while the interior of Titania heated due to decay of radioactive elements present in its rocks. The cooling near-surface layer contracted, while the interior expanded. This caused strong extensional stresses in the moon's crust leading to cracking. Some of present-day canyons may be a result of this process, which lasted for about 200 million years, implying that any endogenous activity ceased billions years ago.

The initial accretional heating
Accretion (astrophysics)
In astrophysics, the term accretion is used for at least two distinct processes.The first and most common is the growth of a massive object by gravitationally attracting more matter, typically gaseous matter in an accretion disc. Accretion discs are common around smaller stars or stellar remnants...

 together with continued decay of radioactive elements were probably strong enough to melt the ice if some antifreeze like ammonia (in the form of ammonia hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....

) or salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 was present. Further melting may have led to the separation of ice from rocks and formation of a rocky core surrounded by an icy mantle. A layer of liquid water (ocean) rich in dissolved ammonia may have formed at the core–mantle boundary. The eutectic temperature of this mixture is 176 K. If the temperature dropped below this value the ocean would have frozen by now. The freezing of the water led to the expansion of the interior, which may have been responsible for the formation of the majority of canyons. Still, the present knowledge of the evolution of Titania is quite limited.

Exploration



So far the only close-up images of Titania have been from the Voyager 2
Voyager 2
The Voyager 2 spacecraft is a 722-kilogram space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space...

probe, which photographed the moon during its flyby of Uranus in January 1986. Since the closest distance between Voyager 2 and Titania was only 365,200 km, the best images of this moon have a spatial resolution of about 3.4 km (only Miranda and Ariel were imaged with a better resolution). The images cover about 40% of the surface, but only 24% was photographed with the precision required for geological mapping. At the time of the flyby, the southern hemisphere of Titania (like those of the other moons) was pointed towards the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, so the northern (dark) hemisphere could not be studied.

No other spacecraft has ever visited the Uranian system or Titania, and no mission is planned in the foreseeable future. One possibility was to send Cassini–Huygens to Uranus, and another is the Uranus orbiter and probe
Uranus orbiter and probe
A Uranus orbiter and probe mission to explore the planet Uranus, its atmosphere, rings, and moons, was recommended to NASA in 2011 by its . A mission study was conducted which also considered Neptune; however, for feasibility reasons Neptune was dropped in favor of Uranus. Two white papers on...

 concept, evaluated around 2010. Uranus was also examined as part of one trajectory for a interstellar precursor probe concept, Innovative Interstellar Explorer
Innovative Interstellar Explorer
Innovative Interstellar Explorer was a NASA "Vision Mission" study funded by NASA following a proposal under NRA-03-OSS-01 on 11 September 2003. This study has focused on the elusive quest to reach and measure the interstellar medium, the "undiscovered country" outside of the influence of the...

.

External links